The analytic solution for surrounding rock of roadway is of significance for stability analysis and roadway support. However, analytical solution for surrounding rock of roadway which took influences of water seepage, strain softening, dilatancy and intermediate principal stress all into account did not receive much reporting. To promote research in this aspect, a mechanical model simultaneously considering water seepage, strain softening, rock dilatancy, and intermediate principal stress was established based on porous elastoplastic mechanics, and then unified analytical solution for surrounding rock of roadway was obtained. Based on an example, influences of water seepage, strain softening, rock dilatancy, residual cohesion and intermediate principal stress on surrounding rock of roadway were thoroughly investigated using single factor analysis. The obtained results are as follows: radii of plastic zones and surface displacement of roadway would increase exponentially with water pressure increasing and their magnitudes are greater than corresponding values without water seepage considered; with softening modulus increasing, peak circumferential stress location would slightly shift to deeper surrounding rock, while broken zone radius and surface displacement of roadway would increase in a decay velocity; rock dilatancy has little effect on peak circumferential stress and plastic softening zone radius, while broken zone radius and surface displacement of roadway increase linearly with dilatancy coefficient α1 increasing indicating their magnitudes are overestimated if associated flow rule is adopted; with weighted coefficient increasing, stress components in plastic zones at the same distance from roadway center would increase, while radii of two plastic zones and surface displacement of roadway are reduced, i.e., self-bearing capacity of rock is enhanced considering intermediate principal stress effect compared to Mohr–Coulomb criterion; with residual cohesion increasing, peak circumferential stress remains unchanged, while stress components in plastic zones at the same distance from roadway center would increase and radii of two plastic zones decrease significantly. The above results implicated that water seepage effect should be carefully considered for roadway stability under groundwater environment; strain-softening and flow rule of rock should be reasonably analyzed and chosen to accurately predict surface displacement and broken zone radius of roadway; rock bolt length should be increased with softening modulus increasing, while it can be decreased with intermediate principal stress effect considered; grouting measure is an effective measure to improve roadway stability. In short, the research provides a theoretical basis and some practical engineering implication for roadway support.

An innovative roadway layout in a Chinese colliery based on gob-side entry retaining (GER) with thick and hard roof (THR) was introduced. Suspended roof is left with a large area in GER with THR, which leads to large area roof weighting...

Deep underground coal mines are severely threatened by dynamic coal rock disasters such as mine pressure bumps and coal and gas outbursts, and coal seam pressure relief technology is widely recognized as the key measure for mitigating these hazards. To investigate the pressure relief effect of coal seam slot cutting using a diamond beaded wire saw, a combined strategy integrating physical similarity simulation and numerical simulation was applied. The stress distribution characteristics of the coal and rock mass during the wire saw cutting procedure were evaluated, and the influence of beaded wire saw diameter on pressure relief efficiency was further examined. (1) Wire saw cutting can substantially decrease the vertical stress within the coal seam; the average pressure relief rate above the slot can reach as high as 61.70%, and the pressure relief effect is clearly stronger than that below the slot. (2) After slot cutting along the roadway, the fully pressure-relieved zone displays an annular spatial pattern; the pressure relief effect at both ends of the slot and around the roadway is particularly evident, whereas the pressure relief degree in the middle part is comparatively low because of the closure effect. (3) Slot closure causes notable changes in the pressure relief state. Before closure, the pressure relief effect above the slot remains satisfactory; after closure, stress recovery appears in the middle part, but the overall pressure relief rate still stays above 10%, and the pressure relief rate at both ends of the slot and near the roadway exceeds 50%, with the fully pressure-relieved zone still maintaining an annular distribution. (4) A positive correlation exists between the wire saw diameter and the height of the fully pressure-relieved zone. For every 0.5 cm increase in diameter, the height of the fully pressure-relieved zone rises by an average of 0.6 m. When the wire saw diameter reaches 3 cm, the full-thickness and adequate pressure relief of a 3 m thick coal seam can be realized.

Diamond bead wire saw cutting technology for coal seams is an effective approach for relieving pressure and enhancing permeability by forming internal slits within a coal seam. However, the current lack of solid theoretical guidance for cutting force models in loaded coal bodies makes it difficult to accurately predict cutting forces under underground conditions. This study established a three-dimensional cutting force model for wire saw cutting of loaded coal bodies. At the same time, comparative experiments were conducted using a self-developed experimental apparatus for cutting loaded coal with a wire saw. The research findings indicate that, during wire saw cutting of loaded coal bodies, increasing the cutting depth of the cutting force of a single abrasive grain by changing the load on both sides of the coal body changes the removal patterns of abrasive particles at different orientations on a single bead. This leads to a shift from plastic deformation to brittle deformation while widening the cutting contact area on both sides of the wire saw. The interaction of these aspects changes the cutting force exerted by the wire saw on loaded coal bodies. The experimental results revealed that under high-load conditions, the cutting force on the coal further increased during wire saw cutting. This suggests that the expansion of the cutting range plays a more significant role in increasing the cutting force than does the decrease resulting from changes in removal mode. These findings offer valuable theoretical insights for the process design of wire saw coal cutting technology.