What do holes and voids mean?
‘Voids’ can mean anything from cracks and crevices, up to the huge volume voids caused by a major tunnel collapse.
Holes and voids can be either concealed or open cavities that present naturally as a result of erosion and geological changes, or due to building, mining, and other commercial or industrial ground activity. Ranging from small to large, all holes and voids underneath structures will contain air, and possibly water, which can cause instability. Filling these spaces can prevent wider damage to the ground, on-ground structures, and the surrounding environment.
Some holes and voids may need to be backfilled after operations cease, to prevent them becoming a hazard.
Terefil® Used to Fill and Decommission Ageing Wastewater Infrastructure in New Zealand Parkland
Mainmark filled
the existing sewer system situated beneath an area of
public parkland that had limited access.
Lift shafts stabilised for disabled access to Museum Station
Lift shafts needed to be adequately supported whilst grout was poured at 1 MPa in less than 24 hours for each pour.
Filling holes and voids under civil and infrastructure sites
Filling holes and voids ultimately aims to stabilise tunnels, buildings, bridge approaches, bridge abutments, runways, roads, rail lines and other operating or decommissioned structures. The chosen material mix is often developed specifically for the project, and may be trial batched, cured and independently tested prior to the works to ensure pumpability and compliance with the project’s specifications. The right void filling and stabilisation solution can help to minimise maintenance costs and the need for ongoing patchwork repairs.
Tunnels
Mainmark can safely decommission tunnels with Terefil®, working effectively as a large hole filler. The lightweight formula delivers strengths of between 400 and 6,000 kPA, so it’s ideal for withstanding heavy loads. A fast solution that causes no disruption to the ground above, Terefil doesn’t require breather holes or injection points. Instead, it can be pumped directly into the tunnel.
Buildings
Sinkholes and voids under buildings can quickly make the structure unstable. Mainmark uses Terefil® to fill the void area and improve the ground stability, reduce exposure to further erosion and thus re-support the above ground structure. Using a permeable form of Terefil ensures any water entering the void filled zone can freely drain, minimising the risk of future hydrostatic pressure build-up.
Retaining walls
Terefil®’s engineered load bearing compressive strength and a wet density that’s more than 50 per cent lighter than traditional grout reduces pressure where it’s been applied as retaining wall backfill. This cost-effective and minimally-disruptive approach provides residents and property owners peace of mind that the void will not cause the wall to collapse.
Bridge approaches
Mainmark can address voids that form around bridges and their roadway approaches, ensuring the structure can safely bear the weight of constant traffic without leading to settlement. Teretek® resin injection is a proven and commonly used solution for repairing ground subsidence affecting bridge approach slabs. Mainmark’s highly efficient process to re-level the approach is achieved by injecting the engineered resin into the road sub-grade, filling any voids to create a solid supporting foundation for a smoother transition for vehicles.
Bridge abutments
Mainmark assists with stabilising soils around bridge abutments, addressing instability underneath a bridge’s substructure. Using Terefil®, Mainmark can create a mixture of pervious or impervious fill to help stabilise the foundation ground by filling voids and preventing surrounding water from creating further subsidence.
Runways, roads and rail lines
Terefil® is an effective solution to mitigate settlement resulting from voids beneath roads, highways and other transport passages that are consistently under heavy load. It can also assist infrastructure owners to decommission redundant pipes and culverts located beneath road networks, tram and rail lines, and runways. In continuously operating environments, minimising downtime becomes a critical aspect of remediation work. Projects that address holes and voids underneath roads, railway lines and airport runways are managed efficiently by choosing application methods and materials with the least impact, allowing the quickest recovery times for our clients. Mainmark has successfully carried out structural void filling at major transport sites, including the decommissioning of a damaged culvert underneath an airport runway.
What causes holes and voids?
Holes are often dug in mining, building, and infrastructure works, while voids may develop over time due to leaks and weather eroding sub-soils underneath a structure. Something as simple as a leaking pipe may wash away surrounding earth, creating voids (or an empty space) around the pipeline. Filling holes and voids ultimately aims to stabilise mines, tunnels, buildings, bridge approaches, bridge abutments, and other operating or decommissioned structures.
Likely causes:
Construction holes and excavation |
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Earthquake and seismic activity, often resulting in liquefaction |
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Erosion |
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Flooding |
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Joints in culverts |
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Land slippage |
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Leaking pipes washing away sub-soils |
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Abandoned tanks and pipelines |
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Mining and commercial operations |
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Poorly compacted void fill |
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Water ingress |
How to fix holes and voids
Mainmark has a number of void fill solutions such as polyurethane and cementitious grouting. We assess each situation to determine the best course of action and the best material to use. Smaller voids in underground rock strata are generally filled with a void filling foam or concrete void filler; a material like urea silicate or polyurethane resin that not only fills the void but also ‘glues’ the surrounding rock together.
When greater supportive strength is required, such as for retaining wall backfill or large voids, Mainmark’s Terefil® solution can be applied. A lightweight polymer modified cementitious-based void fill material, Terefil can be used for massive voids that require filling quickly and economically. This large hole filler material can also be used across a variety of void-filling situations, including retaining wall fill, abandoned fuel tanks, pipelines, and manholes, voids behind seawalls, and quick-support, easy-flow backfill for service trenches.
In areas where sandy soils dominate, a multi-stage approach may be required to fill voids safely. Large washouts and holes caused by coastal erosion and flooding can be stabilised using permeation grouting, before void filling commences.
Benefits of Mainmark’s methods to fill holes and voids:
Quickly and safely decommissioning culverts, pipes and tunnels |
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Filling pipelines uphill or downhill without the filler spilling out |
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Stabilising bridge approaches and bridge abutments |
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Strengthening the foundation ground under buildings and other on-ground structures |
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Addressing land slippage around infrastructure |
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Retaining wall and wing wall backfill |
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Efficient and economical backfilling of services trenches and manholes |
