Analysis Of Settlement Of Ground Surface Induced By Dewatering In Excavation

The influence of dewatering on the settlement of ground surface surrounding a pit is one of the key problems in excavations. However, there is no a reasonable and reliable evaluating method so far.In this thesis, based on the principles of hydraulic mechanics and soil mechanics, the change of effective stress in soil mass and the settlement of ground surface induced by dewatering during excavation both in homogeneous soil and in layered soil were studied. Analytical formulas for calculating the settlement and the others were derived under the assumption that the seepage induced by dewatering is one-dimensional and vertical. Furthermore, with the formulas as basis, a practical case of excavation was analyzed, and the obtained results were compared with the field measurements. Meanwhile, engineering method was proposed to reduce the damage to surroundings resulted from dewatering in excavation.It was shown that the changes in effective stresses induced by dewatering and seepage are the main factors causing settlement of ground surface. The settlement depends on not only the depth of dewatering but also the permeability of soil. By reducing the permeability of soil at the bottom of pit and selecting optimal dewatering depth, the settlement of ground surface can be well controlled.