Influence of temperature on swelling deformation characteristic of compacted GMZ bentonite-sand mixtures

Abstract

Laboratory swelling deformation tests were carried out on compacted GMZ bentonite and bentonite-sand mixtures with 30% and 50 % sand contents at 20, 40, 60, 80 and 90 °C with infiltration of distilled water. Influence of temperature, initial dry density, and quartz sand content on the swelling deformation characteristic of compacted bentonite specimens was analyzed. Results indicate that the swelling deformation process is accelerated, and the maximum swelling strain increases with the increase in temperature, while the maximum swelling strain tends to be stable with increasing temperature. In the meantime, the temperature effects depend on both of the sand content and the initial dry density of the specimens, the increases of the maximum swelling strain induced by increasing temperature, are enlarged by increasing sand content or initial dry density. Adding of quartz sand to bentonite not only influences the integrality of bentonite specimen, but also increase the microfissuring in area on quartz sand, which are advantageous to the heat transfer, leading to the increase of swelling deformation capacity of the specimen. The increased dry density relatively increases the bentonite content, so the swelling property is enhanced. However, no change on mineral composition of bentonite was observed when temperature was changed from 20 to 90 °C.

摘要

本文对压实GMZ 膨润土及掺砂率为30%和50%的膨润土-砂混合物试样在温度分别为20, 40, 60, 80 和 90 °C 的条件下进行了膨胀变形试验, 试验所用孔隙液为蒸馏水。分析了温度、初始干密度和 掺砂率对膨润土-砂混合物压实试样膨胀变形性质的影响。结果表明, 随着温度的升高, 试样的膨胀 变形过程加速, 最大膨胀率增大并最终趋于稳定。同时, 温度对试样膨胀性的影响会受到掺砂率和初 始干密度的影响。因温度的升高而增大的最大膨胀率, 随着试样掺砂率或初始干密度的增大而增大。 这是因为向膨润土中添加石英砂不仅破坏了试样的整体性, 并且使得在没有石英砂区域的微裂隙增 多, 提高了试样的热传导性和渗透性从而最终导致试样膨胀能力的提高。增大的初始干密度提高了试 样中膨润土的相对含量, 从而使得试样的膨胀性增大。在本研究的条件下, 没有发现膨润土中矿物成 分发生改变。