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METHOD OF COMMON DEFORMATION FOR ANALYSIS OF SUPPORTING STRUCTURE IN DEEP EXCAVATION

Zhang Yang-song, Luo Guo-yu   

  1. Department of Earth Sciences, Nanjing University, Nanjing 210093
  • Received:1999-09-20 Revised:1999-09-20 Online:1999-09-20 Published:1999-09-20

Abstract: Based on the study of the advantages and shortcomings of the general elastic foundation beam method for deep excavation, the authors proposed a computational model and analysis procedure of common deformation method considering interaction between supporting structure and soil layers. The common deformation method comprises the following analysis steps: (1) Calculating of the initial static pressure; (2) Defining the horizontal foundation reacting force coefficients representing soil around the wall, stiffness of the wall, and the struts or anchors; (3) Calculating of the incremental displacement; (4) Recalculation of the earth pressure by adding the initial static earth pressures to the changes in earth pressure, which is derived from the multiplication of incremental displacement by reacting force coefficient; (5) Comparing the earth pressure with soil strength limitation criteria i.e., the convention al active or passive limit. If any strength is infringed, a set of correction forces is calculated, which then will be used to restore the earth pressures consistent with the strength criteria and plastic deformation within the soil. (6) Replacing the forces used in the step (1) new forces. Repeat the step (3) to (5)until convergence is achieved. (7) Calculating the total displacements, earth pressures, strut forces, wall shear stresses and bending moments. A comparison of the results of two computation methods has demonstrated that the horizontal foundation reacting force coefficient, which is same as in the general elastic foundation beam method, could be used in the common deformation method. Different methods (constant or “m” method) of selecting the horizontal foundation reacting force coefficient may have important influence on the results of computation. Our study suggested that the common deformation method is useful in the practice, and more reasonable than the general elastic foundation beam method.