Abstract: Strata in Tianjin area are featured as an alternated multi-aquifer aquitard system. Based on this strata condition, lots of numerical calculations investigate the effect of deep foundation pre-dewatering on lateral displacement of support wall in soft ground under different construction conditions, including dewatering time (t), dewatering depth ( ), pit length (L) and pit width (b). The calculation results were compared with relevant field data, and nonlinear regression analysis was then conducted based on the calculation and observation results. The results indicate that the maximal lateral displacement of support wall ( ) increases nonlinearly with t, and the growth rate decreases continuously. In the first few days of the dewatering, lateral displacement of support wall development can occupy large proportion of its stable value during pre-dewatering. Moreover, has a great influence on the development and the depth of wall with cantilever-type deflection ( ). In general, and will be larger with the increase of . Specifically, before reaches the second permeable stratum of the field, increases linearly with by a small scale. Otherwise, the growth proportion of with increases greatly. Before reaches the center location of the thick aquitard, increases synchronously with increased, and otherwise, the increment is apparently greater than the increment. Furthermore, as to the same pit width (b), when the pit length (L) reaches a specific value, the corner effect induced by dewatering always appears at a specific distance from the pit corner along the pit length direction. In practical pre-dewatering, cross wall can be used to partition the pit into some parts, and let the ratio of cross wall spacing ( ) to b be less than 4, or let / be less than 3.7, using the corner effect to effectively reduce the maximal lateral displacement of support wall induced by pre-dewatering.

Key words: soft ground, deep foundation pre-dewatering, lateral displacement of support wall, finite element calculation, corner effect