Effective Yield Strength for Material Powder Consolidated at Stage II Compaction

This work is concerned with the estimation from the outside of effective yield strength for the stage II consolidated material package of axisymmetric solid particles. Once an appropriate simple representative axisymmetric unit cell is chosen, the kinematical approach of the yield design homogenization method is used in order to obtain external estimates which has been found depending on the loading history (isostatic and closed die compactions) as well as on the relative density of the material powder. For comparison purpose, finite element simulations that describe the behavior of spherical elastic plastic particles uniformly distributed inside the material powder are carried out.

Roof collapse of shallow tunnels with limit analysis method

A new failure mechanism is proposed to analyze the roof collapse based on nonlinear failure criterion. Limit analysis approach and variational principle are used to obtain analytical findings concerning the stability of potential roof. Then, parametric study is carried out to derive the change rule of corresponding parameters on the influence of collapsing shape, which is of paramount engineering significance to instruct the tunnel excavations. In comparison with existing results, the findings show agreement and validity of the proposed method. The actual collapse in certain shallow tunnels is well in accordance with the proposed failure mechanism.

Random failure mechanism method for assessment of working platform bearing capacity with a linear trend in undrained shear strength

A bearing capacity evaluation for the surface strip foundation on a working platform modelled on a twolayered substrate is considered in the study.The upper layer is assumed as man-made and wellcontrolled and thus non-variable.The lower layer modelling natural cohesive soil is subjected to spatial variability of undrained shear strength.The random failure mechanism method(RFMM)is used to evaluate the bearing capacity.This approach employs a kinematic assessment of the critical load and incorporates the averaging of three-dimensional(3 D)random field along dissipation surfaces that result from the failure mechanism geometry.A novel version of the approach considering an additional linear trend of undrained shear strength in the spatially variable layer is proposed.The high efficiency of the RFMM algorithm is preserved.The influences of foundation length,trend slope in the spatially variable layer,fluctuation scales,and thickness of the homogenous sand layer on the resulting bearing capacity evaluations are analysed.Moreover,for selected cases,verification of the RFMM based assessment obtained using random finite difference method(RFDM)based on 3 D analysis is provided.Two types of analyses are performed using RFDM based on associated and non-associated flow rules.For associated flow rule which corresponds to RFMM,the RFMM is conservative and efficient and thus it seems preferable.However,if RFDM employs non-associated flow rule(much lower dilation angle for sand layer),the efficient RFMM is no longer conservative.For this situation,a combined approach that improves the efficiency of the numerical method is suggested.

Measuring accelerating universe with high-redshift GRBs data and other cosmological probes

A kinematical model （a parameterized deceleration parameter） and a dynamical model （a parameterized equation of state for dark energy） are constrained from the current observational data including the high-redshift Gamma-Ray Bursts （GRBs） data with a redshift range from 1.4 to 9. We obtain the stringent constraint on the values of current deceleration parameter q0, current jerk parameter j0, current equation of state for dark energy Woae and transition redshift zT. In addition, we compare the difference of the constraint results between the kinematical and the dynamical scenarios.