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A STUDY ON INFLUENCE OF PHYSICAL AND MECHANICAL PROPERTIES ON CHANGE OF SEDIMENTARY STRUCTURE IN SAND LAYER CAUSED BY LIQUEFACTION

液化引起的砂层沉积结构变化的物理力学性质影响研究

基本信息

批准号：
08455224
负责人：
TOHNO Ikuo
金额：
$ 3.2万
依托单位：
NATIONAL INSTITUTE FOR ENVIRONMENTAL STUDIES
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

In Joetsu City and Muikamachi Town, Niigata Prefecture, which are one of the heaviest snowfall areas in Japan, the groundwater level is much lowered in winter due to the excessive pumping out of groundwater to melt snow. At Saijocho, Joetsu City, annual subsidence in heavy snowfall years is 10 times as much as in little snowfall years. The boring observation was put in operation two districts, which are located the urban Takada, Joetsu City and the urban Muikamachi, Muikamachi Town.Some standard consolidation tests and repeated consolidation tests on undisturbed soil, which was taken from these observation sites, were performed. In order to repeated consolidation tests, automatic oedometer apparatus was improved. The vertical displacement of specimens, which taken from sandy soil in both districts, was measured by digital gages with precision of 1 mum at 0.1 second intervals during the repeated tests. It is believed that the settlement due to repeated loading (unloading and reloading) is more severe than normal loading in the consolidation tests on saturated samples of sandy soil, as cohesive soil.It was developed a new observation system in order to monitoring of land subsidence. This observation system is used the wire made of poly amide for measuring subsidence and tried to miniaturized the observation system. These new observation system used to land subsidence at both sites. Subsidence has been advanced annual changes of groundwater level. Total amount of subsidence by this new system was any time an about equal to the measurement by double tube observation system.

在日本降雪量最大的地区之一的上越市和新泻县舞水町，由于过度抽出地下水融化积雪，冬季地下水位降低很多。在上越市西条町，大雪年的年沉降量是小雪年的10倍。在上越市高田市区和舞日町舞日町市区两个地区进行了钻孔观测，并对这些观测点的原状土进行了标准固结试验和重复固结试验。为便于反复固结试验，对自动固结仪进行了改进。在重复试验期间，采用精度为1 μ m的数字式位移计，以0.1秒的间隔测量了取自两个地区桑迪的试件的垂直位移。桑迪作为粘性土，在饱和土样固结试验中，反复加载（卸载和再加载）引起的沉降比正常加载引起的沉降更为严重。该观测系统采用聚酰胺丝测量沉降，并试图使观测系统小型化。这些新的观测系统用于这两个地点的地面沉降。地下水位的年际变化使地面沉降提前。新系统在任何时刻的沉降总量与双管观测系统的沉降量相当。