Regional spotlight series: How local weather and soil conditions can impact ACT’s ageing residential market

rain flows down from a roof down causing subsidence issues

As part of our regional series, we take a closer look at the Australian Capital Territory (ACT) and how its ground conditions can impact the area’s built environment.

Like in most regions, Mainmark’s operations in Australia’s capital city span residential, commercial and civil infrastructure. While several public infrastructure sites have benefited from Mainmark’s ground remediation expertise, including Lake Burley Griffin and Federation Mall, homeowners in the territory and surrounding areas also keep our team busy.

Understanding the ACT’s ground conditions

The topography surrounding Canberra consists of forested hills and alluvial flats, with much of the urban areas built on gently undulating terrain that features gravelly and sandy soils. However, the broader soil profile in the ACT is primarily clay, ranging from low, medium and high plasticity, and is classified as moderately reactive in accordance with AS2870 “Residential slabs and footings” standard.

The weather also plays a big part in the region’s ground conditions. Depending on the time of year, the ACT can experience temperatures ranging from -8 to 45 degrees, with cyclical weather patterns such as La Nina and El Nino leading to both saturation and dehydration of the ground. This causes reactive clay to shrink and swell much like in many other parts of Australia, creating structural challenges for homeowners.

A typical home in the ACT

While the ACT residential market has become more diverse in styles and architecture over time, it is best known for the colloquial ‘Govie’ style house. Govies are homes that were built quickly and in large volumes to meet high demand. The population growth from politicians and their families moving to the ACT resulted in greater investment and liveability. Govies therefore needed to cater for the influx of residents, built with the most affordable and readily available materials to ensure quick turnarounds.

From the 1920s to 1950s, most houses were built with double brick exterior and a single brick interior, on narrow and shallow concrete strip footings, with little or no articulation in the walls to allow for movement. In the 1960s and 1970s, the government oversaw a large expansion of Canberra, creating the ‘Govie’ design with simple rectangular layouts and wet areas on concrete floors above narrow strip footings. Many of these houses remain standing today and are regularly renovated and extended.

While Govies have always been compliant, they were often constructed quickly, not allowing builders to consider the relationship between the foundations and the reactive clay. During cyclical weather changes, the clay would shrink and swell, affecting the footing and creating a loss in soil volume, resulting in foundational settlement. In many cases, old Govie footings have not been maintained and over the decades, this has resulted in settlement-related damage such as sunken floors and cracks in the interior and exterior walls.

Overcoming the challenges

Fortunately, building codes have improved over the years. They now better consider the ACT’s ground conditions and its impact on residential construction. However, regardless of the age of a building, footings require monitoring over their lifespan and at times, property owners may need to take action to manage ground moisture levels, which may include removing trees or addressing leaking pipes.

While the ACT’s ground engineering sector has historically relied on conventional remediation methods like traditional underpinning, Mainmark’s Teretek® resin injection solution has become a popular alternative as more homeowners recognise the benefits of using a modern technology that is easier to apply, cost effective and less invasive.

In addition to working directly with local homeowners, Mainmark has also formed relationships with local builders and engineers regarding ground remediation solutions for local infrastructure. For example, the Australian Government’s National Capital Authority (NCA) engaged Mainmark to re-support the Lake Burley Griffin foreshore wall by injecting more than 40 tonnes of Teretek into a 4km section of the lake’s concrete and stone wall. The solution successfully filled voids, increased ground bearing capacity and agglomerated the loose soil to mitigate fines being lost into the lake through cracks in the ageing walls.

Mainmark was also engaged by the NCA to address settlement issues affecting the Federation Mall bridge using Teretek to fill underground voids beneath the bridge’s approach slabs and roadway to rectify ‘dishing’ and minimise the risk of ongoing settlement.

Over the years, Mainmark has established a strong presence in the ACT and is looking forward to continuing to support the region using its innovative range of ground and asset remediation solutions in the residential, commercial and infrastructure sectors.


Alan Reid MainmarkBy Alan Reid

Alan Reid is a Territory Manager at Mainmark Ground Engineering that services the ACT region. Holding a degree in Civil Engineering from University of Sydney he has years of experience in project management and customer acquisition in several industries including construction.

A year in review with Mainmark ANZ general manager, Joe Glanville

Teretek bridge repair and relevel

As 2021 draws to a close and we reflect on the year that has been, I think our biggest achievement this year is that we managed to successfully complete well over 1,800 projects across Australia and New Zealand despite extended lockdowns and border restrictions, which impacted our business in every region.

The Australian and New Zealand economies remained remarkably strong this year, buoyed by record levels of government infrastructure investment. This has had a positive impact on our business, with civil infrastructure and remediation now a huge focus for Mainmark. The increased demand for our specialised products and services is the driving force behind the evolution of Mainmark’s civil and mining division, which offers a unique range of solutions to re-level, repair and rehabilitate assets in the civil infrastructure, mining and seismic environment sectors.

This year, Mainmark had the opportunity to demonstrate its breadth of capabilities by completing a number of significant projects. In Australia we are currently undertaking a major culvert rehabilitation project in South East Queensland involving a wide range of complex remediation solutions, including Terefil®, our flowable lightweight polymer modified cementitious grout which is part of the solution being used to fill significant voiding behind the steel culverts. Terefil was also used as an innovative alternate structural solution for the change of use of an Olympic swimming pool in Sydney. In New Zealand, we also used Terefirm® to strengthen the ground beneath O’Connells, an iconic retail, dining and office complex in Queenstown, to increase liquefaction resistance and increase its NBS (New Building Standard) rating.

We were also honoured to receive a Good Design Award in the engineering category for our Toowoomba Bypass project in Queensland. While Mainmark doesn’t embark on projects to win awards, we were extremely proud to be acknowledged for successfully completing this unique and complex Queensland project which involved upgrades and repair work to culverts along the $1.6 billion bypass. The sheer level of on-site research and development that was required to overcome the design constraints was a significant factor in the successful outcome of this project and the judges summed up our work nicely.

Clearly innovative, the design was clever and had benefits for the project in terms of cost, schedule and quality. This is really impressive design and engineering, and a standout example of good design in this category that deserves to be recognised.”

Mainmark is constantly pushing geotechnical boundaries through research, development and trials. It’s this dedication to innovation that also led us to develop Terefil as a proven alternate solution for gravel raft slab replacement in several building projects, having recently successfully completed the first stage of a large project at Wainuiomata, Wellington.

These projects are just a few examples of why Mainmark is becoming renowned for its innovative approach to solving complex remediation projects and we are well placed to leverage further opportunities as further projects are rolled out under the Australian Government’s $110 billion rolling infrastructure pipeline.

As we enter 2022 filled with optimism, we have significant growth aspirations for all operating divisions. We also look forward to continuing to demonstrate our breadth of applications, which include evolving our specialised resins, gels and coatings for reinforcing ageing or damaged buildings and assets, and water mitigation and control in more infrastructure and tunnelling projects.

I would like to thank all of our clients, industry partners and staff for being flexible, adapting to change, and working collaboratively over the last 12 months. We have achieved great things and are looking forward to an even more productive year ahead.


Joe Glanville MainmarkBy Joe Glanville

Joe Glanville is Mainmark’s ANZ General Manager. He has over 15 years’ experience in the Construction Industry, acquiring broad commercial, construction and project management skills.

Tunnel infrastructure: The key to functional cities are tunnels built to last

Sydney Harbour Tunnel - Australia

With increasing urban population density and traffic loads, tunnel infrastructure is often the difference between commuters reaching their destination and transportation grinding to a halt. Tunnels help to alleviate congestion, promote healthier traffic flow, and minimise disruption in suburban areas making them increasingly important for metropolitan growth areas.

For example, in Greater Sydney, New South Wales, hundreds of thousands of vehicles travel through the city every day. According to the latest motor vehicle census, there were 5,892,206 motor vehicle registrations in New South Wales in 2020[1], suggesting that roads will continue to feel the strain of heavy traffic.

With infrastructure projects currently booming across Australia, there are a number of large-scale tunnels that will commence in the coming months, such as the new Sydney Harbour tunnel in New South Wales and the North East Link project in Victoria. However, while the infrastructure boom is great for the economy, keeping these projects on track and within budget will be critical.

There are several challenges and considerations that make the development and ongoing maintenance of tunnel infrastructure incredibly complex. From Mainmark’s perspective, as a ground engineering industry leader consulting on a number of large-scale tunnel projects, our technicians have seen firsthand what is needed to ensure the safety, quality and longevity of Australia’s most utilised transport corridors.

Considerations for tunnel infrastructure

On the surface (or rather below the surface), tunnels appear sturdy and reliable. However, they are like any piece of infrastructure and require maintenance and repair over time. Tunnels are particularly susceptible to degradation when surrounding ground conditions have not been fully considered during construction. For example, unconsolidated soil can result in a soft and often precarious envelope for tunnels that is prone to shifting.

This can be problematic for Sydney, given the area’s geological profile which consists of weak and unconsolidated sandstone. Water tables, where groundwater saturates spaces between sediments and cracks in rock, are another major consideration for tunnel construction, as well as palaeochannels, which are inactive water channels that have been filled or buried by younger sediment. These geological occurrences, if not identified and planned for in advance, can significantly affect a tunnel’s structural integrity and exposed surface over time either through ground movement and cracking, or significant water ingress that can slowly degrade the structure.

A lack of planning and proactive mitigation of waterproofing and ground reinforcement, are common in tunnel construction. However, this is not always a sign of negligence; tunnels often take decades to deteriorate and the immediate demand, or available funds, can sometimes influence the cost-to-benefit decisions for long term planning and maintenance. In other words, a tunnel’s construction is often planned around the urgency to help keep traffic moving, rather than addressing an unforeseen issue that may arise several decades down the track.

Remediating problems before they occur

With increasing pressure on roads in our expanding urban centres, the need for tunnel infrastructure is always growing. Unfortunately, there is no magic spell to completely alter the existing geological landscape. Instead, successful tunnel construction hinges on a combination of careful pre-construction planning, ground and risk analysis, and the ability to use effective remediation solutions if needed.

While ongoing maintenance is important, the quality and longevity of our tunnels should not be compromised. Fixing problems that have already emerged can be incredibly costly. Instead, detailed planning, site surveying and a thorough geotechnical analysis of the surrounding ground conditions should take place well before construction begins, with tailored solutions introduced before and during the construction phase.

Understanding what solutions and application techniques to use for different tunnel systems and ground conditions is vital to mitigating potential issues. It is why Mainmark is continually developing and trialling new applications and solutions for long term performance.

Mainmark’s specialised resins, gels and coatings can help engineers minimise the risk of issues, such as water ingress, by forming impenetrable barriers tailored to specific substrates. Our range of proven, hard-wearing water stop solutions are non-invasive, easy to apply and cost effective to help to meet project timelines and objectives.

Using the latest technology, Mainmark can tailor the strength, viscosity and flowability of its solutions to help reinforce tunnel substrates and address surrounding weak ground using solutions such as permeation grouting. Our fast-acting water stop solutions are also ideal for urgent emergency works, stopping leaks within minutes, which is a superior outcome for high-risk projects.

Ultimately, Mainmark’s technologies and capabilities challenge traditional standards and approaches to tunnel construction and remediation. By utilising the right solutions, we can ensure the quality and longevity of Australia’s existing and future tunnel infrastructure for decades to come.

[1] https://www.abs.gov.au/statistics/industry/tourism-and-transport/motor-vehicle-census-australia/latest-release


Matt McleanBy Matt Mclean

Matt McLean is the Operations Manager for specialised resins and coatings at Mainmark. He is a concrete remediation, coatings, resins and waterstop injection specialist with a long history of working with ground stabilisation and grouting technologies.

Regional spotlight series: meeting the demand for specialised applications and civil infrastructure remediation in Victoria and Tasmania

Melbourne at dusk

As part of our regional series, where we discuss Mainmark’s operations in different areas across Australia and New Zealand, we turn our attention to Victoria and Tasmania. While Mainmark’s residential division has thrived in these regions for many years, more recently there has been a major focus on infrastructure remediation due to a record level of Government investment, which has resulted in rapid growth for Mainmark.

The geographical area in Victoria and Tasmania includes thriving cities, sprawling low density suburban areas and vast rural farmland, with geotechnical challenges spanning residential and commercial development to major civil infrastructure projects. Our team specialises in identifying and solving a wide range of ground engineering and remediation issues, such as ground re-levelling and soil strengthening, concrete repair and specialist grouting, as well as specialised resin coatings and waterproofing solutions.

The soil composition in Victoria and Tasmania also varies from reactive clay, common in urban areas including metropolitan Melbourne, to sandy and loam soils which are found throughout the state. In contrast, Tasmania contains a more diverse range of soils due to the state’s landscape and geology.

Maintaining assets and critical infrastructure

Infrastructure, civil remediation and concrete repair have become a growing area of focus for our business, perhaps more so here than in any other region in Australia after the Victorian Government announced a $90.2 billion investment into local infrastructure projects over the next four years[1]. Mainmark has consistently demonstrated how our products and expertise are more efficient and cost effective when addressing geotechnical and asset remediation challenges for these sectors.

Commercial remediation projects that require ground improvement works are an important part of Mainmark’s operation, such as this multi-storey business complex in Victoria which was saved from subsidence using our proprietary JOG Computer-Controlled Grouting and Teretek®. The geotechnical site survey revealed that the complex was built on a combination of fill material and highly reactive clay. Water ingress had caused the clay to heave, resulting in building movement and damage to the buildings.

Many single and multi-storey developments experience subsidence due to water ingress, as excessive water can oversaturate and soften the soil underneath foundations. Reactive clay is particularly susceptible to subsidence as the soil swells and shrinks in response to changing moisture levels, which reduces ground bearing capacity and exacerbates the risk of differential soil settlement.

Decommissioning old or damaged pipe infrastructure, including redundant gas, water and sewer pipes, can also be problematic, particularly in inner city areas and older suburbs where ageing infrastructure has started to crack and leak, releasing water into the ground. These pipes cannot be easily removed without impacting the surrounding environment. This is particularly challenging if the pipes are located below roads and rail tracks as the disruption would not only result in the lengthy closure of essential transport corridors but would also be cost prohibitive. For this reason, they usually remain in the ground.

However, abandoned pipes cannot simply be left to deteriorate underground without being filled with an appropriate inert solution. If the pipe was to collapse or if water leaked into the surrounding ground, subsidence and erosion could lead to dangerous voids and sinkholes. Filling redundant pipes with a highly flowable structural fill material, such as Mainmark’s Terefil®, which is designed to be pumped further and faster than traditional concrete fill solutions, is providing a new way to solve the problems associated with pipe abandonments. Projects like the abandoned cast-iron gas main in Brunswick and the ground stabilisation and void fill at a stormwater deck replacement in Fitzroy, particularly benefited from our specialist solutions.

How the pandemic has impacted operations

While COVID-19 has impacted many businesses across the country, including Victoria which experienced numerous hard lockdowns and ongoing restrictions, Mainmark’s civil infrastructure division continued to experience high demand due to our range of specialised applications that are used for projects classified as critical infrastructure.

Mainmark’s reputation as a civil remediation expert has helped maintain the pace for the business, following the completion of a variety of successful projects across Victoria and Tasmania. Back in 2019, Mainmark stabilised the heritage listed Kimberley Rail Bridge in Tasmania by using Teretek to fill underwater voids. This work forged strong relationships with infrastructure maintenance contractors, leading to our range of bespoke solutions being specified for recent major capital works projects such as The West Gate Tunnel, Western Roads Upgrades and the North East Link.

Research and innovation keep Mainmark at the forefront of ground engineering

Mainmark’s innovative products like Terefil, Teretek, JOG and specialised engineered coatings and waterproofing solutions have consistently proven over time to be more cost-effective and time-efficient compared to more traditional remediation alternatives. This has resulted in Mainmark fast becoming recognised as the region’s ‘go-to’ contractor for complex problems.

Research and development have become a crucial reason why Mainmark delivers, and exceeds, customer expectations. Products and advanced delivery methods are continually being developed and tested to ensure the applications are tailored to Australia’s ground and civil remedial challenges. This involves quality assurance and stress tests that push the product’s individual capabilities.

The expertise and tailored solutions-focused approach from Mainmark helps project managers and asset owners across the wider region realise the deeper value and insight that ground engineering specialists can provide. This has steadily strengthened Mainmark’s following and increased our reputation as a reliable problem solver throughout the industry and the local community.

[1] https://infrastructure.org.au/wp-content/uploads/2021/05/MEDIA-RELEASE-PALLAS-DELIVERS-HIGHEST-INFRASTRUCTURE-SPEND-ON-RECORD-SETTING-THE-STATE-ON-STABLE-PATH-TO-RECOVERY.pdf


By Max Kudrenko – Technical Manager

Max Kudrenko is the Technical Manager(Vic/Tas) at Mainmark Ground Engineering. Max is a civil engineer who has experience working with different grout, resin and other cementitious geotechnical and ground improvement technologies in the residential, commercial, gas/oil and civil sectors. He has successfully project managed works throughout Australia, New Zealand and Japan.

Adapting to change with virtual site inspections

Virtual site inspection Mainmark covid safe company

Due to the disruption caused by restrictions that Australia and New Zealand have experienced as a result of COVID-19, many trades and businesses including ground engineering specialists, have been unable to visit homes in some regions to conduct on-site inspections.

Without visiting a customer’s home, it is difficult to assess structural issues like wall cracks and sinking foundations that may be caused by subsidence. However, rather than leaving homeowners to worry about the issues, and their potential to worsen, Mainmark has harnessed digital tools and Apps to continue offering expert ground remediation advice virtually. This enables clients to safely receive professional support and guidance regardless of their circumstances.

Traditionally, the site inspection process has involved visiting the customer’s home face-to-face and conducting a detailed on-site analysis of the issue. Once the problems are identified, Mainmark determines the best solution, process and timeline, before carrying out the work. A virtual site inspection, ideally via video call, can help to pre-qualify work, identifying any significant issues that might need to be addressed urgently and enable Mainmark to provide the homeowner a budget price. It also gives peace of mind to those with a more minor problem that may not need to act immediately. Customers are also encouraged to share videos of their problem areas, like this example from the owner of an ACT residence who shared this video with our local engineer, Alan Reid:

 

Here is Mainmark’s simple three-step virtual site inspection process which is proving to be extremely valuable for worried homeowners, utilising a combination of enhanced customer service and technology.

Step one: Connecting with the homeowner

The process begins as soon as a customer reaches out to Mainmark. Once their site’s issue and symptoms have been established, Mainmark’s team arrange a convenient time for an expert ground remediation representative to “e-meet” the customer.

Everyone has their preferred online or visual method and Mainmark connects with people in ways that make them feel comfortable. Video calls via phone, tablet or laptop are popular using platforms such as FaceTime, WhatsApp, Zoom and Skype. Others may choose to capture a video of their issue and send it to their Mainmark representative for assessment and further discussion via a phone call. Further supporting documentation such as site plans and photographs, and a builder’s or structural engineer’s report can also be sent to the Mainmark team to help with diagnosis and assessment.

Step two: Virtual assessment

Mainmark will then visually assess the customer’s home to better understand the issue. The Mainmark representative will ask the homeowner a series of questions to obtain a detailed understanding of the type of home, the condition of the foundations, the type of soil and ground conditions the home sits on, and any other factors that may be causing the damage, such as a leaking pipe. A walk through of the indoor and outdoor areas may be requested, including close ups of any cracking or other symptoms.

Step three: Solution

Once the home and surrounds have been viewed and remotely examined, the Mainmark representative will analyse the situation and discuss what could be causing the issue. While the virtual diagnosis cannot be confirmed until a physical inspection can take place, Mainmark can provide preliminary advice, explain remediation options and discuss the non-invasive solutions to fix the underlying subsidence problem, including providing budget costs.

When restrictions allow, further onsite assessment can be carried out and the actual remediation works scheduled. Depending on the nature and scope of work required, it can sometimes be possible to accomplish this without Mainmark’s team stepping inside the home.

Despite the challenges presented by the global pandemic, the current landscape has allowed us to adapt in ways that can be beneficial into the future, even after the current restrictions have been removed. Virtual site inspections can provide a starting point for homeowners needing advice, particularly those in more remote locations. The service can also support homeowners impacted by further lockdowns in the future, or residents who are simply more comfortable with an initial virtual assessment.


Lincoln GrodyBy Lincoln Grody

Lincoln Grody is Regional Sales Manager (NSW & ACT) at Mainmark Ground Engineering. Lincoln has a Bachelor of Applied Science in Civil Engineering from University of Colorado and holds a Master’s Degree in Construction Management from The University of Texas. Originally from Colorado, USA, Lincoln began his career in the construction industry as a structural engineer, researching building information modelling and data analysis techniques in the commercial sector. Subsequently, he has spent the last 10 years working in various roles in engineering, project management and sales management for leading global firms in the United States, Europe, South America and Australia.

Mainmark wins Good Design Award for Toowoomba Bypass project

culvert relining on a crane with mainmark technician

In 2019 Mainmark embarked on a project in Toowoomba, Queensland, playing an important role in one of the largest infrastructure projects in the state’s history.

The project was the $1.6 billion Toowoomba Bypass, a 41km long dual carriageway and ring road that was designed to improve freight connections to major ports and markets and reduce the number of trucks on Toowoomba’s local roads.

This week, our work on the Toowoomba Bypass received a prestigious Good Design Award Winner accolade in the Engineering Design category, in recognition of outstanding design and innovation.

Our role in the project was to help reline, repair and future-proof seven concrete drainage culverts which were damaged and threatened the structural integrity of the bypass.

Needless to say, it is thrilling to be acknowledged for our contributions to the ground engineering and asset preservation sector. This important project for Queensland challenged our team to think outside the box and deliver an alternative solution to a complex problem. Being recognised for that effort is a great reward for all involved.

This year, the Australian Good Design Awards attracted 933 submissions, which were evaluated by more than 70 Australian and international jurors, including designers, engineers, architects and thought leaders. Each entry was assessed according to a strict set of design evaluation criteria which includes good design, design innovation and design impact. According to Good Design Australia CEO, Dr Brandon Gien, the standard of design excellence represented in this year’s entries were the best he’d seen in 25 years of running the Awards; an encouraging sign that the design sector is flourishing.

The Good Design Awards Jury said, “Mainmark’s solution was a wonderful example of optimising on a range of parameters within constraints. Clearly innovative, this design was clever and had benefits for the project in terms of cost, schedule and quality. This is really impressive design and engineering, and a standout example of good design in this category that deserves to be recognised.”

About the project

During construction of the Toowoomba Bypass, it was discovered that seven reinforced concrete pipe culverts contained at least one damaged barrel while several were compromised in up to five separate remote and isolated locations. These culverts provided drainage from the invert of a valley beneath the fill under the road alignment. Without these culverts, rainwater and other natural events could potentially degrade the valley and the road, making a vital transport route unsafe and unusable.

Mainmark was contracted to repair and reline the damaged culverts, ensuring that they would last for years to come.

Working closely with Nexus Delivery and Roundel Civil Projects Pty Ltd, Mainmark developed an engineered solution using a multi-faceted approach to relining the RCP culverts which involved the insertion of site based custom manufactured corrugated metal pipes (CMPs) inside the damaged RCP concrete culverts and then filling the void (or annulus) between the CMP and the original RCP concrete culverts with Terefil®.

Terefil®, is our proprietary lightweight cementitious grout containing a uniformly distributed matrix of air bubbles generated by mixing cement slurry with stable, pre-formed hydrocarbon foam. This produces a lightweight concrete mix that provides the most suitable fill which does not require maintenance with additional supporting material, energy or resources. Terefil was instrumental in remediating the compromised culverts underneath the bypass, restoring their structural integrity and ensuring suitable drainage for the bypass upgrade.

Terefil is also highly flowable, making its delivery to the project site simple and stress free. This, as well as its high setting strength, allowed the team to complete the work on time and within budget in compliance with specific project requirements set by the Queensland Department of Transport and Main Roads (DTMR).

Since completion in 2019, the bypass has been able to reduce travel time across the Toowoomba Range by up to 40 minutes for heavy commercial vehicles, improve freight connections and redirect trucks away from Toowoomba’s CBD, which enhances liveability in the Toowoomba and Lockyer Valley areas.


Good design award winner Mainmark

Mainmark is proud to win the Good Design Award in the Engineering Design category, in recognition of outstanding design and innovation for this project. Read the case study here.


Laurie Andrews MainmarkBy Joe Glanville

Joe Glanville is Mainmark’s ANZ General Manager. He has over 15 years’ experience in the Construction Industry, acquiring broad commercial, construction and project management skills.

How trees impact ground conditions and building foundations

Garden bushes, tree and green grass lawn covered with water due to snow melting thaw and flash high water at spring. Natural disaster deluge flooded house backyard pathway ang greenery at countryside.

There is no denying that trees are a beneficial asset to the environment, our lifestyle and a symbol of a healthy landscape. They create shade and privacy, contribute to better air quality, provide habitats for native birds and animals, and help to reduce salinity and soil erosion.

However, without proper consideration and monitoring, trees can also impact our built environment by causing damage to buildings, paths, driveways, and underground infrastructure.

A tree’s influence starts, literally, at the roots; they are responsible for keeping the tree alive by drawing essential nutrients and water from its surroundings. The roots will continue to grow as a tree matures and during this growth, the roots will extend towards anything that will maintain the tree’s life. Roots typically seek out moist soil and will often find entry into old or damaged pipes including stormwater drains, sewage pipes and water mains.

Seasonal change also influences how trees interact with the built environment. During the warmer months of spring and summer, soils can dry out with the lack of moisture causing reactive clays to shrink. In extreme cases, shrinking soil can lead to significant ground movement, subsidence and foundation settlement across the home. Unfortunately, trees can exacerbate this process. In their hunt for moisture, root systems will extend through dried soil, desiccating the ground and absorbing remaining water from the already dry earth.

The combination of dry soil and thirsty tree roots is the perfect recipe for ground movement, and the appearance of worrying subsidence symptoms, including cracks in brick walls, distorted timber frames, and doors and windows that jam. Examples of different causes of subsidence around the home, including those triggered by tree roots, can be viewed on Mainmark’s interactive house: www.mainmark.com/subsidence-problems-around-homes. Understanding the cause of problems is essential before a viable solution can be found.

Assessing the influence of trees

There are several factors to consider when determining whether trees could be the ‘root cause’ of damage to a home. These include:

Groupings

When trees are planted closely together, they are forced to compete for moisture and nutrients in the same area of soil. The larger the group of trees, the greater the impact on soil drying out in the surrounding area. It is therefore more likely for homes or buildings located near large groups of trees to experience effects of adverse ground conditions as the trees absorb more moisture which can contribute to greater ground movement.

Tree types

Tree activity varies across the year depending on its type, so it’s important to identify the trees that are growing near your home. Deciduous trees, for example, hibernate in winter and re-grow in spring. This lifecycle means their water demand is often highest during drier months, which has the effect of increasing the magnitude of soil shrinkage.

Characteristics

A tree’s physical characteristics can determine how much moisture its root system is likely to absorb, but it’s not always just in relation to its overall size. Research into a tree’s influence on ground conditions has indicated that it is the leaf area of the tree rather than its height that ultimately determines its moisture demand[1]. Therefore, thick or tall trees aren’t always the culprit for dry soil; it’s the amount of foliage that can indicate how much water a tree needs to sustain itself.

Surrounding environment

Roads, footpaths, and larger scale developments with limited green space can also prevent moisture from reaching the soil underneath. This lack of permeability can cause dry soil conditions and may force tree roots to draw on the limited moisture available, intensifying soil shrinkage and ground movement. This is common in urban areas where trees are planted for aesthetic or ‘greenscaping’ purposes, without considering the degree of exposed soil and abundance of moisture.

The risk of roots affecting the structural integrity of your property should not be a barrier to planting trees or moving to an area where trees are in abundance. Understanding tree behaviours and their relationship with the surrounding environment can help to manage their influence and reduce the likelihood of damage to the home or a commercial premises.

[1] https://treenet.org/wp-content/uploads/2020/01/A-Geotechnical-Engineer%E2%80%99s-Approach-Towards-Trees.pdf


By James O’Grady

James O’Grady is a Sales and Business Development Manager at Mainmark. He is a civil engineer with 25 years’ experience in structural engineering, construction materials and ground treatment.

“Gender should be irrelevant” Mainmark’s Pip Buunk talks ‘Women in Trades’

Mainmark technicians working on Metro Sports facility in Christchurch

As we continue to work towards shifting the disparity in male or female dominated professions, we look with admiration at individuals who are determined to overcome gender barriers to pursue their passion.

One such individual is Pip Buunk, who is a senior technician at Mainmark in New Zealand and boasts more than 15 years’ experience in geotechnical drilling. Before joining Mainmark, Pip spent much of her early trade career as the only on-site female and New Zealand’s only registered female driller. Throughout her working life, she has managed drill rigs for geotechnical site investigation, water boring and geohazard stabilisation projects.

Pip has experience in a wide range of skills including welding and steel preparation techniques, truck and Moxy driving, operating drilling rigs and geotechnical testing equipment, crane operations, concrete installation and surveying. During her time at Mainmark, she has been able to add resin and grout application for ground remediation and structure re-levelling to her already long list of skills.

Ahead of her appearance at the Women in Trades’ (WIT) ‘Get Into Trades’ event 2021, an annual conference dedicated to educating and encouraging women about careers in the trade sector, Pip shared her advice for job seekers and employers.

Employers need to accept that diversity can be beneficial

Despite her success, Pip is all too aware that there are several barriers that still hold many women back from pursuing careers that have traditionally been dominated by male workers in New Zealand and across the world.

“There is still a handful of the older generation around who aren’t willing to change with the times and accept that diversity can be beneficial; not just to companies but also to industry as a whole. In short, finding an employer willing to take on women,” she said.

“Women are also not being exposed to resources and information on trade career opportunities. Trades have been traditionally marketed to males, especially at the secondary school level. It’s only really become an option marketed to women in more recent years.”

“There is also a general lack of available support for women in the workplace, for example flexibility for those who have children, adequate hygiene facilities and difficulty obtaining PPE with sizing suited to women.”

There has never been a better time for women to choose a trade career

Pip also points out that aside from the active barriers, there are several passive barriers like stereotypes and misconceptions that make women inwardly feel like pursuing a trade is a nonstarter. “Some common misconceptions about women in trades that I have noticed is that you have to be super strong, or that you can’t be feminine in the workplace,” she said.

“The fact is none of this is the case! Firstly, you don’t need to be overly strong, instead you just need to develop safe lifting techniques. Secondly, I’ve also been known to wear makeup because I like it, and I know many others who do too. Finally, if you show up willing to learn, be yourself and put in the work, you’re on the right track.”

Despite the reality of existing barriers and misconceptions, Pip is quick to highlight that there is hope. Dated perceptions of female capability in a trade-based workplace are eroding, and as more employers and companies get on board with gender diversity and inclusion, there has never been a better time to challenge norms and chase your passions.

Companies like Mainmark, for example, recognise that skills and work ethic are not exclusive to gender or specific backgrounds. It is why Mainmark’s employment ethos is driven by diversity and inclusion, and not outdated assumptions about an individual’s capability.

“I feel that the biggest opportunities currently stem from inclusivity and diversity coming to the forefront of many organisations’ goals and plans for the future. It is now a better time than ever to get into a trade career,” Pip said. “Whether you’re a school leaver who isn’t keen on university, or in a corporate career and feel the need for a change, there are endless opportunities out there and growing support from governments to get people into skilled trade apprenticeships and careers.”

“It’s important to figure out what you like doing, what trades might involve those interests, and take it from there. Industry training organisations have a wealth of knowledge regarding skill applications across different trades, so talking to local industry advisors is a good place to start. Work experience is a great way to try out something new and see if it’s a good fit, too. There are many employers who welcome someone who wants to give it a go. You could be like me and have a few weeks school holiday work experience turn into a career!”

Women can approach the job from a different perspective

If Pip could share one message to women interested in pursuing a trade, it would be to stop believing jobs have a gender.

“Everyone brings different experiences and ways of approaching a task or challenge, and we all learn in different ways and at different rates,” she said. “I still come across people who hold the view that trades are simply a steppingstone to a management career and not a complete career option, that they are not appropriate for women who want to have children, or even that trades are a second-rate career choice and lesser than other choices. All of these are fundamentally untrue.”

“Of course, not every trade is suited to every individual, but gender should be irrelevant when it comes to getting into it and getting the work done. It’s ok to try a few different trades before finding the right fit. The basics apply to everyone: show up and put in the work.”

At Mainmark, we are pleased to be supporting the Women In Trades event and believe that fostering a culture of diversity and inclusion brings a unique dynamic to the industry in which we operate.


By Claire Hartley

Claire is a strategic senior marketing and communications professional who joined Mainmark in 2015. She has extensive experience gained in a range of organisations across the APAC region and the UK; from large multinationals and start-ups to industrial B2B, IT and online businesses.

Solutions to help maintain and remediate seawalls

Mainmark technicians injecting and measuring on Bunbury seawall

Australia and New Zealand are surrounded by the sea with coastal living, seaside views and access to water all playing a big part in our way of life. However, when the ocean or an open body of water intrudes too close to urban environments, seawalls are valuable assets for protecting low lying waterfront infrastructure, addressing safety hazards or overcoming access constraints.

While seawalls are often built in coastal or bayside areas, providing protection against large open waters, they can also be found along riverside or lakeside areas where erosion can have a negative impact on urban environments or restrict the enjoyment of recreational activities.

Typically made from steel, rock, or concrete, seawalls are constructed to suit the landscape and water conditions. Vertical seawalls, for example, are sturdy walls that block waves from ocean-facing coastlines while sloped seawalls, or revetments, are designed to dissipate the energy from smaller waves to lower the risk of erosion.

Left unprotected, natural foreshores can be at risk of flooding and weakened ground conditions, which can put waterfront structures in danger of collapse. This was the case at a Gold Coast waterfront property where canal water washed away fine sandy soil behind a revetment wall, causing the property’s footpath and retaining wall to subside and become unsafe.

The effect of deteriorating seawalls

While seawalls are engineered to withstand marine environments and extreme weather, old or poorly constructed seawalls can be hazardous to people, structures and the surrounding environment. A deteriorating seawall can cause waterfront infrastructure to subside, resulting in cracks that can lead to water ingress behind the seawall. This was seen in Sydney, where a historic sandstone seawall, protecting a waterfront apartment on Sydney Harbour, had started to deteriorate as a result of years of tidal currents and water movement. Without proper remediation, the wall would have continued to degrade until it could no longer support the apartment’s patio or the apartment block itself, which would be at risk of collapsing into the harbour.

Entire strips of tourist-attracting waterfront development may also be affected by old or deteriorating seawall infrastructure. Without suitable protection from waves and tides, or a long-term plan to mitigate the ongoing effects of water movement, structures may become unsafe, uninhabitable, and unviable for tourist operators and other businesses who rely on the location’s access and safety.

An example of this was the ongoing subsidence threatening the structural integrity of the stone walls protecting the banks of Lake Burley Griffin, a large artificial lake in the heart of Canberra that is a popular destination for locals and tourists. Mainmark was engaged by the National Capital Authority (NCA) to repair, strengthen and renew the stone wall and surrounding footpaths as part of a three-year lake wall renewal program. Mainmark’s Teretek resin injection was used to consolidate the soils, fill voids and re-stabilise the wall, as well as re-level the surrounding pathways and adjoining grasslands.

What is the solution?

A properly designed seawall is built to stand the test of time and when newly constructed, should last for many decades. However, due to constant contact with water that may be flowing or contain corrosives such as salt, seawalls should be regularly monitored and maintained for signs of deterioration. If sections of the wall are damaged, its footings have eroded, or the soil behind the wall is weakened, the wall may need to be reconstructed or reinforced.

Using tailored solutions that provide long-term stabilisation is key to revitalising ageing or deteriorating seawalls. This was a lesson that the City of Bunbury learnt when they discovered damage to the seawall protecting the Marlston waterfront entertainment precinct. Prolonged exposure to waves and tidal movements had allowed water to penetrate through the wall and under the foundations. A section of the wall had subsided and a large crack had formed in the face of the wall. There was real concern that the wall may collapse. The City of Bunbury carried out emergency grouting on the worst affected area, but it proved to be very expensive. Mainmark worked with the city’s engineers to develop an innovative and cost-effective solution for the entire wall repair.  Mainmark’s Teretek engineered resin proved to be an ideal solution to strengthen the wall by densifying the soil and filling voids where sand had been washed out due to the tidal movement.

As urban development continues to increase, seawalls will remain crucial elements for protecting water frontages. When constructing seawalls, an asset remediation plan should be considered to help address issues that may arise over time, should sections of the wall start to deteriorate due to ground or water conditions.

Mainmark has extensive experience remediating seawalls, including revetments, using a range of proprietary cost-effective solutions that can protect the asset’s longevity and structural integrity without any detrimental effects on the environment.

While seawalls are engineered to withstand the forces of water, to function properly they must be well built and maintained. Using the right materials and reinforcement measures, a structurally sound seawall will allow communities to safely enjoy the waterfront lifestyle for which Australia and New Zealand are famous.


By Steve Piscetek

Steve Piscetek is Mainmark’s Divisional Manager, MCM (Mainmark Civil and Mining). Steve has extensive experience working in construction, road and water infrastructure, the mining and resources sector and offshore construction. At Mainmark, his technical acumen and pragmatic approach to safety and quality assurance has seen him successfully tackle many challenging and complex ground remediation projects.

Regional spotlight series: assessing the geological landscape in Queensland, Australia

Aerial view of Surfers Paradise on Queensland's Gold Coast

Following our recent regional blog that looked at the different ground conditions in New Zealand, we now turn our attention to Queensland, Australia’s second largest state with a total area of 1,852,642 square kilometres, known for its diverse natural environment and extreme weather patterns.

Mainmark services Queensland with a dedicated team based in Brisbane, the Gold Coast and Sunshine Coast, and in Northern Queensland, with expertise in the residential, commercial, civil infrastructure and mining sectors.

While each region has its own unique challenges, Mainmark leverages its collective local expertise and skillsets to provide a range of specialised bespoke ground engineering solutions for customers, tailored to their specific needs.

Surf, sand and the impact of high-rise development

Queensland is affectionately known as the ‘sunshine state’ with the Gold Coast and Sunshine Coast offering a quintessential coastal lifestyle that appeals to home buyers and property developers alike.

The Gold Coast is renowned for its large-scale high-rise developments that are prevalent along the main beachside strip with old houses, originally constructed in the 60s and 70s, being knocked down to make way for multi-storey apartment buildings – some as high as 30 storeys or more. These sites often require deep excavation for basements and underground carparks, however, excavation within these tightly confined spaces can weaken surrounding soils and cause subsidence issues for neighbouring houses and apartment buildings, especially those built to the boundary.

Sites with unstable sandy and non-cohesive soils can be addressed either during or after construction using solutions such as Mainmark’s Permeation Grouting, a widely used low pressure grouting technique that can be used to support excavation, shore up adjacent structures where unstable ground may be a safety hazard, or provide additional ground bearing capacity to accommodate the increased load of a new structure.

While engineers may consider conventional piling and jacking techniques to re-level subsided buildings, these processes require the use of large heavy machinery. Site access is becoming increasingly problematic due to the Gold Coast’s urban density which has made piling an expensive and time consuming option. However, Mainmark’s advanced range of proprietary grout and chemical injection solutions, such as JOG Computer-Controlled Grouting and Teretek® resin injection, can be smart solutions for high rise residential and commercial buildings as cost effective, non-intrusive alternatives to traditional piling.

Building on reclaimed land and low lying flood plains

Poorly compacted land is also a growing concern for homes and businesses built on reclaimed land in the low lying marshy flood plains of South East Queensland where it is not uncommon for a 20m layer of soft, highly compressible soil to extend down from the surface. This issue can also create problems for commercial sites such as transport yards where the movement of heavy vehicles and shipping containers can put pressure on the ground beneath driveways and hardstands, causing subsidence. This was the case at South East Queensland Hauliers (SEQH), a wharf logistics business that was built on reclaimed mangroves. The company’s concrete hardstand area was ‘dishing’ in the middle due to water ingress from the high water table. The company engaged Mainmark to help improve the ground beneath the hardstand and re-level the concrete slab using JOG Computer-Controlled Grouting.

As population migration to the sunshine state grows, so too has the number of wetlands and agricultural farms, such as cane farms located near the Gold Coast, that have been developed into residential housing estates. While building on reclaimed land can bring enormous economic benefit to local regions, the construction process often requires ground improvement modifications prior to building to ensure the ground is suitable for construction. Failure to undertake appropriate ground improvement measures prior to construction can result in serious issues, leaving homes at risk of differential settlement. Mainmark has helped remediate numerous homes built on reclaimed land, including a single storey brick residence in Warner, Queensland where the property’s concrete floor had dropped up to 120mm. Mainmark was able to successfully re-level the floor using Teretek.

The effects of wild weather in tropical North Queensland

As Queensland is a predominantly tropical state, the region is prone to extreme weather conditions which can cause havoc on building foundations. The issue is largely due to the prevalence of clay soils which swell during wet weather and shrink during extended dry conditions such as drought.

In some Queensland areas, the state’s tropical wet weather can cause soils to swell and shrink by up to 70mm throughout the year with Mainmark receiving many enquiries from homeowners worried about cracks that have appeared in the walls of their home as a result of such movement. The constant ground shift can cause serious cracking and structural damage with cracks becoming bigger and more pronounced the longer the dry spell continues.

Extreme weather not only affects homes but also infrastructure, particularly in North Queensland where Mainmark has seen an increase in demand for remediation work on culverts and bridges that have been damaged due to torrential rainfall. Underground culverts are vital for North Queensland’s road network as they allow the flow of flood water and runoff, however, sometimes the infrastructure struggles to cope during heavy rain events as water gradually compromises the culvert lining and causes voids to form around the culvert as surrounding soil is washed away. This was the case on a North Queensland windfarm, when two culverts located beneath an access road and an embankment were seriously damaged during a tropical cyclone. Mainmark was able to successfully restore the culverts’ structural integrity by injecting the area surrounding the culverts with Teretek engineered resin.

Mainmark’s team addresses the geotechnical challenges of Queensland’s diverse geography, extreme weather and high density development by thoroughly assessing the underlying ground conditions to understand what is achievable. With more than 25 years’ experience and intimate knowledge across the Queensland region, our highly skilled engineers and technicians assist homeowners, engineers and civil contractors to address a range of ground problems with innovative, state-of-the-art ground engineering solutions and methodologies that are non-invasive, efficient, cost-effective and environmentally inert.


Dolan NilsonBy Dolan Nilson

Dolan Nilson is Technical Sales Manager at Mainmark Ground Engineering. Dolan is a qualified engineer who has previously worked in the petroleum, oil and gas industries in Scotland, Texas, Indonesia and Malaysia. At Mainmark, he has assisted on a range of complex ground improvement projects in the civil and mining sectors, including re-levelling large structures, remediating ageing infrastructure, and culvert and pipeline abandonment.

Understanding foundations – what you need to know to keep your building structurally sound

waffle foundations

The integrity and longevity of any built structure starts from the ground up, which is why it is often said that a building is only as good as the foundations it is built on. However, different types of foundations are used for different buildings, generally determined by the site’s geological factors, the type of building, and the era in which it was constructed. Importantly, the type of foundation will impact the remediation approach taken should the structure’s stability ever be compromised.

Foundations are more than simply a solid base which a building sits upon. They are a vital element of construction that carries the structural load bearing and weight distribution of a building’s walls, columns and other structural elements.

Factors that influence what type of foundation is best suited to a site are numerous. This can include the weight or scale of the building, drainage requirements and water table, site topography including site slope, construction budget, the type of building materials available, soil composition (geology), local climate, local wind conditions and seismic considerations.

Soil is of particular concern as foundations must be fit for purpose and adaptable to a site’s conditions, which can range from stable, non-reactive rock with no moisture-based ground movement, to highly reactive clay sites that experience significant ground movement following changes in moisture levels. Some sites may be in highly desirable areas with unmissable real estate opportunities but present challenging ground conditions, the building is more likely to be affected by factors such as moisture conditions, reactive soils, landslips, sink holes and voids.

Foundation 101

Whether building, renovating or remediating a property, understanding the different types of foundations will help determine the best path forward. Foundations are broadly classified as ‘shallow’ or ‘deep’ and are differentiated by the depth beneath the ground’s surface. Shallow foundations are placed closer to the surface and are suitable for stable conditions where ground movement is less likely, while deep foundations are recommended for structures that are being built on sites with reactive ground conditions. Deeper foundations mitigate against the impact of seasonal moisture variation and tree root intrusion.

Waffle Raft-Slab foundations are perhaps the most common in modern buildings and are an inexpensive foundation type as the foundation requires minimal excavation. Waffle slabs, also known as waffle pods, are a reinforced concrete footing and slab system created with concrete that is poured around polystyrene forms that sit on top of the soil.

Raft foundations are a type of shallow foundation within the slab family. Usually used as the foundation for new houses and extensions, raft foundations are applied as a solid continuous base across the entire building. They help to evenly distribute weight carried by walls and columns, allowing for loads to be supported by edge and internal beams. The depth and spacing of these beams is determined by the ground reactivity, the construction type and the degree of articulation in the building envelope. Raft foundations are preferred in areas where soil is highly susceptible to moisture changes because of climate and composition.

Strip foundations, or strip footings, form a continuous, linear line of support underneath walls. Strip footings are placed within a shallow trench and reinforced with steel. These footings are popular in Australia and are preferred for light loads, like the interior or exterior walls found in residential properties. The material of the strip footing is typically determined by the construction of the time. Prior to the late 1800s, most strip footings were made of stone. The stone could be dressed blocks or natural stone. From the late 1800s to the early 1900s, bricks were the predominant strip footing type. With increased availability of ready-mix concrete, concrete strip footings replaced brick strip footings from the 1930s. Strip foundation structures are used in combination with stump footings for the internal load bearing.

Stumps, referred to as a pile footing in New Zealand, are the simplest and most familiar systems used for the vertical support and transfer of building loads to the foundation. Stumps are used to support timber-framed houses for which they are typically the most cost effective. The stumps are made from timber, concrete or steel and must have a concrete or timber footing placed underneath the base of the stump.

Pile foundations are a type of deep foundation that comprise of pillars – or ‘piles’ – that provide support for a building by being placed deep into the ground. Pile foundations are preferred when the soil conditions near the surface are too soft or reactive. Such soil conditions can cause loads to shift, making slabs and other shallow foundations less effective. However, pile foundations can prevent differential settlement of foundations by transferring the weight of a building through its columns to a stiffer, deeper soil strata.

Remediation

Foundations are often subject to the surrounding ground conditions, which may change due to changing climate, minor seismic activity or urban influence such as digging, plumbing and tunnelling. Over time, foundations may need maintenance to overcome these factors and continue to perform their design function. In such events, Mainmark can provide guidance and solutions to help re-support foundations to benefit structural performance. For example, Mainmark helped a heritage building in Sydney increase its foundation’s load bearing capacity from 140kPa strength to 200kPa using its Teretek® resin injection solution, which improved and consolidated the soils, preventing the risk of future settlement. In New Zealand, Mainmark used Terefirm® Resin Injection to strengthen the ground and re-level the foundations beneath the Northwood Supa Centa in Christchurch after the shopping centre experienced liquefaction induced ground deformations following the Christchurch earthquakes in 2010 and 2011.

Understanding the characteristics of the different foundations types will put you in the best position to help ensure your building, regardless of its age, location or site conditions, has the ability to stand the test of time.


By Max Kudrenko – Technical Manager

Max Kudrenko is the Technical Manager(Vic/Tas) at Mainmark Ground Engineering. Max is a civil engineer who has experience working with different grout, resin and other cementitious geotechnical and ground improvement technologies in the residential, commercial, gas/oil and civil sectors. He has successfully project managed works throughout Australia, New Zealand and Japan.

Regional spotlight series: how geological considerations differ in Auckland, Wellington and Christchurch, New Zealand

Auckland city skyline Waitemata harbour New Zealand

When it comes to ground engineering, topography and geological conditions will often impact the built environment. The ground conditions will also inform the remediation approach Mainmark uses for different projects. With a global footprint spanning from Australia and New Zealand to Japan and the United Kingdom, Mainmark has considerable experience working in different regions, many with complex issues specific to local areas.

In the first of our regional spotlight series, Mike Baker, Area Manager in NZ, takes a closer look at ground conditions in New Zealand, in particular those in the three major hubs of Auckland, Wellington and Christchurch. We delve into the unique ground engineering challenges in each city, and some of the solutions that Mainmark frequently uses to address the varying issues, often impacted by local soil conditions.

While each region has unique challenges, Mainmark’s approach is not simply about quick fixes. Instead, we look closely at the site and apply tailored ground improvement solutions that can address the underlying cause of the problem.

In New Zealand, the complex weather patterns range from subtropical conditions in the North Island to a cooler alpine climate in the South Island. Often referred to as the ‘Shaky Isles’, New Zealand is also an earthquake-prone region due to the number of fault lines running almost the entire length of the country.

Here, we take a closer look at the geotechnical considerations in New Zealand’s three biggest cities.


Auckland

Auckland’s climate has two distinct ‘wet’ and ‘dry’ seasons. In summer, New Zealand’s largest city experiences subtropical conditions, compared to the rest of the country, which enjoys a more temperate climate. With the prevalence of reactive clay soils, weather and seasonal shifts can play havoc on Auckland’s buildings due to the ‘shrink and swell’ effect that sees soils expand when it gets wet in the winter and shrink back in the summer when it dries out. Visible cracking may appear in the ground’s parched surfaces, and these weakened soils may cause a home’s foundations to ‘sink’.

This ground reaction is something that property owners in Auckland need to consider when cracks appear in the walls of their home. The Mainmark team has seen a number of structural problems stemming from subsidence – the propensity for upward, lateral, or downward ground movement which can result in structures moving – including cracks forming in walls, and windows and doors failing to open or close properly. If subsidence worsens, larger cracks in the home’s brickwork can form, visible both inside and outside the home, and the sinking foundations might also lead to floors becoming unlevel. These signs of subsidence can become serious and very costly if left untreated.

Recent drought conditions in the Auckland area have led to drier than usual ground conditions. Mainmark’s Auckland team has received an increasing number of calls from concerned homeowners wanting to rectify problems relating to subsidence. In many of these cases, Teretek® engineered resin injection solution is used to help to raise and re-level sunken homes, both cost-effectively and non-invasively.


Wellington

New Zealand’s capital, Wellington, sits on the southernmost point of the North Island. The city is regularly shaken by small and medium-sized earthquakes due to the Wellington region being crossed by a number of major faults, including the Wairarapa, Wellington and Ohariu faults. Wellington currently experiences minor seismic activity every few months, but these tremors have not been a significant threat to homes or lives. However, the ongoing study of these fault lines has prompted concern from scientists that a large earthquake may occur in the future, like the 7.5 magnitude 2016 Kaikōura earthquake which left Wellington with cracked buildings, windows smashed and without power in several areas. This seismic activity has prompted an increased awareness of the hazard and Mainmark has undertaken several ground resilience and liquefaction mitigation projects in the area since.

As the country’s administrative centre, Wellington is home to many government agencies and departments that have received investment for building upgrades and structural reinforcement to help protect these buildings from the effects of a future earthquake. For example, in 2019, the Mainmark team undertook a very large ground strengthening project for the Seaview Wastewater Treatment Plant, using Mainmark’s proprietary Terefirm® Resin Injection technique to densify the soils and increase its New Building Standard (NBS) rating to ensure the facility can continue operating following an earthquake.

While ground improvement projects are increasing in Wellington, the area’s ground conditions consist largely of soft sand and silt with clays and gravels sometimes present. One of the key challenges for new home builds is that many buyers are unaware of the potential long term foundational implications that can affect homes built on soft ground. The ground must be adequately prepared which may include a site excavation to remove the soft soils before laying the foundation. This type of foundation, where a more stable layer of material is placed beneath the foundation, is known as a gravel raft and provides greater foundation support prior to pouring the slab for a new home. Mainmark’s Terefil® is also a great alternative to gravel rafts as the lightweight cementitious fill creates a stable slab that helps protect structures against liquefaction and future subsidence. The solution was used for a four-unit complex in Christchurch and an electricity substation in Auckland.

Wellington’s topography can also present a challenge to building stability, with many of the city’s houses located on steep hills with critical retaining walls and often no vehicle access. Many older homes, some more than a century, are in desperate need of repair including ground remediation work.


Christchurch

Located on the east coast of New Zealand’s South Island, Christchurch has been an important focus for the Mainmark business following the 2010-2011 earthquakes which caused significant damage to infrastructure and buildings due to liquefaction. Homes, businesses, public buildings and historical monuments either sunk, shifted, or crumbled and many are still awaiting remediation.

Mainmark has played an important role in helping the Christchurch community remediate their properties, including the re-levelling of significant large-scale structures using JOG Computer-Controlled Grouting. In 2013, the company initiated a series of liquefaction mitigation trials using expanding polyurethane resin which was found to be a viable ground strengthening and re-levelling solution for use underneath existing buildings. While it has been 10 years since the earthquakes, Mainmark continues its work in Christchurch by remediating structures affected by earthquake damage and liquefaction. Many building owners are seeking to future proof their buildings to ensure they can withstand the impact of a potential future earthquake. Commercial properties are also required to comply with the Building (Earthquake-prone Buildings) Amendment Act 2016, which identifies high risk buildings that must be structurally remediated.

While much of Mainmark’s work in the South Island has focused on Christchurch, the organisation also services the entire region including Queenstown, a growing trade and tourist hub. Mainmark was recently contracted to remediate O’Connells, the city’s largest indoor shopping centre, helping the building achieve an increased NBS rating, a seismic standard indicator that rates a building’s ability to withstand an earthquake.

New Zealand may be a relatively small geographic area, however each of these three regions presents unique ground engineering and remediation challenges, which the Mainmark team tackles using a range of solutions tailored to the individual site requirements. As a solutions-based business, Mainmark goes to great lengths to understand the individual ground problems of each project, and creates bespoke solutions by working through the process with its customers. With more than 25 years’ experience, Mainmark is continually broadening its capabilities, working across the different geotechnical nuances from one end of the country to the other.


By Mike Baker

Mike Baker is Mainmark New Zealand’s Area Manager in Wellington. After joining Mainmark in 2013, Mike supervised remediation of the modern Christchurch Art Gallery which was shaken by the 2010 and 2011 earthquakes that hit New Zealand’s South Island. In 2019 he led the first of its kind Seaview Wastewater Treatment Plant liquefaction mitigation project in Wellington.