渗透吸力对重塑黏土的压缩和渗透特性影响的试验研究

已有研究表明孔隙水盐分对黏土的力学性质有着重要影响,但相关的定量研究仍需进一步深入。以渗透吸力作为宏观参数,将商用高岭土与钙基膨润土的混合土作为研究对象,用不同浓度的NaCl溶液与土混合,进行饱和重塑土的固结试验,探究孔隙水盐分对饱和重塑黏土压缩特性和渗透特性的影响规律。试验结果表明重塑饱和黏土的压缩指数C_c随着渗透吸力的增加而呈指数规律衰减,回弹指数未产生明显变化;在Burland体系下,渗透吸力对曲线初始段有较大影响;而屈服后,压缩曲线可以在I_v-lgσ^’_v分析体系中进行归一化。相同固结压力和孔隙比下,渗透吸力越小,次固结系数越大;次固结系数与压缩指数的比值 C_α/C_c的比值并不为常数,随着渗透吸力的增大而减小。同样的初始孔隙比,比例系数C_k=Δe/Δlgk_v随渗透吸力增加而非线性递减,延拓了Tavenas认为比例系数C_k与初始孔隙比e₀线性相关的认知。

Experimental investigation of osmotic suction effect on hydro-mechanical behaviour of remolded clay

The chemistry of pore water obviously affects the hydro-mechanical behaviour of clay, but the quantitative evaluation of pore water effect needs to be further conducted. The oedometer tests on kaolinite and Ca-bentonite mixtures saturated with different concentrations of NaCl solution are performed to investigate pore water chemical effect on the hydro-mechanical behaviour of remolded clay, where the osmotic suction is adopted as the characterization parameter. The results indicate that the compression index exponentially decreases with the osmotic suction, while the swelling index is almost constant. The compression behaviors after pre-yielding can be normalized in the I_v-lgσ^’_v system proposed by Burland, but it is not suitable before pre-yielding. There is a negative correlation between the secondary consolidation coefficients and the osmotic suctions, furthermore, the ratio of the secondary consolidation coefficient to the compression index decreases with the osmotic suction. The coefficient of C_k =Δe/Δlgk_v to depict the hydraulic conductivity is related to the initial void ratio and can be expressed as a function of the osmotic suction, which extends the understanding of this parameter.