不同胶结和孔隙比结构性黏土的三轴固结不排水试验研究

    EXPERIMENTAL STUDY ON TRIAXIAL CONSOLIDATED UNDRAINED OF STRUCTURAL CLAYS WITH DIFFERENT BONDS AND VOID RATIOS

    • 摘要: 室内外试验表明部分天然沉积黏土具有较强的结构性,而黏土的结构性会直接影响地基的变形及稳定性计算,因此对结构性黏土的力学特性进行深入研究具有重要的工程意义。本文在扰动土样中添加水泥和盐粒,在室内通过击实法人工制备了具有不同胶结强度和初始孔隙比的高岭结构性黏土和天津结构性黏土试样,对不同胶结和孔隙比的结构性黏土进行了三轴固结不排水试验。试验结果表明:(1)当试样的胶结强度较小和初始孔隙比较大时,在固结阶段可能会导致试样的胶结发生破坏、孔隙比产生较大程度的减小。在实际工程中应考虑前期施工扰动对结构性黏土的胶结强度和孔隙比的影响。(2)试样剪切前的胶结强度越大、孔隙比越小,在相同轴向应变下的偏应力越大,试样的峰值强度越大,应力-应变曲线的应变软化特征越明显,应力路径中偏应力的最大值越大。(3)试样达到峰值强度时还存在结构性时,具有结构破损阶段的应力路径。高岭结构性黏土呈现出先剪缩后剪胀的趋势,表现出过渡性土的相变行为。天津结构性黏土只表现出剪缩的趋势,应力路径先向左上方移动,然后由于结构破损向左下方移动。

       

      Abstract: Laboratory and in situ tests show that some natural sedimentary clays possess strong structures, and the clay structure directly affects the calculation of ground deformation and stability. Therefore, intensively studying the mechanical characteristics of structured clays is of great engineering significance. In this study, cement and salt were added to disturbed soil samples, and Kaolin and Tianjin clay specimens with different bonding strengths and initial void ratios were artificially prepared using a compaction method. Triaxial consolidated undrained tests were conducted on structured clays with varying bond strengths and void ratios. The test results show that: (1) When the bonding strength of the specimen was relatively low and the initial void ratio was relatively high, the bonding might be damaged, and the initial void ratio might be significantly reduced during the consolidation stage. The effects of previous construction disturbance on the bonding strength and void ratio of structured clays should be considered in practical engineering. (2) The greater the bonding strength and the smaller the initial void ratio before shearing, the greater the deviator stress at the same axial strain, the higher the peak strength of the specimen, the more obvious the strain softening characteristic of the stress-strain curve, and the greater the maximum deviator stress in the stress path. (3) If the clay structure remained when the specimen reached peak strength, the stress path exhibited a structural damage stage. The Kaolin structured clays showed a tendency of shear contraction followed by shear dilation, exhibiting the phase transformation behavior of transitional soil. The Tianjin structured clays only exhibited a tendency of shear contraction. The stress path initially moved to the upper left, then to the lower left due to structural degradation.

       

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