Study On Rock-Breaking Mechanism Of Shield Hob In Contact Surface Of Upper Soft And Hard Composite Strata

This paper takes the shield construction of Yaozhuang Station-Wenboyuan Station of Xuzhou Metro Line 2 as an example.For the case where there are many soft and hard composite strata in the shield section and the construction is difficult,the theoretical calculation and numerical simulation method are used to analyze and study the whole process of rock fragmentation in the fracture zone of shield hob.This paper comprehensively expounds the research status of shield hob rock-breaking,which provides a theoretical basis for this research.This paper comprehensively expounds the research status of shield hob rock-breaking,which provides a theoretical basis for this research.According to the existing survey data,the characteristics of the study interval rock strata are analyzed,which is used as the preliminary analysis basis for analyzing the rock stratum damage during the rock-breaking process of the shield hob.The discrete element method is used,and MatDEM software is used to analyze the whole process of rock breaking by hob under the form of shield hob cutter,aiming at the physical and mechanical characteristics of different rock formations and the physical and mechanical characteristics of rock strata,which provides guidance for the selection of rock breaking parameters of shield hob cutters in practical construction.Some conclusions are formed by analyzing the results of the calculations:(1)During the rock-breaking process of the upper and lower soft composite strata of the shield hob,there are mainly crushed rock,sheared rock and tensile fractured rock.Under the synergistic effect of three types of rock breaking,the rock formation below the contact surface of the hob is fractured and fractured,and finally a fracture pit is formed.The factors that determine the volume and shape of the fracture pit are the nature of the rock mass,the slope angle of the hob cutting edge,the thickness of the hob,and the radius of the hob.(2)During the rock-breaking process of the shield hob,the most influential factor for the rock-breaking effect of the shield hob is the rock dip angle,the form of the second-order shield hob,the rock-breaking effect of the shield hob and the rock-breaking direction and the tendency of the rock stratum.Relationship has nothing to do.(3)Through comparative analysis,the rock breaking effect of the shield hob under the optimized conditions is higher than that of the shield hob under the actual engineering parameters.Selecting a reasonable optimization scheme for different rock dip angles can improve the rock breaking effect of the shield hob.