Experimental Study On Shield Cutters Abrasion Of Earth Pressure Balance Shieldin Sandy Strata

With the large-scale development of urban rail transit construction,the earth Pressure Balance Shield tunneling method plays a more and more important role in the construction of urban subway tunnels by virtue of its superiority.For a long time,the fast abrasion of shield tool has become an important problem to restrict the long distance,fast and continuous tunneling of shield.Especially in sand formation,quartz and other abrasive mineral content high,resulting in serious wear of the tool,easy to cause the knife disk torque too large,low tunneling efficiency,and even the inability to continue digging and forced to open a cabin change knife.The working mechanism and failure mode of the shield cutting tool under the condition of sand stratum are studied.In order to obtain the influence rule of sand soil abrasion characteristics under the main control factors,the paper puts forward the protection measures of shield cutters,which is significant for prolonging the effective service period of shield tool and guaranteeing the long distance,fast and safe excavation of shield tool.In this paper,the use of a wide range of shield construction,a large number of cutting knives easy to wear as the research object.The motion characteristics,cutting mechanism and failure mode are analyzed in detail,The factors affecting the wear of tool are summarized.In view of the common sandy soil strata,the effects of particle gradation,water content and mineral composition on the abrasion of sandy soil were investigated,and the construction parameters were analyzed by orthogonal test,and the shield cutting tool grinding and safety protection measures were studied.The main work is summarized as follows:(1)The motion characteristics of the shield cutter are analyzed,such as axial direction,circumferential direction and cutting depth,the working mechanism and failure mode of the shield cutter are revealed,and it is pointed out that the shield tool is mainly abrasive wear in sand stratum.Through ANSYS finite element software,this paper simulates the process of the surface metal material’s deformation process by pressing the hard abrasive grains such as quartz into the cutting tool and sliding on the surface of metal materials,and studies the relationship between the abrasive and the micro-contact mechanics of the tool.(2)Soil abrasion tests were carried out to analyze the effects of particle gradation,water content and mineral composition on abrasive properties of sandy soil.The abrasion coefficient has a good exponential correlation with the fine grain content of sandy soil and the limited particle size,which decreases with the first increase of water content,and peaks near the optimal water content of sand,it is linearly correlated with the average Rosiwal hardness value of mineral components.(3)According to the actual engineering background,select the test factor level,the key construction parameters,such as the pressure,rotational speed and foam injection ratio,are orthogonal tested for the influence of the wear capacity of the shield cutters.The results of the test data show that the pressure of the soil cabin in the selected parameters has the most influence on the wear,the second is the rotational speed,and finally the foam injection ratio.According to the experimental results,the paper puts forward the method of reducing grinding of shield cutting tool which controls the thrust,adjusts the speed,coordinates the pressure,and improves the multiple construction parameters linkage control.