Research and application of combined load-bearing shell support for deep soft rock roadway

There are many influencing factors and complex conditions in deep soft rock roadway support. The theoretical research is still in the exploratory stage. Moreover, the method of relying on improving the strength of support materials and the use of grouting bolts can not fundamentally solve the problems and the cost is high. This paper analyzed the stress distribution of deep soft rock roadway surface surrounding rock. The deformation characteristic was that the stress transferred to deep mine and the stress of roadway surface surrounding rock reduced while the deformation increased. It was found that the crucial methods to solve the deep soft rock roadway support problems are to maximize the strength of supporting structure and to reduce the tangential stress around the supporting structure. This meant that the small inner supporting structure should be well designed and the intermediate stress reduction layer should be constructed. The inner supporting structure and the large outer structure of original rock were designed to form a deep soft rock roadway support system to enhance the self-supporting capacity of surrounding rock. According to the requirement of the small inner supporting structure, a full-section anchor shed grout joint support technology of load-bearing shell combined with active and passive support was proposed. On the basis of anchor (cable) support, steel supporting structure and filling structure behind walls formed inner supporting structure with certain thickness and high strength. Therefore, the structure reduced the contact between the roof, the coal wall and the air. At the same time, the filling grouting material spread and solidified in the deep soft rock cracks. The steel frame acted as a radial restraint after certain pressure-relief deformation of the surrounding rock, which could strengthen the surrounding rock load-bearing ring and ensure the stability of the surrounding rock. In the windstone gate restoration project of No.2 West Mining Area of Dingji Coal Mine, a full-section anchor shed grout joint support technology of high preload anchor cable + U-shaped steel shed + anchor shed grout injection was adopted. And the intermediate stress reduction layer was constructed by deep hole blasting method. The mine pressure observation results showed that the maximum value of the two sides of the roadway was 349 mm, the maximum value of the roof subsidence was 323 mm and the roadway deformation was effectively controlled.