Kinematic Numerical Analysis And Its Application For Evaluating The Influence Of Surrounding Soil Due To The Construction Of Pneumatic Caisson

Based on the construction characteristics of pneumatic caisson, a type of numerical simulation method to evaluate the influence of surrounding soil deformation and the corresponding control technique are presented in this paper. The innovation mainly includes the following three aspects: (Da type of nonlinear finite element dynamic simulation method and technique to track the entire process of pneumatic caisson sinkage is presented based on the special construct technics of pneumatic caisson. (2) the main parameters to impact the strata deformation and the influence in the sinkage of pneumatic caisson are analyzed quantitatively based on a series of numerical simulations and working-state analysis. (3) a suit of whole construction control technique of pneumatic caisson sinking and surrounding environmental protection measures are presented based on the results of numerical analysis and the special construct technics.This thesis consists of the following eight parts:In chapter 1, the project source and background, research meaning and objective, main content, research program and main innovation are generally introduced.In chapter 2, the present application and development situation of pneumatic caisson method are systematically summarized and the research measures and results of general pit engineering are analyzed. On previous basis, the research results on the surrounding environment effect due to pneumatic caisson construction are discussed in detail incorporating domestic open caisson research data. In addition, non-linear finite element analysis method applied in underground engineering is briefly mentioned.In chapter 3, the process flow of automated pneumatic caisson sinkage is introduced briefly and the main factors which induce strata deformation are presented. Then, based on the dynamic mechanical characteristics and the physical mechanical model of entire process of caisson sub-section sinkage, a type of nonlinear finite element dynamic simulation method and technique to track the entire process of pneumatic caisson sinkage is creatively proposed.In chapter 4, unlike other construction method the pneumatic caisson sinkage real-time monitoring technology and method are presented. Moreover, the measurement project and data are analyzed, including the ground surface settlement, the horizontal displacement of surrounding soil and the heave of soil in the working chamber of the first tunnel air shaft constructed by automated pneumatic caisson method in China.In chapter 5, by the proposed nonlinear finite element dynamic simulation method, the entire process of pneumatic caisson sinkage is simulated and the influence of surrounding soil doformation is analyzed based on the actual construction status incorporating the first tunnel air shaft constructed by automated pneumatic caisson method in China. The ground surface settlement, the horizontal displacement of surrounding soil and the heave of soil in the working chamber are simulated and compaired with the measure data. It is validated that the presented FEM analysis is valid and accurate for the construction of pneumatic caisson.In chapter 6, by the proposed nonlinear finite element dynamic simulation method, the sensitivity of parameters for the influence to adjacent environment are analyzed, including the soil physical parameters: elastic modulus E, cohesion C, angle of internal frictionφ, unloading-reloading modulus E_ur, and the pressure of compressed air in the working chamber, the side friction between the caisson and soil, the temporary retaining wall.In chapter 7, according to the results of soil deformation by numerical analysis and the effect to soil deformation of main factors, the corresponding control techniques and protective measures are proposed, which include the caisson construction technique, the sinkage state control, the air management in the working chamber, the management of construction equipment, the sinkage real-time monitoring, the spout technique outside caisson, the overbreak control under the cutting curb, the setting of temporary retaining wall,local foundation reinforcement and so on.In chapter 8, the summary of conclusions from this thesis with associated objectives for future studies is presented.