Improvement of Static and Dynamic Properties of Soft Clay Using High Pressure Jet Grout

A proposed subway project is located in an area marked by a number of soft clay layers situated at depths from 60 ft to 100 ft below the ground surface. With unconfined compressive strength less than 0.6 tsf these natural soils are not strong enough to support on coming heavy loads and vibrations that the subway may be subject to in future. Hence the soil was trial grouted in-situ using high pressure jet grout technique to improve the engineering properties of the natural clay. A series of static and dynamic property tests were carried out on 18 samples selected from the site. Results show that the static and dynamic strength of the grouted clay improved significantly and the improvement depends on several parameters like confining pressure, cement content and water/cement ratio. The study provides a reasonable estimate of the extent of improvement (with respect to natural soil) and leads towards a better understanding of the static and dynamic properties of cement-treated clays and their behavior under various conditions