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.

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.

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

Earthquake and seismic activity, often resulting in liquefaction



Joints in culverts

Land slippage

Leaking pipes washing away sub-soils

Abandoned tanks and pipelines

Mining and commercial operations

Poorly compacted void fill

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

Filling pipelines uphill or downhill without the filler spilling out

Stabilising bridge approaches and bridge abutments

Strengthening the foundation ground under buildings and other on-ground structures

Addressing land slippage around infrastructure

Retaining wall and wing wall backfill

Efficient and economical backfilling of services trenches and manholes

Mainmark hole and void filling methods used for Infrastructure: