Research On Shield Machine-ground Similar System In 3D Geomechanical Model Test

At present,in the climax of underground construction in China,the shield method is being used more and more.Shield construction is a multi-element,multi-parameter synergistic process.There are still many unruly laws in the construction of shield construction,such as the relationship between shield parameters and surface settlement,deformation of enclosure structure.In order to find out these disciplines,the current more intuitive method is the 3D geomechanical model test.Through the 3D geomechanical model test,a certain discipline is found,and the discipline in the prototype project can be obtained through strict similarity ratio transformation.In this paper,the Beijing sand layer is used as the engineering background,and the 1:5 geometric scale is used as the research basis.The experimental research and theoretical derivation method are used to study the Shield Machine-Ground Similarity System,including the model material ratio test,the design research of the simulated shield machine,and the similar research on the shield construction.This research makes the theory of Shield Machine-Ground Similarity System of 3D Geomechanical Model Test more complete,and it is convenient for follow-up scholars to carry out model tests on shield.The specific results of the study are as follows:1)Through the dimensional analysis method and the equation analysis method,the similarity criterion of each corresponding physical quantity in the similar system is derived.According to the 1:5 similar scale,the corresponding physical quantities of each prototype and model in the ground and shield machine are calculated respectively.2)Through calculation and analysis,the similarities between the simulated shield machine body and the ground are explained,and the general formula of thrust calculation during the tunneling process of the simulated shield machine is summarized,and its accuracy is verified.The formula contains shield machine parameters and model ground parameters,which closely link the simulated shield machine to the model ground.The calculation of tunneling thrust for various simulated shield machines is a very important theoretical supplement for the shield tunneling part in the model test.Through the calculation and analysis,the relationship between the tunneling speed,the cutter speed and the geometric scale in the tunneling process of the simulated shield machine is derived,and the "time" is considered into the similar system,so that the theoretical system of the entire Shield Machine-Ground Similarity System is more perfect.3)Combined with the theoretical research results,through the geotechnical test,the similar materials with the geometric scale of 1:5 were successfully developed,and the specific values of the model materials were given.The sensitivity analysis of the test results was carried out.The influence of Magnetite powder,Silty silt,Silty sand and water content on the physical properties of similar materials in the model;the test process was summarized and the corresponding suggestions were put forward.4)Combined with the theoretical research results,the simulated shield machine with geometrical scale of 1:5 was designed independently.The simulated shield machine can complete the main excavation functions such as cutting out.The main contents include the main shield of the shield machine,namely the cutter head and the shield shell.Main drive,main pusher cylinder and screw conveyor;auxiliary equipment is slag discharge system,reaction frame,originating and receiving base,stop device,hole seal,measuring system and control and operation platform;The corresponding parameters of each system of the shield machine,with reference to these contents,can produce a simulated shield machine.