Bearing characteristics and parameter optimization of high-strength reticulated shell composite support for deep soft...

With the increase of coal mining depth, deep soft rock roadways face the "five-high" complex environment (high erosion, high ground temperature, high osmotic pressure, high ground pressure, strong disturbance), leading to prominent problems such as severe surrounding rock deformation, floor heave, and large sidewall deformation. Traditional support structures are difficult to adapt due to defects like concrete deterioration and insufficient floor strength. To solve this problem, a composite support system of "high-strength steel mesh shell + shotcrete + bolt" was designed. Taking the roadway of Dingji Coal Mine as the engineering background, numerical simulation (ABAQUS) and similar model tests were conducted to study its bearing characteristics and optimize key parameters. Through orthogonal tests of 16 working conditions, the influence degree of parameters on the support effect was determined as: burial depth of reticulated shell floor > concrete strength > longitudinal reinforcement diameter. The optimal parameter combination (burial depth 1.0 m, longitudinal reinforcement diameter 12 mm, concrete strength C20) achieved a minimum floor heave of 14.32 mm. The stress analysis shows that the roof and floor surrounding rock are mainly under compressive stress (stress concentration at the sidewall foot), while the reticulated shell steel bars mainly bear tensile stress with a peak value of 48 MPa under long-term stable service conditions; under ultimate load, the local tensile stress of the outer secondary arc reinforcement reaches the yield strength (235 MPa), forming a 'compression-dominant, tension-compression synergy' bearing system, forming a "compression-dominant, tension-compression synergy" bearing system. Similar model tests verified that the composite structure delays crack propagation through synergistic action, maintaining good integrity even when the arch foot stress increases from 4.4 MPa to 9.02 MPa under 0.7 MPa load. This study confirms that the optimized high-strength composite support structure effectively improves the stability of deep soft rock roadways, providing theoretical and technical support for complex geological conditions.