Use of CPT as a soil mixing verification tool: some practical observations

Mass soil mixing is a versatile ground improvement technology for marginal and brownfield sites. Dry soil mixing is relatively common in the UK for the improvement of ground with very wet and/or organic materials. Wet mixing is less commonplace and involves introduction of a fluid grout with simultaneous rotavating of the soil with a mixing tool. This paper presents the results of CPT investigations into wet mixed soils with a view to use the results as a means to verify the strength and consistency of the mixed materials. A high volume of data has been extracted from two active sites. CPT soundings are found to be purposeful in terms of demonstrating the overall improvement effect and integrity of the mixed soil volume spatially and with depth. Existing CPT testing of mass mixed soil is very limited and this testing has allowed the mixed soil to be compared to existing CPT soil behaviour indexes to give an insight into their usefulness for characterising mixed material and its behaviour.