Post-peak mechanical characteristics of the high-water material for backfilling the gob-side entry retaining: from experiment to field application

Abstract

The gob-side entry retaining (GER) technique enables pillarless coal mining by using roadside backfilling body (RBB). Due to the advantages of fast curing and high bearing capability after a large post-peak deformation, high-water material is commonly used to construct the RBB. The post-peak properties of the high-water material sample and the concrete sample were compared through uniaxial compression test (UCT) and acoustic emission (AE) test. It is found that the uniaxial compressive strength (UCS) of the high-water material sample is 10.29 MPa with a relatively high post-peak strength. When the strain of the high-water material sample is 12.7 times that of the concrete sample, the loading capacity of the high-water material sample remains 59% of UCS. It is shown that the internal damage of the high-water material sample is very slow in the post-peak stage and remains much less undamaged than the concrete sample. The procedures of GER were studied by numerical simulation. The numerical results suggested that the high-water material roadside backfilling body (HMRBB) underwent elastic deformation, followed by plastic deformation as the panel advanced. The loading stress in RBB increased first and decreased to 74% of its peak strength. The final deformation of the backfilling side was 9% of its width. In the field, the post-peak bearing capacity of HWRBB was pronouncedly enhanced after the bolt reinforcement, leading to a 56% decrease of the deformation of the backfilling body side. The deformation and loading capacity of the backfilling body satisfied the safe operation requirements.