Failure analysis and control technology of intersections of large-scale variable cross-section roadways in deep soft rock

Abstract In deep underground mining, achieving stable support for roadways along with long service life is critical and the complex geological environment at such depths frequently presents a major challenge. Owing to coupling action of multiple factors as high stress, adjacent faults, cross-layer design, weak lithology, broken surrounding rock, variable cross-sections, wide sections up 9.9 m, clusters nearby chambers, there was severe deformation breakdown in No. 10 intersection roadway large-scale cross-section − 760 m level coal mine. As are insufficient examples engineering methods pertaining described above, numerical calculation model oversimplified theory underdeveloped; therefore, it imperative develop an effective system stability sustenance roadways. this study, quantitative analysis through field observations, borehole-scoping, ground stress testing carried out establish FLAC 3D crossing model. This combined strain softening constitutive (surrounding rock) Mohr–Coulomb (other rock formations) models construct compression arch mechanical soft based on quadratic parabolic Mohr criterion. An integrated control technology bolting grouting that mainly composed high-strength hollow cable bolt equipped modified cement materials high-elongation developed by analyzing strengthening properties before after bolting, Heok-Brown result on-site practice, following conclusions drawn: (1) The plastic zone roof cross approximately 6 environment, tectonic nearly 30 MPa, severely fractured. (2) progressively increases from small large almost doubling largest cross-section. concentrated top plate shoulder decreases two sides bottom corner. range concentration close passageway wider higher. (3) 7 m-thick reinforced constructed under scheme has bearing capacity enhanced 1.8 2.3 times increase thickness structure 1.76 compared original scheme. (4) parameters c φ anchoring causes significant σ t ; pulling force beneath new material more than twice ordinary grout, according test, supporting shows 7.24 compacted strengthened addition providing strong foundation (cable). On-site monitoring 60-days convergence less mm, indicating successful.