Abstract:
The liquefaction-induced ground settlements have been frequently observed in past earthquake events such as the 2010-2011 Canterbury Earthquake Sequence (CES) in New Zealand and the 2011 Tohoku earthquake in Japan. Various ground improvement methods have been used in engineering practice to lessen the effects of soil liquefaction at shallow depths, among which installing sheet piles around the foundation is one of the mitigation methods. However, the extent of the sheet pile length that needs to be embedded into a non-liquefiable soil layer beneath the liquefiable soil layer for bottom fixity is still not fully understood. Limited research has been carried out to investigate the behaviour of sheet piles as a mitigation measure in liquefaction-induced foundation settlement. Therefore, a series of moderate-scale 1g shake table tests are conducted to evaluate the effective embedded sheet-pile length into non-liquefiable soil. In this research, a 1/5 scaled model is prepared based on a large-scale shake table test carried out by UNR. The scaled model consists of three soil layers with relative densities of 50% for the top crust, 40% for the middle liquefiable, and 85% for the bottom dense layers. Then, a shallow foundation is seated over the crust layer. After the preparation of the model, a sheet pile at 0.25*B distance from the edge of the foundations with various embedded lengths is inserted into the soil using the press-in technique. Later, the scaled models are subjected to harmonic input motions with amplitudes and dominant frequencies scaled based on the large-scale shake table test. This study assesses the optimum embedded length required into the non-liquefiable layer to minimize foundation movements (i.e., settlements and tilting) and generated excess pore water pressures. In addition, a regression analysis is performed to introduce a relation between the sheet pile's embedded depth and the foundation settlement.