中文摘要：

被动群桩中具有明显的土拱效应和遮拦效应，运用岩土数值计算程序FLAC3D，对不排水条件下的被动群桩进行了平面应变数值模拟研究．土体采用摩尔-库伦本构关系，桩基采用线弹性本构关系，桩土之间建立接触面．研究结果表明，埋深对桩侧极限土压力有影响，在浅层桩侧极限土压力随着深度的增加而增大，达到一定深度后随着埋深的增大基本保持不变．单排桩时桩后具有明显的土拱效应，随着桩间距增大桩的荷载分担比降低，达到稳定的桩荷载分担比所需要的桩土相对位移量增大．双排桩时随着排间距增加，后排桩和前排桩的桩侧极限土压力都增加，当排间距达到6D 以后，后排桩和前排桩之间基本没有遮拦和加筋作用．

英文摘要：

There were obvious soil arching effects and shadowing effects in passive pile groups.Using the geotechnical numerical calculation program FLAC3D,the paper conducted a plane strain numerical simulation study on the group effect of the lateral soil pressure of the passive pile group under the undrained condition.The Mohr-Columb elastic-plastic constitutive model was employed to model the non-linear stress-strain soil behavior;the piles were assumed to have linear elastic behavior;the interface model incorporated in FLAC3D code was used to simulate the soil/pile contact.The results of the numerical analysis indicated that the depth of the piles had some influence on the ultimate pressure of the lateral soil;in the shallow soil,the ultimate soil pressure increased with the depth increasing,but the ultimate soil pressure almost remained constant with the depth increasing in the deep soil.In the single pile rows,there were obvious soil arch effects behind the piles;with the increase of spacing between piles,the pile bearing ratio decreased,but the relative displacement to reach the stable pile bearing ratio increased with the increase of pile spacing. In the two pile rows,with the increase of row spacing,the ultimate pressure of lateral soil on the two row piles increased;there were almost no shadowing effects and reinforcing effects in the two pile rows when the spacing of the two pile rows increased to 6D.