Advanced Materials Research Vols. 368-373

Abstract: Earthwork excavation, as the primary work of the project, the calculation method in quantity not only affects the project budget, but also has a significant impact in the overall project design and construction schedule. This paper applies Kriging algorithm, in combination with 3D modeling, to build accurate 3D solid model through close space, and uses graphic element Boolean operations to create accurate calculation method in quantity of Earthwork in complex engineering, which can display the data of quantity of Earthwork respectively as well as the space, achieve visual design of Earthwork to make up for the deficiency of traditional method, provide accurate calculation for organizing excavation engineering and visual decision-making information.

Abstract: In the re-pressed tests of jacked pipe piles in soft clay, it was observed that the re-pressed starting pressure can reach to more than 2.5 times of the final pressure for 25 days after finishing the installation; and it increased more rapidly in early period than later. Through the study of the time effect mechanism, it is found that the increment of ultimate bearing capacity of the single pile is mainly caused by side soil resistance. The end resistance has little influence on the time effect of bearing capacity of pile. According to the simulation result of the test data, the relationship between pile side resistance and time can be described with logarithmic curve. By this new computing model, the side frictional resistance in different resting time can be obtained, and then the ultimate bearing capacity. It is proved that this method is feasible because the values of side soil resistance calculated by the computing model with software are well consistent with the field tests results.

Abstract: This paper obtains function index system of excavation by FAST method and introduces fuzzy comprehensive evaluation to estimate function index system. By analyzing function system of the excavation obtains the evaluation method for excavation design cost, proposing new evaluation standard for excavation design. At last establishing value engineering (VE) optimization model for excavation design, and put it into engineering practice to prove that the model is convenient and practical.

Abstract: Based on the Barton-Bandis non-linear deformation structural plane model, displacement discontinuity method (DDM) is used to iteratively calculate the distribution of in-situ stress field around the structural plane, and then the parameter sensitivity analysis of the structural plane and rock is carried out. The results show that near the structural plane, especially near the tips, stress concentration is quite significant, the closer to the tips, the greater the principal stress difference is; the stress concentration around the structural plane decreases as the stiffness of structural plane grows; with the growth of the ratio of structural plane thickness to length, the stress concentration around the structural plane increases, but when reaching a certain level, the increasing slows down; as the friction angle of the structural plane grows, the stress concentration decreases.

Abstract: Structural plane is different from common crack, as it is often under pressure and has non-linear normal and tangential deformation behavior. This paper simulates the propagation of non-linear deformation structural plane by 3D displacement discontinuity method (DDM). Through least square regression of the elements near the tip, the stress intensity factor (SIF) of the tip is obtained. Maximum energy release rate criterion is adopted to be the fracture criterion in this paper, assuming the propagation occurred in the normal plane of the front edge, K_I is modified to consider the effect of mode Ⅲ crack. The structural plane model is considered as a hyperbolic non-linear model, the Barton-Bandis model is adopted as the normal deformation model, the Kulhaway model is adopted as the tangential deformation model, and the Mohr-Coulomb criterion is adopted as the shear strength criterion. The result shows that the propagation direction is along the direction of the load, DDM could efficiently trace this process.

Abstract: This paper analyzed the board of reliability on the elastic half space model. Considered the random of the larger variability parameters, such as foundation, board, load, the paper studied the reliability of this issue application of first order second moment method. This paper analyzed the influence of the random parameter variability on the reliability index β and failure probability, obtained some useful conclusions and had some engineering referencing.

Abstract: the results of deep artificial permafrost 's tri-axial compression test showed that the stress-strain relationship of deep original frozen clay presents a character that is weak and soft From the view point of engineering application , the paper gives a exponential model containing two parameter, Comparative analysis showed that the model not only gives a good description of frozen clay stress-strain relationship before peak stress, but also has the advantages of less model parameters, easy to determine and clear physical meaning. The analysis results showed that the model parameters a linear increase with the decrease of the temperature, and the change rule of parameters is contrary.

Abstract: Based on the theory of shear displacement method, the transfer matrix of pile in layered soils was deduced, so the analytical theory of settlement of single pile in layered soils is established, which can take into account the nonlinear influence of soils, and with which settlement, distribution of axial force, displacement and skin resistance of single pile along the depth in layered soils can be easily attained. By contrast with the practically measure data, it can be seen that the method proposed in this paper is simply and comparatively accurate in calculating the pile settlement under working load.

Abstract: Based on Biot saturated soil theory, steady state dynamic response of the system is studied in the frequency domain when the inner boundary of a fractional derivative viscoelastic type circular lined tunnel is under the axisymmetric load and fluid pressure respectively. On the basis of introducing a partial permeable boundary condition, the solutions of stress, displacement and pore pressure of the lining and saturated soil are obtained by the inner boundary of the lining and continuity conditions of the interface, besides, the stress-displacement constitutive behavior of the lining is described by fractional derivative viscoelastic constitutive model. The influence of physical parameter on the system response is investigated. It is shown that the order of fractional derivative model has a great influence on the system dynamic response, and it depends on material parameter of the lining when the inner boundary of lining is subjected to axisymmetric load. The permeability parameter of lining has significant effects on system response induced by fluid pressure.

Abstract: Based on the three-dimension rheological model for unsaturated soil the constitutive equations are deduced by Laplace transformation. Then the time-dependent analytic expressions of vertical strain and lateral total stress in confined compression situation are also obtained. The modified confined rheological test has been carried out to get time-varying data of vertical strain and lateral total stress. Thus all the model parameters in the constitutive model can be calculated by the methods of curve fitting and formula inversion. At last, the method of the parameters solving is proved reasonable by an example.