以某超大基坑为例,借助FLAC^3D有限差分软件建立考虑土体、地下连续墙、结构梁板等共同作用的三维模型,研究墙体产生侧向位移时基坑外主动土压力的变化趋势墙体发生鼓型侧移时,基坑外主动土压力呈“R”分布;并对影响围护挡墙结构侧移和主动土压力分布的几个参数(内摩擦角、墙土摩擦角、挡土墙入土深度,以及基坑长宽比等)进行敏感性分析,并归纳出变化规律:土体内摩擦角和黏聚力对挡土墙侧移影响较大,随着内摩擦角和黏聚力的增大,挡土墙上的主动土压力和墙体侧移逐渐减小;挡土墙入土深度对挡墙的主动土压力影响不明显,而对挡墙侧移有一定影响。随着挡墙插入深度增大,上部墙体侧移逐渐增大;而下部墙体却相反,当插入比在1.2左右时,墙体侧移最小。在开挖面以上,随着基坑长宽比增大,挡墙上主动土压力逐渐减小;而在基坑开挖面以下,特别在靠近挡土墙底部范围内,随着基坑长宽比增大,挡墙上的主动土压力强度逐渐增大。

With a deep excavation pit as an example, FLAC^3D is employed to simulate the trends of active earth pressure in the presence of lateral displacement of retaining wall in consideration of the joint action among retaining wall, beam and soil mass. The active earth pressure distributes in “R” shape when drum-type displacement of retaining wall occurs. Furthermore, the influences of several parameters (including internal friction angle, cohesion, embedded depth of retaining wall, aspect ratio of excavation pit) on the lateral displacement and active earth pres-sure are analyzed. Results reveal that internal friction angle and cohesion of the soil have great influences on the lateral displacement of retaining wall. With the increase of internal friction angle and cohesion, the active earth pressure and the lateral displacement of retaining wall decrease gradually. The embedded depth of retaining wall has no obvious effect on active earth pressure, but affects the lateral displacement: the lateral displacement of the upper retaining wall increases gradually when the embedded depth of retaining wall is increasing; while for the lower part of the retaining wall, the regularity is the opposite, with the lateral displacement reaching the minimum when insert ratio is about 1.2. Above the excavation face, the active earth pressure on the retaining wall decreases gradually with the increase of aspect ratio; while below the excavation face, especially near the bottom of the retaining wall, the active earth pressure on the retaining wall gradually increases with the increase of aspect ratio.