Abstract
Deep roadway deformation due to soft rock, rock dip, and horizontal tectonic stress is uneven and asymmetrical primarily in large loose zones. Traditional anchor support is influenced by the yield strength and shear strength of the anchors and has a limited prestress capacity or shear resistance. When the roadway roof is laminated rock or when the roadway passes through layered rock or rock interfaces, interlayer sliding commonly occurs, which can easily lead to anchor cables being sheared off. The tape tunnel in the Zhengling Mine passes through several rock strata and requires anchors to achieve a high shear resistance and prestress. To solve these problems, an anchor cable and C-shaped tube that can bear lateral shear forces were developed, and a full-section anchor cable and C-shaped tube support system were created based on extruded arch theory. Numerical results from FLAC3D show that the new scheme effectively controls surface convergence and plastic zone extension. Field tests have demonstrated that the amount of surface displacement was at least 42% smaller in the new support scheme. The extruded arch formed by the highly prestressed anchor cable and concrete spray layer can effectively control the bulking load within the loose zone, and the ACC effectively resists interlayer shear.
Highlights
Coal-bearing strata are common stratified formations, where roof separation and sliding between rock strata are observed during roadway excavation [1, 2]
A high shear capacity, high pretightening force ACC was developed based on existing anchor cables, and a fullsection ACC support system was constructed based on the shear load distribution characteristics of deep roadways and extruded arch theory
Numerical simulations and field tests proved that the full-section ACC support scheme effectively controlled crushing and swelling loads within the loose zone and resisted interlayer shear forces
Summary
Coal-bearing strata are common stratified formations, where roof separation and sliding between rock strata are observed during roadway excavation [1, 2]. Anchor cables need to resist the axial tension generated by the deformation of the surrounding rock and the lateral shear forces caused by interlayer sliding, resulting in tensile failures and a large number of shear failures. When the pretightening force is increased, the prestress field formed in the surrounding rock expands and the shear stiffness of the anchor system increases significantly. The pretightening force should generally not exceed 50% of the bolt yield load [20], which limits the positive effect of prestressing the jointed rock. A shear resistant anchor cable with a high pretightening force and high shear resistance was developed based on anchor cables and shear load distribution in deep roadways [23]. A full-section anchor cable and C-shaped tube support was constructed based on the extruded arch theory, and an ACC optimization scheme was proposed and tested in the field
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