Study On Mechanical Characteristics And Anchoring Performance Of Tension Dispersion Twist Bolt Under Different Lateral Pressure Coefficients

With the development of coal mining to the deep,the deformation of surrounding rock is large and has obvious time effect.The shear bearing capacity provided by the traditional tensile concentrated anchor can not balance the deformation pressure generated by surrounding rock after roadway excavation.In order to adapt to the surrounding rock deformation characteristics of coal mine under complicated conditions,reduce the anchoring side stress concentration,to improve the ultimate bearing capacity of the anchored body,enhance the capacity of resistance to deformation of the anchored body,to adapt to the large deformation of surrounding rock and supporting effect,improve the anchoring bolt supporting,developing new products,new materials,new technology and give full play to the bolt anchorage is role of one of the key scientific problems.This paper takes the new type of tension dispersion twist bolt as the research object,and carries out in-depth research on its tensile and anchoring properties,which has important theoretical significance and engineering application value for enriching the bolt support technology and theory of mining roadway.In this paper,the damage characteristics of the bolt anchoring system and the mechanical characteristics of the anchoring interface are explored,the deformation characteristics and engineering mechanical characteristics of deep rock mass are studied,and the deformation characteristics of roadway surrounding rock are recognized.To elucidate the characteristics of in-situ stress of deep rock strata and to understand the variation characteristics of in-situ stress.According to these studies and discussions,numerical simulation,laboratory experiment and theoretical analysis are adopted to analyze the mechanical properties of the new type of tensile dispersion bolt,and the anchorage failure and stress variation rule of the new type of twist bolt under complex stress conditions are studied.The conclusions are as follows:(1)Through the comparison and analysis of the numerical simulation and optimization results of the single screw bolt,according to the parameter of the single bolt is the best when the number of turns is 5,it is inferred that for the double twist bolt,in order to obtain the optimal parameters,the number of screw turns should be 5 and the spacing should be2.When the number of spiral rings of the tension distributed twist bolt is 5,the corresponding pitch of twist bolt is 200 mm.According to the results of the numerical simulation,the anchor model of the laboratory test is designed.(2)In this experiment,twist anchor destruction form are bolt fracture,through the analysis of the process of screw bolt,we deduce the test twist anchor for end USES is the two steel welded together,thus leading to the strength of the bolt has taken a knock in welding place,lower than the strength of the actual bolt,so the stress after the first damage occurred here.By analyzing the anchoring failure modes of different bolt types under different lateral pressure coefficients,it is found that under the same anchoring length and the same lateral pressure coefficient,the anchoring performance of bolt with helical anchoring segment is better than that of bolt with straight bolt without helical anchoring segment.(3)When other conditions of anchor matrix are the same,the tensile load of twist bolt increases with the increase of lateral pressure coefficient.The results show that the anchoring force of twist bolt can be improved under the action of lateral pressure.(4)When other conditions of anchor solid are the same and only the type of bolt is changed,it can be concluded that the large-deformation resistance of double spiral twist bolt is better than that of the other two types of bolt.(5)The bolt body is mainly subjected to tensile stress,and the maximum axial force appears in the vicinity of the hole in the anchorage section.The axial force of the bolt decreases gradually from the drawing end inward,and the distribution of axial force in each anchorage section shows the law of power function.The maximum axial force of bolt body appears at the ends of the two anchoring segments respectively,which indicates that the tensile dispersion twist bolt used in the test has a certain tensile dispersion effect.(6)Drawing load under the action of anchorage feel broken,forming a broken area,increase with the misconduct drawing force,the broken area will continue to increase,for the interaction between bolt and friction is increasing,and under the action of lateral pressure coefficient,the broken area can contact closely with bolt,generated a radial expansion stress.At this stage,the anchoring force is mainly provided by the bulging action of the broken anchor solids.The change of lateral pressure coefficient outside the anchor matrix will change the radial stress of the anchor interface,resulting in the increase of bolt anchoring force,which is the mechanical mechanism that the lateral pressure coefficient will improve the bolt anchoring force.