正断层作用下高承台群桩基础的破坏机制数值模拟

Numerical Simulation of Failure Mechanism of High-Rise Pile Cap Foundation Subjected to Normal Fault

基于FLAC3D有限差分软件,模拟正断层错动下高承台群桩基础的破坏过程,分析上覆砂土和群桩的相互作用,对比相同条件下1×3群桩和3×3群桩破坏机制的差异.计算结果表明:正断层错动作用下,1×3群桩的存在对土体破裂带的扩展影响较小,土体剪切带仍保持80°倾角向上发展,在地表形成一条陡降带,而3×3群桩则明显改变破裂带的发展轨迹,使得土体剪切带在中间基桩的桩端位置发生分叉,在地表形成两条陡降带;正断层错动使得群桩向上盘一侧倾斜,1×3群桩和3×3群桩的承台位移和倾斜没有明显差异,其数值计算结果和理论计算结果保持一致;基岩错动使得基桩间承担的竖向荷载发生重分布,中间基桩受拉,竖向荷载向两侧基桩转移;随着基岩错动量的增加,1×3群桩和3×3群桩具有相同的轴力和弯矩发展规律.

Based on finite difference software FLAC3 D,the failure process of high-rise pile cap foundation subjected to normal fault was simulated,the interaction between overlying sand and group piles was analyzed,and the failure mechanism of 1×3 pile group and 3×3 pile group was compared under the same conditions.The calculation results show that the existence of 1×3 pile group has little effect on the extension of the rupture zone.The shear rupture zone still maintains 80°inclination angle and then extends to the surface.While the 3×3 pile group obviously changes the extension of the rupture zone,which causes the soil shear zone to bifurcate at the pile end position of the intermediate pile,and forms two steep descending zones on the surface.The normal fault forces the group pile to tilt to hanging wall.There was no significant difference in displacement and inclination of pile caps between 1×3 pile group and 3×3 pile group.The numerical calculation results are consistent with the theoretical calculation results.The bedrock faulting redistributes the vertical load among the foundation piles,the middle foundation pile is under tension,and the vertical load transfers to the two sides of the foundation pile.With the increase of bedrock faulting,1×3 pile group and 3×3 pile group have the same axial force and bending moment development rules.