A study on measuring method of in-situ Ko-value for sandy and gravelly soils

土的强度和变形特性受应力水平的影响很大，因此了解土的地应力非常重要。遗憾的是，到目前为止，还没有一种有效的方法来测量砂质和砾质土壤的原位水平应力。本文提出了一种测量砂质和砾质土壤水平应力的新方法。将一个圆柱形测试探头安装在冻土层孔中，测试探头外表面安装有6个负载传感器，冻土层孔是通过取芯来获得高质量的原状样品。探头插入冻土层孔后，使冻土层解冻。当冻土完全融化时，荷载传感器测得的应力显示的是地面的水平应力。消除了融化过程中地面温度变化和液压压力的影响。在东京湾的一个填海土地上进行了实地试验。通过初步测试，发现测试探针有一些电气故障。经砂压实法稳定后，将其精制后用于复垦土地的主要试验。用该方法测得的压实砂土的ko值在0.41 ~ 0.98之间。这些值与作者先前提出的利用高质量未扰动样品用v -等效法得到的ko值（0.92-1.06）吻合良好。这些结果表明，本研究提出的方法可用于测量砂质和砾质土壤的原位水平应力。根据夯实前未受扰动的复垦土地优质样品CD试验得到的内摩擦角，利用Jaky方程估计ko值为0.38。结果表明：沙土压实作用使复垦土地的ko值由0.38增加到1.0左右；少

It is very important to know the in-situ stress of soils, because the strength and deformation characteristics of soils are significantly affected by stress level. Unfortunately, until now, there is no efficient method was developed for measuring the in-situ horizontal stress of sandy and gravelly soils. A new method was developed in the present study to measure the horizontal stress in sandy and gravelly soils. A cylindrical shape test probe, with 6 load transducers mounted on the outside surface of the test probe was installed into the frozen ground hole, which was made by coring the frozen ground to obtain high-quality undisturbed samples. After the probe was installed into the frozen ground hole, the frozen ground was allowed to thaw. When, the frozen ground was completely thawed, the stress measured by load transducers show the horizontal stress in the ground. The effect of temperature change of ground during thawing and the hydraulic pressure were canceled. Field test were perfor … More med at a reclaimed land located at Tokyo Bay. Though the preliminary test, the test probe was found to have some electric troubles. It was refined and used in main test for reclaimed land after it was stabilized by Sand Compaction Method. The Ko-value of the compacted sandy soil measured by the present method was ranging 0.41 to 0.98. These values are well consistent with the Ko-value(0.92-1.06) obtained by using Vs-equivalent method using high quality undisturbed samples which is also proposed previously by the authors. These results indicate that the proposed method developed in the present study is useful for measuring the in-situ horizontal stress for sandy and gravelly soils. Based on the internal friction angle obtained from CD tests on high-quality undisturbed samples of reclaimed land before compaction, Ko-value was estimated to be 0.38 by using Jaky's equation. These results firstly show that the Ko-value of the reclaimed land increased from 0.38 to about 1.0 due to sand compaction. Less