Void Filling Void space can develop underneath a structure or within a soil matrix. For example, a water leak can quickly erode soil from underneath a slab leaving void space below and subsequently a high potential for rapid settlement. In some cases, water can erode soil from behind tunnel walls, creating void space between the tunnel and surrounding earth. When void space developes, the earth and structure lose their “positive contact” and unwanted movement/subsidence can occur. Void filling is a grouting process for eliminating these empty spaces and restoring the integrity of the structure and/or soil matrix. The process is generally done by strategically injecting a grout into the void space, eliminating as much water and air from the soil matrix as possible.