荆门压实弱膨胀土的排水抗剪强度
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摘要
黏性土体的长期稳定性主要受排水抗剪强度控制.为深化对压实弱膨胀土峰值强度、完全软化强度、残余强度3种排水抗剪强度间量化关系的认知,以荆门弱膨胀土为研究对象,开展泥浆固结样的固结慢剪试验以获得完全软化强度,开展压实样的排水反复直接剪切试验以获得峰值强度与残余强度.在此基础上,获得了制样压实度、应力水平、剪切次数与剪切位移等因素对排水抗剪强度及剪切过程中体变行为的影响规律.结果表明:对于制样压实度95%的试样,峰值强度与完全软化强度的有效内摩擦角接近,约为20°;峰值强度有效黏聚力为18.4 k Pa,完全软化强度有效黏聚力为0;残余强度呈现出较强的非线性,可用Lade(2010)建议的幂函数形式抗剪强度公式描述.以上结果可为压实弱膨胀土长期稳定分析的抗剪强度参数选择提供参考.
The long-term stability of clay slopes is mainly controlled by drained shear strengths. Drained shear strengths,including the peak,fully softened and residual shear strengths,are suitable for different conditions. The drained shear strengths of Jingmen compacted expansive soil are investigated experimentally. Drained direct shear tests on specimens reconstituted from slurry are performed to obtain fully softened shear strengths. Drained multiple reversal direct shear tests on compacted specimens are performed to obtain the peak and residual shear strengths. The effects of percent compaction,stress level,shear displacement on drained shear strengths and volume change behavior during shearing are investigated. The conclusions are drawn as follows:( 1) The effective stress friction angle of peak shear strength is approximately equal to that of fully softened shear strength,which is about 20°.( 2) The effective stress cohesion of peak shear strength is 18.4 k Pa,and that of fully softened shear strength is zero.( 3) The drained residual failure envelope is nonlinear,which can be perfectly described by the power function equation presented by Lade( 2010).
The long-term stability of clay slopes is mainly controlled by drained shear strengths. Drained shear strengths,including the peak,fully softened and residual shear strengths,are suitable for different conditions. The drained shear strengths of Jingmen compacted expansive soil are investigated experimentally. Drained direct shear tests on specimens reconstituted from slurry are performed to obtain fully softened shear strengths. Drained multiple reversal direct shear tests on compacted specimens are performed to obtain the peak and residual shear strengths. The effects of percent compaction,stress level,shear displacement on drained shear strengths and volume change behavior during shearing are investigated. The conclusions are drawn as follows:( 1) The effective stress friction angle of peak shear strength is approximately equal to that of fully softened shear strength,which is about 20°.( 2) The effective stress cohesion of peak shear strength is 18.4 k Pa,and that of fully softened shear strength is zero.( 3) The drained residual failure envelope is nonlinear,which can be perfectly described by the power function equation presented by Lade( 2010).
引文
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[18]LADE P V. The mechanics of surficial failure in soil slopes[J]. Engineering Geology,2010,114(1):57-64.
[2]孔令伟,郭爱国,赵颖文,等.荆门膨胀土的水稳定性及其力学效应[J].岩土工程学报,2004,26(6):727-732.KONG Lingwei,GUO Aiguo,ZHAO Yingwen,et al. Water stability of Xiangjing expansive soils and their mechanical effect[J]. Chinese Journal of Geotechnical Engineering,2004,26(6):727-732.
[3]马全国,张彦钧,汤致松,等.压实膨胀土饱和抗剪强度的变动性[J].信阳师范学院学报(自然科学版),2016,29(4):629-635.MA Quanguo,ZHANG Yanjun,SHANG Zhisong,et al. Variation of saturated shear strength of compacted expansive soil[J].Journal of Xinyang Normal University(Natural Science Edition),2016,29(4):629-635.
[4]MITCHELL J K,SOGA K. Fundamentals of soil behavior[M]. Hoboken:John Wiley&Sons,2005.
[5]SKEMPTON A W. Residual strength of clays in landslides,folded strata and the laboratory[J]. Geotechnique,1985,35(1):3-18.
[6]EID H T,RABIE K H. Fully softened shear strength for soil slope stability analyses[J]. International Journal of Geomechanics,2017,17(1):04016023.
[7]GAMEZ J A,STARK T D. Fully softened shear strength at low stresses for levee and embankment design[J]. Journal of Geotechnical and Geoenvironmental Engineering,2014,140(9):06014010.
[8]American Society for Materials and Testing. Standard test method for torsional ring shear test to measure drained fully softened shear strength and stress dependent strength envelope of fine-grained soils:ASTM D7608-18[S]. West Conshohocken:ASTM International,2018.
[9]STARK T D,HUSSAIN M. Empirical correlations:Drained shear strength for slope stability analyses[J]. Journal of Geotechnical and Geoenvironmental Engineering,2013,139(6):853-862.
[10]CASTELLANOS B A,BRANDON T L,VANDENBERGE D R. Correlations for fully softened shear strength parameters[J].Geotechnical Testing Journal,2016,39(4):568-581.
[11]MESRI G,HUVAJ-SARIHAN N. Residual shear strength measured by laboratory tests and mobilized in landslides[J].Journal of Geotechnical and Geoenvironmental Engineering,2012,138(5):585-593.
[12]EID H T,RABIE K H,WIJEWICKREME D. Drained residual shear strength at effective normal stresses relevant to soil slope stability analyses[J]. Engineering Geology,2016,204:94-107.
[13]孔令伟,周葆春,白颢,等.荆门非饱和膨胀土的变形与强度特性试验研究[J].岩土力学,2010,31(10):3036-3042.KONG Lingwei,ZHOU Baochun,BAI Hao,et al. Experimental study of deformation and strength characteristics of Jingmen unsaturated expansive soil[J]. Rock and Soil Mechanics,2010,31(10):3036-3042.
[14]中华人民共和国水利部.土工试验规程:SL237-1999[S].北京:中国水利水电出版社,1999.Ministry of Water Resources of the People’s Republic of China. Specification of soil test:SL237-1999[S]. Beijing:China Water&Power Press,1999.
[15]中华人民共和国交通运输部.公路路基设计规范:JTG D30-2015[S].北京:人民交通出版社,2015.Ministry of Transport of the People’s Republic of China. Specifications for design of highway subgrades:JTG D30-2015[S].Beijing:China Communications Press,2015.
[16]KNAPPETT J A,CRAIG R F. Craig’s soil mechanics[M]. Abingdon:Spon Press,2012.
[17]李广信,张丙印,于玉贞.土力学[M].北京:清华大学出版社,2013.LI Guangxin,ZHANG Bingyin,YU Yuzhen. Soil mechanics[M]. Beijing:Tsinghua University Press,2013.
[18]LADE P V. The mechanics of surficial failure in soil slopes[J]. Engineering Geology,2010,114(1):57-64.