滨海软土地区综合管廊基坑开挖钢板桩支护性状分析

Analysis of Steel Sheet Pile Wall Behavior for Utility Tunnel Excavation in Coastal Soft Soil

采用PLAXIS 2D对比分析了基坑开挖过程中钢板桩支护体系的土压力、钢板桩水平位移、钢板桩弯矩、基坑周边地表沉降以及支撑轴力等。结果表明:随着基坑的开挖,主动侧土压力减小,在内支撑处应力集中,在开挖较浅时主被动土压力相对静止土压力改变均不大,被动土压力在基坑开挖时每一步的开挖面上有增大的趋势;钢板桩最大的水平位移增加和弯矩增量均在最后开挖步产生,最后的开挖步为综合管廊基坑开挖的关键和最危险步;基坑地表沉降随着开挖逐渐发展,最后一步开挖依然是沉降变形最大的关键施工阶段;支撑轴力表现为一道支撑轴力一直增加,两道支撑时第二道支撑会超越第一道支撑成为主支撑。

The development of the surface settlement and steel sheet pile retaining system mechanical response during construction are fully discussed,in which lateral earth pressures,wall deformations,wall bending moments,surface settlements,and strut forces are studied by PLAXIS 2D. The analysis results show that active earth pressures are gradually decreased in excavation,and there are the cases that the stress concentration around the strut level. Both the active earth pressures and passive earth pressures change a little compared with earth pressures at rest in shallow excavation,however,passive earth pressures tend to increase at surface excavation steps. The maximum wall deformations and bending moments occur during the last stage of construction,and the final step is the most significant and dangerous stage of the construction. With the development of surface settlement,the final step in the excavation is still the key construction phase. Strut forces are increasing in the case that just one,the forces of the second strut will be beyond that of the first,and become the main support in those cases with two struts.