Study on factors affecting Iiquefaction properties of natural sandy soils containing fines and their evaluation procedures

含细粉天然砂土液化特性影响因素及其评价方法研究

• 批准号: 17360221
• 负责人: KOSEKI Junichi
• 金额: $ 5.13万
• 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: 2005
• 资助国家: 日本
• 起止时间: 2005 至 2007
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17360221/
• 关键词: Triaxial test; Hollow cylindrical tosional shear test; Liquefaction; Fines content; Sandy soil; In-situ frozen sample; Reconstituted specimen; Elastic deformation property

Liquefaction properties of sandy ground under its natural state are not well understood. For example, the relationship between the SPT N-value and the liquefaction resistance of sands containing fines has been derived from a limited number of data, and thus its applicability is not yet fully verified. The in-situ freezing sampling method, which is believed to be the most reliable technique, is not the exception, since the retrieved sample may be disturbed to certain extents due to the possible volume expansion of pore water during the freezing process, in particular with sands containing larger amount of fines The details of the time effect that may cause changes in the soil particle structures are not known either. In view of the above, in the present study, experimental investigations are conducted on three kinds of in-situ frozen samples and their reconstituted specimens, focusing on their different degrees of time effects and possible link between the liquefaction properties and the small strain properties. As a result, the small strain stiffness and the liquefaction resistance of the in-situ frozen sample were larger than those of the corresponding reconstituted specimen. The difference was larger with Pleistocene samples than with Holocene sample, reflecting the time effects. By applying a large number of cyclic loading history on reconstituted specimens in advance under drained condition, these properties could be improved, while they could not be restored to the levels of the in-situ frozen samples in case of the Pleistocene ones. In addition, large strain properties of these samples after liquefaction on the order of several tens of percent could be evaluated by using a modified version of hollow cylindrical torsional shear apparatus. Effects of the level of confining pressure that is applied to in-situ frozen samples during their thawing process on the liquefaction properties could be also revealed.

砂土在自然状态下的液化特性尚不清楚。例如，含细粒砂的SPT n值与抗液化能力之间的关系是由有限的数据推导出来的，因此其适用性尚未得到充分验证。被认为是最可靠的原位冻结取样方法也不例外，因为在冻结过程中，孔隙水可能会体积膨胀，特别是含有大量细粒的砂土，可能会对回收的样品造成一定程度的干扰，可能导致土壤颗粒结构变化的时间效应的细节也不清楚。鉴于此，本研究对三种原位冻结试样及其重构试样进行了实验研究，重点研究了它们不同程度的时间效应以及液化特性与小应变特性之间可能存在的联系。结果表明，原位冻结试样的小应变刚度和液化抗力均大于相应的重构试样。更新世样品的差异大于全新世样品，反映了时间效应。通过在排水条件下对重建后的试样进行大量的循环加载历史，这些性能可以得到改善，而在更新世的情况下，这些性能无法恢复到原位冷冻样品的水平。此外，利用改进的空心圆柱扭剪仪，可以评估这些样品液化后的大应变性能，液化后的大应变性能为几十个百分点。同时还揭示了原位冷冻试样在解冻过程中所施加的围压水平对其液化特性的影响。

项目成果

Variations of shear strain alongheight and perimeter of hollow cylinder specimens during cyclic torsional shear loadings

循环扭转剪切载荷期间空心圆柱体试样沿高度和周长的剪切应变变化

• 发表时间: 2006
• 期刊: Proc. of 8th International Summer Symposium, International Activities Committee, JSCE
• 作者: DeSilvaL.I.N.;Sato;T.;Koseki;J.
• 通讯作者: J.

Liquefaction properties of Toyoura sand in cyclic torsional shear tests under low confining stress

低围应力下循环扭剪试验丰浦砂的液化特性

• 发表时间: 2005
• 期刊: Soils and Foundations 45・5
• 作者: Koseki;J.;Yoshida;T.;Sato;T.
• 通讯作者: T.

ねじり三軸試験用中空円筒供試体における局所変位計測の改良

扭转三轴试验空心圆柱试件局部位移测量的改进

• 发表时间: 2005
• 期刊: 第40回地盤工学研究発表会
• 作者: 古関潤一;佐藤剛司;DeSilva;L.I.N.
• 通讯作者: L.I.N.

Liquefaction resistance and dynamic shear moduli of in-situ frozen and reconstituted sandy soils

原位冻结和重构砂土的液化阻力和动剪模量

• 发表时间: 2007
• 期刊: Proc. of International Workshop on Earthquake Hazards and Mitigations
• 作者: Kiyota;T.;koseki;J. and Sato;T.
• 通讯作者: T.

大ひずみ中型中空ねじりせん断試験装置の開発

大应变中型空心扭剪试验设备的研制

• 发表时间: 2007
• 期刊: 第42回地盤工学研究発表会講演概要集 (CD-ROM)
• 作者: 佐藤 剛司;清田 隆;古関 潤一
• 通讯作者: 古関 潤一