Study On Numerical Simulation Of Basic Process And Real-time Optimizing Of Deep Foundation Pit

About analysis of building foundation pit and cofferdam of reservoir, it was difficult to choose constitutive model of material, and learned less about saturation-unsaturation seepage and coupled seepage and stress field as well as time-space effect. It not only had low precision and calculating efficiency in methods of inverse analysis of parameters and predicting, but also had not appropriate system and criterion of safety evaluating, thus it led to restrict the development of deep foundation pit. In order to raise the scientificity of supervising the practice of deep excavation engineering, it is important to develop the study on numerical simulation of basic process and real-time optimizing. Aiming at the existent problems of the study about deep foundation pit, finite element method, time-space effect, inverse analysis of parameters, predicting, safety evaluating and so on are studied entirely merged in lots of theories and methods of finite element method(FEM), artificial intelligence(AI), and mathematic methods, and that is the main results as follows.1. Based on lots of national and international research results, the headway and the existent problems of numerical simulation of basic process and real-time optimizing of deep foundation pit are summarized systemically, thus the direction and content of the paper are advanced.2. Modified D-P model, D-P cap model, extended Cambridge model are applied in the analysis of building foundation pit and cofferdam.(1) Modified D-P model, D-P cap model, extended Cambridge model are introduced. Moreover, methods of finite element analysis are expatiated based on the characteristics of foundation pit and cofferdam, and analysis of examples is carried out. By contrast analysis of shoring process of deep excavation with modified D-P model, D-P cap model, and extended Cambridge model, we know that the extended Cambridge model is suit to analysis of foundation pit of clay soil. In the model, the effect of the three stress invariants and the characteristic of strain hardening/softening can not only be considered, the hardening law can but also be defined by a piecewise linear form or by an exponential form as well as it accords with the speciality of cohesion materials, thus the model is better in precision.(2) By FEM, lots of laws are summarized systemically about level displacement surrounding frame and slope, sedimentation of the earth's surface around pit, feedback of pit bottom, and those have good reference value to guidance of design and construction of deep excavation.(3) Under water pressure, the analysis of the second period cofferdam of the Three Gorges Project shows that distortion trend leans mainly to backward position, and themaximal displacement and maximal sedimentation of cofferdam locate at the 2/3 of the altitude, and the maximal and minimal main stress locate at the lower part of cofferdam near backward diaphragm wall, and the displacement and stress of cofferdam body are the same as the general dam of soil and rock.(4) To the second period upward cofferdam, when the single wall of diaphragm wall bears water pressure, the displacement of wall will increase with the difference of water pressure after pumping water from pit. When the two walls bear water pressure, the 1/2 difference of water pressure is partaken approximately by two walls. Moreover, the displacement of wall will increase with the difference of water pressure after pumping water from pit, and the computing maximal displacement is lower than the real measure result. The study shows the analysis precision will increase after the characteristic of creep taken into account.3. Aiming at real work situation of deep foundation pit, seepage and seepage and stress field coupling of saturation-unsaturation are analyzed and the contrast study is carried out with saturation seepage.(1) Examples of seepage analysis in different conditions such as rainfall and the dam with or without diaphragm wall are analyzed about saturation and saturation-unsaturation seepage, and the analysis re...