Experimental Study On Deformation Laws Of Surrounding Rock In Shield Tunnel Of Composite Formation By Transparent Rock-and-Soil

With the continuous acceleration of urbanization process,the number of urban subway construction was increasing,and the application of shield method has become more and more extensive.Shield tunnel construction will encounter various accidents in the composite formation of Upper soft and lower hard as internal deformation of surrounding rock,such as face failure,surface subsidence and so on.The currently process of construction can not accurately explore the inner deformation evolution laws of surrounding rock,so observation and analysis internal deformation of surrounding rock show very important.At present,domestic and foreign scholars has made remarkable achievements in the study of deformation evolution laws research about shield tunnel in the composite formation,but the study of evolution laws of the internal deformation of surrounding rock was not comprehensive and profound.With the help of combined transparent rock and soil experimental technology and numerical simulation software(FLAC^3D)method depth study the internal deformation evolution laws of surrounding rock of upper soft and lower hard in the process of shield tunnel construction.The main research results are as follows:?1?A set of physical simulation experiment system of transparent rock-and-soil of shield tunnel was developed,that composed of optical platform,vacuum equipment,laser,image acquisition device,test model box and excavation equipment.Among them,model box and excavation device can simulate the stress release effect in the process of tunnel excavation,at the time,by increase the sealing and fastening device solve the liquid leakage problem between model box and excavation equipment,improve the bearing capacity of model box.?2?Through exploring study,the selection principle and configuration process of similar materials about transparent rock-and-soil were further defined,the method of reusing transparent sand material was put forward and influence-factors of the transparency of transparent soil samples were analyzed,the basic physical and mechanical properties of transparent sand were studied,a transparent composite layer with different particle sizes was configuration preliminary,at the same time,two methods for making cavity in a transparent sand model was explored.?3?It was found by model test and numerical simulation that compound with tilted strata of surrounding rock deformation laws and homogeneous formation had obvious differences,and show the distinctive layered effect,the deformation of surrounding rock was serious in upper strength of lower,the deformation of surrounding rock was smaller in lower strength of large;The existence of cavity had a significant influence on the deformation law of the surrounding rock mass,and the deformation velocity of the cavity lower rock-and-soil mass was intensified,and the upper rock-and-soil mass was inhibited.?4?It was found by studying the transparent compound formation configurationed with size range 0⁰.25 mm with 1³ mm of quartz sand that maximum internal deformation of surrounding rock was measured in vaults by used digital photogrammetry marked point and no marked point,when retreating distance of simulate excavation was 6.0 mm,the maximal displacement was 5.0 mm by marked point technique;the maximal displacement the vault was4.0 mm at the top of arch and was 1.5mm at the bottom of arch by no marked point technique,the maximum displacement differential of arch at the top and bottom was about 2.7 times.?5?It was found by analysis of engineering problem that layered effect of internal deformation of surrounding rock.was obviously in the composite formation,stress release of face was caused by shield tunnel construction and deformation at the top of arch was bigger than bottom,lead to accident,such as face failure,surface subsidence and so on.The selection and design of shield tunnel construction and support parameters should accordance with the internal deformation law of surrounding rock.