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Zhou Y.,University of Science and Technology Beijing | Wang L.,PowerChina Road Bridge Group Co. | Ding J.-F.,Shandong Gold Mining Laizhou Co. | Wu H.-Y.,University of Science and Technology Beijing
Yantu Lixue/Rock and Soil Mechanics | Year: 2016

Based on the in-situ observations of a high-steep rock slope in Baiyun Ebo eastern open-pit iron mine, and the data of mechanical properties of rocks and joints, an equivalent rock mass (ERM) model is developed to describe the joint distribution characteristics at multi scales from laboratory tests, in-situ tests to engineering applications. Uniaxial compression tests are conducted on rock mass ERM models to investigate the scale effect and anisotropic properties of uniaxial compressive strength and elastic modulus. The results show that the existence of joints results in the size effect and anisotropic behaviour of rock mass, and these properties tend to gradually weaken with the increase of rock block size. The representative elementary volume, uniaxial compressive strength and elastic modulus of rock mass in the selected research area are 20 m×10 m×10 m, 1.46 MPa and 3.91 GPa, respectively. The relation between uniaxial compressive strength, elastic modulus and the axial size of rock mass is approximately a gradual exponential function which can directly represent mechanical parameters of rock mass. © 2016, Science Press. All right reserved. Source


Wu S.-C.,University of Science and Technology Beijing | Huang X.-Q.,University of Science and Technology Beijing | Chen F.,PowerChina Road Bridge Group Co. | Chai J.-F.,University of Science and Technology Beijing | Wu H.-Y.,University of Science and Technology Beijing
Yantu Lixue/Rock and Soil Mechanics | Year: 2016

During the process of earthquake and rock fracturing, the fracture mechanisms, source parameters and rupture energy can be obtained by moment tensor inversion. In this paper, the moment tensor theory and its inversion method are introduced in detail; and then a comparison of merits and demerits about three major inversion methods, namely the absolute moment tensor, the relative moment tensor and the hybrid moment tensor is conducted. On the basis of detailed classification and summary of the domestic and foreign references, the application status of moment tensor is reviewed in the fields of hydraulic fracturing, mining and deep tunnel, etc., and combining with its application example in analysis of the focal mechanisms of Hamm Heringen region microseismic events. The results show that the focal mechanisms solution and seismic parameters can be achieved by moment tensor inversion, which played a vital role in the fields of disaster warning and prevention of rock engineering, monitoring and control of hydraulic fracturing, etc. Finally, the factors which influence the accuracy of moment tensor inversion and the insufficient factors including the low precision of microseismic events location and difficult of waveform identification and processing when it is applied to rock engineering fields are analyzed. Meanwhile, the application prospect in the rock engineering field about mining, petroleum engineering, etc., the improvement, as well as the problems need further study are discussed, so as to provide an important reference for applications of moment tensor inversion method. © 2016, Science Press. All right reserved. Source


Wu S.-C.,University of Science and Technology Beijing | Geng X.-J.,University of Science and Technology Beijing | Gao Y.-T.,University of Science and Technology Beijing | Zhao G.-J.,PowerChina Road Bridge Group Co. | And 2 more authors.
Yantu Lixue/Rock and Soil Mechanics | Year: 2015

The longitudinal deformation profile (LDP) can reflect the spatial effect of excavation face in tunneling. Most of the previous studies on LDP, however, ignore the influence of surrounding rock quality and stress level. Based on the Hoek-Brown failure criterion and the finite difference method, functions of LDP which can quantify the difference of spatial excavation effect are given. LDP with various surrounding rock qualities and stress levels can be calculated by using these functions. By means of an error analysis, and by comparing with other equations, the rationality and universality of the proposed method are shown. The results indicate that, when basic quality indices (BQ) of rock masses have the same value, LDP tends to become flatten as the tunnel depth increases, implying that the relaxation process of stress and displacement is slowing down. When tunnel depths are the same, LDP also tends to become flatten as the BQ decrease. These features of LDP behind the excavation face are even more salient compared to that at the front of the excavation surface. The longitudinal deformation at the excavation face depends also upon the surrounding rock quality and the stress level, and its maximum value is not more than 30% of the final longitudinal deformation. ©, 2015, Academia Sinica. All right reserved. Source


Li Y.,University of Science and Technology Beijing | Zhou Y.,University of Science and Technology Beijing | Wu S.,University of Science and Technology Beijing | Wang C.,PowerChina Road Bridge Group Co. | Wang Y.,PowerChina Road Bridge Group Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2015

Based on the finite difference and the particle flow theory, FLAC and PFC code were used as the implementation platform. The bonded particle model was embedded in the finite difference grid, and the communication function of computational data between the continuous and discrete element was compiled using the fish language. The coupled continuous-discrete model of the circular tunnel in 2D plane strain condition was constructed to investigate the deformation and failure mechanism of the surrounding rock under different confining stresses from perspective of macro and meso scales. At lower confining stress, the elastic deformation was generated in the surrounding rock after tunnel excavation. When the horizontal and vertical confining stresses were equal, the deformation values of the surrounding rock with the identical radial distance were the same. Under higher confining stress, the failure of surrounding rock was mainly generated in the upper and bottom plate of the tunnel with side pressure coefficient K>1, while the failure of surrounding rock was mainly generated in the tunnel sides with K<1. Both the failure modes of surrounding rock were the shape of hat. At higher confining stress, the number of cracks was increased and the time of crack formation was extended with the increase of confining stress. The failure of surrounding rock exhibited the zonal disintegration phenomenon with K=1. ©, 2015, Academia Sinica. All right reserved. Source


Yang K.,University of Science and Technology Beijing | Yang K.,PowerChina Road Bridge Group Co. | Wu S.-C.,University of Science and Technology Beijing | Wu Q.-L.,University of Science and Technology Beijing | And 2 more authors.
Gongcheng Kexue Xuebao/Chinese Journal of Engineering | Year: 2015

Considering the broken rock zone support, tangential and radial stress component analytical solutions of each layer in full contact conditions are deduced in a deep circular tunnel based on the elastoplastic theory. Then an optimization objective function of circular concrete lining layers with different elastic moduli is constructed by choosing different failure criteria and different stress states of concrete and rock materials and by introducing the idea of functionally graded materials, that is, when the objective function is minimum, the most reasonable design is that the I, II and III layer structures destroy at the same time. Finally, the elastic modulus and thickness of the lining is designed separately. The analysis of examples shows the following. (1) With the increase of surrounding rock stress, E2/E1 and E2/E3 both decrease. Under the same stress, there is always E2/E12/E3, therefore it is suggested that the elastic modulus of the I layer should be greater than the broken rock zone supporting's. (2) With the increase of surrounding rock stress, the thickness of the I layer increases. Under the same stress, when E2/E1>E2/E3, the thickness of the I layer is always less than that obtained when E2/E12/E3, therefore the thicknesses of the I and II layers can be adjusted by changing the elastic moduli of the I layer and the broken rock zone support. ©, 2015, The Editorial Board of CHINESE JOURNAL OF ENGINEERING. All right reserved. Source

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