Cement Pile Composite Pile Wall Supporting Structure Design Computing Model Studies

At present, the status of deep excavation engineering is promoting day by day in foundation work with the popularizing of high-rise building, super high-rise building and the sufficient use of underground space.The increased depth of the foundation ditch, huge excavation area, hash surrounding environment, high under groundwater level has brought many problems to the excavation of foundations and challenges the classical and single supporting structures.Facing this condition, the designers and constructors of deep excavation engineering find that it may get good effect of supporting by combining two or more than two supporting structures. People call this new supporting structure combining two or more supporting composite supporting. Composite supporting structure has become one of development tendencies of deep foundation supporting structures. And the study of the Composite supporting is a new developing filed in deep foundation ditch engineering. The compound pile wall is a new composite supporting structure. It is composed by cement soil piles, some of little piles, a concrete linking plate on the top of supporting structure. Sometimes horizon anchors or inclined anchors may be used in compound pile wall. The compound pile wall which has the double technology effects of cutting off water and supporting is a supporting technology of retaining wall.The technology meaning of the compound pile wall can be summarized by "cement soil piles wall + some rows of little piles + concrete top linking plate". The compound pile wall not only has good economic efficiency, but also has good performance in saving the underground space, reducing the displacement of the soil, protecting surrounding environment, shortening the period of the engineering. Though the compound pile wall has had successful application examples in ZHENG Zhou area and got good supporting effect, it has many questions to be study.Based on previous researches, the two-dimensional finite element analysis has brought out to the single-row-little pile compound pile wall by the software ANSYS in this paper. In this paper, the main ideas include that:1) A two-dimensional finite element analytic model of the compound pile wall has been created in this paper. The method for simulating the excavating process of deep foundation pit by "Element Birth and Death" function in ANSYS has also been introduced in this paper; 2) The calculation results and general laws of the horizontal lateral displacement, settlement of the soil, soil pressure, axis force of the single-row-little pile compound pile wall supporting structure in the different work conditions of the excavating process has been given in this paper;3) When the excavation depth is less than 6m and the aspect ratio is greater than 0.3, the cement soil piles could work together with little piles. So they can be looked as a whole body; when the excavation depth is greater than 6m and the aspect ratio is less than 0.3, the overturning moment created by the earth pressure may count on the embedded depth and the tensile force of the little piles. The cooperation work degree of the cement soil piles and the little piles may mainly rely in the constrain condition of the top linking plate in the second condition;4) The integral type design calculation method of the compound pile wall has been given in this paper. A case study also has been given to explain this method.