Zaiquan Wang

Bio: Zaiquan Wang is an academic researcher from Qingdao University. The author has contributed to research in topics: Acoustic emission & Shear (geology). The author has an hindex of 8, co-authored 17 publications receiving 247 citations. Previous affiliations of Zaiquan Wang include Qingdao Technological University.

Energy evolution analysis and failure criteria for rock under different stress paths

Abstract: Triaxial loading and unloading tests on marble specimens under different stress paths were conducted to investigate the characteristics of energy evolution in rock deformation process. Results show that tensile failure occurred in rock specimens under uniaxial compression, while shear failure dominated under triaxial loading and unloading. The energy storage limit of rock specimens under triaxial loading was higher than that under uniaxial compression or triaxial unloading. A nonlinear energy evolution model of rock was established based on the interaction mechanism of energy accumulation and energy dissipation. Results from the theoretical model are in good agreement with the test results. Since the evolution of energy was characterised by bifurcation and chaos, a strain value corresponding to the energy iterative growth factor at the first bifurcation of the energy equation was chosen as the initiation criterion for rock failure. The critical strain accounted for 77%, 72–76%, and 72–81% of the peak strain under uniaxial compression, triaxial loading, and unloading, respectively.

Experimental study of factors affecting fault slip rockbursts in deeply buried hard rock tunnels

Abstract: As civil tunnelling and mining have progressed to ever greater depths, the magnitudes of the stresses resulting from these activities have also risen significantly, leading to increasingly frequent excavation-induced seismicity and rockbursts that pose a great threat to workers and equipment on site. Although considerable research effort has been devoted to understanding the factors that influence strain bursts, few studies have addressed the factors affecting fault slip rockbursts triggered by slip on discontinuities such as structural planes. Thus, in the present work, shear tests were performed under constant normal load (CNL) conditions on joints with rough surfaces and interlocked asperities to study their shear behaviour and acoustic emission characteristics. The effects of rock type, normal stress, surface morphology, infilling, and shear history on slip rockbursts were investigated. The test results indicated that slip bursts occur more easily in granite joints because of either sudden and violent post-peak stress drops or stress drops during stick slip. Static shear failure dominated in marble and cement mortar joints, except when the joint surface was extremely irregular, and rockbursts took place when asperities were sheared off or when tensile ruptures occurred on the joint. The value of the stress drop immediately after peak stress and the value of the average stress drop during stick slip of granite joints both increased with normal stress; thus, the probability and intensity of rockbursts rose with normal stress. The failure modes of the joints were strongly influenced by the normal stress level; fillings and previous shearings (i.e. a shear history) reduce the risk of rockbursts because they reduce the amount energy released.

The Mechanics Of Earthquakes And Faulting

Abstract: • Stability of steady frictional sliding, inertia and the quasi-static limit • work on ps 4; see course web site

Experimental studies of scale effects on the shear behaviour of rock joints

Abstract: The effect of scale on the shear behaviour of joints is studied by performing direct shear tests on different sized replicas cast from various natural joint surfaces. The result show significant scale effects on both the shear strength and deformation characteristics. Scale effects are more pronounced in the case of rough, undulating joint types, whereas they are virtually absent for planar joints. The key factor is the involvement of different asperity sizes in controlling the peak behaviour of different lengths of joints. It is shown that as a results both the joint roughness coefficient (JRC) and the joint compression strength (JCS) reduce with increasing scale. The behaviour of multiple jointed masses with different joint spacing is also considered. It is found that despite unchanged roughness, jointed masses consisting of many small blocks have higher peak shear strength than jointed masses with larger joint spacing. These scale effects are related to the changing stiffness of a rock mass as the block size or joint spacing increases or decreases. Economic methods for obtaining scale-free estimates of shear strength are described.

Case Studies of Rock Bursts Under Complicated Geological Conditions During Multi-seam Mining at a Depth of 800 m

Abstract: A serious rock burst (“4.19” event) occurred on 19 April 2016 in the No. 4 working face of the No. 10 coal seam in Da’anshan Coal Mine, Jingxi Coalfield. According to the China National Seismological Network, a 2.7 magnitude earthquake was simultaneously recorded in this area. The “4.19” event resulted in damage to the entire longwall face and two gateways that were 105 m in long. In addition, several precursor bursts and mine earthquakes had occurred between October 2014 and April 2016 in the two uphill roadways and the No. 4 working face. In this paper, the engineering geological characteristics and in situ stress field are provided, and then the rock burst distributions are introduced. Next, the temporal and spatial characteristics, geological and mining conditions, and other related essential information are reviewed in detail. The available evidence and possible explanations for the rock burst mechanisms are also presented and discussed. Based on the description and analysis of these bursts, a detailed classification system of rock burst mechanisms is established. According to the main causes and different disturbance stresses (i.e., high/low disturbance stresses and far-field/near-field high disturbance stresses), there are a total of nine types of rock bursts. Thus, some guidelines for controlling or mitigating different types of rock bursts are provided. These experiences and strategies not only provide an essential reference for understanding the different rock burst mechanisms, but also build a critical foundation for selecting mitigation measures and optimizing the related technical parameters during mining or tunnelling under similar conditions.