南水北调中线膨胀岩膨胀特性试验研究

南水北调工程中经常遇到膨胀岩,膨胀岩的膨胀性对膨胀岩开挖料的循环再利用以及膨胀岩地区换填土的施工都有很大的影响。针对这个问题,对南水北调中线膨胀岩进行了膨胀性试验研究。试验结果表明:存在一含水率拐点,当膨胀岩的初始含水率小于拐点含水率时,其膨胀率随时间的关系曲线分为4个阶段:直线匀速膨胀阶段、直线快速膨胀阶段、减速膨胀阶段、膨胀缓慢稳定阶段。其中直线快速膨胀阶段其膨胀速度大于直线匀速膨胀阶段膨胀岩的膨胀速度。当膨胀岩的起始含水率大于拐点含水率时,其膨胀率随时间的关系曲线将没有直线匀速膨胀阶段,只有后面3个阶段。随着初始含水率的增加,膨胀岩的膨胀率逐渐减小。但是不同的膨胀岩试样初始含水率与膨胀率之间的关系曲线不同。随着上覆压力的增大,膨胀岩膨胀率逐渐减小。当超过某一压力时,岩样不但不会膨胀,反而会被压缩。这一试验结果,可为对膨胀岩地区的施工提供一定参考依据。

Experiment on swelling property of expansive rock in middle route project of south to north water diversion

Expansive rock is often met in Middle Route Project of South to North Water Diversion. The expansion of expansive rock has a great influence on the reuse of expansive rock and the exchange soil construction in the area. Experiment on the expansion of expansive rock in the Middle Route of South-North Water Diversion Project were carried out aimed at this problem. The results show that there exists a water content deflection point,if the initial water content is smaller than the water content of deflection point, there are four obvious stages of load-free swelling rate with time such as uniform linear swelling stage, linear rapid swelling stage, slow inclining stage, and steady stage. The expansion speed of the first stage is larger than the second stage. If the initial water content is larger than that of deflection point, there are only three stages except for the first stage in the expansion curve. With the increase of initial water content, the expansion rate decreases. But for different samples, the relationship curves between the initial water content and expansion rate are different. The expansion rate decreases with the increase of burden pressure. When the burden pressure is larger than a certain value, the expansive rock will be compressed instead of expansion. These results provide a basis for the construction in expansive rock area.