Abstract: In order to ensure the smooth construction of subway in northwest China, the deep foundation pit dewatering projects of subway stations in Xi’an and Lanzhou are studied and analyzed, and the additional settlement estimation formula for the ground settlement deformation around the foundation pit caused by the deep foundation pit dewatering of the subway station is summarized and the seepage is considered. The settlement calculation formula under the action of force, combined with the actual project, compares the two theoretical calculation results with the measured settlement results. The results show that the calculation results of the additional settlement estimation formula are conservative compared to the actual measured settlement results, and empirical coefficients should be brought in to make the results to match the actual situation better. The accuracy of settlement calculation formula considering the seepage force is greatly improved in comparison with the additional settlement estimation formula, and it is closer to the measured settlement results, which can be used as a calculation formula for the impact of dewatering on the surrounding environment of subway foundation pits in the northwestern region.

Key words: metro station foundation pit, foundation pit dewatering, settlement calculation, seepage force