Experimental investigation of determining of optimum improvement depth of the homogeneous soil

In this research, improvement depth under a foundation which constructed on weak soil, is experimentally determined. When the building loads exceed bearing capacity of soil, a soil improvement technique should be used. Jet grouting is a very frequently used soil improvement method in our country. In this method, cement slurry injected into the soil with high pressure and velocity. Soil improvement should be applied to the all weak soil layers. If weak soil that extended to great depths, engineers choose an improving depth by using theory of elasticity. In this theory, soil assumed as a solid, incompressible and elastic material. According to this theory, stresses beneath the foundation, extends 1.5-2 times of the width of the foundation (B). Engineers generally don't improve soils to this depth because of the cost of the soil improvement. Soil improvements are stops at shallower depths. In this research, improved sandy soils with different depth are prepared. Bearing capacity of foundations which settled on these soils are determined. Thus it is tried to prevent excessive or insufficient improvement. In order to model the weak soils and foundation, soft- medium dense sand and steel model foundation is used. Improved soil layers are modeled as concrete blocks in laboratory. All experiments are modeled by using finite element method. Then numeric and experimental results are compared.