Abstract
Controlling the large deformation caused by bed separation failure of thick and soft surrounding rock in gob-side entry retaining is difficult. The deformation and failure modes of thick and soft surrounding rock are summarized and classified based on field research, theoretical analysis, laboratory tests, and actual measurements. Systematic research is conducted on the lithologic characteristics, failure characteristics, and control methods of the surrounding rock. The research findings are as follows: (1) The low strength, softening, and water swelling of thick mudstone, as well as its cataclasis, dilatancy, and long-term creep under strong mining and high stress are the objective reasons for large deformation of the surrounding rock. (2) Due to the weak stability of the surrounding rock-support structure and low collaborative roof side bearing capacity, no complete supporting structure is formed with the supporting system, causing the support body in each area to be crushed one by one, which is the subjective reason for the deformation and failure of the surrounding rock. (3) The deformation and failure characteristics of thick and soft surrounding rock in gob-side entry retaining are primarily divided into eight types: roof bending and sinking type, roof cutting along filling body, rib spalling type, roof fall type, filling body rotation type, filling body crushing type, roof step type, and roof cutting along the coal side. The initial points and key points for a chain reaction of each failure type are determined. (4) The surrounding rock is divided into 10 support zones at four levels, and control technology for “zonal support and overall reinforcement” is put forward. The mechanical effect of the support body in each zone and its role in maintaining the stability of surrounding rock are analyzed. This technology can ensure the integrity of the surrounding rock structure and improve the roof side collaborative bearing capacity.
Highlights
Characteristics of Thick-Soft Mudstone in Huainan Mining AreaAccording to laboratory testing analysis and engineering field results, it is believed that the large deformation of thick and soft surrounding rock in gob-side entry retaining in deep mines primarily originates from two aspects, namely, the natural condition of coal-bearing rock strata and man-made control factors
Introduction e Huainan Mining Area in Anhui Province is defined by complex geological features, including numerous faults and well-developed deep fractures
After long-term practice, a set of new concepts has been formed for the application of deep gob-side entry retaining in the Huainan Mining Area [2], namely, Shock and Vibration
Summary
According to laboratory testing analysis and engineering field results, it is believed that the large deformation of thick and soft surrounding rock in gob-side entry retaining in deep mines primarily originates from two aspects, namely, the natural condition of coal-bearing rock strata and man-made control factors When the former is determined, the latter plays a driving role. From the surrounding rock deformation and failure types, the support type and support strength of surrounding rock structure in gob-side entry retaining cannot achieve coupling, and no complete bearing body is formed in the support system and the bolt (anchor cable) in the area with the stress concentration breaks and the coal-rock mass fractures, further causing the support systems to be successively crushed. Strengthening the support structure of the side of the coal-rock mass plays an important role in guaranteeing roof stability in gob-side entry retaining, which can improve the roof bearing capacity and restrain floor heave. Carrying out floor construction is inconvenient, the support reinforcement requires a large amount of work, and it is difficult to do repair; no-support countermeasures are commonly taken for the floor
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