Papers by Author: Quan Sheng Liu

Abstract: In the coastal areas, deep mixing method or high pressure jet grouting method are usually used to form cement soil during the ground treatment. It’s easy to inflict corrosion damage of cement soil when the underground confined water is connected to the brine. Therefore, research of the cement soil’s durability under the brine erosion is of important significance to engineering. Start from the theory of chemical dynamics and damage mechanics, based on the chemical reaction formula between MgCl2 and the cement soil, with appropriate assumption, the relationship between ion concentration and corrosion time is deduced: (C1/C2)β=t2/t1, that is: when the soil eroded to equivalent mechanic effect, the relationship of corrosion time can be obtained in the solution with high and low concentration. Based on stress strain relationship, incorporate chemical damage factor into compression modulus, suggest certain assumptions, the same relationship between corrosion time and ion concentration is deduced.

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.

Abstract: Thermodynamic properties of water during phase transition in fractured rock are discussed. Thermodynamic equations of water in fractured rock while freezing were analyzed, and an example was simulated by FLAC3D. The stress field as well as the temperature field is obtained. The results demonstrated mechanical and thermal influences on rock due to phase transition of water in fractures.

Abstract: With the increase of mining depth，most coals in China have been deep mining stage. Compared to the shallow roadway, the characteristics of deformation-failure of surrounding rock show significant differences in the deep roadway, and the deep rock features of the surrounding rock are not considered in the traditional classification of roadway. So it is needed that systematical study on the surrounding rock classification for the stability evaluation of the deep roadway to meet the demand of the support design and the construction of the deep roadway in coal mine of China. The paper puts forward classification system of surrounding rock in deep roadway of coal mine according to on-the-spot geological investigation, rock ultrasonic testing, in-situ ground stress testing and comprehensive analysis on the surrounding rock stability of deep roadway in typical ore area.

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.

Abstract: This paper analyzes the normal section capacity of the reinforced concrete paste with CFRP. Based on the models under different pasting conditions(U model, one layer at the bottom plus one layer of U model, two layers in the bottom), and experiments on the reinforced concrete beams with CFRP, we will analyze the failure mechanism and failure mode of reinforced concrete beams, and calculate the limit bending capacities. The results are directly applied to practical project.

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.

Abstract: Coupled THM simulator on FEBEX case is a highly nonlinear system including several nonlinear sub-models. To better understand the coupled THM processes and their influence on the prediction of disposal system behavior, this paper presents an uncertainty study and model optimization on coupled THM simulation under DECOVALEX-THMC framework. It focus on the effect of complexity on model uncertainty which is based on the hypothesis stating that as a model becomes more complex in terms of increased number of processes involved and parameters, the error between simulations and measurements decreases and the overall model sensitivity increases. An uncertainty function is defined which minimizes both error and sensitivity. The result of comparative study basing on different complexity level models of FEBEX case study verifies this hypothesis and indicates that method presented can address uncertainty of numerical model and give us a criterion to choose most suitable model in a relative manner.

Abstract: This paper introduces the principle of minimum energy dissipation and its general procedures to establish development equation of internal variable. With the accepted viewpoint that the damage is only mechanics of energy dissipation during the rockburst and utilizing the total strength criterion based on released strain energy, the general damage evolution equation is deduced. Compared with the traditional research method of damage evolution equation, this method has universal and objective characteristics.

Abstract: Considering the influence of phase change and temperature variation on the physical and mechanical properties of low-temperature rock in cold regions, the mathematical model for the Thermo-Hydro(TH) coupled problem is proposed based on the theory of convective heat transfer for porous medium. In this model, the influence of moisture migration on heat conduction in rock is taken into account, as well as the influence of temperature gradient on the seepage. The involved parameters are determined according to the related equations given in this paper. Then the finite element model of a gas transmission pipeline in cold region is established using the proposed mathematical model. By selecting suitable boundary conditions, initial conditions and heat computation parameters, the freezing problem of low-temperature rock surrounding the pipeline is analyzed. The calculated values of the temperature field and the measured data are basically consistent, which indicates that the proposed TH coupling model for rock in cold regions is reasonable and reliable.