Conventional triaxial tests on peats are strongly criticised due to the very high shear strength parameters obtained from standard data elaboration, leading to unrealistic factors of safety when used in geotechnical design and assessment. Various operational approaches have been proposed in the literature to overcome this difficulty; however, they seem to lack consistent mechanical background. Some of the issues related to the shear strength evaluation of peats from triaxial tests come from the non-uniform stress and strain states developing in the samples well before failure is attained, due to end restraint effects. Undrained triaxial compression tests were performed on reconstituted peat to examine the influence of end restraint on the deviatoric stress, excess pore pressure and deviatoric strain response. Samples were tested with standard rough end platens and with modified platens to reduce the friction between the sample and bottom and top caps. Four different initial height-to-diameter ratios were examined, to reduce the consequences of rough end platens on the sample response. The results indicate that end restraint contributes dramatically to overestimating the shear strength of peat, due to the increase in both the calculated deviatoric stress and the measured excess pore pressure at the bottom of the sample. Suggestions are given to quantify the influence of end restraint in the interpretation of standard data, in an attempt to suggest viable procedures to determine more reliable effective and undrained shear strength parameters from standard triaxial tests.

中文翻译：

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根据标准不排水三轴试验确定泥炭的剪切强度的实验：校正端部约束的影响

由于从标准数据中获得的很高的抗剪强度参数，对泥炭的常规三轴试验提出了强烈的批评，这在岩土工程设计和评估中会导致不切实际的安全因素。文献中提出了各种操作方法来克服这一困难。但是，它们似乎缺乏一致的机械背景。与三轴试验中的泥炭抗剪强度评估有关的一些问题，是由于端部约束效应而导致在未达到破坏之前，样品中出现的不均匀应力和应变状态。对再生泥炭进行了不排水的三轴压缩试验，以检验端部约束对偏应力，过大孔隙压力和偏应变响应的影响。用标准的粗糙端压板和改进的压板测试样品，以减少样品与底盖和顶盖之间的摩擦。检查了四个不同的初始高度与直径比，以减少粗糙的压板对样品响应的影响。结果表明，由于计算出的偏应力和样品底部测得的过大孔隙压力的增加，端部约束作用极大地高估了泥炭的剪切强度。提出了一些建议，以量化末端约束对标准数据解释的影响，以尝试提出可行的程序，以从标准三轴试验中确定更可靠的有效且不排水的抗剪强度参数。