Study On The Mechanical Interaction And Wear Between Shield Cutting Tools And Rock Or Soil

With its characteristics and comprehensive advantages,the cross-river tunnel has gradually become an important transportation link connecting rivers,sea areas and even national regions.With the rapid development of cross-river tunnels at home and abroad,the number of constructions is increasing.How to ensure the shield safety and tunneling efficient is a huge challenge.Shield cutting tools for long-distance boring and reasonable selection of the timing of opening the warehouse for checking and changing tools are one of the key issues for safe tunneling under high water pressure and complicated formation conditions.In this paper,with field surveys of shield engineering practices in Dalian,Wuhan,Jinan Metro,etc.,field surveys,theoretical and numerical analysis,laboratory tests,and field measurements were used to develop the wear mechanism,wear laws,and wear prediction models of shield cutters.The main research work and results are as follows.(1)An indoor tool wear test system with the advantages of simple operation,high hydraulic precision,high repeatability,real-time control and data acquisition was independently developed.The model tool and soil material can be replaced as required.The operation is simple and repeatable.It fills the shortage of domestic tool wear test equipment and methods.(2)Many indoor tool wear tests have been conducted.The influences of the tool rake angle,hardness,installation radius,formation water content,particle gradation,equivalent quartz content and mud on the wear coefficient are discussed.A test method for tool wear coefficient of sandy soil based on a linear correlation between the wear coefficient and equivalent quartz content was proposed.(3)Based on the theory of metal tribology,it is proposed that the main source of shield cutter wear is the interaction between metal and rock sample crushing area.The wear is not caused by one single mechanism,but by the interaction of various wear forms.By the analysis of SEM micrograph and energy spectrum after wear test,it is found that the wear types mainly include adhesive wear,abrasive wear,fatigue wear and corrosion oxidation wear.Adhesive wear and abrasive wear is the main component type.The form of wear does not change with the change of tool shape,hardness and formation material.(4)Based on the existing mechanical model of cutting soil and rock breaking with shield cutter,the mechanical model of rock breaking considering the uniform wear of disc cutter,the mechanical model of cutting soil considering the wear of cutter into an arc tip and the mechanical model of cutting soft rock considering the wear of cutter into a plane are proposed.The influences of cutter parameters,stratum parameters and construction parameters on the three models are discussed.The constitutive models of HJC and JC,which can consider deformation and failure,are used to simulate the rock breaking mechanics model.And the accuracy of the theoretical model is verified.the indoor cutting soil and rock breaking experiments are carried out,and the accuracy of the theoretical model is verified from the experimental point of view.(5)Based on the micro mechanism of tool wear,the micro calculation models of adhesive wear,abrasive wear and fatigue wear are introduced.Combined with the mechanical models of shield cutting tools,the wear prediction models of shield cutting tools in soft-hard uneven interactive composite rock stratum,full section hard rock stratum and soft-hard uneven composite stratum are established.Based on the field measurement datas of Dalian and Wuhan Metro,the error is small,which shows that the tool wear prediction models are accurate and reliable.(6)Based on the measured datas of shield tunneling parameters and tool wear in Dalian Metro shield section,the interaction rule of shield tunneling parameters under the change of different strata in the same shield interval was studied.The partial least square method,which integrates multiple linear regression analysis,typical correlation analysis and principal component analysis,is proposed to predict and analyze the wear.The empirical prediction model of tool wear based on the linkage law of the tunneling parameters was established.The accuracy of the prediction model is verified by the subsequent measured data.