砂-膨润土混合屏障材料渗透性影响因素研究

建立了一个新的结构-尾流振子耦合模型. 流场近尾迹动力学特征被模化为非线性阻尼 振子，采用van der Pol方程描述. 以控制体中结构与近尾迹流体间受力互为反作 用关系来实现流固耦合. 采用该模型进行了二维结构涡激振动计算，得到了合理的 振幅随来流流速的变化规律和共振幅值，并正确地预计了共振振幅值$A_{\max}^\ast$ 随着质量阻尼参数$\left( {m^\ast + C_A } \right)\zeta $的变化规律，给出了预测$A_{\max }^\ast $值的拟合公式. 采用该模型计算了三维柔性结构在均匀来流和简谐波形来流作用下的VIV 响应. 结构在均匀来流作用下振动呈现由驻波向行波的变化过程, 并最后稳定为行波振动形态. 在简谐波形来流作用下，结构呈现混合振动形态，幅值随时间呈周期变化.

INFLUENCE FACTORS OF SAND BENTONITE MIXTURES ON HYDRAULIC CONDUCTIVITY

Bentonite is attracting a greater attention as buffer and backfill material of the engineering barrier for geological disposal of high level radioactive nuclear waste,because it can offer impermeability and swelling properties. But the pure compacted bentonite strength decreases with increasing hydration,which will reduce the buffer capability in the practice engineering. To solve this problem,sand is often used to form compacted sand bentomite mixtures(SBMs)to provide high thermal conductivity,excellent compaction capacity,long time stability,and low engineering cost. The factors affecting the hydraulic conductivity of SBMs are studied in this paper. They include bentonite content,grain size distribution,moisture content,dry density,compacting method and energy,and bentonite type. The studies show that the hydraulic conductivity of SBMs is controlled by the hydraulic conductivity of the bentonite. It also decreases as dry density and bentonite content increase. But when the bentonite content reaches a critical point,the influence of increasing bentonite to decrease the hydraulic conductivity is limited. A fine and well graded SBM is likely to have a lower hydraulic conductivity than a coarse and poorly graded material. The internal erosion or erodibility based on the grain size distribution of the SBMs has a negative effect on the final hydraulic conductivity. The lowest hydraulic conductivity is gained when the mixtures are compacted close to optimum moisture content. Also,the mixtures compacted at moisture contents slightly above optimum values give lower hydraulic conductivity than when compacted at slightly under the optimum moisture content．