Effects of soil improvement treatments through injection of expanding resins on the hydrologic behaviour of cohesive soils

The application of soil improvement techniques by injection of expanding resins has greatly increased over recent years, especially following the development of novel be-spoke materials and methods. The purpose of resin-based consolidation techniques is to remove the causes of foundation settlement by injecting an expanding polymer material into the ground. Ground settlement may be due to the alternation of dry/wet seasons, sewer leaks, heavy vehicle traffic, nearby excavations, growth of tree roots and variation of applied loads. The interaction between water and foundation soil is a critical factor for settlement of all types of ground. Fine-grained soils may undergo swelling due to signifi-cant water absorption. On the other hand, loss of water manifests itself in a volume de-crease. When subjected to cyclic variations of water content, the ground volume under-goes cyclic swelling and shrinking, leading to the risk of differential settlement. Many factors affect the process of soil improvement by resin injection, regarding both the ge-otechnical and hydrogeological context, and the specific resin-based improvement tech-nique. Although the use of resin injection has been growing in recent years, the full com-prehension of the processes involved is far from being achieved. To better understand the complex processes involved, two experiments were carried out at full-scale test sites. The first one was mainly devoted to assess the treatment efficiency in terms of geotechnical behaviour (strength and elasticity improvement) and its relation with resistivity variations, by performing geotechnical tests and 3D Electrical Resistivity Tomography (Apuani et al, 2015). The second test, performed at the same location, fo-cused on the effects induced on the soil hydrological properties, by performing laboratory (among which triaxial cell permeability) tests and monitoring the site infiltration process in natural and treated soil for one year. This article mainly concerns the second experi-ment, discussing the changes in saturated hydraulic conductivity, suction pressure and water content on clay soils subjected to resin injections.