Effects of pore solution concentrations on shear strength of clay
YU Hai-hao1, 2, WEI Chang-fu1, 2, YAN Rong-tao1, 2, FU Xin-hui3, MA Tian-tian4
1. Guangxi Key Laboratory of New Energy and Building Energy Saving, Guilin 541004, China; 2. College of Civil Engineering and Architecture, Guilin University of Technology, Guilin 541004, China; 3. Fujian Provincial Institute of Architectural Design and Research, Fuzhou 350001, China; 4. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
Abstract:Pore solutions play an important role in the shear strength of soils. A series of shearing and microcosmic tests are performed on the samples saturated with NaCl solutions with different concentrations to investigate the effects of pore solution concentrations on the effective strength of clay. The experimental results show that the pore solution concentrations have strong effects on cohesion of samples. The cohesion decreases with the increase of pore solution concentrations. As the concentration approaches 0.1 mol/L, the cohesion decreases to below 0 kPa. The cohesion depends on the block effect of physical and chemical forces between particles on the interparticle sliding. The repulsion decreases with the increase of the pore solution concentration which makes the interparticle sliding more easily. Due to the development of real pore pressure in the samples, the cohesion decreases to below 0 kPa. The environmental scanning electron microscopy tests on the microstructures confirm that clays form flocculation in NaCl solution and form aggregation in water.
于海浩, 韦昌富, 颜荣涛, 傅鑫晖, 马田田. 孔隙溶液浓度的变化对黏土强度的影响[J]. 岩土工程学报, 2015, 37(3): 564-569.
YU Hai-hao, WEI Chang-fu, YAN Rong-tao, FU Xin-hui, MA Tian-tian. Effects of pore solution concentrations on shear strength of clay. Chinese J. Geot. Eng., 2015, 37(3): 564-569.
[1] 孙重初. 酸液对红黏土物理力学性质的影响[J]. 岩土工程学报, 1989, 11(4): 89-93. (SUN Zhong-chu. The effect of acidizing fluid on the physico-mechanical properties of red clay[J]. Chinese Journal of Geotechnical Engineering, 1989, 11(4): 89-93. (in Chinese)) [2] NAGEL N. Ekofisk geomechanics monitoring[C]// Proceedings of the International Workshop on Geomechanics in Reservoir Simulation. Reuil-Malmaison, 2010. [3] 王 洋, 汤连生. 水土作用模式对残积红黏土力学性质的影响分析[J]. 中山大学学报 (自然科学版), 2007, 46(1): 128-132. (WANG Yang, TANG Lian-sheng. Effects of water-soil interaction on mechanical strength of residual red clay[J]. Acta Scientiarum Naturalium Universitais Sunyatseni (Natural Science), 2007, 46(1): 128-132. (in Chinese)) [4] SPAGNOLI G, RUBINOS D. Undrained shear strength of clays as modified by Ph variations[J]. Bull Eng Geol Environ, 2012, 71: 135-148. [5] 汤连生. 水-土化学的力学效应及机理分析[J]. 中山大学学报(自然科学版), 2000, 39(4): 104-109. (TANG Lian-sheng. Mechanical effect of chemical action of water on soil and analysis on its mechanism[J]. Acta Scientiarum Naturalium Unversitatis Sunyatseni (Natural Science), 2000, 39(4): 104-109. (in Chinese)) [6] 王 军, 曹 平. 水土化学作用对土体抗剪强度的影响[J]. 中南大学学报(自然科学版), 2010, 41(1): 245-249. (WANG Jun, CAO Ping. Influence of chemical action of water on soil shear strength[J]. Journal of Central South University (Natural Science), 2010, 41(1): 245-249. (in Chinese)) [7] NAEINI S A, JAHANFAR M A. Eeffect of salt solution and plasticity index on undrain shear strength of clays[J]. World Academy of Science, Engineering and Technology, 2011, 49: 982-986. [8] WARKENTIN B P, YONG R N. Shear strength of montmorillontite and kaolinite related to interparticle forces[J]. Clays and Clay Minerals, 1962, 9: 210-218. [9] STUDDS P G, STEWART D I , COUSENS T W. The effects of salt solutions on the properties of bentonite-sand mixtures[J]. Clay Minerals, 1998, 33: 651-660. [10] PI MAIO C. Exposure of bentonite to salt solution: osmotic and mechanical effects[J]. Géotechnique, 1996, 46(4): 695-707. [11] RAND B, PEKENC E. Investigation into the existence of edge-face coagulated structures in na-montmorillonite suspensions[J]. Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistryin Condensed Phases, 1980, 76: 225-235. [12] SL237—1999土工试验规程[S]. 1999. (SL237—1999 Specification of soil tests[S]. 1999. (in Chinese)) [13] MICHELE C, MARILENA L, ROBERTO V, et al. Compressibility and residual shear strength of smectitic clays: influence of pore aqueous solutions and organic solvents[J]. Italiana Geotechnical, 2005, 1: 34-46. [14] SANTAMARINA J C, KLEIN K A. Micro-scale aspects of chemical-mechanical coupling: interparticle forces and fabric[M]// Chemo-Mechanical Coupling in Clays: from Nano-Scale to Engineering Applications, MAIO C D, HUECKEL T, LORET B, ed. A.A. Balkema, Lisse, Maratea, 2002: 47-64. [15] WEI Chang-fu. A theoretical framework for modeling the Chemo-mechanical behavior of unsaturated soils[J]. Vadose Zone Journal, 2014, 13(9): 1-21. (in Chinese)) [16] JAMES K. Mitchell and kenichi soga[M]// Fundamentals of Soil Behavior, MITCHELL James K, SOGA Kenichi, ed. New York: Wiley, 2005 [17] LAME T W, ASCE F. A mechanistic picture of shear strength in clay[C]// Soil Shear Strength Confence. Boulder, 1960: 555-580.