Pressure Arch Study Of Non-circular Tunnel Surrounding Rock

Domestic and foreign scholars have conducted lots of research on pressure arch,but studies almost are concentrated on circular tunnel,and the methods of discriminating pressure arch boundary have not been unified.Neither the factors that affecting pressure arch nor the application of pressure arch theory in engineering is deeply studied.Therefore,comprehensive analysis method that containing theoretical analysis,model test and numerical simulation is adopt to study the morphological characteristics of the plastic zone and the pressure arch of non-circular tunnel,and the application of pressure arch theory in engineering is studied.The main research work is as follows:1.Based on the plastic zone distribution formula of the circular tunnel that deduced from the elasto-plastic theory,the factors that influencing the plastic zone distribution of the tunnel surrounding rock are studied.The plastic zone of the circular tunnel is drawn by means of Matlab,and the circular tunnel excavation simulation is performed by using FLAC 3D.The plastic zone distributions that resulted from elasto-plastic theory analysis and the numerical simulation are compared.2.The relationship between plastic zone and pressure arch is studied by physical model test and numerical simulation test.It is found that the plastic zone is closely related to the pressure arch,traditional pressure arch discriminant methods which simply treat the shear stress increasing part as the pressure arch without considering the plastic zone are proved wrong.According to the results of model tests and numeral calculations,new judgment criterion and judgment method of pressure arch are proposed.3.According to the new pressure arch criterion and method,the morphological characteristics of plastic zone and pressure arch of non-circular tunnels under variousinfluencing factors are studied by numerical simulation.4.The pressure arch theory is applicated to surrounding rock stability analyzing.Through numerical calculations,it is found that applying a lining contributes to the formation of pressure arch,and based on pressure arch theory,the time to apply the lining is analyzed.