Papers by Author: Quan Sheng Liu

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Authors: Yu Yong Jiao, Quan Sheng Liu, Shu Cai Li
Abstract: This paper presents a three-dimensional numerical model for simulation of blocky rock structures based on static relaxation approach. The proposed method utilizes static equilibrium equations to calculate the displacements of blocks, compared to Newton’s second law applied by the traditional DEM. In order to obtain displacements simultaneously, the technique of global stiffness matrix is introduced in to form the global equilibrium equations. Because large displacements come from the accumulation of small displacement increments, an iteration procedure is adopted in the calculation. A C++ program is developed based on the proposed algorithm, and an illustrative example is computed for verification.
Authors: Xiao Yan Liu, Cheng Yuan Zhang, Quan Sheng Liu
Abstract: Task_D of the DECOVALEX_THMC project focus on predictive analysis of the long-term coupled processes(up to 10,000 years) in two generic repositories, FEBEX type and Yucca Mountain Project type for comparison. To better understand the coupled THM processes and their influence on the system behavior, we have introduced a set of generic coupled THM governing equations. Basing on these equations, we develop simplified models according to given Task_D model inception phase request. Boiling model and empirical bentonite swelling model are introduced into general simulation which makes model more practical. Our numerical code FRT-THM upon this practical models is developed and used in two BMT case study of Task_D. Simulation results are shown and verified in the 3rd and 4th workshop of DECOVALEX_THMC in 2005. There is a good agreement with results of different participant teams which enhances confidence in prediction of coupled THM processes.
Authors: Cheng Yuan Zhang, Xiao Yan Liu, Quan Sheng Liu
Abstract: Stochastic simulation method considering the heterogeneity of hydraulic conductivity is suggested in this paper. Hydraulic field is simulated by using our FEM code for THM coupling processes. The results show that hydraulic gradient at different location around the cavern is differently dependent on water-curtain pressure in deterministic model. A probability range of hydraulic gradient at each point with 10m space between each was examined by means of stochastic realization of spacial variability of hydraulic conductivity. These analyses are contributed to determine the values interval of water-pressure and groundwater flux into the cavern with a given security for LPG containment design and evaluation considering the spacial variability of hydraulic conductivity.
Authors: Xiao Yan Liu, Cheng Yuan Zhang, Dao Ying Xi, Quan Sheng Liu
Abstract: Most rocks are saturated or partly saturated with different fluids under different depth, temperature and pressure conditions. It is generally acknowledged that fluids have the most important effect on the attenuation and dispersion of seismic waves. There exists a relation between frequency- and temperature- dependence on rock’s seismic properties. It is not yet clear in literature whether there exist other equally important attenuation mechanisms as that in Biot’s model, since there are other sources of dissipation, also related to fluids, that are not considered in Biot theory but that may also contribute to the overall dissipation of seismic energy. Identifying the precise relaxation mechanisms is still the subject of experimental and theoretical research. In this article, a series of experiments are conducted on dry and saturated rocks (sandstone, marble, granite) at different temperatures and frequencies to find the attenuation mechanism of interaction between rock skeleton and pore-fluid. Fluid viscosity generally depends on temperature, so the effect of pore fluid on attenuation is confirmed in terms of apparent viscosity variation of rock caused by the change of pore-fluid conditions (such as frequency or temperature). Based on our experimental data, we develop a new model of macroscopic apparent viscosity in saturated rock which is consistent with the nonlinear relaxation law. It helps to derive the analytical expressions to compute velocity dispersion and attenuation as functions of frequency and temperature.
Authors: Bin Liu, Quan Sheng Liu
Abstract: Based on the stress characteristics of freeze shinking shaft lining at construction and operation stages, it is set up that The anisotropic damage model including initial damage, which suit to make Damage and Fracture Mechanics analysis for the shaft lining. A 3 dimensional anisotropic damage program is compiled using FEPG software, which take the following factors into consideration: temperature, conduction conditions, concrete facture energy and its aggregate gradation. Take the liangbosi mine shaft lining for example, its damage evolutionary process under complicated stresses such as permanence field stress, the gravity and vertical additional stress changed with time is obtained. It is discussed that the facture’s position and its development process, and the mechanical mechanics of the shaft lining structure failure.
Authors: Bin Liu, Quan Sheng Liu, Yue Xiu Wu
Abstract: It is common to use the damage mechanics to study the deformation of fractured rock mass. The geometric damage tensor is always used to describe the effect of distributed joints on mechanical properties of rock mass. The disadvantages of the traditional determination method about geometric damage is that the natural section of rock mass, mining section and the measurement section are not perpendicular to each other. In this paper, a method combining with the probability theory and field scale line method is adopted to determine the geometric damage tensor. This method is convenient and fast. The solution of initial damage in damage evolution equation can be settled with this method. An effective proof is provided for the later analysis of damage stress of fractured rock mass.
Authors: Quan Sheng Liu, Yun Hua Hu, Yu Yong Jiao
Abstract: The instability of the roadway is a general problem for most of the deep mine roadways due to high geo-stress and large deformation, which require that the more reasonable and effective support measures are designed and employed. By applying the 3-D explicit finite difference software FLAC3D, this paper establishes the numerical calculation model of a roadway located in about 700m depth based on the geologic condition of the site which the roadway is in as well as the results of the in-situ stress measurement and the laboratory tests for the physical-mechanical properties of rock. Furthermore, three different support scenarios are raised and the optimum one is determined by calculating and analyzing the distribution of the plastic zone and displacement field in the rock surrounding the roadway with the above three scenarios.
Authors: Yong Shui Kang, Quan Sheng Liu, Kai Shi, Xiao Yan Liu
Abstract: The modeling method for freezing tunnel with fractured surrounding rock is discussed. Frost weathering of rock in cold regions poses serious threat to the stability of geotechnical engineering. Fracture in the freezing rock plays an important role in the mechanical features of the rock mass. However, most of the previous study on freezing rock considered the rock as continuous media, in which the effects of fracture are not reflected sufficiently. This paper overcomes the above-mentioned insufficient and considers the fracture as an important factor while modeling. The model of frost fracture is built by AutoCAD and then transferred into ANSYS for meshing, and finally imported into FLAC3D for calculating by converting procedure. The method of equivalent coefficient of thermal expansion is used to simulate the expansion of water while freezing. The stress and thermal fields after some steps of calculation are ultimately simulated and the influence of fractures is reflected in the results.
Authors: Chong Ge Wang, Zhao Qing Song, Wei Zhong Chen, Quan Sheng Liu, Chien Hsin Yang
Abstract: This paper introduces temperature effect to rock model. It sets up a thermo-visco-elastic-plastic rock model. Based on the rock model which consists of spring, dashpot and plastic elements under the condition of un-axial compression, the behaviors of the thermo-visco-elastic-plastic in rock are discussed, and the equations of the constitutive, creep, unload and relaxation have been obtained. This model can reflect the rock or rock mass average thermo-rheology character. Meanwhile, this study gives a explanation of the significances of this kind of model in the practical use.
Authors: Quan Sheng Liu, Guang Miao Xu, Yun Hua Hu, Xiaoxiao Chang
Abstract: Basic mechanical behaviors of rocks at different temperatures and with different moistures are required to be investigated for studying and designing rock engineering in cold regions. In this paper, two typical rocks, i.e., red sandstone and shale sampled from Jiangxi and Hubei in China, respectively, are tested by uniaxial and triaxial compressive tests at different temperatures ranging from 20°C to -20°C and in dry and fully saturated states. The test results show the different behaviors of them. The values of the uniaxial and triaxial compressive strengths, Young’s modulus, cohesion, and friction angle, increase with the lowering of the testing temperatures, but the tendencies are different for these two kinds of rock.
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