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This study presents a series of physical model tests and numerical simulations using PFC2D (both with a dip slip angle=60° and

a soil bed thickness of 0.2 m in model scale)at the acceleration conditions of 1g, 40g, and 80 g to model reverse faulting. The soil

deposits in prototype scale have thicknesses of 0.2 m, 8 m, and 16 m, respectively. This study also investigates the evolution of a

surface deformation profile and the propagation of subsurface rupture traces through overlying sand. This study proposes a

methodology for calibrating the micromechanical material parameters used in the numerical simulation based on the measured

surface settlements of the tested sand bed in the self-weight consolidation stage. The test results show that steeper surface slope

on the surface deformation profile, a wider shear band on the major faulting-induced distortion zone, and more faulting appeared

in the shallower depths in the 1-g reverse faulting model test than in the tests involving higher-g levels. The surface deformation

profile measured from the higher-g physical modeling and that calculated from numerical modeling show good agreement. The

width of the shear band obtained from the numerical simulation was slightly wider than that from the physical modeling at the

same g-levels and the position of the shear band moved an offset of 15 mm in model scale to the footwall compared with the results

of physical modeling.

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In soft soil areas, equal-length piles are often adopted in the retaining system. A decrease in the bending moment value borne by the retaining structure along the pile depth (below the excavation bottom), leads to an inadequate use of the pile bending capacity near the pile bottom. This paper presents retaining systems with long and short pile combinations, in which the long piles ensure integral stability of the excavation while the short piles give full play to bearing the bending moment. For further analysis on pile and bottom heaves deformations and inner-force characteristics, three-dimensional models were built in order to simulate the stage construction of the excavation. The ratio between long and short pile numbers, and the effects on short pile length pile horizontal deformation, pile bending moment and bottom heave are investigated in detail. In the end, a feasible long-short pile combination is established. Obtained results from the simulation data and the field data prove that the long-short pile retaining system is feasible.