基于压水试验资料的岩体透水性分形特征研究

采用R/S分析方法对钻孔常规压水试验资料进行了分析,给出了能反映岩体透水性特征的分维数。通过对不同水电工程中压水试验的分析,探讨了不同岩性、构造条件下裂隙岩体透水性的分形特征。

Softening response under undrained compression following anisotropic consolidation

Experimental evidence has indicated that clay exhibits strain-softening response under undrained compression following anisotropic consolidation.The purpose of this work was to propose a modeling method under critical state theory of soil mechanics.Based on experimental data on different types of clay,a simple double-surface model was developed considering explicitly the location of critical state by incorporating the density state into constitutive equations.The model was then used to simulate undrained triaxial compression tests performed on isotropically and anisotropically consolidated samples with different stress ratios.The predictions were compared with experimental results.All simulations demonstrate that the proposed approach is capable of describing the drained and undrained compression behaviors following isotropic and anisotropic consolidations.

Analysis of semi-solid response under rapid compression tests using multi-scale modelling and experiments

Simulating semi-solid metal forming requires modelling semi-solid behaviour.However, such modelling is difficult because semi-solid behavior is thixotropic and depends on the liquid-solid spatial distribution within the material.In order to better understand and model relationships between microstructure and behavior, a model based on micromechanical approaches and homogenisation techniques is presented.This model is an extension of a previous model established in a pure viscoplastic framework to account for elasticity.Indeed, experimental load-displacement signals reveal the presence of an elastic-type response in the earlier stages of deformation when semi-solids are loaded under rapid compression.This elastic feature of the behaviour is attributed to the response of the porous solid skeleton saturated by incompressible liquid.A good quantitative agreement is found between the elastic-viscoplastic predicted response and the experimental data.More precisely, the strong initial rising part of the load-displacement curve, the peak load and the subsequent fall in load are well captured.The effect of solid fraction on mechanical response is in qualitative agreement with experiments.

Shear creep parameters of simulative soil for deep-sea sediment

Based on mineral component and in-situ vane shear strength of deep-sea sediment, four kinds of simulative soils were prepared by mixing different bentonites with water in order to find the best simulative soil for the deep-sea sediment collected from the Pacific C-C area. Shear creep characteristics of the simulative soil were studied by shear creep test and shear creep parameters were determined by Burgers creep model. Research results show that the shear creep curves of the simulative soil can be divided into transient creep, unstable creep and stable creep, where the unstable creep stage is very short due to its high water content. The shear creep parameters increase with compressive stress and change slightly or fluctuate to approach a constant value with shear stress, and thus average creep parameters under the same compressive stress are used as the creep parameters of the simulative soil. Traction of the deep-sea mining machine walking at a constant velocity can be calculated by the shear creep constitutive equation of the deep-sea simulative soil, which provides a theoretical basis for safe operation and optimal design of the deep-sea mining machine.

Changing of Properties of Unsaturated Compacted Bentonite due to Hydration Effort

Radioactive waste disposal is important facility for human and environment in the world. Compacted bentonite in radioactive disposal engineer barrier design really experience hydration effort as decreasing of suction during long-time. Hydration effort develop macro-micro void structure in bentonite under deeply geological environment. The bentonite occurred uncertainly problems or translation in various experimental interaction boundary conditions such as thermal-hydration-chemical condition. To detect accumulation of deformation or changing of bentonite behaviour due to these processes is important that the modified experimental methods are required. In addition, to interpret laboratory experimental results combine to establish mathematical modelling in possible. The overall investigation or performance of the bentonite have contributed to represent the intrinsic properties of engineer barrier systems. This study focused on changing of properties of unsaturated compacted bentonite related to hydration effort due to increasing of relative humidity. Changing of some properties revealed to become instability or uncertainly problems in practice. Soil-water characteristic curve was measured with considering of various temperatures using vapor pressure technique. Swelling pressure and creep behaviour such as mechanical components were described with hydration effort.