Failure mechanism and control countermeasures of surrounding rock at deep large section chamber intersection in the Wanfu Coal Mine

In order to solve the problem of large deformation at the intersection of deep large section soft rock roadway, this paper takes the intersection of kilometer-deep roadway in the Wanfu Coal Mine as an engineering example and applies Negative Poisson's Ratio (NPR) steel anchor cable in roadway support for the first time. By combining numerical simulation indoor test, theoretical analysis and field test, the deformation mechanism of surrounding rock at the intersection of deep-buried roadway was analyzed, and the control strategy with micro NPR steel anchor cable as the core was put forward. Through numerical simulation, the numerical analysis model of roadway intersection with different intersection angles and excavation sequence was constructed, and the impact of two key variables of rake angle and excavation sequence on the stability of surrounding rock at roadway intersection was studied. The optimal dip angle is 90 & DEG; and the optimal excavation sequence was determined as pump house -pump house passage - substation. The mechanical properties of the micro-NPR steel anchor cable were studied through the static tensile test in the laboratory. The results showed that the micro-NPR steel anchor cable showed high constant resistance, uniform tensile, no yield platform, and no obvious necking phenomenon during breaking. Through theoretical derivation, it was calculated that the vertical stress of roadway intersection is 45 MPa, and the bearing capacity of superposed arch composed of micro NPR steel anchor cable is 1257 kN, which is enough to guarantee the overall stability of intersection. Support application test and monitoring were carried out on site, and it was verified that the combined support strategy of short and long micro NPR steel anchor cable has a good control effect on large deformation of surrounding rock at intersection, which provides a new support material and support means for the safety and stabilization control of surrounding rock at intersection.