USE OF JET GROUTING TO INCREASE LATEARAL PILE GROUP RESISTANCE IN SOFT CLAY

Lateral load tests were performed on a full-scale pile cap in clay before and after construction of a soilcrete wall on one side of the cap using seven 1.22-m m diameter jet grout columns to a depth of 3.76 m. Jet grouting with a cement content of about 400 kg/m 3 (20% by weight) increased the average compressive strength of a soft, plastic clay from 40 to 60 kPa to an average of 4500 kPa. The lateral resistance was increased by 1950 kN or 155% and the initial stiffness was increased by 400%. About 75% of the increased resistance could be accounted for by passive pressure and side/base shear on the jet grout mass; however, the remaining 25% increase must be due to the interaction between the piles and the strengthened soil. Jet grouting provides a method to significantly increase the lateral resistance of pile group foundations at costs much lower than typical structural approaches.