Applied Mechanics and Materials Vols. 477-478

Abstract: The Viscoelasto-Plastic Model with Double Yield Surface is introduced in detail. Finite element equations are introduced when the deformation is considered under Coupled Deformation and Seepage Fields. The response of one soil slope is simulated during rapid drawdown of water level by FEM. The results calculated show that the critical slip surfaces and safety factors by two ways are pretty close. To assure the safety of the slope, the design of anti-slide piles is carried out. Those ways used may provide reference to engineering practice.

Abstract: Effective unit weight, inner friction angle and cohesion are the main engineering indices of rock-soil mass anti-slide. Deviant leakage brings about obvious decrease of effective unit weight, inner friction angle and cohesion under combined action of thrust, buoyancy, and lubrication. So as to slip in unstable rock-soil mass. Deviant leakage schleps out weensy particles, induces seepage failure, so geotechnical engineering would collapse. Therefore the reasonable anti-leakage in unstable mountain is one of the key technologies that urgently to be solved in geotechnical engineering. Combined with the typical landslide geology, several groundwork anti-leakage were studied for earth-rock dam, correlative processes and technologies were discussed, and construction parameters were designed. The abnormal situations that may occur in construction were analysed, and preparative schemes were put forward. The results had been validated in practical engineering.

Abstract: Based on the Hele-Shaw smooth flat model, the theoretical model of the diffusion radius-time relationship of the power-law fluid in single fracture plate model can be deduced according to the force balance of fluid micro element in cylindrical coordinate, the rheological equation of power-law fluid and the equation of mass conservation. The calculation procedures of the derived theoretical model are compiled by applying the Matlab software, and are employed to analyze the affecting elements of diffusion. The results show that the slurry diffusion radius is widened with the increase of the fracture apertures, the grouting pressure difference and the grouting time; and the bigger the water cement ratio, the easier the grouting spreads under the equivalent fracture opening conditions. The grouting infection efficiency in the early stage is much higher than that of the later stage, and reduces with the increase of the diffusion radius, which is in accord with the rule of the grouting in practice. The Grouting Diffusion Model will serve as a theoretical basis for the cement grout with low water cement ration in the fractured rock.

Abstract: Based on the fluid-solid coupling theory, we describe the fractured rock mass as a continuous porous medium and consider the rock mass permeability coefficient a function of the stress and strain. By using the multi-physics coupling analysis software COMSOL, we achieved the dynamic change of permeability coefficient, and found that serious damage due to micro cracking occurred in the excavated damage zone of rock mass due to the yield and failure of rock mass. Corrodingly, permeability will remarkably increase, which is basically consistent with the experimental results. The simulations indicated the "indirect coupling" effect of seepage and stress. Therefore, the coupled analysis of the seepage and stress in fractured rock masses is important for the practical rock mechanics and rock engineering.

Abstract: Ballast-glue is a chemical material severed to adjust ballast stiffness and stabilize railway infrastructure, and its ballast-glue characteristics is less of microscopic research. The ballast-glue cubic sample compressed tests were carried, with curing time alteration, then a 3D discrete-element method (DEM) is used to investigate the glue bonding effects of the tests, where the ballast is made of real size irregular clumps, the ballast-glue is represented by bonds to simulate the tensile and shear strength, results show that ballast curing time is a key factor to govern the ballast-glue integrity and strength, ballast-glue increases the maximum compressed force up to 0.99Mpa, and the DEM bonding function is a potential tool for ballast-glue structure investigation.

Abstract: The mechanical performance of GFRP soil nailing in the supporting structure is an important and difficult problem. By implanting the fiber bragg grating sensor (FBG) into GFRP soil nailing, pull-out tests were done on filed,and stress rules of soil nailing bar were determined.The more reasonable and effective force data of soil nailings were also gathered through FBG senor.Test results show that the tension of soil nailing gradually adds with external pulling force, the variation of tension is divided into two stages, the total pulling force is within 50kN, growing linearly with about 2.5% rate ,after that, its growth rate is approximately 50% to 60%. After the force exceed a certain value, the load is transmitted backward.FBG sensing technology overcomes the failure problem of traditional strain sensor,is a precise measurement method.

Abstract: Glass Fiber Reinforced Polymer (GFRP) soil nailing is great different from steel bar soil nailing in mechanical parameters and the properties. According to a excavation engineering supported by soil nailing, the support structure of soil nailing was simulated by finite element method. By analyzing the displacement, the force, the plastic area and other aspects in sensitive position, the results show that two types of soil nailing can ensure the stability of the slope under the same arrangement. The maximum displacement of GFRP soil nailing on control points of the slope is more 7% to 10% than steel bar soil nailings. Plastic zone of GFRP soil nailing support structures are more obvious in the range and the extent. The arrangement of GFRP soil nailing had been optimized by finite element software, the distance 1.6~1.8m between soil nailings is more appropriate for support structure.

Abstract: In this paper, roads analysis software bisar 3.0 be used to build an elastic layered system analysis model for cement stabilized macadam base. Different construction methods and structures contact conditions between the layers were comprehensive considered based on the actual pavement structure, in order to analyze the internal stress-strain state of cement stabilized macadam. The results show that interlayer contact conditions is approximately smooth state when cement stabilized macadam base used the traditional two layered construction method, which may occur structural damage between cement stabilized macadam base caused by partial stress concentration. However, the interlayer contact conditions is approximately completely continuous state when used the overall construction methods, and the stress-strain state of cement stabilized macadam can significantly improve by changing interlayer contact conditions. Finally, by changing the construction methods for to change interlayer contact conditions, the stress-strain state of cement stabilized macadam can be effectively improved, and the road performance and service life also be significantly improved.

Abstract: Dayanwan tunnel in Shanghai-Kunming high-speed railway is deeply buried and its rock lithology is brittle and hard. The typical tunnel cross section was selected to do hydraulic fracturing field geostress test. The stress in the measured depth was obtained. In order to forecast the rock burst in the whole tunnel, the finite element inversion method has been used based on field geostress test. Lastly, the stress conditions, lithology, structure characteristics and groundwater conditions of surrounding rock were made as the general conditions to predict the rock burst comprehensively in Dayanwan tunnel. The results show this comprehensive prediction method is more accurate than the single rock burst prediction method used before. And it has a certain guiding significance in practice.

Abstract: The ultimate fracture of rock depends on flows which rock contains, and the process of fracture is nonlinear and unbalanced. Materials like rocks are inhomogeneous, and geometric shapes of crack are usually complicated and irregular. The macroscopic fracture of limestone is studied by using SWA-2000 Electro-hydraulic Servo-controlled Rock Mechanics Testing System and fractal geometric methods. The results indicate that the magnitude of confining pressure is related to the fractal dimension, and macroscopic fracture can be described quantitatively by using fractal geometric methods.