Ground Stabilisation Beneath Property Foundations
Oxford Hydrotechnics use advanced resin injection techniques to effectively stabilize mobile ground beneath the foundations of a row of properties.
Oxford Hydrotechnics were called upon to address issues of unstable and voided shallow level ground, following deep level grouting treatment; to stabilize the ground beneath a row of properties. A recent collapse of the road running alongside the properties had revealed extensive voids, resulting in the threat of further subsidence should the soils remain untreated.
The solution, put forward by H2OX engineers, was to treat the areas of unstable, shallow level ground, using advanced resin injection techniques. The technique involved the injection of a lightweight polyurethane resin, to permeate and consolidate the granular soils, dramatically improving the bearing capacity of the ground. Resin was injected using a single component pump, through injection lances placed at systematic intervals. Each injection of resin created a bulb of stabilised ground of around 500mm diameter. These stabilised bulbs could then be overlapped in order to achieve the required results.
Initially, it was planned that the ground would be treated up to a depth of 3 metres. However, during treatment, it was discovered that the lower levels of the ground consisted primarily of clay, which was not porous enough for the resin to penetrate. The decision was made to treat the ground to the maximum depth at which resin was accepted during injection.
Further shallow voids were discovered using trial drilling, internally, beneath the floor slabs within the property. In locations where voids were discovered, Oxford Hydrotechnics injected a lightweight hard foam product to adequately fill them, and to prevent further ground movement.
Each property was treated around its full perimeter. In each location of injection, the resin permeated the ground, filled the pores and bound the ground together into a stabilized mass, resulting in increased bearing capacity in the treated locations.
The works were completed in 18 days, significantly quicker than expected and at a reduced cost. Savings were primarily the result of an adjustable methodology relating to the depth of injection and an efficient, pro-active working relationship between Oxford Hydrotechnics and the client.
Additional uses for the technique
Using this technique, ground can be consolidated to a tailorable compressive strength depending on the requirements of the project. Soils can be stabilised to a level that is as hard as concrete, or to that which could be excavated using hand tools, particularly in locations where the treated soils are required to be excavated or tunnelled through.
The technique is of particular use when constructing basements or lift pits in areas where mobile ground is an issue. A stabilised perimeter, and sometimes base, can be formed, within which excavations can take place. The fact that the stabilised ground can then be excavated through means that the technique doesn't encroach on the overall size of the basement construction in the same way that piled solutions would. The technique can also alleviate some of the issues faced where party walls are concerned, as the areas of stabilised ground can be excavated if required.