Research On Pseudo Three-dimensioned Analysis Method For Foundation Pit Braced With Row Piles

Along with our country city new construction and utilities land increasingly nervous, reasonable development of underground space becomes the inevitable choice, resulting in the number and size of deep foundation pit engineering is also increased, at the same time, foundation pit excavation is more and more dangerous, given the cause of foundation pit engineering accidents is one of the most popular because the supporting structure design method improper, and therefore the use of row pile supporting foundation pit design more reasonable calculation method is particularly important. At present, more widely used foundation pile supporting foundation pit plane elastic foundation beam method, which considers the process of excavation, support structure interaction under the premise, put forward a more three-dimensional analysis method is reasonable and it is of important practical value.This paper will first horizontal is approximately rectangular pile of foundation pit for the whole support structure is divided into4bearing surfaces covering the respective independence, and then to any one surface on a pile as the research object, aiming at the different stages of excavation and support are provided, the force equilibrium equation is established and the displacement coordination equation; Then through the coordination of the top beam, the middle beam, the research object is extended to the entire surface, considering the excavation, supporting and soil-pile-top beam-middle beam interaction surface displacement and force equations to pseudo three-dimensional condition is derived, using FORTRAN language program, and obtained the excavation stage the top beam, the middle beam and pile at any cross section of the internal force, horizontal displacement and the support force. This paper gets following main achievements:1. In pseudo three-dimensioned condition is derived, considering both the excavation process, support setting and soil-pile-top beam-middle beam interaction and force equations. By solving the equations can calculate all pile, the middle beam, the middle beam and supporting internal force and deformation.2. The proposed quasi3D analysis method is reasonable considering interaction between retaining pile, the top beam, the middle beam and internal support and supporting effect, including supporting pile and anti-bending effect; the top beam, the middle beam anti-bending, resisting shear and anti-torque effect, compression effect of internal support.3. The paper analysis method through a case1the calculation results show that, the program can calculate the reasonable, convenient the supporting structure of ideal internal force and deformation, and with the method of references[39] on the pile top horizontal force analysis and calculation of value, part of the calculation of bending moment of pile, by the top beam calculated and measured displacement comparison the results show that, the two methods are in good agreement with the calculated results can reasonably, and validating the feasibility of this method.4. Through the show case2results, this method can also used in calculation conditions, multi-channel support, the support structure effect of foundation pit supporting structure internal force and deformation of excavation, and by contrast the31st pile calculated with monitored displacements under excavation stage2and excavation stage3, the value of comparative analysis with the measured values, horizontal displacement obtained by the two methods are in good agreement, further verify the accuracy of three dimensional analysis method.For the proposed method by pseudo three-dimensioned analysis for foundation pit braced with row piles in this paper, has been worked out the corresponding calculation program FORTRAN.