膨润土-红黏土-石英砂基毛细阻滞覆盖层的实验研究

Experimental Study of the Capillary Barrier Based on Bentonite,Laterite and Sand

针对下伏防护层的毛细阻滞覆盖层的防渗特点,使用膨润土-红黏土-石英砂混合物对常用的黏土防护层进行改进实验研究。为了确定混合物中膨润土和石英砂的质量百分比对防护层功能的影响,首先采用变水头渗透、自由膨胀率测定和直剪实验研究了不同膨润土和石英砂含量的混合物,确定了两者作为防护层材料时的合适配比;其次,对膨润土-红黏土-石英砂基毛细阻滞覆盖层边坡模型和无防护结构边坡模型分别进行降雨条件下的对比实验,研究了毛细阻滞覆盖层的防渗效果。结果显示,膨润土和石英砂的质量分数分别为12%和5%时,试样的饱和渗透系数、自由膨胀率和抗剪强度均比其他组合更符合作为防护层材料的要求;毛细阻滞覆盖层边坡在中段和坡顶的入渗深度分别比无防护结构边坡浅10 cm和15.5 cm,其总排水时间比无防护结构边坡的长217 min,毛细阻滞覆盖层整体表现出了较好的防渗与导排效果。

According to the impermeable characteristics of the capillary barrier(CB)with underlying protective layer,the mixture of bentonite,laterite and sand was used for improvement experiments compared to the frequently-used clay protective layer.In order to determine the influence of the mass percentage of bentonite and sand in the mixtures on the function of the protective layer,variable-head infiltration tests,free swelling tests and direct shear tests were firstly used to study the mixtures with different content of bentonite and sand,the appropriate ratio of these two materials as the protective layer material was thus determined.Then,the compare experiments under rainfall were conducted to the slope models with CB based on bentonite,laterite and sand,and the slope models without protective structure and the impermeability effect of CB was thereby studied.The results show that when the mass percentage of bentonite and sand is 12%and 5%respectively,the saturated permeability coefficient,free swelling rate and shear strength of the samples are more in line with the requirement of protective layer material than other combinations.Also,the infiltration depth of slope with CB in the middle section and top of the slope is 10 and 15.5 cm shallower than those of the slope without protective structure,and its total drainage time is 217 min longer than the slope without protective structure.Hence,the CB shows a good anti-seepage and drainage effect as a whole.