Capacity and failure mechanism of laterally loaded jet-grouting reinforced piles: Field and numerical investigation

This study presents the results of field and numerical investigations of lateral stiffness, capacity, and failure mechanisms for plain piles and reinforced concrete piles in soft clay. A plastic-damage model is used to simulate concrete piles and jet-grouting in the numerical analyses. The field study and numerical investigations show that by applying jet-grouting sur- rounding the upper 7.5D （D = pile diameter） of a pile, lateral stiffness and beating capacity of the pile are increased by about 110% and 100%, respectively. This is partially because the jet-grouting increases the apparent diameter of the pile, so as to en- large the extent of failure wedge and hence passive resistance in front of the reinforced pile. Moreover, the jet-grouting pro- vides a circumferential confinement to the concrete pile, which suppresses development of tensile stress in the pile. Corre- spondingly, tension-induced plastic damage in the concrete pile is reduced, causing less degradation of stiffness and strength of the pile than that of a plain pile. Effectiveness of the circumferential confinement provided by the jet-grouting, however, diminishes once the grouting cracks because of the significant vertical and circumferential tensile stress near its mid-depth. The lateral capacity of the jet-grouting reinforced pile is, therefore, governed by mobilized passive resistance of soil and plastic damage of jet-grouting.