膨润土-碳酸钙混合物的力学特性

doi:10.12066/j.issn.1007-2861.2066

摘要/Abstract

摘要：

通过在膨润土中掺入不同量的 CaCO₃ 模拟高放射性核废料(high-level radioactive waste,HLW)处置库周围地下水侵入屏障生成 CaCO₃ 后膨润土性状的变化。通过配置 4 组不同 CaCO₃掺入量的膨润土进行了有荷膨胀试验、压缩试验和直剪试验,运用太沙基一维固结理论计算了渗透系数,并采用扫描电子显微镜(scanning electron microscopy,SEM)对样本进行了微观分析。结果表明：最终膨胀率与竖向应力、CaCO₃含量有关,竖向应力越大, CaCO₃ 含量越高,最终膨胀率越小;压缩指数随 CaCO₃含量的增大而小幅下降;随着 CaCO₃ 含量的增多,膨润土-碳酸钙混合土渗透性变差;非饱和样的抗剪强度随 CaCO₃含量变化存在一个峰值,黏聚力先增后减,饱和样则相反;电镜扫描图显示,CaCO₃ 的掺入填充了膨润土中的孔隙,使其结构更加致密。

关键词: 膨润土-碳酸钙混合土, 膨胀, 压缩, 渗透系数, 抗剪强度

Abstract:

Different amounts of CaCO₃ are mixed in bentonite for the purpose of simulating the characteristic changes of bentonite mixed with CaCO₃ that precipitates from groundwater around high-level radioactive waste (HLW) repositories. In the process of the project, four groups of bentonite-CaCO₃ mixtures are prepared with different contents of CaCO₃. Then a series of experiments including swell-under-load, compression and direct shear tests are carried out. The permeability coefficient is calculated through Terzaghi consolidation theory. The microstructure changes are photographed by the scanning electron microscopy (SEM). Test results indicate that: (1) The final swelling strains are related to vertical stress and CaCO₃content. While vertical stress and CaCO₃ content increase, the final swelling strains decrease. (2) The compression index deceases slightly as the content of CaCO₃ crystals increases. (3) The permeability turns worse with increasing CaCO₃ content. (4) With the content of CaCO₃crystals changing, the shear strength of unsaturated samples will come to its peak value. Contrary to saturated samples, the cohesive of unsaturated samples increases firstly and then increases with the increasing CaCO₃ content. (5) The photographs show that the existence of CaCO₃ fills the pores which makes the structure denser.

Key words: bentonite-CaCO$_{3}$ mixture, swelling, compression, permeability conductivity, shear strength

中图分类号:

TU443

秦爱芳, 傅贤雷, 阮坤林, 贾旭. 膨润土-碳酸钙混合物的力学特性[J]. 上海大学学报(自然科学版), 2020, 26(4): 628-639.

QIN Aifang, FU Xianlei, RUAN Kunlin, JIA Xu. Mechanical properties of bentonite-calcium carbonate mixture[J]. Journal of Shanghai University（Natural Science Edition）, 2020, 26(4): 628-639.

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[1]	王驹, 刘月妙. 高放废物地质处置与岩石力学研究[C]// 2003 年全球华人中青年学者岩土力学与工程学术论坛. 2003: 636-638.
[2]	蒋江红, 孙德安. 温度对高庙子膨润土浸水膨胀特性的影响[J]. 上海大学学报(自然科学版), 2017,23(5):762-771.
[3]	Yong R N, Boonsinsuk P, Wong G. Formulation of backfill material for a nuclear fuel waste disposal vault[J]. Canadian Geotechnical Journal, 1986,23(2):216-228. doi: 10.1139/t86-031
[4]	Ye W M, Wang Q, Chen Y G, et al. Advances on buffer/backfill properties of heavily compacted Gaomiaozi bentonite[C]// International Symposium on Geoenvironmental Engineering. 2009: 370-379.
[5]	Wang J. High-level radioactive waste disposal in China: update 2010[J]. Journal of Rock Mechanics and Geotechnical Engineering, 2010,2(1):1-11.
[6]	孙德安, 邵莉娜. 高庙子膨润土和砂混合物膨胀变形特性及其预测[J]. 上海大学学报(自然科学版), 2013,19(2):197-202. doi: 10.3969/j.issn.1007-2861.2013.02.017
[7]	Zhu C M, Ye W M, Chen Y G, et al. Impact of cyclically infiltration of CaCl$_{2}$ solution and de-ionized water on volume change behavior of compacted GMZ01 bentonite[J]. Engineering Geology, 2015,184:104-110. doi: 10.1016/j.enggeo.2014.11.005
[8]	Zhang L, Sun D, Jia D. Shear strength of GMZ07 bentonite and its mixture with sand saturated with saline solution[J]. Applied Clay Science, 2016,132:24-32.
[9]	孙德安, 张龙. 盐溶液饱和高庙子膨润土膨胀特性及预测[J]. 岩土力学, 2013(10):2790-2795.
[10]	郭永海, 王驹, 吕川河, 等. 高放废物处置库甘肃北山野马泉预选区地下水化学特征及水-岩作用模拟[J]. 地学前缘, 2005,12(S1):117-123.
[11]	郭永海, 李亚伟, 王海龙 , 等. 高放废物处置库甘肃北山区域地下水化学特征研究[C]// 第三届废物地下处置学术研讨会论文集. 2010: 19-24.
[12]	刘红艳, 党旭红, 王超, 等. 高放废物处置库膨润土中微生物多样性分析[J]. 环境科学与技术, 2016(S1):61-65.
[13]	Sridharan A, Rao A S, Sivapullaiah P V. Swelling pressure of clays[J]. Geotechnical Testing Journal, 1986,9(1):24-33. doi: 10.1520/GTJ10608J
[14]	Wang Q, Tang A M, Cui Y J, et al. Experimental study on the swelling behaviour of bentonite/claystone mixture[J]. Engineering Geology, 2012,124:59-66. doi: 10.1016/j.enggeo.2011.10.003
[15]	Gao Y, Sun D A, Wu Y J. Volume change behaviour of unsaturated compacted weakly expansive soils[J]. Bulletin of Engineering Geology and the Environment, 2018,77, 837-848. doi: 10.1007/s10064-017-1142-0
[16]	孙文静, 刘仕卿, 孙德安, 等. 饱和高庙子膨润土的渗透特性[J]. 地下空间与工程学报, 2015,11(1):115-119.
[17]	Sridharan A, Gurtug Y. Swelling behaviour of compacted fine-grained soils[J]. Engineering Geology, 2004,72(1):9-18. doi: 10.1016/S0013-7952(03)00161-3
[18]	Rao S M, Thyagaraj T. Swell-compression behaviour of compacted clays under chemical gradients[J]. Canadian Geotechnical Journal, 2007,44(5):520-532. doi: 10.1139/t07-002