Key Engineering Materials Vols. 306-308

Abstract: This paper puts forward a damage-fracture mechanical model and a damage-rheology mechanical model for the jointed rock mass of the high slopes in the ship lock area of Three Gorges Project. These two models are used to analyze the slopes’ stability. A comparison of the computed displacements at numbers of points on the slope surfaces with the results from 3-D analysis is also made. In addition, some computing results are compared with the in-situ measured ones, showing that the model proposed is basically reliable.

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.

Abstract: Based on the theory of irreversible process thermodynamics, non-linear stress-strain-temperature equations are derived, together with an expression for time-temperature equivalence. In addition, an equation of shift factor for time-temperature equivalence is also obtained. The parameters in the equations are experimentally determined and the main curves for creep compliance and cohesion of TGP granite are obtained by a series of creep tests. It is proved that both deformation and strength of the TGP granite follow the time-temperature equivalent principle.

Abstract: The stratum movement and surface subsidence is considered as a whole system in the research work. The key of the surface subsidence control lies first in having thorough knowledge of the dynamic changeable of the overlaying strata movement as the face advances so as to establish the corresponding structure mechanics subsidence model in flat seam and deep mining. The common characteristic of stratum movement and the development procedure of crack arch are described in this paper. The structure constituents of subsidence and their influencing factors are also analyzed. Meanwhile, the surface subsidence is determined by the compressing of coal wall and the bending of the overlying strata. Based on the ground observation by the global positioning system, the boundary angle and the motion angle are determined. Furthermore, according to the research law, one can predict and control the surface subsidence damages for the special geologic conditions.

Abstract: An extension of Hoek-Brown criteria to include unsaturated behavior of argillite in porous medium is presented. The model is applied to simulate evolution of saturation degree in argillite and concrete in an experimental tunnel where field investigation of thermo-hydro-mechanical response of argillite and concrete will be done. Based on the laboratory experimental data, two different flow rules of water relative permeability and water saturation degree were suggested. The general evolution rules of saturation degree in argillite and concrete with time considering the effects ventilation are obtained.

Abstract: The propagation of blast waves in intermittent jointed rock masses will result in a complex interaction between propagating waves and rock joints. Such being the case, the analysis of dynamic response of rock masses is important to rock engineering design and stability prediction. In this paper, the fracture process of intermittent jointed rock mass subjected to blast waves and initial static field, including wing crack initiation, propagation and arrest, is analyzed using linear superposition principle and sliding crack model. Crack initiation conditions and propagation lengths under incident P-waves is put forward, and the kinking effect of propagating wing cracks subjected to S-wave is also discussed. Additional, it is demonstrated that crack arrest is controlled by static field. In order to validate the correctness of dynamic response analysis, experimental investigations were performed using lucite specimens, and the experimental results show good agreement with the analytical results.

Abstract: Synchronous explosion forming, which takes advantage of the thixotropy of concrete or cement mortar and the condensability of soil under blasting concussion, is a newly developed method to construct underground cavities. In this paper, the mechanism of the new method is elucidated first, and then the zonal characteristics in soil are investigated emphatically. In order to accomplish comparative analysis, both synchronous explosion forming and conventional compression blasting experiments are conducted under same soil and explosive conditions. Experimental results indicate that the zonal characteristics in soil by synchronous explosion forming differ from that of by conventional compression blasting. When the new method is applied, formation and growth of cracks in soil during blasting is restrained, and the crannied region, which is usually produced in conventional compression blasting can be substituted by a soil- cement mortar occlusive region. Additional, the compaction range in soil is large when the new method is used. The zonal characteristics of synchronous explosion forming are more advantageous to the bearing capacity of soil and secular stability of cavity.

Abstract: A damage mechanics model for jointed rock mass is established by the simulation of the multi-cleavage behaviour by introducing the damage tensor and by considering the jointed rock mass as continuous medium with damage. The data exchange technique with FLAC-3D is discussed by applying FISH Language that is inserted in FLAC-3D. The coupling analysis between the rock mass damage and FLAC-3D is realized by the computer program for damage mechanics analysis set up by Visual Basic, which is applied in the simulation analysis of the south slope of Yanqianshan Iron Mine.

Abstract: As a kind of porous medium made of grains, water and air, under some transfer influences, the soil in some certain atmosphere circumstances has the transfer of heat, water and air, which leads to people’s interesting. The change of temperature influences engineering, such as soils’ consolidation, expansion, grains’ force and pore pressure and so on. The paper gives a coupled numerical simulation of atmosphere rain, temperature of soils and gives the correlation between rain and temperature in unsaturated soils. The different clock of the rain begin in day little influences seepage field, due to the superficial part the sun influences; otherwise the temperature has an great influence on the permeability coefficient and diffusion coefficient.

Abstract: At present the energy dissipation rate per unit volume of deforming region is expressed with the function of principal strain rates in upper-bound analysis for Coulomb material and this restricts the application of deforming failure mechanisms in upper-bound method. In this paper, a general method of expressing the energy dissipation rate of deforming region with bulk strain rate was put forward and the conditions that the assumed velocity field of deforming region should meet were pointed out. The general method simplifies the solving process of the energy dissipation rate. Finally, the method was employed to calculate the energy dissipation rate of the logspiral shear zone and was proved practical.