Cause Investigation of Abnormal Settlement Phenomenon in Pleistocene Clay Layers by Experimental Examination of Clay Structural and Mineralogical Composition Changes

通过粘土结构和矿物成分变化的实验检验研究更新世粘土层异常沉降现象的原因

• 批准号: 14350258
• 负责人: UCHIDA Kazunori
• 金额: $ 8.26万
• 依托单位: Kobe 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 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14350258/
• 关键词: Strain Path Control; K_0 Consolidation; Triaxial Compression Test; Consolidation Test; Bender Element; Shear Modulus; Pleistocene Clay; Holocene Clay; K_o圧密

In this research, the K_0-consolidation characteristics of Pleistocene clay were examined using the strain-path controlled triaxial apparatus. The advantages of this test are described when compared with the conventional tests. Shear modulus was measured using bender element system to observe the change of particle structures indirectly. In addition, the particle structures were observed directly using the scanning electron microscope. The following concluding remarks can be obtained from this work.1. The advantages of the strain-path controlled test were shown in the following : Strain and excess pore pressure in a specimen can control freely and can keep homogenous even in the large strain domain ; the drained mode and the K_0-consolidation mode of clays can be controlled exactly and their testing times can be shortened.2. The result of this strain-path controlled K_0-consolidation test showed the very characteristic consolidation behavior of Pleistocene clay ; the void ratio decreas … More ed rapidly just after the pre-consolidation stress. This behavior is not apparent in a reconstituted kaolin clay sample. The K_0 value decreased to the pre-consolidation stress, then increased rapidly after that, and became a steady value. It seems that such results were due to structural change occurring in the clay just after the pre-consolidation stress.3. The shear modulus G during the K_0-consolidation test gradually increased to 100 (MPa), then it almost kept constant after that. The void ratio of this changing point in G precisely agrees with the one changed rapidly just after the pre-consolidation stress. The main cause of this change G can be recognized to be structural changes of Pleistocene clay significantly just after the pre-consolidation stress.4. The microscopic structure of Pleistocene clay was observed using the scanning electron microscope (SEM). A large number of diatoms destroyed were observed in the sample taken after a test although intact diatoms were observed in the one before a test. It can be considered that one of the causes for the rapid reduction of the void ratio just after the pre-consolidation stress is the frame of diatoms destroyed. In this research, the change of link structures of clay particles was not observed, which was considered as another cause of the rapid reduction of void ratio near the pre-consolidation stress. Less

本研究利用应变路径控制三轴装置对更新世粘土的K_0固结特性进行了研究。与传统测试相比，描述了该测试的优点。利用弯曲元件系统测量剪切模量，间接观察颗粒结构的变化。此外，使用扫描电子显微镜直接观察颗粒结构。从这项工作中可以得到以下结论： 1．应变路径控制试验的优点如下： 试件内的应变和超孔隙压力可以自由控制，即使在大应变域内也能保持均匀；可以准确控制粘土的排水模式和K_0固结模式，缩短测试时间。2．应变路径控制的K_0固结试验结果显示了更新世粘土非常典型的固结行为；预固结应力过后，孔隙率迅速下降。这种行为在再生高岭土样品中并不明显。 K_0值下降至预固结应力后迅速增加，并趋于稳定值。看来这种结果是由于在预固结应力作用后粘土发生了结构变化所致。3． K_0固结试验过程中剪切模量G逐渐增加至100(MPa)，之后几乎保持恒定。 G中这一变化点的孔隙比与预固结应力刚发生后迅速变化的孔隙比恰好一致。造成这种G变化的主要原因可以认为是更新世粘土在预固结应力作用后发生了显着的结构变化。 4．使用扫描电子显微镜（SEM）观察更新世粘土的微观结构。尽管在试验前的样品中观察到完整的硅藻，但在试验后采集的样品中观察到大量被破坏的硅藻。可以认为，预固结应力作用后孔隙率迅速降低的原因之一是硅藻骨架的破坏。在本研究中，没有观察到粘土颗粒链接结构的变化，这被认为是预固结应力附近孔隙比迅速降低的另一个原因。较少的

项目成果

Uchida.K., Stedman, D.J., Shimizu, M.: "Strain-Path Controlled Ko Consolidation Test of Marine Clays with Bender Element"Proc.14^<th> Int.Offshore and Polar Eng.Conf.. ISOPE2004-TM10(CD-ROM). (2004)

Uchida.K.、Stedman, D.J.、Shimizu, M.：“使用 Bender 元件对海洋粘土进行应变路径控制 Ko 固结试验”Proc.14^<th> Int.Offshore and Polar Eng.Conf.. ISOPE2004-TM10(

Uchida.K., Stedman, D.J., Sakagami, T.: "Strain-path Control Ko Consolidation of Marine Clays"Proc.13^<th> Int.Offshore and Polar Eng.Conf.. ISOPE2003-TM20(CD-ROM). (2003)

Uchida.K.、Stedman, D.J.、Sakagami, T.：“海洋粘土的应变路径控制 Ko 固结”Proc.13^<th> Int.Offshore and Polar Eng.Conf.. ISOPE2003-TM20(CD-ROM)

Uchida.K., Sakagami, T., Yoshiizumi, N: "Soil Behavior under Strain-Path Controlled Triaxial Test"Proc.3rd Internl.Symon Deformation Characteristics of Geomaterials. Vol.2(CD-ROM). (2003)

Uchida.K.、Sakagami, T.、Yoshiizumi, N：“应变路径控制三轴试验下的土壤行为”Proc.3rd Internl.Symon 土工材料变形特征。

Uchida.K., Stedman, D.J., Sakagami, T.: "Strain-path Control Ko Consolidation of Marine Clays"Proc.13^<th> Int.Offshore and Polar Eng.Conf.. (CD-ROM). ISOPE2003-TM20 (2003)

Uchida.K.、Stedman, D.J.、Sakagami, T.：“海洋粘土的应变路径控制 Ko 固结”Proc.13^<th> Int.Offshore and Polar Eng.Conf.（CD-ROM）。

Uchida.K., Sakagami, T., Yoshiizumi, N: "Soil Behaviour under Strain-Path Controlled Triaxial Test"Proc.3rd International Symposium on Deformation Characteristics of Geomaterials. CD-ROM(Vol.2). (2003)

Uchida.K.、Sakagami, T.、Yoshiizumi, N：“应变路径控制三轴试验下的土壤行为”Proc.第三届土工材料变形特征国际研讨会。