Research On The Mechanism And Application Of Deep Tunnel Support Based On Unified Strength-bearing Ring Theor

With the development of mining to the deep,the roadway is subject to challenging circumstances like high stress,powerful mining,and fault fracture zone.The insufficient strength of traditional steel support in the stability control of roadway surrounding rock is one of the difficult problems restricting the safe and efficient production of the mine.Taking the deep highstress roadway of Jinfeng Gold Mine in southwest Guizhou as the engineering background,aiming at the support problems of deep roadway,this study analyzes the deformation and failure law of deep roadway and its influencing factors by means of a comprehensive combination of field investigation,theoretical analysis,physical test and numerical test,and studies the bearing performance of short concrete-filled steel tube columns and supports.A unified strength-bearing ring theory roadway mechanical model was established,Clarification of the deep roadway support mechanism and application of the research findings to engineering practice.The following are the key findings of the study:(1)Through field investigation,surrounding rock physical and mechanical tests,and raw rock stress measurement and analysis,the deformation and failure laws of deep roadway in Jifeng Gold Mine are obtained,which are mainly manifested as large displacement of two sides,large initial deformation rate,long duration of deformation and failure,asymmetric deformation of roadway and large fracture at the intersection.Factors influencing large deformation of deep roadway mainly include large section of roadway,low strength of surrounding rock,poor quality of rock mass,large horizontal ground stress,frequent mining disturbance and low support strength.(2)The bearing capacity and mechanical properties of short circular and square concretefilled steel tubular columns with different wall thickness and concrete strength were studied by theoretical calculation and axial compression test combined with digital speckle monitoring technology.The results show that the axial compression capacity,flexural strength and flexural capacity of the circular CFST short column are greater than those of the square CFST short column when the amount of steel used,concrete strength and wall thickness are the same.(3)The interaction and coupling model between concrete filled steel tube and deep roadway was established by ABAQUS,and the bearing performance of round and square concrete filled steel tube supports was examined under different lateral pressure coefficients(1.0,1.2,1.4).The results show that the force distribution of the two kinds of supports is symmetrical,and the deformation is positively correlated with the lateral pressure coefficient.When the lateral pressure coefficients are the same,the maximum stress and deformation of circular cfsts are smaller than those of the square concrete-filled steel tube bracket.(4)By introducing the unified strength criterion into the bearing ring theory,a unified strength-bearing ring mechanical model was established,and the geometric thickness of the unified strength-bearing ring,the mechanical boundary conditions and the criterion of roadway stability were defined,and the supporting mechanism between the anchor net spray and concretefilled steel tube support was clarified.When b=0,the unified strength-bearing ring roadway stability criterion is consistent with that of bearing ring roadway stability criterion,indicating the correctness of the unified strength-bearing ring theory.The theory takes into account how the stability of a bearing ring highway is affected by intermediate primary stress.(5)Aiming at the difficulty of roadway support in the middle section of 0m,A deep roadway support scheme based on unified strength-bearing ring was proposed and applied in the field.In non-test section,the displacement of two sides is 221 mm,and the subsidence of roof is 93 mm.In the test part,two sides have moved 39 millimeters,and the ceiling has sunk 25 millimeters.The roadway’s two sides and roof each had a reduction in deformation of 82.35% and 73.12%,respectively.In the test stretch,no evident concrete cracking appeared in the surrounding rock of the roadway after the construction of concrete-filled steel tube supports.This demonstrates that concrete-filled steel tube support method is effective.CFSTS can effectively solve the large deformation problem of deep high-stress roadway in karst area.