Advanced Materials Research Vols. 838-841

Abstract: The main chlorides that pollute soil are NaCl, KCl, MgCl₂ and CaCl₂, who will change the physicochemical properties of soil. It takes Jiuzhoutai loess as the object, using methylene blue method and ethylene glycol monoethyl ether method to determinate the specific surface area of loess, which was immersed by chloride with different concentrations and cations to analyze the influence of chloride contamination, respectively. The specific surface area decrease with the increase of chloride concentration, while has the negative correlation with the affinity of cations to clay which immersed by different cations. Different absorbents that have lead to the difference of test results, and the results of ethylene glycol monoethyl ether method are always bigger than methylene blue method.

Abstract: The influence of the single cavern blasting excavation in underground caverns on the stability of surrounding rock of adjacent caverns can not be ignored.In–situ blasting vibration test and dynamic finite element analysis were used to study the laws of blasting seismic wave propagation, two different material constitutive models were adopted, compared with measured data,to select material constitutive model which was more in line with the dynamic characteristics of rock mass in underground caverns.On this basis, the influence mechanism for blast–induced EDZ(Excavation Damage Zone) of the adjacent cavern is studied through the method of numerical simulation. The results show that the numerical simulation resulted by adopting kinematic hardening model were more close to measured data than adopting ideal elastic–plastic model; the middle part of adjacent tunnel side wall facing blasting had the largest damaged rock mass range; both sides of the arch and the foundation rock of the adjacent cavern emerged damaged rock mass area, and the area of adjacent tunnel side wall facing blasting was larger than side wall not facing blasting.

Abstract: Taking the every arranged uplift pile in a practical project for example and selecting the column strip on the scale board as the research object, this paper analysis mainly focuses on the pullout capacity of piles at different locations with different vertical loads from columns by using the Winkler elastic foundation beam model. The results show that design with assumption that uplift piles evenly share the net buoyance would lead to successive failure of the piles. Then further parametric analysis was conducted to study the influence of stiffness, thickness and column space on the vertical forces of piles. The conclusions could provide positive reference to related uplift pile design.

Abstract: There are some coupling methods based on Finite Element Method and some other numerical methods, such as Infinite Element Method, Boundary Element Method, Finite Difference Method, etc. But these methods have their own limitations on simulation the foundation. For overcome these disadvantages, a coupling method is presented in this paper, which be proposed to analyze the effect of soil - foundation on seismic response of structures. In this coupling method, the structure and the surrounding soil are simulated with Finite Element method, and the other part of the soil with Explicit Finite Element - Finite Difference Method. Compared to other coupling methods, it is more flexible and its calculation amount is acceptable. The accuracy and effectiveness of the coupling method have been verified through Numerical experiment in this paper.

Abstract: Based on the idea presented in literature [4]:when to calculate the safety coefficient by strength reduction FEM, The material's shear strength parameters c and φ will be deducted,it is suggested that sinφ≥ 1-2v.This paper study on the development of slope's plastic zone with different v and by strength reduction FEM, research show that the effect of v on the safety coefficient is not obvious,but when φ=20 and v beside critical value,the effect to the development of the plastic zone is obvious. When the value is bigger, the development of plastic zone occurs in the deep and the potential sliding channel cannot feed through.According this ,this paper puts forward a comprehensive evaluation method that combined with three instability criterions that finite element calculation does not converge,plastic zone run through,displacement of feature points appear inflection point.

Abstract: Take the silty clay and clay as the research object, the correlation between bulk density, moisture content, cohesion, friction angle and unconfined compressive strength was analyzed using laboratory tests, and the results showed that soil cohesion, friction angle and unconfined compressive strength with good correlation, the correlation coefficients were all above 0.9, while severe and soil moisture content and unconfined compressive strength of correlation is weak, followed by the correlation formulas of the index and unconfined compressive strength were established, these formulas can used to predict the unconfined compressive strength of soil.

Abstract: The skin friction of Y-section pile is non-uniform distributed along its inverted arch arc, the calculation of additional stress for the uniform distribution can not take the resulting deviation of actual distribution into account. Combine the function expression of non-uniform distribution model and mindlin formula to establish the calculation method of additional stress coefficient by numerical integration and analyze the influences of the parameters LRθsδ, then compare the conclusion with the uniform distribution solution and Geddes solution. Additional stress factor of non-uniform distribution model is larger than that based on uniform distribution model,the additional stress decreases with the increase of R, s, δ and increases with the increase of θ and L, and the Mechanisms of the changes coursed by these parameter are also analyzed. Some significant conclusions are obtained.

Abstract: The side friction of Y-section pile is non-uniform distributed along its inverted arch arc, the load - settlement law of Y-section pile distinguishes to the traditional piles' as there is abnormality effect of side friction. Computation theory of settlement and ultimate bearing capacity needs to be studied. Calculate the settlement under different loads based on the model of skin friction, ultimate tip resistance and additional stress coefficient, and then predict ultimate bearing capacity by loads-settlement laws, the theoretical values of settlement and ultimate bearing capacity are in good agreement with the results of Static load test. The influences of five variables R, θ, δ, s, and L on settlement of Y-section file are analyzed, the settlement of Y-section pile under the constant load decreases with the increase of R, δ, s, δ and increases with the increase of θ. The influences of Relevant parameters on ultimate bearing capacity are also analyzed, the ultimate bearing capacity of Y-section pile decreases with the increase of θ and increases with the increase of R, δ, s and L.

Abstract: Biaxial compression tests are performed on 450mm*450mm*450mm cubic specimens of big aggregate concrete at five kinds of stress ratios,0:-1, -0.25:-1, -0.5:-1, -0.75:-1 and-1:-1 after exposure to freeze-thaw cycles of 50, 100, 150, 200, 250 and 300 times by employing a large static-dynamic true triaxial machine. Failure modes of the specimens are observed and described. The two principally static compressive strengths are measured. Based on the test data, the influences of the freeze-thaw cycles and stress ratios on the biaxial strengths of big aggregate concrete after exposure to freeze-thaw are analyzed respectively. The relationships between the ultimate compressive strength and freeze-thaw cycles, stress ratios are given respectively. The unified failure criterion with consideration of the influence of freeze-thaw cycles and stress ratios is proposed, which provides the experimental and theoretical foundations for strength analysis of big aggregate concrete structures subject to complex loads in cold environment. Key words: big aggregate concrete; freeze-thaw cycle; stress ratio; biaxial compressive strength; failure criterion

Abstract: While using the big circle method, Fourier Bessel series expansion technique, and the coordinate conversion of Graf's addition formula, an analytical solution for the scattering of non concentric arc layered alluvial valleys subjected to plane primary waves was derived. Then the precision of the numerical result was checked up and analyzed. Finally, by using the analytic solution, the surface displacement was analyzed at different shear wave velocity of covering layer. The analysis results show that shear wave velocity change has little effect on the crest value of displacement at lower frequency incidence, however the influence becomes significant with the increase of incident frequency. In general, lower the shear wave velocity is, higher the crest value of displacement will be. Compared with the existing conclusions, the covering thickness variation has little effect on the influence of shear wave velocity change on the scattering of elastic waves.