| As a comprehensive and systematic project, foundation pit engineering refers to structural engineering, material engineering, geological engineering, construction mechanics and optimization design in many research fields, and with strong regional characteristics. It is necessary to consider either the influence factors of the excavation depth, width, horizontal and vertical displacements of the support structure, groundwater conditions, and the changing situation of the factors during the excavation process as well as the soil characters which also change with the the time-varying. So the soil creeping effect, time-varying earth pressure, the mechanics properties and the process design during the construction progress are very important questions for the foundation pit engineering.During the construction process, the foundation pit engineering inluding the strucuture, the foundation and the surrounding rock endure the changes of the geometry and physical properties gradually, the force process of the non-complete construction under the changing construction loads and sudden load. So it is necessary to consider the relation characteristic of the time-varying material, physical and geometry with the structure nonlinear and coupling effect of the passive loads. Time-variation mechanics is just the new branch of science on the time-varying geometry, time-varying physics, and time-varying boundary condition of the objects. Therefore, to combine the construction mechanics and time-varaiation mechanics is doubtless an important part of the development and a new growing point of the modern mechanics.Due to existing many difficulties, such as to decide the maximum of the time-variation structure time-varying spatial and temporal distribution and internal force re-established under the action of construction loading, the non-completed structure and construction works safety analysis, the material stiffness and strength varying with time and the superposition effects caused by construction process different periods of non-stable viscous stress field, and so on. In this article, attempting to establish the mechanical analysis ideas and methods of the construction process based on studying time-variation mechanics and spatial development structure in the time series for the study of the environmental geotechnical engineering construction mechanical effects were studied. The independent innovation achievements were made in the following:1. It is researched on the time-varying characteristic of the soil material based on Zhengzhou engineering geological condition. By analyzing the soil time dependent properties based on the theory of time-varying mechanics, visco-elastic flow problems and visco-elastic-plastic rheological questions were computed and studied by establishing finite element model according to temporal characteristics of soil excavation by the time step-the beginning of viscous strain, comprehensive considering of geotechnical engineering compositeity of each factor and using soil constitutive between the beginning of the viscous strain as strain. It revealed that the soil time dependent properties in deep excavating would be guidance significance of construction and this method was validable and reliable, by buliding visco-elastic-plastic model and calculating its parameter, and the practical computing and targeted analyzing Zhengzhou loess.2. It is researched on the time-variation mechanics of the construction process of the pile-anchor and soil-nail composite retaining foundation pit excavation. The concept of different properties composite supporting structure was brang up by summarized composite supporting structure and its each component working propertie was analyzed. To have assayed and summarized the time-varying mechanical principles and methods of foundation pit construction process, the time-varying mechanics basic equations of visco-elastic-plastic rheological soil was derived, and the construction analysis formula of anchored-pile combined soil-nail structural was established to analyze the foundation construction process mechanical time-varying effects, and the chance constrained programming model was established also to analyze the bottom stability of foundation pit time-varying process. Using finite element analysis software to build models to simulate the excavation process and the foundation pile anchor effect, make up the traditional algorithm in the external foundation, soil parameters and soil retaining structure coupled with the uncertainty of the role of shortcomings, the practical calculation to better predict the foundation soil, pile deformation and bending moment, also received a good trends of foundation groundwater movement and on the soil and supporting structure, while before the simulation of composite pit and choice of measurement points provides a strong theoretical basis for making the construction process of the numerical simulation can be effective optimization and adjustment.3. It is researched on the mechanical response analysis and the co-operation mechanics of the construction process of the pile-anchor and soil-nail composite supporting structure. Modeling the nonlinear visco-elastic-plastic geotechnical material, the model and theory were used in the pile-anchor and soil-nail composite supporting structure construction process in the visco-elastic-plasti medium, and its mechanical effect was analyzed. Based on time-varying mechanical analysis, pile-anchor and soil-nail compositeed support structure mechanics equations were founded, analyzing and checking the coupling mechanical effect of excavation, support change and soil viscous. According to the mechanical equations of pile-anchor and soil-nail retaining composite structure construction, construction mechanics effect analysis system was set up, which can simulate soil viscousion and excavation of pile-anchor and soil-nail support and supporting. Due to changes in external loads on the mechanical effects of time-varying calculations, and based on finite element method numerical simulation of visco-elastic-plastic equations to achieve the co-operation mechanics and working behaviour of pile-anchor and soil-nail retaining composite structure.4. It is researched on the time-varying earth pressure of the pile-anchor and soil-nail composite supporting structure. In terms of time-varying characteristics during excavation earth pressure, the concept of time-varying earth pressure was firstly proposed, by studying the formation course and change characteristics of the time-varying earth pressure and the active soil pressure of finite soil body in deep excavation construction and the time-history axial force of soil-nail. According to inversion theory, excavation earth pressure was inversed in the light of practical engineering inclinometer-curve data and validation test results were compared, and then to dynamic design foundation pit according to excavation earth pressure changes in force structure by utilizing this method at any time. In order to better calculation and design soil-nailing structure and anchored-pile structure, by estimating combined support system earth pressure distribution mechanism adopting inversion system, so that the joint excavation support structure deformation trends more reasonable, instead be based on deformation estimate the experimental results effectively support system level.
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