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In this study, a 3D DEM model containing a mortar-bolt interface subjected to shearing was established in the context of the simplified rock bolt model (SRBM) proposed in a companion paper. The DEM model was calibrated against a series of laboratory experiments to reproduce the mechanical characteristics of a cement mortar with a uniaxial compressive strength of 30 MPa. The DEM simulation has led to a detailed observation and an in-depth understanding of the mode II progressive debonding of the mortar-bolt interface and subsequent mortar rupture (due to mechanical interlocking). In addition, the effects of particle size of mortar and profile configurations of rebar bolts (i.e., different rib spacings and rib heights) on simulation results were discussed. The numerical findings in the study were validated against laboratory measurements and a broad agreement was observed.

In this paper, we report a new multi-function servo control dynamic shear test apparatus, DJZ-500. This apparatus consists of five parts, including power system, loading frame, servo control unit, cooling system and PC console. The normal load and shear load are measured by load cells with an accuracy of 0.1 kN; normal and shear displacement are measured by LVDTs with an accuracy of 0.1 μm. DJZ-500 has the dynamic and static loading modules, which can perform the force and displacement servo control experiments in both vertical and horizontal directions. In addition, the dynamic loading modules can execute the custom waveforms, which can be utilized to investigate the seismic response of rock and soil masses. We presented six sets of representative tests on sands to demonstrate these functions. Moreover, DJZ-500 can also preform the coupled shear-flow test with the pumping system to investigate the flow behavior in sheared rock fractures. This device makes up for the deficiency of the existing equipment, and promotes the study of frictional properties of geomaterials.

The prior aim of lab testing is the determination of parameters. However, the measurements do not only reflect the rock or soil properties, but contain also, at least to some extent, the influence of the test equipment. Even if measurements are designed to minimize the influence of the test equipment often some measurement values are effected by an unknown amount. Therefore, it is proposed to build detailed numerical models of the test device including the specimen and to duplicate the lab test completely. This paper presents experimental and numerical tests performed with a shear box device. Multi-stage direct shear tests were conducted on smooth plane joints in artificial rock-like material under constant normal loading (CNL) conditions. A 3-dimensional numerical model of the shear box device including the sample was built and the laboratory tests were simulated. The numerical model comprises the loading frame, the hydraulic pistons, the shear boxes and the sample and considers the measuring devices. The numerical model was able to reproduce the non-uniform stress distribution at the joint connected with sample rotation, which in turn produces unwanted frictional forces at the upper shear box. Consequently, only 91–94% of the applied and measured normal force really acts at the joint. Moreover, numerical simulations also shows, to what extend the different parts of the loading frame deform.

The effect of dynamic normal loading (DNL) on the direct shear behavior of a plane joint has been first time investigated using a dynamic direct shear box device. Multi-stage normal loading tests with superimposed normal cyclic excitation at different frequencies were conducted at constant horizontal shear velocity of 3000 μm/min. Experimental results show, that peak shear force increases with increase of normal stress, and amplitude ratio between shear and normal stress decreases with the increase of normal stress. A significant phase shift between peak normal stress and peak shear stress is observed, which decreases with increasing normal load, while the relative time shift between peak normal stress and peak friction coefficient is nearly constant. Impact frequency has little effect on relative time shift. The dynamic normal stiffness is significantly higher than the static one. Finally, a new shear strength criterion is proposed for a joint under constant shear velocity and sinusoidal normal loading.

Understanding the shear-induced evolution of aperture size is critical for controlling fracture permeability in rock engineering projects. This study reports a robust procedure to evaluate the change of aperture size and its effect on fluid flow. A Finite Element Model is first calibrated based on the direct shear tests on a rough fracture to reproduce the uneven deformation of the fracture. A Fluent Computational Fluid Dynamics analysis is subsequently used to illuminate flow characteristics in the fracture without and with asperity deformation. The results indicate that the aperture size of the fracture increases dramatically with increasing shear displacement. However, the aperture size can be reduced slightly due to asperity deformation. Both the shear displacement and asperity deformation jointly influence flow characteristics in the sheared fracture (e.g., the development of eddy flow regions) and the accurate estimation of fracture permeability.

According to the actual conditions in Sanshandao Gold Mine, the cancelling ore pillars mining method was researched. Firstly, a series of tests for the physical and mechanical characteristics of rock mass were carried out and a quality classification system of rock mass applied in coastal metal deposit was established. Secondly, the reasonable demarcation depth of cancelling ore pillars was simulated using the finite element method, and the simulation results show that the ore pillars can be cancelled below the level of −555 m. Thirdly, a novel layer-backfill mining method of room-pillar alternation was designed to reduce the disturbance and settlement of terrain in mining area. Engineering practice shows that the new mining method enhanced the mining output and relieved rock disturbance. Furthermore, the settlement of the roof strata was small and no disaster occurred. The new mining technology effectively controlled the deformation of the terrain, indicating that the mining of the large-scale gold coastal deposit in Sanshandao Gold Mine was achieved safely, efficiently, and with a low loss rate.

The exploration of undersea resources becomes popular as land resources decrease. Researches were conducted with emphasis on the safety and efficiency of undersea mining of the large gold deposit in Xinli District of Sanshandao Gold Mine. A series of tests for the physical and mechanical characteristics of rock mass were carried out, and the three-dimensional geo-stress distribution was tested in the mining area. Further, a similar experimental simulation platform, which revealed the mechanism of water inrush and ascertained the reasonable thickness of the safety isolate layer, was established for the undersea mining. Meanwhile, the feasibility of cancelling the ore pillars and the safety conditions was checked by numerical simulation. The simulation results show that it is safe to exploit the ore body below the −85 m level (presently, the exploitation level is below −160 m in Xinli District), and the ore pillars can be cancelled below the −560 m level. Furthermore, a novel backfill method was designed to reduce the rock strata disturbance and settlement, and the settlement of roof strata was monitored during the mining process. Engineering practice shows that the settlement of roof strata was small and that no disaster happened. This indicates that the undersea safety mining technology of the large gold deposit is achieved in Xinli District.