裂隙和土体软化效应双重影响下膨胀土边坡的稳定性分析
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摘要
天然膨胀土经历长期干湿循环,反复胀缩使其具有多裂隙性和超固结性。在膨胀土边坡稳定分析中,应考虑上述性质的共同作用对边坡稳定性的影响。采用FLAC3D中的双线性应变硬化/软化遍布节理模型,对不同裂隙面位置和土体软化效应共同影响下的膨胀土边坡进行了稳定性分析。结果表明:裂隙面的存在会显著降低膨胀土边坡的稳定性。随着裂隙面与水平正向夹角的减小,边坡安全系数呈现出"增—减—增—减—增"的波形关系,峰值安全系数出现在20°和115°,谷值安全系数出现在80°和160°。考虑在裂隙面位置和土体软化效应的双重影响下,边坡稳定性会进一步降低,其中土体软化效应对边坡稳定性的影响要小于裂隙面的影响。反倾向小倾角的裂隙面一定程度上可提高边坡的整体稳定性,其与裂隙面的强度参数及土体的软化效应密切相关。
Natural expansive soil has the properties of over-consolidation and more fissures through long term drying-wetting cycles and repeated swelling and shrinking.The impact from the common effect of both the properties mentioned above on the slope stability must be considered in the analysis of expansive soil slope stability.A stability analysis on the expansive soil slope under the common impact from different locations of fissure-planes and soil mass softening effect is made with the bilinear strain-hardening/softening ubiquitous-joint model in FLAC3 D.The result shows that the stability of the expansive soil slope can be significantly lowered by the existence of fissure-plane.Along with the decrease of the included angle between the fissure-plane and the horizontal positive direction,the safety coefficient of the slope shows a wave-relationship of up-down-up-down-up,while the peak safety coefficients appear at 20° and 115° and the valley safety coefficients appear at 80° and 160°.The slope stability is considered to be further lowered under the dual impact from both the location of the fissure-plane and the soil mass softening effect,in which the soil mass softening effect on the slope stability is less than that from the fissure-plane.Moreover,the reversed inclined fissure-plane with small inclined angle can enhance the whole stability of the slope to a certain extent,which is closely correlated to the strength parameter and the soil mass softening effect of the fissure-plane.
Natural expansive soil has the properties of over-consolidation and more fissures through long term drying-wetting cycles and repeated swelling and shrinking.The impact from the common effect of both the properties mentioned above on the slope stability must be considered in the analysis of expansive soil slope stability.A stability analysis on the expansive soil slope under the common impact from different locations of fissure-planes and soil mass softening effect is made with the bilinear strain-hardening/softening ubiquitous-joint model in FLAC3 D.The result shows that the stability of the expansive soil slope can be significantly lowered by the existence of fissure-plane.Along with the decrease of the included angle between the fissure-plane and the horizontal positive direction,the safety coefficient of the slope shows a wave-relationship of up-down-up-down-up,while the peak safety coefficients appear at 20° and 115° and the valley safety coefficients appear at 80° and 160°.The slope stability is considered to be further lowered under the dual impact from both the location of the fissure-plane and the soil mass softening effect,in which the soil mass softening effect on the slope stability is less than that from the fissure-plane.Moreover,the reversed inclined fissure-plane with small inclined angle can enhance the whole stability of the slope to a certain extent,which is closely correlated to the strength parameter and the soil mass softening effect of the fissure-plane.
引文
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[2]包承纲.非饱和土的性状及膨胀土边坡稳定问题[J].岩土工程学报,2004,26(1):1-15.
[3]赵艳林,曾召田,吕海波.大气作用下膨胀土地基的水分迁移与胀缩变形分析[J].防灾减灾工程学报,2011,31(6):659-665.
[4]沈珠江.理论土力学[M].北京:中国水利水电出版社,2000.
[5]SKEMPTON A W.Long-term stability of clay slopes[J].Geotechnique,1964,14(2):77-102.
[6]BJERRUM C.Progressive failure in slopes of over consolidated plastic clay and clay shales[J].SMFE,ASCE,1967,93(5):3-49.
[7]BISHOP A W.The influences of progressive failure in the choice of the method of stability analysis[J].Geotechnique,1971,21(2):168-172.
[8]刘华强.膨胀土边坡稳定的影响因素及分析方法研究[D].南京:河海大学,2008.
[9]陈铁林,邓刚,陈生水,等.裂隙对非饱和土边坡稳定性的影响[J].岩土工程学报,2006,28(2):210-215.
[10]LU T H,WU J H,YANG S,et al.Study on mechanism of expansive soil slope failure and numerical simulation[C]//HUANG B S,BOWERS B F,MEI G X,et al.1stInternational Symposium on Pavement and Geotechnical Engineering for Transportation Infrastructure.Reston,VA:ASCE,2013:162-174.
[11]郑颖人,沈珠江,龚晓南.岩土塑性力学原理[M].北京:中国建筑工业出版社,2002.
[12]吴珺华,杨松.超固结膨胀土抗剪强度特性及边坡稳定研究[J].重庆交通大学学报(自然科学版),2016,35(4):70-74.