高压实膨润土-砂混合物膨胀性能实验研究

Experimental study of swelling characteristics of highly compacted bentonite-sand mixture

采用自主研制的岩土三向膨胀仪实验装置,探讨了不同干密度(1.6 g/cm^(3)、1.7 g/cm^(3)、1.8 g/cm^(3)、1.9 g/cm^(3))和掺砂率(0%、10%、20%、30%)条件下,高压实膨润土-砂混合物试样吸水过程中的膨胀特性。结果表明,在30℃下,膨胀应力的发展经历了快速膨胀阶段、减速膨胀阶段和缓慢膨胀阶段,快速膨胀阶段主要处于350 min之前,达到了极限膨胀力的80%,膨胀力发展稳定在1200 min内。混合物膨胀应力存在各向异性,竖向膨胀力大于水平向膨胀力,水平向膨胀力与竖向膨胀力的比值约为0.9。混合物的三向膨胀力与掺砂率和干密度均呈指数关系,随掺砂率增加而减小,随干密度增加而增加。掺砂率从0%增加到30%,竖向膨胀力从4.62 MPa降低到1.23 MPa,干密度从1.6 g/cm^(3)增加到1.9 g/cm^(3)时,竖向膨胀力由0.8 MPa增大到3.1 MPa。实验结果对高庙子膨润土膨胀性能的正确判定具有重要意义。

Self-developed geotechnical three-dimensional swelling permeameter is used to explore swelling property of bentonite-quartz sand mixtures as buffer material in different dry density(1.6 g/cm^(3),1.7 g/cm^(3),1.8 g/cm^(3) and 1.9 g/cm^(3))and mixed sand ratio(0%,10%,20%and 30%).The test results show that the time-history curve of swelling pressure has experienced the rapid swelling stage,the slow expansion stage and the stable expansion stage at the temperature of 30℃.The rapid swelling stage occurred during the saturation process at about 350 min,basically reaching 80%of the ultimate swelling pressure,and the specimen attained equilibrium swelling pressure within 1200 min.The swelling pressure of bentonite-sand mixtures has anisotropy.The ratio of the horizontal swelling pressure and the vertical swelling pressure is about 0.9,and the horizontal swelling pressure is smaller than the vertical swelling pressure.The three-dimensional swelling pressure increases exponentially with the dry density,and decreases exponentially with the sand content.When the sand contents increased from 0%to 30%,the vertical swelling pressure decreased from 4.62 MPa to 1.23 MPa.When the dry density increased from 1.6 g/cm^(3) to 1.9 g/cm^(3),the vertical swelling pressure increased from 0.8 MPa to 3.1 MPa.The test results are important for the study of expansive properties of Gaomiaozi bentonite.