废旧轮胎胶粉-黏土混合土的击实性能

废旧轮胎橡胶颗粒用于填埋场衬垫材料改性,有望提高衬垫系统的有效性。击实性能是衬垫设计和施工的基础,但目前缺乏针对性研究,击实机理不够明确。开展废旧轮胎胶粉-黏土混合土的击实试验研究,探讨橡胶颗粒粒径、掺入比等因素对混合土击实性能的影响规律和压实机制。研究表明,当橡胶掺入比从0增大到25%时,胶粉-高岭土的最优含水率增大,胶粉-红黏土的最优含水率减小,变化在2.4%范围内; 混合土的最大干密度从1.65gcm-3减小至约1.40gcm-3; 试验选用的橡胶颗粒粒径对最优含水率和最大干密度差异不显著。在击实过程中橡胶颗粒回弹和橡胶颗粒比表面积变化两种效应下,最优含水率随橡胶掺入比的增加表现出减小(大颗粒时)、不变和增加(小颗粒时)的变化规律,并与基质土的性质密切相关。给出了初步设计时改性黏土含水率和干密度的控制方法,能够基本满足规范中对压实黏土的含水率和压实度的要求,且其渗透系数小于1.010-7cms-1。

COMPACTION PERFORMANCE OF GROUND RUBBER AND CLAY MIXTURES

As a modified material, the waste tire granulated rubber is expected to enhance the effectiveness of liner system in landfill. The existing results of compaction tests are in conflict to some extent since the compaction mechanism is complex. The compaction test of waste tire ground rubber and clay mixtures is conducted and the effect of rubber properties on compaction performance is studied. When the rubber mixing content increases from 0% to 25%,the optimum water content of the Kaolin mixture increases and that of the red clay mixtures decreases. The change of optimum water content of the mixtures is within 2.4% and the maximum dry density decreases from 1.65gcm-3 to 1.40gcm-3.The 12-mesh and 30-mesh rubber used in the present study show no significant difference on the compaction performance. Under the two effects of rubber particle rebound and specific surface area change, the optimum water content can either decrease(for coarse rubber),be about the same, or increase(for fine rubber) with the increasing of rubber mixing content,.The change is closely related to the properties of the matrix soil. The control parameters of water content and dry density at the preliminary design are put forward, which can basically meet the water content and degree of compaction requirements of compacted clay liner in the specification. The hydraulic conductivity of the mixtures is below 1.010-7cms-1 and also meets the requirements.