Study on improvement of accuracy in evaluating cyclic deformation properties of geomaterials by torsional shear tests on hollow cylindrical specimens

空心圆柱试件扭剪试验提高岩土材料循环变形性能评价精度的研究

• 批准号: 14350252
• 负责人: KOSEKI Junichi
• 金额: $ 3.46万
• 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: 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-14350252/
• 关键词: Torsional shear tests; Sand; Local deformation measurement; Young's modulus; Poisson's ratio; Shear modulus; End restraint; Bedding error

In seismic response analyses based on equivalent linear elastic modeling that are frequently employed in practice, cyclic deformation properties of geomaterials need to be evaluated accurately. Since level ground is subjected to cyclic shear stress acting on horizontal-vertical planes during earthquakes, it is more appropriate to use torsional shear tests on hollow cylindrical specimens than to use conventional triaxial tests on solid cylindrical specimens in simulating such stress conditions in the laboratory.In view of the above, in order to improve the accuracy of evaluating cyclic deformation properties, the quasi-elastic deformation properties of dry, dense Toyoura sand at very small strain level were investigated by conducting a series of triaxial and torsional shear tests on hollow cylindrical specimens. Strains were measured locally by a newly developed pin-typed local deformation transducer.In the tests, effect of end-restraint at the top cap and pedestal on small strain shear modulus that was measured externally by applying small unload/reload cycles in the torsional direction was found to be significant. Similar tendency was observed in the other tests conducted by changing the density and the soil gradation.A new hypo-elastic model was proposed to simulate the inherent and stress-induced anisotropies of quasi-elastic deformation properties of sand, considering rotation of principal stress axes from material axes. Good agreements between experimental and simulation data were observed. In the simulation, effect of inherent anisotropy on the quasi-elastic deformation properties of Toyoura sand was found to be small.

在实践中经常采用的基于等效线弹性模型的地震响应分析中，需要准确评估岩土材料的循环变形特性。由于水平地面在地震过程中会受到作用于水平和垂直面的循环剪应力，因此在实验室模拟这种应力条件时，采用空心圆柱试件的扭剪试验比传统的实心圆柱试件的三轴试验更合适。鉴于此，为了提高循环变形特性评估的准确性，拟弹性 通过对空心圆柱形样品进行一系列三轴和扭转剪切试验，研究了干燥、致密的丰浦砂在非常小的应变水平下的变形特性。通过新开发的销式局部变形传感器对应变进行局部测量。在测试中，发现顶盖和基座处的端部约束对小应变剪切模量的影响非常显着，小应变剪切模量是通过在扭转方向上施加小卸载/重加载循环在外部测量的。在通过改变密度和土级配进行的其他试验中也观察到了类似的趋势。提出了一种新的亚弹性模型来模拟砂准弹性变形特性的固有各向异性和应力引起的各向异性，考虑主应力轴相对于材料轴的旋转。实验数据与模拟数据之间观察到良好的一致性。在模拟中，发现固有的各向异性对丰浦砂的准弹性变形特性的影响很小。

项目成果

Modeling quasi-elastic deformation properties of sand

模拟沙子的准弹性变形特性

• 发表时间: 2003
• 期刊: Proc. of International Symposium on Deformation Characteristics of Geomaterials Vol.1
• 作者: Hong Nam;N.;Koseki;J.
• 通讯作者: J.

Hong Nam, N., Koseki, J.: "Effect of shear stress on quasi-elastic deformation properties of Toyoura sand"第37回地盤工学研究発表会講演概要集. 419-420 (2002)

Hong Nam, N., Koseki, J.：“剪应力对丰浦砂准弹性变形特性的影响”第 37 届岩土工程研究会议摘要 419-420 (2002)。

Improvement of local deformation measurement for hollow cylindrical specimens in torsional shear and triaxial tests

扭剪和三轴试验中空心圆柱试样局部变形测量的改进

• 发表时间: 2005
• 期刊: Proc.of 40th Annual Conference of Japanese Geotechnical Society, (in Japanese) (in press)
• 作者: Koseki;J.;Sato;T.;DeSilva;L.I.N.
• 通讯作者: L.I.N.

Hong Nam, N., Koseki, J.: "Modeling quasi-elastic deformation properties of sand"Proc.of International Symposium on Deformation Characteristics of Geomaterials. Vol.1. 275-283 (2003)

Hong Nam, N., Koseki, J.：“模拟砂的准弹性变形特性”岩土材料变形特征国际研讨会论文集。

Local and external measurement of quasi-elastic deformation properties of dry Toyoura sand in torsional shear and triaxial tests

扭剪和三轴试验中干燥丰浦砂准弹性变形特性的局部和外部测量

• 发表时间: 2004
• 期刊: Proc. of 6th International Summer Symposium, International Activities Committee, JSCE
• 作者: DeSilva;L.I.N.;Sato;T.;Koseki;J.;Wang;L.
• 通讯作者: L.