application of long-short pile retaining system in braced excavation

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.