Stability analysis and asymmetric structure control for surrounding rock of deep dynamic pressure weak roadway
摘要
The control of surrounding rock in deep dynamic pressure weak roadways is a critical challenge for coal safe and efficient as underground engineering extends to greater depths. However, existing deep combined support technologies lack a quantitative design theory that accounts for the dynamic migration of the deviatoric stress peak zone (DSPZ) in the surrounding rock and the evolution of yield moment points of the U-shaped steel shed under asymmetric pressure conditions. This leads to empirically determined cable lengths and layouts, ambiguous compensation of weak positions in the steel shed, and poor matching between grouting parameters and the anchorage range. To address this deficiency, a comprehensive investigation integrating field tests, laboratory experiments, numerical simulations, mechanical analysis, and engineering practice was conducted. Results show that: (1) The primary factors contributing to surrounding rock failure are high in-situ stress combined with asymmetric mining-induced dynamic pressure, inherent weakness of the rock mass (uniaxial compressive strength of 10–15 MPa), large-section excavation (20 m2), and an unreasonable original support scheme. (2) The DSPZ migrates with the lateral pressure coefficient k: when k<1, it concentrates in the two ribs and shoulder corners; when k>1, it shifts to the roof, floor, and shoulder corners; and when k=1, it distributes annularly around the roadway. (3) Active support components must fully penetrate the DSPZ, which forms the design criterion for cable length. (4) Under isobaric conditions, the most dangerous point of the U-shaped shed is at the column leg 1.2 m above the floor; under roof eccentric pressure, shoulder corner eccentric pressure, and rib eccentric pressure, the key compensation positions are the arch crown, the loaded shoulder corner plus shed legs, and both shed legs, respectively. (5) Alternating shallow hole (depth 3 m, pressure ≥3 MPa) and deep hole (depth 8 m, grouting≥6 MPa) grouting repairs fractures in the excavation-disturbed zone and reinforces the fractured zone outside the anchorage range, establishing a gradient stress structure of “shallow constraint and deep load-bearing.” Based on these findings, a synergistic technology integrating “full-cable active anchoring, coupled reinforcement of the overall shed-cable system, asymmetric cable compensation at yield bending moment points of the U-shaped shed, and weak rock modification through alternating shallow and deep hole grouting” is proposed. Field application in the Dongpang Mine demonstrates that this technology effectively stabilizes the surrounding rock, confirming its practical viability for similar deep dynamic pressure weak roadways.