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Fan H.,University of Sichuan | Zhang S.,Henan Polytechnic University | Gou X.,University of Sichuan | Wang Q.,University of Sichuan | Wang Q.,State Key Laboratory for Geo mechanics and Deep Underground Engineering
Yingyong Lixue Xuebao/Chinese Journal of Applied Mechanics | Year: 2011

International Society for Rock Mechanics (ISRM) proposed cracked chevron notched Brazilian disc (CCNBD) to test mode I fracture toughness of rock, however, calibration of the critical dimensionless stress intensity factor, i.e. Y*min, should be further improved to achieve better accuracy. In this paper, wide-ranging Y*min values are recalibrated systematically, with valid range of the geometric parameters for CCNBD defined as 0.44≤αB≤1.04, 0≤α0≤0.69, 0.4≤α1≤.8. Three-dimensional numerical analysis is done with finite element method, totally 435 CCNBD specimens are calibrated to derive their Y*minvalues, based on these results, u, v values used in the formula to calculate Y*min for CCNBD are completely modified. Furthermore, an approximate expression used to calculate CCNBD directly without using the tabulated u, v values is presented, the accuracy of the expression is within 1.87% as compared with the calibrated Y*min values. For the Y*min value of the ISRM suggested CCNBD standard specimen, 0.84 was the value given by the ISRM, 0.947 was the value obtained with the slice synthesis method, 0.943 was the value derived with the sub-model method, while 0.957 is the value presented in this paper. It is especially emphasized that for any CCNBD specimen its Y*min value should stand properly between the corresponding upper bound and lower bound, this criterion is vital in judging whether the Y*min value is reasonable or not. Source

Li D.J.,State Key Laboratory for Geo mechanics and Deep Underground Engineering | Li D.J.,China University of Mining and Technology | Ding Z.L.,China University of Mining and Technology | Li C.L.,Yanshan University | And 2 more authors.
Journal of Engineering Science and Technology Review | Year: 2014

The corner bolt is proved to be effective in the control of floor deformation of roadway, and the relevant studies on bolting mechanisms are of great significance in improving roadway stability. In this paper, two types of shear tests on six forms of bolts are performed by using self-designed shear test device, the electro-hydraulic servo triaxial testing system. The shear characteristics of different types of bolts are obtained. The results show that different bolt rods or different internal filling conditions result in large differences in shear resistance and different deformation adaptability. We find that the filling materials added can improve the shear performance of bolt significantly, and the bolt with steel not only can improve the strength of bolt body, but also has the bimodal characteristic that makes the bolt have the secondary bearing capacity and withstand larger deformation range during the process of shear, and shows a better support performance. Hoping to provide the experiment basis for support design and field application in the future. © 2014 Kavala Institute of Technology. Source

Jia F.,State Key Laboratory for Geo mechanics and Deep Underground Engineering | Jia F.,China University of Mining and Technology | Lv H.,State Key Laboratory for Geo mechanics and Deep Underground Engineering | Lv H.,China University of Mining and Technology | And 4 more authors.
2011 International Conference on Electric Technology and Civil Engineering, ICETCE 2011 - Proceedings | Year: 2011

The influences of replacement of Portland cement by ground limestone as well as its specific surface on the mortar strength were discussed. The binder was composed of cement and limestone, which was prepared by eight replacement levels of limestone powder (0, 5, 10, 15, 20, 25, 30 and 35) of binder by mass and four levels of specific surface Blaine (350, 600, 800 and 1000m 2/kg). The specimens demoulded were cured in water, which was controlled temperature (20+1) C until 3d, 7d, 28d, 56d and 90d and then the strength were tested. The results demonstrate that the compressive strength and flexible strength of samples incorporating different replacement levels and various specific surfaces of limestone powder increases steadily with ages. The strength decreases generally with the increase of replacement level of limestone powder when the SSB is constant, while as the strength is higher than controlled mortar without limestone powder when the replacement level is low and the effect becomes visible for flexible strength. The composite cement strength with 15% limestone powder replacement meet the requirement of the 52.5R. Furthermore, the hydration products and microstructure are investigated by scanning electron microscope (SEM) at different ages and the hydration characteristics of mortar with limestone powder replacement is theoretically revealed. © 2011 IEEE. Source

Xia J.-W.,State Key Laboratory for Geo mechanics and Deep Underground Engineering | Xia J.-W.,China University of Mining and Technology | Sun D.-M.,China University of Mining and Technology | Dong Z.-Z.,State Key Laboratory for Geo mechanics and Deep Underground Engineering | Dong Z.-Z.,China University of Mining and Technology
Gongcheng Lixue/Engineering Mechanics | Year: 2012

Based on the fuzzy membership degree theory, fuzzy rotation angle of joint is provided in terms of its flexible displacement. The element stiffness matrix of space flexible beam and the relationship between fuzzy rotation and spring stiffness were derived based on the concept of fuzzy rotation angle of joint. The axial stiffness of truss member was presented considering the effect of connection slippage. Program of space flexible joint model with the function of analyzing slippage of joints (SFJS) was developed in MATLAB. SFJS is used to obtain the axial force of legs and diagonals of JJ3-type transmission line steel tower. The numerical results and full-scale test results matched fairly well. By means of the space flexible joint model with slippage, the internal force distribution in the bar of transmission line steel tower can be solved more accurately than the traditional space frame model. The SFJS provides theoretical foundation for design, calculation and protection of transmission line steel tower located in mining areas. Compared with the traditional modal of space truss, SFJS can calculate more accurately the internal force of truss members induced by the deformation of foundation. Source

Yang X.,China University of Mining and Technology | Hou D.,China University of Mining and Technology | Tao Z.,China University of Mining and Technology | Peng Y.,State Key Laboratory for Geo mechanics and Deep Underground Engineering | Shi H.,State Key Laboratory for Geo mechanics and Deep Underground Engineering
International Journal of Mining Science and Technology | Year: 2015

Landslides have occurred frequently in the Luoshan mining area because of disordered mining. This paper discusses the landforms and physiognomy, hydro-meteorology, formation lithology, and geologic structure of the Luoshan mining area. It also describes the factors influencing the slope stability of landslide No. III, determines the general parameters and typical section plane, analyzes the stress-strain state of the No. III slope, and calculates its safety factors with FLAC3D under saturated and natural conditions. Based on a stability analysis, a remote real-time monitoring system was applied to the No. III slope, and these monitoring data were collected and analyzed. © 2015. Source

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