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程明书, 汪时机, 毛新, 陈正汉, 江胜华. 结构性损伤膨胀土三轴加载下的裂隙形态及力学表征[J]. 岩土工程学报, 2016, 38(z2): 73-78. DOI: 10.11779/CJGE2016S2012
引用本文: 程明书, 汪时机, 毛新, 陈正汉, 江胜华. 结构性损伤膨胀土三轴加载下的裂隙形态及力学表征[J]. 岩土工程学报, 2016, 38(z2): 73-78. DOI: 10.11779/CJGE2016S2012
CHENG Ming-shu, WANG Shi-ji, MAO Xin, CHEN Zheng-han, JIANG Sheng-hua. Fissure morphology and mechanical characterization for structure-damaged expansive soil under triaxial compression tests[J]. Chinese Journal of Geotechnical Engineering, 2016, 38(z2): 73-78. DOI: 10.11779/CJGE2016S2012
Citation: CHENG Ming-shu, WANG Shi-ji, MAO Xin, CHEN Zheng-han, JIANG Sheng-hua. Fissure morphology and mechanical characterization for structure-damaged expansive soil under triaxial compression tests[J]. Chinese Journal of Geotechnical Engineering, 2016, 38(z2): 73-78. DOI: 10.11779/CJGE2016S2012

结构性损伤膨胀土三轴加载下的裂隙形态及力学表征

Fissure morphology and mechanical characterization for structure-damaged expansive soil under triaxial compression tests

  • 摘要: 基于Kachanov连续损伤变量及Fredlund非饱和土有效应力理论,提出了结构性损伤膨胀土的强度表征方法。以南水北调中线工程南阳膨胀土为研究对象,利用改进型非饱和土三轴仪对不同损伤程度的三组15个重塑试样进行控制净围压分别为50,100,150 kPa的三轴压缩试验,定量分析荷载作用下初始孔洞损伤基元及裂隙演化形式对膨胀土力学特性的影响。实验表明:考虑结构性及损伤的非饱和土力学表征能够很好地描述土体的力学行为;孔洞损伤对膨胀土强度没有一致的强化或弱化效果,而裂隙发育形态、演化形式对土体结构及强度起主导作用;围压能够一定程度上抑制裂隙的开展,通过裂隙面咬合产生强度。根据破坏机制将该力学关系表示为裂隙发育及残余强度两个阶段,线性硬化破坏、弹塑性破坏、脆塑性破坏、线性软化破坏四种破坏模式。研究可为揭示膨胀土边坡破坏的力学机制及预测提供新的参考。

     

    Abstract: Based on the Kachanov’s continuous damage variable principle and the Fredlund’s effective stress theory for unsaturated soil, a strength characterization method for structure-damaged expansive soil is proposed. The soil taken from South-to-North Water Transfer Project in Nanyang is reconstituted. 15 specimens are divided into three groups with different cylindrical-pore damages. Whereafter, triaxial compression tests are conducted by using a modified multifunction unsaturated soil triaxial apparatus under controlled net confining pressures of 50, 100 and 150 kPa respectively. The influences of the initial pore-damage primitives and fissure evolution under triaxial loading on the mechanical behaviors of expansive soil are analyzed quantitatively. The results indicate that the mechanical characterization of unsaturated soil associated with structure and damage can describe the mechanical behaviors of soil commendably. Cylindrical-pore damage has no consistent weakening or strengthening effect on the strength, while the fissure morphology and evolution forms of soil play a significant role in the structure and strength. The development of fissures can be restrained by the net confining pressure at a certain extent, and the strength is kept through the fissure surface occlusion. Particularly, its mechanical behaviors are characterized by two stages of fissure development and residual strength, and four damage types of linear-hardening, elastic-plastic, brittle-plastic and linear-softening failure modes. The study may provide new references for revealing and predicting the failure mechanism of expansive soil slopes.

     

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