饱和度对风化花岗岩边坡土体抗剪特性的影响
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摘要
强降雨易诱发风化花岗岩边坡浅层滑坡,其滑坡滑动面多位于具有较大孔隙尺寸的强风化带。通过对广西玉林与梧州交界处风化花岗岩边坡浅层滑坡的现场勘查和对不同层位的土体进行物理力学试验,研究了饱和度对湿热地区风化花岗岩双层土质边坡抗剪强度的影响,发现两个风化带土体都存在一个"最优饱和度"使抗剪强度达到峰值,但饱和度对抗剪强度指标的影响规律不同,即饱和度对黏聚力影响很大,对内摩擦角影响很小;花岗岩全风化带与强风化带土体性质差异明显,尤其表现在饱和度影响下抗剪强度特性方面,从基质吸力理论和颗粒间胶结作用角度分析所发现的现象,可以清楚地解释产生差异的机制,为风化花岗岩边坡的开挖和滑坡的防治提供理论基础。
The shallow landslides are often triggered by heavy rainfall in weathered granite soil slopes. These slope failures usually occur in a strongly weathered granite layer which has a big pore size. These can cause great casualties and property losses. Through field investigation and laboratory experiments, the effect of saturation on the shear strength of highly weathered soils and completelyweathered granite soils taking from the intersection of Yulin and Wuzhou are investigated. It is found that there exists an "optimal saturation" at which the shear strength of the soil reaches the maximum. The influence of saturation on both cohesion and internal friction angle does not show a unique trend. It is also shown that the cohesion is significantly effect by the saturation of the soils; but the friction angle is not. Completely weathered granite soils and the highly weathered granite soils are significantly different in their lithological, composition, construction and shear properties. The characters of the highly weathered soil and completely weathered granite soil are significantly different, especially in the relationship between saturation and shear strength.Based on the analysis of cementation effect and the principles of matric suction, a sound explanation for the mechanisms underlying the above-observed discrepancy is provided.
The shallow landslides are often triggered by heavy rainfall in weathered granite soil slopes. These slope failures usually occur in a strongly weathered granite layer which has a big pore size. These can cause great casualties and property losses. Through field investigation and laboratory experiments, the effect of saturation on the shear strength of highly weathered soils and completelyweathered granite soils taking from the intersection of Yulin and Wuzhou are investigated. It is found that there exists an "optimal saturation" at which the shear strength of the soil reaches the maximum. The influence of saturation on both cohesion and internal friction angle does not show a unique trend. It is also shown that the cohesion is significantly effect by the saturation of the soils; but the friction angle is not. Completely weathered granite soils and the highly weathered granite soils are significantly different in their lithological, composition, construction and shear properties. The characters of the highly weathered soil and completely weathered granite soil are significantly different, especially in the relationship between saturation and shear strength.Based on the analysis of cementation effect and the principles of matric suction, a sound explanation for the mechanisms underlying the above-observed discrepancy is provided.
引文
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[15]SEBOONG O H,NING Lu,KIM Y K,et al.Relation between the soil water characteristic curve and suction stress characteristic curve:Experimental evidence from residual soils[J].Journal of Geotechnical And Geoenvironmental Engineering,2012,138(1):47-57.
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[2]赵晓彦,胡厚田.类土质边坡特性初探[J].工程地质学报,2005,13(1):81-84.ZHAO Xiao-yan,HU Hou-tian.Preliminary study on a soil-like slope[J].Journal of Engineering Geology,2005,13(1):81-84.
[3]张永波,张云,陈戈,等.花岗岩残积土工程类型划分体系研究[J].地球学报,1997,18(2):200-204.ZHANG Yong-bo,ZHANG Yun,CHEN Ge,et al.The system of engineering category dividing of granite residual soils[J].Bulletin of the Chinese Academy of Geological Sciences,1997,18(2):201-204.
[4]刘云鹏,黄润秋,霍俊杰.某高速公路花岗岩边坡稳定性评价及防护措施研究[J].防灾减灾工程学报,2008,28(1):19-25.LIU Yun-peng,HUANG Rui-qiu,HUO Jun-jie.Study on stability evaluation and protection measures of weathered granite slope in a certain expressway[J].Journal of Disaster Prevention and Mitigation Engineering,2008,28(1):19-25.
[5]刘新喜,夏元友,蔡俊杰,等.降雨入渗下强风化软岩高填方路堤边坡稳定性研究[J].岩土力学,2007,28(8):1705-1709.LIU Xin-xi,XIA Yuan-you,CAI Jun-jie,et al.Study on stability of high-filled embankment slope of highly weathered soft rock under rainfall infiltration[J].Rock and Soil Mechanics,2007,28(8):1705-1709.
[6]陈晓平,周秋娟,蔡晓英.高液限花岗岩残积土的物理特性和剪切特性[J].岩土工程学报,2011,33(6):901-908.CHEN Xiao-ping,ZHOU Qiu-juan,CAI Xiao-ying.Physical properties and shear strength characteristics of high liquid limit granite residual soil[J].Chinese Journal of Geotechnical Engineering,2011,33(6):901-908.
[7]汤连生,桑海涛,宋晶,等.非饱和花岗岩残积土粒间联结作用与脆弹塑性胶结损伤模型研究[J].岩土力学,2013,34(10):2878-2885.TANG Lian-sheng,SANG Hai-tao,SONG Jin,et al.Research on soil particle joint function and brittle-elastoplastic cement damage model of unsaturated granite residual soil[J].Rock and Soil Mechanics,2013,34(10):2877-2888.
[8]郭璇,赵成刚,于威威.非饱和土边坡稳定的安全分析及进展[J].中国安全科学学报,2005,15(1):14-18.GUO Xuan,ZHAO Cheng-gang,YU Wei-wei.Stability analysis of unsaturated soil slope and its progress[J].China Safety Science Journal,2005,15(1):14–18.
[9]魏宁,茜平一,傅旭东.降雨和蒸发对土质边坡稳定性的影响[J].岩土力学,2006,27(5):778-786.WEI Ning,QIAN Ping-yi,FU Xu-dong.Effects of rainfall infiltration and evaporation on soil slope stability[J].Rock and Soil Mechanics,2006,27(5):778-786.
[10]建设部综合勘察有限责任公司.GB 50021-2001岩土工程勘察规范[S].北京:中国建筑工业出版社,2002.Comprehensive Institute of Geotechnical Investigation and Surveying Ministry of Construction.GB50021-2001The code for prospecting the geological engineering[S].Beijing:China Architecture and Building Press,2002.
[11]赵建军,王思敏,尚彦军,等.全风化花岗岩抗剪强度影响因素分析[J].岩土力学,2005,26(4):624-628.ZHAO Jian-jun,WANG Si-jing,SHANG Yan-jun,et al.Control factors on shear strength of completely decomposed granite[J].Rock and Soil Mechanics,2005,26(4):624–628.
[12]刘胜利,陈善雄,刘伟,等.风化片岩残积土剪切特性研究[J].岩土力学,2005,34(12):3520-3526.LIU Sheng-li,CHEN Shan-xiong,LIU Wei,et al.Study of shear properties of weathered schist residual soil.Rock and Soil Mechanics,2013,34(12):3520–3526.
[13]LU N,Godt J W,WU D T.A closed-form equation for effective stress in unsaturated soil[J].Water Resources Research,2010,46(5):W05515.
[14]赵成刚,李舰,刘艳,等.非饱和土力学中几个基本问题的探讨[J].岩土力学,2013,34(7):1825-1831.ZHAO Cheng-gang,LI Jian,LIU Yan,et al.Discussion on some fundamental problems in unsaturated soil mechanics[J].Rock and Soil Mechanics,2013,34(7):1825-1831.
[15]SEBOONG O H,NING Lu,KIM Y K,et al.Relation between the soil water characteristic curve and suction stress characteristic curve:Experimental evidence from residual soils[J].Journal of Geotechnical And Geoenvironmental Engineering,2012,138(1):47-57.
[16]王丽,梁鸿.含水率对粉质黏土抗剪强度的影响研究[J].内蒙古农业大学学报,2009,30(1):170-174.WANG Li,LIANG Hong.The influence of the water ratio on the shearing strength of silty clay[J].Journal of Inner Mongolia Agricultural University(Natural Science Edition),2009,30(1):170-174.
[17]ZHAO C G,LIU Y,GAO F P.Work and energy equations and the principle of generalized effective stress for unsaturated soils[J].International Journal for Numerical and Analytical Methods in Geomechanics,2010,34(9):920-936.