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超载预压处理后软土地基在使用荷载过大时超固结土会出现塑性软化，这将导致路基塌陷、建筑物倾斜倒塌等工程灾害.基于汕头淤泥质软土的三轴不排水剪切实验，探究了先期固结压力和超固结比对软土塑性力学特性的影响规律，试验结果显示：在相同先期固结压力下，超固结比越大，超固结软土的应变软化现象越明显.在塑性软化阶段超固结软土存在明显的剪切带，超固结比越大土体的剪切带越宽越明显，剪切带倾角越小；超固结土的塑性软化现象与土体剪切带密切相关，土体由正常固结状态转变为超固结状态时土体出现剪切带，土体应变软化现象也随之出现.基于上述试验结果并结合土体的抗剪强度机理，从微观尺度出发建立了超固结土抗剪强度分析模型；基于土体孔隙水的运移作用下土颗粒之间的静摩擦力与滑动摩擦力的转换，揭示了超固结土塑性软化机理；提出了工程上预防超固结土因塑性软化导致土体强度下降的指导方案，可为超固结软土地区工程实践提供参考.
Abstract：When the overloading preloading method is used to treat soft soil foundations, the plastic softening of over-consolidated soil will lead to subgrade collapse, building tilting collapse,and other engineering disasters. Based on the triaxial undrained shear test of unaltered soil samples in Shantou, the influence of different pre-consolidation pressures and different over-consolidation ratios on the plastic mechanical properties of soft soil is investigated. The test results show that under the same pre-consolidation pressure, the larger the over-consolidation ratio is, the more obvious the strain-softening phenomenon of over-consolidated soft soil is. There are obvious shear bands in the plastic softening stage of the over-consolidated soft soil. The larger the over-consolidation ratio is, the wider the shear band is, the more obvious the shear band is, and the smaller the shear band inclination is. The plastic softening phenomenon of over-consolidated soil is closely related to the shear band of soil. When soil changes from a normal consolidation state to an over-consolidation state, the shear band and strain-softening phenomenon of soil occurs. Based on the above experimental results and combined with the shear strength mechanism of soil, a shear strength analysis model for over-consolidated soft soil was established from a microscopic scale. Based on the transformation of static friction force and sliding friction force between soil particles under the action of soil pore water migration, the plastic softening mechanism of over-consolidated soil is revealed, and the guiding scheme for preventing the soil strength decline caused by plastic softening of over-consolidated soil is proposed, which can provide a reference for engineering practice in over-consolidated soft soil area.
[1]聂年圣，牛瑞森.海相软土成因及其工程特性的研究[J].工程建设与设计，2010(12):72-74.
[2] ANDERSEN K H. Bearing capacity under cyclic loading-offshore,along the coast,and on land. The 2lst Bjerrum Lecture presented in Oslo, 23November 2007[J]. Canadian Geotechnical Journal, 2009, 46(5):513-535.
[3] QIAN J,LI S,ZHANG J,et al. Effects of OCR on monotonic and cyclic behavior of reconstituted Shanghai silty clay[J]. Soil Dynamics and Earthquake Engineering,2019,118:111-119.
[4] FLEMING L N,DUNCAN J M. Stress-deformation characteristics of alaskan silt[J]. Journal of Geotechnical Engineering,1990,116(3):377-393.
[5] LADD C C. Stress-deformation and strength characteristics,state of the art report[J]. Proc of 9th ISFMFE,1977(4):421-494.
[6] WANG S,LUNA R. Monotonic behavior of Mississippi River Valley silt in triaxial compression[J].Journal of Geotechnical and Geoenvironmental Engineering,2012,138(4):516-525.
[7] REN X W,XU Q,TENG J,et al. A novel model for the cumulative plastic strain of soft marine clay under long-term low cyclic loads[J]. Ocean Engineering,2018,149:194-204.
[8] ZHOU J,GONG X. Strain degradation of saturated clay under cyclic loading[J]. Revue Canadienne De Géotechnique,2001,38(1):208-212.
[9] YASUHARA K,MURAKAMI S,SONG B W,et al. Postcyclic degradation of strength and stiffness for low plasticity silt[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2003, 129(8):756-769.
[10]韩剑，姚仰平，尹振宇.超大次循环荷载下超固结黏土的长期不排水力学特性研究[J].岩土工程学报，2017,39(12):2219-2225.
[11]姚海林，马时冬，卢应发.正常固结土与超固结土的一些特性及其应力历史的确定[J].岩土力学，1994(3):38-45.
[12]温国胜.重塑软土力学特性试验研究[J].广东建材，2023,39(10):79-83.
[13]姚爱敏，王运霞.正常固结土与超固结土主要力学特性的比较[J].北方工业大学学报，2007(1):86-90.
[14]孙德安，陈波，周科.重塑上海软土的压缩和剪切变形特性试验研究[J].岩土力学，2010,31(5):1389-1394.
[15] HICHER P Y,WAHYUDI H,TESSlED D. Micro-structural analysis of strain localization in clay[J].Computers&Geotechnics,1994,16:205-222.
[16] OTANI J,MUKUNOKI T,OBARA Y. Characterization of failure and density distribution in soils using X-Ray CT scanner[C]//China-Japan Joint Symposium on Resent Development of Theory&Practice in Geotechnology. Shanghai:[s.n.],1997,45-50.
[17] GYLLAND A S,JOSTAD H P,NORDAL S. Experimental study of strain localization in sensitiveclays[J].Acta Geotechnica,2014,9(2):227-240.
[18] WU X. Onset,propagation,and evolution of strain localization in undrained plane strain experiments on clay[D]. Manhattan:Kansas State University,2016.
[19] JIANG M J,SHEN Z J. Microscopic analysis of shear band in structured clay[J]. Chinese Journal of Geotechnical Engineering,1998,20(2):102-108.
[20]万航，周跃峰，邓茂林，等.三轴加载条件下粗粒土剪切带的细观演化规律[J/OL].水力发电学报，1-10[2024-08-20]. https://link.cnki.net/urlid/11.2241.TV.20240820.1020.002.
[21]李蓓，赵锡宏，董建国.上海粘性土剪切带倾角的试验研究[J].岩土力学，2002(4):423-427.
[22]蒋明镜，彭立才，朱合华，等.珠海海积软土剪切带微观结构试验研究[J].岩土力学，2010,31(7):2017-2023+2029.
基本信息:
DOI：
中图分类号:TU447
引用信息:
[1]周子玉,王震,杨永雨等.超固结淤泥质软土塑性软化与剪切带形成机理实验研究[J].汕头大学学报(自然科学版),2025,40(01):53-63.
基金信息:
国家自然科学基金（41831278）; 汕头大学科研启动基金（NTF21015）