In this study, a series of consolidated, undrained triaxial compression tests were conducted to investigate peat shear behaviour on samples from 1.65 m depth when subjected to different stress levels from 10.4 kPa to 40.5 kPa. At the consolidation stage, the triaxial test specifically investigated the peat isotropic compressibility at low stress levels, showing an agreement with oedometer test data available in literature. The subsequent triaxial shearing stage results show most of the test data failed to reach the tension cut-off line (q/p’ = 3), which indicated that the deviator stress may represent more of an interparticle connection than the tension of fibres and woods in peaty soils. For peat, the membrane correction effect on peat shear resistance is strain dependent; generally, small within 10% shear strain, but becomes significant above 10% shear strain. A critical state line for peat was determined based on the maximum curvature approach, where the Mohr-Coulomb model has difficulty in determining the friction angle for peat. Of the data recorded for the peat, 78% fell within the range of 30 to 60 degrees, increasing to 90.4% when ignoring points lower than 10 kPa; the previous test data for very low stress level (less than 10kPa) might not be sufficiently reliable due to limitations of conventional triaxial testing apparatus, specimen preparation and etc. In addition, organic content also plays an important role on the peat shear behaviour. In general, when the organic content exceeds 75%, the deviator stress behaves like organic soils, otherwise, the peat behaves more like a mineral soil. In peat samples with organic content higher than 75%, the direct shear box test gives higher estimates of shear strength than the triaxial shear test, but not necessarily accurate — the mechanism of direct shear acts only at the centre of a specimen, while triaxial shear can shear throughout the specimens.

中文翻译：

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不同应力水平下泥炭的剪切行为

在这项研究中，进行了一系列固结、不排水的三轴压缩试验，以研究在 10.4 kPa 至 40.5 kPa 的不同应力水平下，1.65 m 深度的样品的泥炭剪切行为。在固结阶段，三轴试验专门研究了低应力水平下泥炭的各向同性压缩性，与文献中可用的固结仪试验数据一致。随后的三轴剪切阶段结果显示，大部分测试数据未能达到张力截止线（q/p' = 3），这表明偏应力可能更多地代表了颗粒间的连接，而不是纤维和木材的张力在泥炭土中。对于泥炭，膜对泥炭抗剪力的修正效果取决于应变；通常，在 10% 的剪切应变范围内很小，但在 10% 剪切应变以上变得显着。基于最大曲率法确定了泥炭的临界状态线，其中 Mohr-Coulomb 模型难以确定泥炭的摩擦角。在泥炭记录的数据中，78% 落在 30 至 60 度范围内，忽略低于 10 kPa 的点时增加到 90.4%；由于传统三轴试验设备、试样制备等方面的局限性，先前针对极低应力水平（小于 10kPa）的试验数据可能不够可靠。此外，有机物含量对泥炭剪切行为也起着重要作用。一般来说，当有机质含量超过 75% 时，偏应​​力表现得像有机土壤，否则，泥炭表现得更像矿质土壤。在有机物含量高于 75% 的泥炭样品中，