| When tunneling in the composite stratum,there are at least two strata with different mechanical properties in the excavation face of the shield,which results in complex and variable motion patterns and stress behaviors of the disc cutter in the composite stratum.In soft rock,the disc cutter is often rolling and rolling due to insufficient rolling displacement,which eventually leads to abnormal wear of the disc cutter;at the interface of soft rock and hard rock,the disc cutter is subjected to extreme abrupt loads due to geological changes,the cutter ring will be damaged if there are hidden dangers such as structural cracks in the cutter ring itself.Based on the method of numerical analysis,this paper studies the complex motion and mechanical state of the disc cutter in the composite formation.The research results can provide technical reference for shield type selection and cutter design.The main research results are as follows:(1)The domestic and foreign literatures on shield disc cutter numerical analysis were analyzed and summarized through data investigation.The development history of geotechnical discrete element numerical analysis and cutter excavation simulation,and compare the domestic and foreign research problems.It is found that there are certain discrepancies between the disc cutter motion setting and the actual working conditions in current numerical simulation,and the disc cutter motion setting mode is over-idealized.(2)A detailed analysis and summary of the currently used discrete element contact theory is carried out through data research.The differences between the contact theories are analyzed in detail and the application objects of the relevant contact theories are clarified.On the other hand,a comparative analysis of the currently used commercial discrete element calculation software is carried out.(3)Based on the research of the calculation framework and secondary development methods of EDEM discrete element calculation software,the implementation of complex operations in EDEM is studied.Rapid accumulation of particles is completed in EDEM by the "document reading" method.The basic theoretical calculation process of discrete elements in EDEM that requires mode judgment is generalized.And the stress,temperature and other contact pair information judgment standards in The processing method are clarified in the calculation process,and the method of using the concurrent＿hash＿map container in the TBB tool library to achieve multi-threaded CPU calculation is proposed.Through the analysis of the actual motion mode of the disc cutter,the disc cutter is implemented in the discrete element numerical analysis to perform the rigid body dynamics coupling calculation,and the calculation conditions of the current numerical analysis of disc cutter discrete elements have been improved.(4)Consolidated drainage test and unconsolidated and undrained test for strongly weathered granite were carried out by triaxial tests.The relevant macro-mechanical properties and pattern of the test soil were obtained,which is used as the calculation object of the discrete element of the soft rock.By the method of data investigation,the range of the discrete element calculation parameter of the weak / lightly weathered rock is sorted out.Using the numerical analysis method of rigid body dynamics-discrete element coupling calculation,the effects of penetration in soft rock,tool motion speed,tool shape on tool motion law were analyzed.And the impact of instantaneous shocks caused by different angles of disc cutter penetration at the interface between soft and hard rock was analyzed.Based on the mechanical laws obtained from the numerical analysis,the reasons for the uneven wear of the disc cutter and cutter ring cracking in the composite stratum shield at the project site are explained. |
PDF Full Text Request