Void Filling Melbourne

Voids formation can develop through a variety of natural and human activity. These voids can lead to ground subsidence, sinkholes, or other geotechnical issues that affect the stability of structures and the safety of the surrounding area. The main methods of void formation are:

The presence of localised cavities developing within the soil profile are infrequent but may destabilise the ground depending upon the cohesion and strength of the soil. Reactive soils shrink and swell and extended drying can cause cracks to propagate, forming networks of anastomosing shrinkage planes. This can lead to instability and a loss of bearing capacity caused by the aeration of the soil mass and subsoil settlement, causing voids below ground.

Water migrating through the soil can mobilise fine particles and progressively strip material from a soil horizon, carrying it away and resulting in the formation of voids that can continue to grow. Sinkholes are a phenomenon that develops unseen over a period of time before sufficient material is lost and the overlying ground loses support and collapses. Poorly consolidated soils are susceptible when large volumes of running water are present, such as during floods or through broken water or waste pipes. In certain environments, dissolution of bedrock, typically limestone, causes underground cavities to develop that can lead to the formation of sinkholes with the collapse of the surface.

Abandoned earthworks, particularly associated with mining activities, are well known to suffer collapse over time. Shafts sealed decades earlier may suddenly open as supporting sleeper timbers fail under the weight of the overburden. Or alternatively, capping layers may be compromised exposing the open shafts below.

When constructing tunnels for roads, railways or utilities, deep ground movement can occur due to potential loss of soil support, and loosening of surrounding soil and rocks. If the surrounding soils are soft, soil compaction may also occur. This can lead to formation of voids.

The process of void filling is determined by the extent of the cavity formation and volumes involved. For soil treatment, injecting a range of engineered expanding polyurethane resins that target weak planes within the ground is capable of both filling the cavities and compacting the surrounding soil to re-introduce strength and bearing capacity. Where larger voids are involved, such as sink holes and mine openings, calculations can be made and flowable cellular cementitious fill can be pumped in to create a monolithic mass of light weight concrete that has a design strength and density suited to the application.

At Rectify Group, we have two options to void fill:

• Polyurethane injection: Utilising our advanced two-part foam, we utilise foams of differing densities and expansion rates to inject into the void. As the foam expands it rapidly fills the void, and binds to surrounding soils. Once cured it forms a hard, encapsulated soil mass.
• Lightweight Cellular Concrete: A specialised polymer solution is hydrated and aerated. This lightweight foam is then mixed with grout or concrete to form lightweight concrete, as light as 300kg/m3. It is poured into voids as engineered bulk fill, and once the LCC is cured, and hardened it forms a permanent replacement to soil and a permanent fill to void. It is self-compacting, with high flowability and minimal creep.