关键词: 基坑, 抗隆起破坏, 离心模型试验, 地下水位, 强度折减法, 安全系数

Abstract: Centrifugal model test is designed to simulate basal heave failure of narrow-deep foundation pit in soft clay. The bending moment and horizontal displacement of retaining wall, the earth pressure distribution as well as basal failure mechanism of excavation at different groundwater levels are analyzed. Based on fundamental parameters and excavation procedures of the centrifugal model test, a finite element model is established to analyze the basal heave stability factors and failure modes of foundation pit, comparing with the centrifugal test results. The results of centrifugal model test show that, with the excavation depth increases and groundwater level rises, the bottom uplift and deformation increase. Horizontal displacement towards pit occurs at the bottom of retaining wall, because of the lateral restraint reduction and greater uplift, at the same time, the axis force of internal struts increases. Eventually, retaining wall rotates around a braced point of its own, resulting in a skirting failure. The results of numerical simulation show that, with the increase of groundwater level outside the pit, the safety factor of basal heave stability gradually reduces. When foundation pit collapses due to basal heave failure, the uplift displacement at bottom is greater. The basal failure mechanisms revealed by centrifugal model test and numerical simulation are similar.

Key words: foundation pit, basal heave failure, centrifugal model test, groundwater level, strength reduction method, factor of safety