Abstract: Taking a close range excavation to a metro line in southern area of Jiangsu province as the research object, a set of HS-Small constitutive model parameters are proposed preliminarily by empirical methods and soil tests. And then, based on the measured data of horizontal deformation of retaining structures and ground surface settlement in the field, inversion analysis is carried out to replay the excavation process by finite element method in order to further optimize and calibrate HS-Small model parameters. On this basis, the finite element model of the adjacent excavation of subway bridge pile foundation is built; and the influenced area of the existing pile deformation is established. The results show that: (1) When the spacing between pile and pit is less than 0.6 times of the depth of foundation pit, pile foundation settlement doesn’t perform an obvious trend to decrease; but when the spacing between pile and pit is more than 0.6 times of the depth of foundation pit, the settlement of pile foundation quickly decreases; pile horizontal displacement also shows similar pattern, but the critical point is located on the 1 times of the depth of foundation pit. (2) The close range excavation has a more obvious effect on pile horizontal displacement than vertical settlement; but when the pile-pit spacing is greater than 1.37 times of the depth of excavation, the deformation of pile foundation will not exceed the limit value; when the pile-pit spacing is greater than 1.90 times of the depth of excavation, the deformation of pile foundation will be less than the warning value (60% of the limit value). (3) The influenced zone of pile foundation deformation is divided into three grades as A, B and C, and the protection measures are put forward accordingly.

Key words: HS-Small constitutive model, excavation of foundation pits, pile deformation, influenced zone