Experimental study on mechanical behavior of weakly structured soft clays
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摘要: 对取自不同地区的两种弱胶结结构性软黏土原状（undisturbed）样、重塑（remolded）样和泥浆（reconstituted）样进行了单向压缩和三轴剪切试验,分别得到土样的压缩曲线和应力-应变曲线。试验结果表明：原状样的压缩曲线为陡降型曲线,而不同制样土样的压缩曲线存在明显的差异;由于孔隙比和孔径分布对土体抗剪强度的综合影响,不仅导致相同围压下三轴剪切时孔隙比不同的重塑样和原状样强度差异较大,且孔隙比相近的不同土样的强度也存在不同程度的差异;若同一孔隙比下,两种软黏土的不同制样土样的强度关系均为原状样的强度最高,重塑样的强度最低,并可通过相近孔隙比下孔径大于0.2 μm的孔隙体积量和孔径分布均匀性可合理地解释3种制样土样强度高低的关系。由于不同制样土样的孔径分布的差异不会随固结压力的增大而消失,用参考孔隙比e* 10,简单表示土的孔隙比和孔径分布(即组构)参数,对压缩和剪切试验结果进行归一化整理后,发现不同土样的试验结果可归一化为相关度高的e/e* 10-σv曲线和ef/e* 10-qf曲线,证明结构屈服应力后,不同土样变形和强度差异主要是由孔隙比及孔径分布(即组构)的不同引起的,用参考孔隙比e* 10简单表示土的组构参数是有效的。Abstract: The oedometer and triaxial shear tests on undisturbed, remolded and reconstituted samples of two different weakly bonding soft clays are carried out to obtain the compression curves and stress-strain curves. The test results show that the compressibility abruptly increases in the compression curves of undisturbed samples, and the difference among compression curves of different samples is obvious. The strength is not only different for undisturbed and remolded samples for the difference in void ratio, but also different for samples with the close void ratio when they are sheared under the same confining pressures, because the strength of clay is affected by both void ratio and pore-size distribution. The undisturbed samples will have the highest strength and the remolded samples will have the lowest strength if they have the same void ratio, and it is valid for different soft clays used in the tests. The relation of strength among different samples can be explained reasonably by the volume of pore per unit soil volume with its diameter greater than 0.2 μm and the uniformity of pore-size distribution. Because the difference of the pore-size distribution curves among different samples cannot be eliminated by the increasing consolidation pressure, the reference void ratio e* 10, a parameter simply describing the void ratio and pore size distribution of soil (fabric) is introduced. The compression and shear test results of different samples dealt with by the reference void ratio e* 10 show that they can be normalized to unique e/e* 10-σv and ef/e* 10-qf curves with high correlation. The normalized results show that if the stress is larger than the structures yield stress, the difference in compression and shear characteristics among the samples are caused by the void ratio and pore-size distribution (fabric), and it can be simply and usefully described by the reference void ratio e* 10.
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Keywords:
- soft clay /
- compression curve /
- stress-strain curve /
- pore-size distribution /
- reference void ratio
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