Foundations come in two forms, shallow foundations or deep foundations. A shallow foundation is used where the loads imposed by a structure are low relative to the bearing capacity of the surface soils.
The vast majority of houses and light domestic buildings are built using shallow foundations, with deep foundations used to accommodate pads on weaker ground or where significantly higher loads are required.
Geobear provides solutions where foundations fail through subsidence or settlement.
Types of shallow foundation
This type of foundation is a form of shallow foundation used to provide a strip of support to a linear structure such as a wall. Strip foundations are used in many subsoils and are particularly suited to light structural loadings such as those found in many residential properties; commonly a mass concrete strip foundation is used.
Why do they fail?
The effect of subsidence causes the strip to sink in one corner or down the length of entire walls. This is usually the consequence of either shrinkage of clay subsoil or erosion of the ground below the foundations due to excess water such as leaking drains.
The most frequent use of our geopolymer solutions is on houses affected by subsidence. We identify the affected area through soil investigations and design a solution that sees bulbs of geopolymer material injected at intervals beneath the strip foundation. The material expands and forms a solid base beneath the existing strip preventing any further movement (subsidence). The solution is commonly used ahead of underpinning, which is an older traditional method.
Pad foundations are rectangular or circular pads used to support localised loads such as columns. They are more common on larger purpose built structures such as industrial units or other commercial buildings to support large roofed structures.
Why do they fail?
Pad failure is less common than strip foundation subsidence, but in the event it happens there are a couple of possible reasons. Settlement can be the cause, meaning the load from the building is higher than the subsoil beneath the pad can withstand, this can be caused by compaction of the subsoil. Subsidence can also occur due to erosion from excess water.
We can strengthen the ground beneath a pad to prevent any further movement. We inject material at several depths beneath the pad, depending on the extent of the weak soil and this solidifies creating a firm base beneath the pad foundation.
The selected material we use also provides additional bearing capacity to the soils, this will allow greater loads to be placed upon the existing pad foundation. This is the perfect solution where a new storey or roof is being built.
Raft foundations are formed by reinforced concrete slabs that cover often the entire footprint of a building. They spread the load imposed by a number of columns or walls over the area of foundation and are commonly used for light domestic buildings on poorer soils.
Why do they fail
Raft foundations are prone to settlement overtime and are designed to tolerate downward movement. However excess downward movement can be caused by poor compaction of the fill material beneath or water ingress through cracks causing voiding.
In these instances Geobear will design a solution whereby geopolymer material is injected just beneath the slab in a grid pattern across the affected area. The material will expand to fill voids and compact the existing fill, and in some cases we can use our material to lift the slab back to datum levels.
If the foundation is required to hold a greater load, we can also use our material in localised areas to improve the ground strength, this will enable new support columns to be fixed to the raft.