Effect of Jet-Grout Columns on the Seismic Response of Layered Soil Deposits

Ground-improvement techniques, such as jet-grout columns, may have positive effects on structures founded on soft soil when subjected to earthquake loading. The main objectives of this paper are first to evaluate the effects of soil-improvement width and depth on the ground response of a layered soil and, second, to define critical zones in which cemented columns might crack. A series of numerical calculations are performed by means of the finite-element method, considering a linear viscoelastic model for soil layers and rigid bedrock condition, and also by applying an advanced constitutive model for simulating the behavior of jet-grout columns. The soil profile consists of a 10-m loose sand layer overlain and underlain by a 5-m dense sand layer. The acceleration time recorded during the Loma Prieta earthquake in 1989 is used as the input motion. The results show that the seismic load is decreased or may increase as a result of ground improvement. In addition, it is shown that by applying an advanced model, possible crack zones in cemented columns can be identified.