兰州某地铁车站深基坑降水对地表沉降的影响分析

Analysis of the Effect of Deep Foundation Pit Dewatering on GroundSurface Settlement at a Subway Station in Lanzhou

基坑降水会使地下水产生流动,从而产生渗流附加应力,基坑周围土体发生应力重分布,在渗流场与应力场耦合作用下,对地表一定范围产生不同的影响与破坏。以兰州东方红广场地铁车站基坑工程为例,通过理论研究、数值模拟及现场监测,分析基坑降水对地表沉降的一般规律,并验证改进算法的合理性。研究结果表明:(1)地表沉降总体趋势呈非线性增长,且随降水稳定趋于稳定;(2)考虑渗流力算法结果略小于规范法,更接近实际监测值;(3)距坑边相同距离处各点最大沉降量不同,受降水深度及周围环境影响。

The foundation pit dewatering will cause the flow of groundwater and thus produce additional stress of seepage and stress redistribution of the soil around the pit,which will affect and damage the terrain surface within certain region to different degrees under the coupling of the seepage field and the stress field.Taking the foundation pit project in Lanzhou Dongfanghong Square subway station as an example,the general law of the effect of foundation pit dewatering on the surface settlement was analyzed through theoretical research,numerical simulation and on-site monitoring,and the rationality of the improved algorithm was also verified.The results show that(1)the overall trend of surface settlement grows in a nonlinear way and tends to be stable with the stability of dewatering.(2)When considering the seepage stress,the calculation results are slightly smaller than that with the specification method and closer to the actual monitoring value.(3)The maximum settlements at points with same distance from the pit edge are different,due to the impact of dewatering depth and surrounding environment.