Characterization of low placement ratio SCP and deformation of SCP ground under backfilled

低安置率SCP特征及回填下SCP地面变形

基本信息

批准号：
11650501
负责人：
TAKEMURA Jiro
金额：
$ 2.24万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650501/
关键词：
soft clay sand compaction piles caisson type quay wall centrifuge model tests light weight material cavity expansion theory cone penetration

项目摘要

Short and long term behavior of soft clay improved by sand compaction piles with low replacement ratios, which is subjected to backfilled caisson loading, have been investigated through a series of centrifuge model tests. In the model tests the construction sequence from the installation of the caisson to the backfilling was simulated in-flight. Effects of replacement ratio, A_s, improvement width, SCP location and loading rate on the behavior of the caisson were studied. From the model tests the following were derived :(1)Both during and after back filling, settlement of the caisson can be effectively reduced by higher replacement ratio. The settlement of caisson after backfilling is highly influenced by the settlement of the ground behind the SCP portion.(2)Wider improvement area towards the fill is more effective in reducing the lateral displacement of the caisson both during and after backfilling and the degree of consolidation of clay part in SCP ground has a significant effect on … More the short-term lateral deformation.(3)Using light-weight material as the back fill, both short-term stability and long-term settlement behavior can be effectively improved.Furthermore, by using cavity expansion theory, theoretical equations on the cone tip resistance and shaft resistance were derived, in which the effect of replacement ratio of the SCP is taken into account as the stiffness of spring assumed surrounding a SCP. The effect of replacement ratio on the stiffness was investigated by pressure-meter tests and applicability of the derived equation was examined by cone penetration tests in the SCP with different replacement ratio in the centrifuge. From these studies, the followings were obtained :(4)Subgrade reaction, k_h, of SCP is much smaller than the uniform sand with same density and the k_h, decreases with decreasing replacement ratio. As a result, the cone tip resistance and shaft resistance decrease with decreasing A_s.(5)Comparing the calculated cone tip and shaft resistance with the observations, the possibility of the determination of fiction angle of SCP from the cone resistances was confirmed. Less

通过一系列离心模型试验，研究了低置换率压实砂桩在回填沉箱荷载作用下软粘土的短期和长期性能。在模型测试中，从沉箱安装开始的施工顺序进行了研究。模拟飞行中回填的情况，研究了替换率、A_s、改进宽度、SCP 位置和加载速率对沉箱性能的影响。：（1）无论是回填过程中还是回填后，通过较高的置换率都可以有效减少沉箱的部分沉降，回填后沉箱的沉降受SCP改良区后面地面沉降的影响较大。有效减少回填期间和回填后沉箱的横向位移，SCP地基中粘土部分的固结程度对短期横向位移有显着影响(3)采用轻质材料作为回填土，可有效改善短期稳定性和长期沉降行为。此外，利用空腔膨胀理论，建立了锥顶阻力和轴阻力的理论方程。导出，其中将 SCP 的替换率的影响考虑为假设围绕 SCP 的弹簧刚度。通过压力计测试研究了替换率对刚度的影响，并通过以下方法检查了导出方程的适用性。锥入度通过在离心机中对不同置换率的SCP进行试验，得出以下结论：(4)SCP的路基反应k_h远小于相同密度的均匀砂，并且k_h随着置换率的减小而减小。结果表明，锥尖阻力和轴阻力随着A_s的减小而减小。(5)将计算的锥尖阻力和轴阻力与观测值进行比较，从锥阻力确定SCP摩擦角的可能性为少确认。