特殊应力路径下岸坡饱和土体变形特性模拟
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摘要
库岸边坡土体受到库水位涨落的周期性影响,其受力过程可描述为在前期固结压力范围内有效应力的多次循环加、卸载过程。通过室内应力路径三轴试验模拟土体孔隙水压力的循环加、卸载,并通过对统一硬化模型的扩展和加、卸载准则的修正,来预测土体的变形发展规律,研究结果表明:循环加、卸载过程中,土体的体积变形呈周期性弹性变化,剪应变呈螺旋上升趋势且增幅随循环次数逐渐减小;卸围压屈服阶段,土体变形呈现体积膨胀的剪胀特征和剪应变增幅加快的脆变趋势,且土体剪切变形在6%左右时即出现实测孔压骤减和峰值强度点;建立压缩曲线系数与加、卸载次数的关系,并修正超固结土的加、卸载准则,扩展后的统一硬化模型能够较好地预测特殊应力路径下岸坡饱和土体的变形特性。
The bank slope soils are periodically influenced by the fluctuation of reservoir level, and its stress process can be described as multi-cyclic loading-unloading process of the effective stress in the pre-consolidation pressure range. The triaxial test of soil stress path is used to simulate the cyclic loading-unloading of soil pore water pressure, and the deformation and development laws of soil are predicted by extending the unified hardening model and modifying the loading-unloading criteria. The results show that during the cyclic loading-unloading process, the volume deformation of the soil is periodically elastic, and the shear strain is in a spiral upward trend and its increment gradually decreases with the number of cycles. During the unloading and confining pressure yielding stage, the soil deformation shows a dilatancy feature of volume expansion and a brittle trend of shear strain increase. The measured pore pressure drops dramatically and the peak intensity point occours when the shear deformation is at about 6%. The relationship between the compression curve coefficient and the number of loading-unloading is established, and the loading-unloading rules of the overconsolidated soil are modified. The extended unified hardening model can predict the deformation characteristics of the bank saturated soil under the special stress paths.
The bank slope soils are periodically influenced by the fluctuation of reservoir level, and its stress process can be described as multi-cyclic loading-unloading process of the effective stress in the pre-consolidation pressure range. The triaxial test of soil stress path is used to simulate the cyclic loading-unloading of soil pore water pressure, and the deformation and development laws of soil are predicted by extending the unified hardening model and modifying the loading-unloading criteria. The results show that during the cyclic loading-unloading process, the volume deformation of the soil is periodically elastic, and the shear strain is in a spiral upward trend and its increment gradually decreases with the number of cycles. During the unloading and confining pressure yielding stage, the soil deformation shows a dilatancy feature of volume expansion and a brittle trend of shear strain increase. The measured pore pressure drops dramatically and the peak intensity point occours when the shear deformation is at about 6%. The relationship between the compression curve coefficient and the number of loading-unloading is established, and the loading-unloading rules of the overconsolidated soil are modified. The extended unified hardening model can predict the deformation characteristics of the bank saturated soil under the special stress paths.
引文
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[2]LAMBE T W,MARR W A.Stress path method:Second Edition[J].Journal of the Geotechnical Engineering Division,ASCE,1979,150(6):727-738.
[3]张荣堂,陈守义.减P路径下饱和软粘土应力应变性状的试验研究[J].岩土力学,2002,23(5):612-616.ZHANG Rong-tang,CHEN Shou-yi.An experimental study on stress-strain behavior of soft clay along decreasing average normal stress[J].Rock and Soil Mechanics,2002,23(5):612-616.
[4]黄质宏,朱立军,廖义玲,等.不同应力路径下红粘土的力学特性[J].岩石力学与工程学报,2004,23(15):2599-2603.HUANG Zhi-hong,ZHU Li-jun,LIAO Yi-ling,et al.Mechanical properties of red clay under different stress paths[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(15):2599-2603.
[5]陈善雄,凌平平,何世秀,等.粉质黏土卸荷变形特性试验研究[J].岩土力学,2007,28(12):2534-2538.CHEN Shan-xiong,LING Ping-ping,HE Shi-xiu,et al.Experimental study on deformation behavior of silty clay under unloading[J].Rock and Soil Mechanics,2007,28(12):2534-2538.
[6]HIRD C C,PIERPOINT N D.Stiffness determination and deformation analysis for a trial excavation in Oxford Clay[J].Géotechnique,1997,47(4):665-691
[7]殷宗泽.一个土体的双屈服面应力-应变模型[J].岩土工程学报,1988,6(4):24-40.YIN Zong-ze.A stress-strain model for soil with double yield surfaces[J].Chinese Journal of Geotechnical Engineering,1998,6(4):24-40.
[8]方祥位,陈正汉,申春妮,等.残积土特殊应力路径的三轴试验研究[J].岩土力学,2005,26(6):932-936FANG Xiang-wei,CHEN Zheng-han,SHEN Chun-ni,et al.Test study on residual soil under special stress paths[J].Rock and Soil Mechanics,2005,26(6):932-936.
[9]姚仰平.UH模型系列研究[J].岩土工程学报,2015,37(2):24-40.YAO Yang-ping.Advanced UH models for soils[J].Chinese Journal of Geotechnical Engineering,2015,37(2):24-40.
[10]YAO Y P,GAO Z W,ZHAO J D,et al.Modified UHmodel:constitutive modeling of overconsolidated clays based on a parabolic Hvorslev envelope[J].Journal of Geotechnical and Geoenvironmental Engineering,2012,138(7):860-868.
[11]陈勇,韦双,CHAN Dave.库水循环加卸载条件下岸坡饱和土体变形特性试验研究[J].水利学报,2015,46(5):6124-618.CHEN Yong,WEI Shuang,CHAN Dave.Experiment study on deformation characteristics of slope deep soil under the cyclic loading and unloading action of reservoir water[J].Journal of Hydraulic Engineering,2015,46(5):6124-618.
[12]路德春,姚仰平,张在明,等.循环加载条件下土的应力路径本构模型[J].水利学报,2008,39(8):907-915.LU De-chun,YAO Yang-ping,ZHANG Zai-ming,et al.Constitutive model for soils under the condition of cyclic loading[J].Journal of Hydraulic Engineering,2008,39(8):907-915.