Mechanism of cyclic softening of non-plastic silt and its countermeasures

非塑性粉土循环软化机理及对策

• 批准号: 14350250
• 负责人: YASUHARA Kazuya
• 金额: $ 7.3万
• 依托单位: IBARAKI UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14350250/
• 关键词: Liquefaction; Post-liauefaction; Lateral deformation; Silt; Cyclic degradation; Earthquake; Countermeasure; Gravel drain; 液状化; 剛性劣化; 排水履歴; 側方変位; 鉛直変位; 対応策; グラベルドレーン; シルト質土; 剛性低下; 変状低減

Lateral flow is a large lateral movement of the ground that occurs horizontally as a result of liquefaction during and after earthquakes. Lateral flow is inferred. to cause most damage to foundations of structures and lifelines during earthquake-induced disasters. For clarifying vulnerabilities to liquefaction of silts, we require a method of forecasting the deformation according to ground liquefaction. This study proposes a method for predicting the liquefaction-induced deformation of silty soil and proposing the countermeasure to reduce damage due to post-liquefaction deformation.Results of the present study are summarized as follows :1)Results from post-cyclic triaxial tests on silt indicate that stiffness decreases gradually as excess pore water pressure rises. However, that rigidity decreases rapidly when a ratio of 0.8 of the excess pore water pressure is exceeded. Ground deformation after earthquakes can be decreased considerably if the excess pore water pressure is maintained b … More elow 0.8 using gravel drains as a countermeasure.2)The excess pore water pressure model was adopted to predict changes in the deformation modulus after liquefaction. It was incorporated into the FEM code for predicting silt ground deformation in model tests. Using the proposed FEM code, we obtained good agreement between observed and predicted deformation of sloping silt ground.3)In 1G model tests on sloping silt ground, deformation attributable to the liquefaction of silty soil differs depending on the ground slope : lateral flow is exceptional when the ground is severely sloping ; vertical deformation is dominant when the slope is gentle. Moreover, comparison of the actions of silt with that in sand before and after liquefaction showed remarkable delay of silt deformation in the transformation, but the amount of sand displacement is greater immediately after liquefaction. Moreover, the final amount of displacement is nearly identical to that of sand. These results emphasize that, during earthquakes, attention should be given to post-liquefaction deformation of silt as well as that of sand.4)The tire-chip drain was adopted for reducing post-liquefaction deformation of silt ground along with the conventionally used gravel drain. Results of model tests demonstrated that the tire-chip drain method is available for reducing not only lateral displacement but also vertical displacement. These effects are almost identical to those of the cases in which gravel drains are installed in the same condition. This suggests that the tire-chip drain method can be an economical countermeasure for preventing liquefaction-induced silt deformation. Less

横向流动是地震期间和地震后由于液化而水平发生的地面的大的横向运动。侧流被推断。在地震引发的灾害中，对建筑物和生命线的基础造成最大的破坏。为了明确粉土的液化脆弱性，需要一种根据地基液化预测变形的方法。本文通过对粉质土的动三轴试验研究，提出了粉质土液化后变形的预测方法，并提出了减小液化后变形破坏的对策。主要研究结果如下：1）粉质土的动三轴试验结果表明，随着超静孔压的增加，粉质土的刚度逐渐减小。然而，当超过0.8的超孔隙水压力的比率时，刚度迅速减小。保持超静孔隙水压力B，可以大大减小地震后的地面变形 ...更多信息 采用超静孔隙水压力模型预测液化后土体变形模量的变化。并将其应用于粉土地基变形的有限元模型试验中。3）在1G模型试验中，粉土液化引起的变形随地面坡度的不同而不同：当地面坡度较大时，侧向流动是例外;当地面坡度较缓时，竖向变形占主导地位。液化前后粉土与砂土的作用比较表明，粉土变形在转化过程中具有明显的滞后性，但液化后砂土的位移量较大。此外，最终的位移量几乎与沙子的位移量相同。研究结果表明，在地震作用下，粉土地基液化后变形与砂土地基液化后变形一样应引起重视。4）在常规碎石排水的基础上，采用轮胎碎石排水来减小粉土地基液化后变形。模型试验结果表明，轮胎碎石排水法不仅能有效地减小侧向位移，而且能有效地减小竖向位移。这些影响与在相同条件下安装砾石排水管的情况几乎相同。这表明，轮胎碎片排水法可以是一种经济的措施，防止淤泥变形。少

项目成果

Postcyclic degradation of strength and stiffness for tow plasticity silt

丝束塑性粉土的强度和刚度的循环后退化

• 发表时间: 2003
• 期刊: Journal of Geotechnical Engineering (Proc.ASCE, Aug.) Vol.129, No.8
• 作者: Yasuhara;K.;Murakami;S.;Song;B-W.;Yokokawa;S.;Hyde;A F L
• 通讯作者: A F L

海野, 安原, 村上, 小峯: "非塑性シルトと砂の繰返履歴による剛性劣化特性の比較"地盤工学会講演発表論文集. 1159-1160 (2002)

Unno、Yasuhara、Murakami、Komine：“由于非塑性淤泥和沙子的循环历史而导致的刚度恶化特性的比较”岩土工程师学会会议记录，1159-1160 (2002)

余裕間隙比の概念に基づいた非塑性シルトの繰返し強度と剛性劣化の評価

基于边缘间隙比概念的非塑性粉土循环强度和刚度劣化评价

• 发表时间: 2004
• 期刊: 土木学会論文集 No.764
• 作者: 宋;安原;村上;小峯
• 通讯作者: 小峯

村上, 安原, 鈴木: "GISに適用する広域地盤沈下の観測的予測法"地下水学会誌. 第45巻、第4号. 391-408 (2003)

Murakami、Yasuhara、Suzuki：“应用于 GIS 的大面积地面沉降观测预测方法”，日本地下水研究会杂志，第 45 卷，第 4. 391-408 期（2003 年）。

Yasuhara, K., Murakami, S., Mitsuyama, S.: "Instability of foundations undergoing rise in groundwater level"Proc. International Symp. on Groundwater Problems Related to Geo-environment (IS-Okayama),. Vol.1. 205-210 (2003)

Yasuhara, K.、Murakami, S.、Mitsuyama, S.：“地下水位上升导致地基不稳定”Proc。