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Providing support in deep and complex roadways is one of the major challenges in the mining industry; thus, a square-steel confined-concrete (SQCC) support system has been proposed and an SQCC quantitative pressure-relief arch (SQCC arch) has been developed for roadways in complex environments that are subject to high stress or are affected by faults or mining operations. A self-developed full-size large-scale test system for underground confined-concrete arches has been used to perform indoor comparative tests on a vertical-wall semicircle SQCC arch vs. a U29 arch, which is commonly used in mining. A combination of an indoor test and numerical analyses has shown that the SQCC arch deformation and failure pattern is ‘bulged arch top, retracted arch leg’. The most severe damage position occurs in the area between the middle of the arch leg and the spandrel, and the quantitative pressure-relief device can be used effectively. Compared with the U29 arch’s ‘Z’-shaped bending failure pattern at the arch leg, overall out-of-plane instability and rapid decline in bearing capability, the SQCC arch’s ultimate bearing capability is 2.15 times that of the U29 arch. In addition, the SQCC arch has an excellent bearing capability in the late stage. The SQCC arch support system is implemented in the fault-affected Zhaolou coal mine roadway to reinforce control over the surrounding rock. After 157 d, the maximum deformation at the arch measurement point is 33.1 mm, and the surrounding rock deformation is well controlled. [ABSTRACT FROM PUBLISHER]

The deep roadway with thick top coal is a typical roadway difficult to support in deep mining project, and resolving this sophisticated problem to control the stability of surrounding rock is of great significance in safety production of coal mines. In order to explore the surrounding rock deformation and failure mechanisms of such deep roadways, with Zhaolou coal mine in Juye mining area of China as the engineering background, a large-scale geomechanical model test was carried out. The displacement and stress evolution laws of surrounding rock supported by the pressure relief anchor box beam system were researched. Meanwhile, the related results validate and analyze main failure characteristics and mechanisms of the surrounding rock by comparing with field test. [ABSTRACT FROM AUTHOR]

Surrounding rock control is a tough issue in roadway with soft rock in deep underground. To solve this problem, the original supporting scheme is monitored and analyzed on site with Liangjia coal mine of China as engineering background. Located in Longkou seashore mining area, Liangjia coal mine is a typical deep mine with soft rock in China. The analysis shows that roadway deformation is large with a big damage range; anchor bolts are generally in seriously broken surrounding rock; the support potential fails to be played; the support strength of arch is insufficient and the post bearing capacity is low. All of these mainly lead to the failure of the roadway bearing capacity. Numerical test is conducted with the consideration of arch strength, geostress, mechanical parameters of surrounding rock and other factors; it is to comparatively analyze the deformation of surrounding rock, the range of plastic zone and the mechanical properties of support components under different factors; therefore, the failure and control mechanism are defined on deep roadway with soft rock; and a concept of “high-strength, integrity, and pressure-relief” is proposed. Meanwhile, a confined concrete (CC) support system is developed; and a laboratory comparative test for full-size arch is carried out on its core component - CC arch and the conventional U36 arch as well. The research shows that the instability and failure of the entire U36 arch is caused by partially bending and buckling of the arch, and its bearing capacity is drastically reduced. The bearing capacity of CC arch is 2.03 times compared with that of U36 arch, and also has a good post bearing capacity. On the basis of these numerical and laboratory tests, a comparative test is carried out on-site. The monitoring results in the test show the rock deformation in CC support testing section is only 22.4% of that in U36 arch support; and no yield and failure phenomenon occurs in CC support test section, which proved the effectiveness of CC support system on surrounding rock control. [ABSTRACT FROM AUTHOR]