Experimental study on mitigation of damage induced by lateral displacement of liquefied subsoil

减轻液化地基侧向位移损伤的试验研究

基本信息

批准号：
10555160
负责人：
TOWHATA Ikuo
金额：
$ 6.91万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

The present study aims at developing a mitigation measure by which liquefaction-induced deformation of embankment is reduced to an acceptable magnitude. This measure is intended to be practiced in such a situation as densification and other prevention of liquefaction are not feasible. Shaking table tests were conducted on models of embankment resting on liquefiable sandy deposit. Firstly, two rows of sheet pile walls were installed at the foot of the embankment so that lateral spread of foundation sand might be mitigated by the stiffness of sheet pile walls. Although this idea worked well when the frequency of shaking was high, still there observed certain extent of subsidence in the embankment due to minor amount of boiling sand near the wall as well as consolidation settlement of foundation sand.Low frequency shaking demonstrated the problem of sheet pile wall measure. Since the displacement of wall was large, cracks opened near the wall and a large amount of sand boiled out from there, leading to significant subsidence of the embankment. This problem was overcome by placing additional berm above the walls in order to prevent boiling. This idea was shown to be satisfactory in a shaking table test. Special sheet pile walls were attempted which had drainage capability. When the drainage was attached beneath the slope of embankment, pore pressure was reduced near the surface and a rigid soil block was formed therein.This soil block prevented the aforementioned boiling of sand and reduced subsidence. On the contray, sheet pile walls installed from the top of an embankment with tie-rod connection at the top did not worked well because the unprotected slope failed and consequently the sheet pile walls distorted substantially.

本研究旨在制定一种缓解措施，将液化引起的路堤变形减少到可接受的程度。该措施旨在在致密化和其他防止液化不可行的情况下实施。对可液化砂质沉积物上的路堤模型进行了振动台试验。首先，在路堤底部安装两排板桩墙，通过板桩墙的刚度来减轻地基砂的横向扩展。虽然这种想法在振动频率较高时效果很好，但由于墙边有少量沸腾砂以及基砂固结沉降，仍然观察到路堤有一定程度的沉降。低频振动表明了板材问题桩墙测量。由于墙体位移较大，墙体附近出现裂缝，大量沙子从墙体处涌出，导致路堤严重下沉。通过在墙壁上方放置额外的护堤以防止沸腾，解决了这个问题。这个想法在振动台测试中被证明是令人满意的。尝试了具有排水能力的特殊板桩墙。当排水装置安装在路堤斜坡下方时，地表附近的孔隙压力降低，并在其中形成坚硬的土块。该土块防止了上述沙子的沸腾并减少了沉降。相反，从路堤顶部安装并在顶部采用拉杆连接的板桩墙效果不佳，因为无保护的边坡失效，导致板桩墙大幅变形。