The effect of the depth of cutter soil mixing on the compressive behavior of soft clay treated by alkali-activated slag

Cutter soil mixing (CSM) is a fairly new technique for shallow to deep soil stabilisation that mostly uses cement based slurry to improve the in-situ properties of soft soils. This research aims to experimentally investigate the effect of the depth of cutter soil mixing on the compressive strength of a saturated soft clay treated with alkali-activated slag slurry. Various percentages of additives were added to the saturated soft clay to increase the compressive strength and to make it suitable for constructing shallow to deep CSM panels as earth retaining walls that are used for excavations. Several high-pressure curing apparatuses were used to simulate insitu field stress due to the depth/weight of CSM panels. Then a set of compressive strength tests were conducted to investigate the effect of different curing pressures, additives content and curing time on the compressive behavior and strength of CSM panels. Microstructural studies were also performed to understand the reactions of the mixtures. The results showed that the compressive behavior of CSM panel changes significantly by increasing the mixing depth. Moreover the influence of curing pressure equivalent to the depth of CSM panels on increasing unconfined compressive strength of specimens is partially more than the effect of additives and considerably more than the effect of curing time. The microstructural studies also showed that the main hydration products are cementitious products such as calcium silicate hydrates (C-S-H) and the addition of alkali-activated slag in a treated clay results in production of the cementitious products in a faster rate.