Papers by Keyword: Mohr-Coulomb Criterion

Abstract: The paper deals with the impact of explosion on the damage development in the structure that forms a boundary of closed or semi-closed space – tunnel - the explosion in which is initiated. In the previous publications of the author the penalty formulation of the problem was used; now Uzawa’s algorithm is applied, which appears to be more promising algorithm accelerating the iterative process of damage development in the structure. Shock waves propagating in the airspace can be described by non-linear conservation equations starting with Euler’s equations which are used to be solved by forward differences of the system of pseudo-linear equations, using Arbitrary Lagrangian-Euler Method (ALE). Conservation equations are formulated for two phases: air and solid. In the solid phase, concrete lining, the time-dependent elasticity of free rectangular elements undergoing the damage, is solved by uniformly distributed boundary elements. The paper is focused on damage to the concrete lining due to impact of the explosion in the tunnel.

Abstract: A structural failure model is presented for the rock mass with a discontinuous weak structural plane. The present model takes into account the effect of weakening of both deformation and strength parameters. And it can degenerates into classical Mohr-Coulomb model or Jaeger model according to corresponding conditions. The numerical tests by Particle Flow Code demonstrate that the capability and performance of the proposed model in capturing behaviors of the mass rock.

Abstract: The strength of massive jointed rock mass can be estimated based on Mohr-Coulomb criterion and Hoek-Brown criterion without making expensive experiment of massive jointed rock mass in site. Only using regression analysis, through transformation，Mohr-Coulomb criterion is compared with Hoek-Brown criterion, the strength of jointed rock mass can be economically obtained. In this paper, based on Geological Strength Index GSI and parameter Jv(Joint/m3), the strength of massive jointed rock mass can be obtained. As an example of GSI 24 for massive jointed rock mass is taken, generalized Hoek-Brown criterion is analyzed linearly and approximately using regression analysis, strength of jointed rock mass can be economically obtained That provide economical and effective method for practical engineering analysis

Abstract: Dalian speed railway tunnel is located in complex soft rock and soil, the road foundation deform and surrounding rock stability control is a concern problem. Along with the unloading process of excavation, surrounding rock moving to inner hole, while exceeding the elastic limitation, the plastic deform and the surrounding rock destroy then occurred. The paper adopted three dimensional elastic-plastic method based on Mohr-Coulomb yielding criterion and carried out numerical simulation of excavation process, in order to analyze and compare the surrounding rock vertical displacement contour, ground surface settlement and damage zone corresponding to different construction sequence. The elastic-plastic numerical method can reflect the damage and destroy character of nonlinear soil material of surrounding rock corresponding to different construction scheme, the simulation result has active guiding meaning for the Dalian speed railway tunnel construction design and dynamic analysis.

Abstract: In order to implement the non-linear Hoek-Brown (HB) shear strength reduction (SSR) on commercially available softwares, this paper derives the relationship between the Drucker-prager (DP) criterion and HB criterion under the condition of plane strain. The equivalent DP parameters can be approximately estimated after serious transformations of parameters between the HB and Mohr-Coulomb (MC) yield functions. To assess the effect of dilation on the stability of slope, the non-associated flow rule, which cannot be contained in the existing limit equilibrium methods, is selected in our analysis, and the SSR-based results of a simple slope indicate that: If the angle of dilatancy ψ is taken to be zero, the factor of safety calculated by the SSR method is very close to that by the limit equilibrium method; if ψ is greater than zero, the factor of safety calculated by the SSR method is greater than that by the limit equilibrium method, and the effect of dilation on the stability of slope can be approximately described by a liner function.

Abstract: In order to solve the question of safe distance between cross-cut and lower lane bolt tunnel and support, aim at geological and mining conditions of north mining area in sanjiaohe coal mine, and analysis mechanism of surrounding rock deformation, analysis the upper roadway surrounding rock stress, displacement and distruction of plastic by FLAC3D determine the minimum distance between the two tunnel and design support scheme on the basis of on-site roadway conditions. Result of this study can provide a reference not only in this mine but also for another similar situtions roadway.

Abstract: It is a well-known fact that an injection of the borehole fluids into surrounding porous rocks often results in fault reactivation,such as during hydrocarbon production from a reservoir, fluid injection for enhanced oil recovery, hot dry rock geothermal energy extraction, and waste disposal or carbon dioxide sequestration. However, no rigorously derived method for the description of spatial and temporal distribution of seismic events and for the estimation of the critical value of pore pressure of a porous rock sufficient for the generation of an microseismic has ever been developed. There a model developed within the context of Biot’s theory of poroelasticity is used to obtain the distribution of pore pressure, then the pore pressure is substituted into a Mohr–Coulomb failure criterion to predict the fault stability and the spatio-temporal cluster of microseismic events in a reservoir. in this model, the Biot system of equations is formulated for the radial symmetry case and is supplemented by the relevant boundary conditions, Then the solution is constructed analytically. A key advantage and the novelty of the proposed approach is it allows one to monitor an influence of pressure applied at the borehole within and surrounding reservoir and to predict the lower and upper bounds for the critical state of a natural rock, and it can be used in different reservoirs.

Abstract: The layered rock mass consists of kinds of stratifications whose mechanical properties are not wholly identical with each other. In order to figure out its strength failure criterion, the variable bond strength failure criterion is proposed depending on Mohr-Coulomb yield criterion and the change law of the strength parameters varying with the dip angle of stratification plane (that is the angle between the maximum principal stress and the stratification plane). What’s more, the criterion is verified by physical model test and numerical simulation adopting assembly language VC++6.0. Compared with the results of physical model tests and numerical simulation, it is shown that the stress distributions and failure regions are elliptic in shape and that the maximum failure regions are vertical to the stratification planes. That the results obtained in the physical model test are compatible with those numerically obtained verifies the correctness of variable bond strength failure criterion.

Abstract: Shuibuya hydroelectric project is the most upstream power station in the Qingjiang cascade development of China. The power plant is designed as underground powerhouse, from seventh to eighth construction step, how to ensure the stability of surrounding rock mass of generator socket and controlling the displacement of lower side wall where the soft stratum located in is a key problem. To solve the problem, the three dimensional numerical model of the underground powerhouse was established based on the results of geological investigation. Then, the detailed construction processes, including the replacement of soft rock, excavation as well as support, were numerically simulated. In order to improve the simulation accuracy, the rock mechanics parameters were back analyzed based on in-situ monitor data before sixth construction step, then using Mohr-Coulomb criterion, the paper simulated and analyzed the damage zones of surrounding rock and displacement of lower side wall corresponding to different schemes. The best scheme was recommended by synthetically considering the stability indexes of each scheme. The study had a scientific meaning to guide Shuibuya project construction. Introduction When the underground cavern is excavated, the initial ground stress is released

Abstract: Based on the experimental and theoretic studies of the frictional materials in literatures, a generalized non-linear strength theory is presented. The generalized strength theory has the same mathematical form as classical Drucker-Prager strength (D-P) criteria. It describes strength characteristics of various materials using a unified formula, and it includes or approximates numerously present strength criterions. The shape of generalized Drucker-Prager (GDP) criteria is convexly smooth curve between the classical D-P criteria (upper bound) and the external contour line of Mohr-Coulomb (M-C) criteria (lower bound) on the deviator-plane, and a straight line on the meridian-plane. Through variation of parameters in the criteria, a series of criterions ranging between these two bounds may be introduced by the unified strength criteria, and the different strength properties of various materials were denoted.