Abstract
The retained rib displacement accounts for roughly 80% of rib-to-rib convergence in gob-side entry retaining in deep coal mines, which shows significant nonsymmetrical feature and long-term rheological phenomenon. Affected by mining-induced stress, cracks spread widely, and broken zones expand beyond the anchoring range. Without grouting and supplementary support in retained rib, the surrounding rock-support load-bearing structure will be in a postpeak failure state, and the anchoring force of the bolting system will be greatly attenuated. After grouting, the compressive strength of grouting geocomposite specimen is significantly higher than the postpeak residual strength of the intact coal specimen, and it is partially restored compared to that of the intact coal specimen. The ductility of the fractured coal specimen increases after grouting, and it has stronger elasticity and plasticity. Broken rock block can become a whole with coordinated bearing capacity, and its stability is improved after grouting. The grouting technique could restore the integrity and strength of the fractured retained coal rib, repair the damaged bolting structure, and make the surrounding rock and supporting structure become an effective bearing structure again. The research result shows that it is feasible to restore the bearing capacity of the retained coal rib by grouting technique.
Highlights
Gob-side entry retaining is a technique to maintain the original roadways along the gob edges after coal mining
Under the rapid development of surrounding rock control theories, coal mining equipment, support techniques, and support materials, gob-side entry retaining has been successfully applied under various conditions [4,5,6,7,8,9]
The loose and broken surrounding rock of the retained coal rib is the weakest part of the whole roadway, and largedeformation often occurs in this part, which may even affect the stability of the whole roadway [12, 13]
Summary
Gob-side entry retaining is a technique to maintain the original roadways along the gob edges after coal mining. During the long-term rotation and subsiding of the main roof above the retained roadway, the original cracks in the surrounding rock gradually expand, and new cracks appear at the same time. Maintaining the bearing capacity of the retained coal rib has an important effect on the overall stability of the surrounding rock of the retained roadway. (2) e roadway surrounding rock is in a state of highspeed deforming for a long time under the disturbance of the main roof rotation and subsiding, and it still shows a long-term rheological phenomenon after the main roof structure is stabilized. If proper reinforcement support is not adopted, the damaged area of the roadway will further increase, and even completely lose stability
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