Ground improvement with lime-cement pillars is becoming increasingly common in the Nordic countries for exploitation of areas with poor stability. However, there is a need for non-destructive methods for volumetric quality control of the ground improvement. The quality control can be divided into two steps where the first include quality control at the installation process with monitoring of production parameters such as rotation and penetration speed, air pressure and binder feed rate. The second step involves determining the spatial continuity and the mechanical properties of the treated subsurface after curing by for example a reversed pillar penetration test, complete exposure or core drilling.
ASSERT (Assessment of Soil Stabilization using Electrical Resistivity Tomography) is an on-oing research project with focus on quality control in direct connection with mixing of the binders based on electrical resistivity tomography (ERT). The ERT-method has in several cases been shown to efficiently differentiate treated soil from untreated. Hence, is the method an interesting option for direct and rapid volumetric quality control of the stabilized soil so that zones which needs to be supplemented can be identified at production stage while personnel and equipment are at site. The ASSERT project involves test and verification of the method in different geological environments and scales, including full-scale tests for different types of stabilization techniques. Additionally, method development and adaptations to make the quality control applicable are also included in the project to enable a robust, rapid and sustainable use in routine operations.