Previously, in situ tests have been conducted in cold regions since infrastructures such as pipelines have been actively built on frozen ground. However, the engineering properties such as shear strength have not been directly evaluated from in situ tests. The objective of this study is to correlate the shear strength of frozen soils determined by the direct shear tests with the dynamic cone penetration index (DCPI) measured by the instrumented dynamic cone penetrometer (IDCP). The IDCP, which incorporates strain gauges and an accelerometer to measure the energy transferred to the cone tip, is used to estimate the energy-corrected dynamic cone penetration index (energy-corrected DCPI). The direct shear apparatus and the calibration chamber for the IDCP application test are placed in the freezer. The sand–silt mixtures are prepared in the shear box and the calibration chamber at the degree of saturation of 10% and relative density of 60%. Vertical confining stresses are applied to the specimens during the freezing and strength evaluating phases, such as direct shearing or penetrating the IDCP, to determine the effect of the vertical confining condition. The experimental results show that the shear strength of the frozen soils increases in a nonlinear parabolic shape with an increase in the vertical confining stress. Furthermore, the vertical confining stress during the strength evaluating phase has more influence on the strength than that during the freezing phase because the degree of saturation of specimens is low. As the energy transferred to the cone tip is affected by the soil conditions under the cone tip, the energy-corrected DCPI, which is inversely proportional to the shear strength, has a better relationship with the shear strength. This study demonstrates that the energy-corrected DCPI can be effectively used for the evaluation of the shear strength of frozen soils.

中文翻译：

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动态锥渗透指数的能量校正，可可靠地评估冻砂-粉砂混合物中的剪切强度

以前，由于诸如管道之类的基础设施已在冰冻的土地上积极建造，因此在寒冷地区进行了现场测试。但是，尚未通过原位测试直接评估工程性能，例如抗剪强度。这项研究的目的是将通过直接剪切试验确定的冻土的剪切强度与通过仪器化的动态锥形渗透仪（IDCP）测量的动态锥形渗透指数（DCPI）相关联。IDCP结合了应变仪和加速计，可测量传递到锥头的能量，用于估算经过能量校正的动态锥体穿透指数（经过能量校正的DCPI）。将直接剪切设备和用于IDCP应用测试的校准室放置在冰箱中。砂粉混合物在剪切箱和标定室中制备，饱和度为10％，相对密度为60％。在冻结和强度评估阶段（例如直接剪切或穿透IDCP），将垂直限制应力施加到样品上，以确定垂直限制条件的影响。实验结果表明，冻土的剪切强度呈非线性抛物线形，且垂直围压应力增大。此外，由于样品的饱和度较低，因此在强度评估阶段的垂直约束应力比在冻结阶段的垂直约束应力对强度的影响更大。由于传递到锥尖的能量受锥尖下土壤条件的影响，因此经过能量校正的DCPI，与剪切强度成反比的曲线与剪切强度具有更好的关系。这项研究表明，经能量校正的DCPI可有效地用于评估冻土的抗剪强度。