Applied Mechanics and Materials Vols. 580-583

Abstract: One-dimensional consolidation equation of unsaturated soils was derived in order to solve this special case of consolidation. The presented equation, not similar to Terzaghi’s equation, is a type of absolute nonlinear partial differential equation, and it was solved by finite difference method. An example was analyzed and the case of incompressible fluid consolidation was compared. Finally the experimental results from laboratory tests reported in the literature, was fitted by the presented equation, and the agreement was good. The results show that (1) the process of pore-air pressure dissipation is similar to that of pore-water pressure of saturated soils; (2) the compressibility of pore fluid is not an advantageous factor to quicken the consolidation; (3) the presented equation is effective to analyze the process of consolidation of unsaturated soils which consolidate mainly due to the dissipation of pore-air pressure.

Abstract: In this article, through aeolian sand sample study in Inner Mongolia Baotou area, to determine the aeolian sand maximum dry density and optimum moisture content. On this basis, the aeolian sand cohesion and internal friction angle were measured by the quick direct shear test when aeolian sand was at the optimum moisture content and near the most largest compactness. And the bearing capacity of retaining wall model which regarded aeolian sand as fillers was determined. Then bearing capacity change of aeolian sand wrapped before and after was compared. Experimental results showed that: when the aeolian sand was in the wet and compacted state, its cohesion was 3.31 kPa and internal friction angle was 36.8°. The aeolian sand bearing capacity was 153.8kPa by the plate loading test. The aeolian sand wrapped with a geotextile bearing capacity was 194.1kPa. Through the aeolian sand research of Baotou area, it provides a useful reference for the construction of highway and railway and application of wrap-reinforced retaining wall which is a new retaining structure in the region, and the aeolian sand is treated as a special filling material in these structures.  

Abstract: The dynamic response of the two dimensional fluid-saturated porous beam has been studied based on the linear elastic theory and the Biot’s model for saturated porous media, in which the compressibility of solid particles and fluid and the viscosity of pore fluid are taken into account. By adopting Fourier series expansion and solving ordinary differential equations, the calculation formula for dynamic response of a two dimensional simply-supported fluid-saturated porous beam is established. The dynamic response characteristics of the forced vibration under uniformly distributed harmonic load are analyzed as a numerical example. Moreover, the solid displacement and pore fluid pressure of the two-dimensional fluid-saturated porous beam would be affected by the surface in filtration conditions, pore fluid permeability coefficient and loading frequency parameters etc.

Abstract: Shape multiformity and formation mechanism of shear band in normal consolidated soil were analyzed based on Modified Cam-Clay model under plane strain condition. The results proved that shear band forms because of impact action caused by strain energy releasing. End restraint and initial defect can induce and control the formation process and shape of shear band. The interaction of different boundary and initial defect settings was analyzed in order to obtain the mechanism and deformation process of shear band.

Abstract: By Applying the Self-Made Field in-Situ Direct Shear Equipment, it Makes a Series of in-Situ Direct Shear Test Researches on the Soil （＜10cm）on the Surface of the Gravelly Gobi in Lop Nor, Xinjiang, Achieving its Shear Strength Parameter. the Conclusion that this Paper Gets Not only Provides the Key Parameters Needed for the Design of the Gobi Surface Soil Collection Machine and the Relevant Assessment Experiments, but also Offers the Reference for Evaluating the Similar Soil Shear Strength of the Gobi Engineering Construction.

Abstract: Structural study of the soil is an important research content of soil mechanics. Based on the previous research results of soil structure, this paper puts forward the Gunary Model as a completely new form to describe the stress-strain relationship of soil, to discuss the method to determine soil strain considering structural parameter under the new model, to give the relevant function of the stress controlling structural parameter with stress. The results show that the Gunary Model is applicable to characterize the stress-strain relationship of soil, the parameter controls the fitting accuracy and decides the curve shape; by using the stress-strain expression of the Gunary Model, this paper finds the calculated value of stress controlling structural parameter and stress meets the two-parameter linear reciprocal function form.

Abstract: Aeolian sand is one commonly used subgrade filling in Xinjiang Oasis-desert region, engineering practices also proved its applicability as subgrade filling. In order to find the law of Aeolian sand subgrade static strength after cyclic loading, the paper studied the static strength of Aeolian sand before and after cyclic loading through the dynamic and static triaxial tests. It is concluded that the greater cyclic loading is, the more Aeolian sand static strength peak decreases. When cyclic loading is small, the bigger confining pressure and consolidation ratio are, the static strength peak increases more after cyclic loading. The bigger initial static deviator stress is, the more Aeolian sand static strength peak reduces. The frequency of cyclic loading has little effect on static strength. In order to keep the stability of low embankment, we should restrict overload , ensure subgrade and foundation consolidation adequately, at the same time using gravel or geosynthetic materials to package edge of roadbed, so as to increase confining pressure. The research results can provide reference for the design and construction of Aeolian sand low subgrade in Xinjiang Oasis-desert region.

Abstract: At present, there is a lot of research for slope stability, the inherent reason of slope instability is geotechnical material will get plastic deformation under load. In this paper, Mohr- Coulomb yield condition is transformed strain expressed to stress expressed.Based on this, analysis the effects that geotechnical material parameters internal friction angle ,cohesion c and Poisson's ratio to Mohr- Coulomb yield condition and the development of soil plastic zone.In addition, using the strength reduction FEM simulating the change of plastic zone distribution caused by change of the geotechnical materials parameters .The results show that the internal friction angle , cohesion c are reducted, the plastic zone expand;Increasing the Poisson’s ratio , narrowing the slope’s plastic zone;Plastic zone’s different distribution is caused by different material parameters affect the yield surface.

Abstract: To obtain the effects of water content on the permeability of coal, briquette specimen were obtained from Wulong Mine, Liaoning Province. The permeability of the air drying, bounding water and saturating specimens were tested with self-made equipment respectively, and the effects of water content on permeability for coal were studied. The results showed that: (1)The permeability of specimens decreases with confining pressure increasing, and the air drying and bounding water specimens take on obvious slippage effect. However the saturated specimens never take on slippage effects. It is because the channels of saturated coal sample are occupied by water. When the gas goes through specimens, gas never is absorbed. Collision between gas and the channel wall decreases, and the slippage effect disappears. (2) With water content increasing, the permeability of specimens decreases. (3)The permeability of specimens increases when pore pressure increases.

Abstract: The rheological long-term strength is determined according to the triaxial rheological test data of diabase at the dam area of Dagangshan Hydropower Station. Firstly, based on the stress-strain isochronous curve method and connected the test points with cubic spline interpolation function, the maximum deviation point in the long-term interval is determined as the turning point and established the long-term strength by nonlinear least square method. The results show that this method is consistent with the other methods. Finally, the advantage and disadvantage of this method is analyzed. This method can overcome the randomness of artificial selecting the turning points. Therefore, maximum deviation point method is relatively a reasonable and effective method to determine the rheological long-term strength of rock.