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基于天津地区透水层和弱透水层交替出现的场地水文地质条件,通过大量数值计算与工程实测对比,结合非线性回归分析,研究了预降水时间t、预降水深度H_d、基坑长宽L,基坑宽度b等参数对基坑预降水过程中支护墙侧移发展的影响规律。随t延长,最大支护墙侧移δ_(hm)呈增长速率不断减小的非线性增长,在预降水刚开始的几天内,支护墙侧移即可占据其预降水过程中稳定侧移的很大比重。其次,H_d对δ_(hm)及支护墙悬臂侧移深度H_c的发展有重要影响,总的来说,δ_(hm)及H_c均随H_d增大而增大,具体地,当H_d达到场区第2透水层前(后),δ_(hm)随H_d的线性增长比例较小(大),当H_d达到场区深厚弱透水层厚度一半之前(后),H_c的增长接近于(明显快于)H_d的增长。另外,对于同一宽度b基坑,当基坑长度L达到一定程度后,预降水引起的基坑长度方向边角效应总是发生在基坑两侧距离坑角某一确定范围之内,在预降水过程中,若支护墙变形需要严格控制时,可通过布置横隔墙,使得相邻横隔墙间距S_(cw)与b之比在4以内,或S_(cw)/H_d在3.7以内,利用基坑边角效应减小预降水引起的最大支护墙侧移。
Based on the site hydrogeological conditions alternating between the permeable layer and the impermeable layer in Tianjin area, the numerical simulation was compared with the actual measured data. Combined with the nonlinear regression analysis, the effects of pre-precipitation time t, pre-precipitation depth H_d, Influence of Parameters of Foundation Pit Width and B Parameters on Side Shifting Development of Retaining Wall during Pre-Dewatering of Foundation Pits. With the extension of t, the maximum support wall displacement δ_ (hm) shows a non-linear growth rate of decreasing growth, in the first few days before the pre-precipitation, retaining wall displacement can occupy the stability of its pre-precipitation side of the process Move a large proportion. Secondly, H_d has an important influence on the development of δ_ (hm) and the cantilever lateral displacement depth H_c. In general, both δ_ (hm) and H_c increase as H_d increases. Specifically, when H_d reaches the field The ratio of δ_ (hm) to the linear increase of H_d was small (large) before and after the second permeable layer (before and after), and the increase of H_c was close to that before H_d reached half of the thickness of deep aquitard At) H_d growth. In addition, for the same width b foundation pit, when the length L of the foundation pit reaches a certain extent, the corner effect in the length direction of the pit caused by the pre-precipitation always occurs within a certain range of the pit angles on both sides of the foundation pit, In the process of precipitation, if the support wall deformation needs to be strictly controlled, the transverse partition wall can be arranged so that the ratio of the adjacent partition wall spacing S_ (cw) to b is within 4 or S_ (cw) / H_d is within 3.7 , The use of foundation pit corner effect to reduce the maximum support wall displacement caused by pre-precipitation.