Comparative Study on Undrained Shear Strength of Osaka Bay Pleistocene Clay Determined by Several Kinds of Laboratory Test
Comparative Study on Undrained Shear Strength of Osaka Bay Pleistocene Clay Determined by Several Kinds of Laboratory Test
复制标题
几种室内试验测定大阪湾更新世粘土不排水抗剪强度的比较研究
DOI：
10.3208/sandf.41.5_47
复制
发表时间：
2001
影响因子：
3.7
通讯作者：
T. Tsuchida
中科院分区：
文献类型：
--
作者：
Y. Watabe;T. Tsuchida
摘要本文介绍了一个岩土工程调查评价大坂湾更新世粘土的抗剪强度。在关西国际机场海堤结构的稳定性评价中，由于给出最小安全系数的滑动圈可能穿过更新世粘土层，因此更新世粘土的抗剪强度剖面对稳定性有很大影响。稳定性分析结果受不排水抗剪强度剖面的影响非常敏感，不排水抗剪强度剖面是根据天然粘土存款的不排水抗剪强度与固结屈服应力之比（s u /py）（Mesri，1975; Tanaka和Tanaka，1994）和该场地的平均表观超固结比（OCR = py / σ′v0）（Horie等人，1984年）。在这项研究中，为了评估不排水抗剪强度的典型测试方法，UC（无侧限压缩）试验，UU，CU，K 0 CU压缩和拉伸三轴试验和DS（直接剪切）试验的原状样品的更新世粘土收集关西国际机场第二阶段建设进行。力学行为和剪切强度剖面得到的每一个测试进行了比较和讨论。不排水抗剪强度及其分散性取决于试验方法。再压缩法是在原应力作用下对试件进行固结处理的一种方法，其试验结果可靠。UC和UU测试中，试样未固结，给出非常分散和不可靠的测试结果。通过对各试验确定的设计不排水抗剪强度与修正系数的比较，发现DS试验的强度小于K 0 CU和CU试验的强度。这是由于更新世粘土具有较大的强度各向异性。在考虑强度各向异性的情况下，得到设计用的不排水抗剪强度随深度的增长率Δsu/Δz为2.09 kPa/m。
ABSTRACT This paper describes a geotechnical survey evaluating the shear strength of Pleistocene clay in Osaka Bay. In the stability evaluation for a seawall structure of Kansai International Airport, as the slip circle giving the minimum safety factor possibly passes through the Pleistocene clay layer, the stability could be greatly affected by the shear strength profile of the Pleistocene clay. The result of the stability analysis is very sensitively affected by the undrained shear strength profile, which is roughly estimated based on a ratio of undrained shear strength to consolidation yield stress (s u /py) of natural clay deposit (Mesri, 1975; Tanaka and Tanaka, 1994) and the average apparent overconsolidation ratio (OCR = py / σ′v0) at this site (Horie et al., 1984). In this study, in order to evaluate the undrained shear strength obtained by typical testing methods, UC (unconfined compression) test, UU, CU, K0CU compression and extension triaxial tests and DS (direct shear) test were carried out for undisturbed samples of the Pleistocene clays collected for the second phase construction of Kansai International Airport. Mechanical behaviors and shear strength profiles obtained by each test were compared and discussed. The undrained shear strength and its scattering depend on the testing methods. The recompression method, in which a specimen is consolidated under the in-situ stress, gives many reliable test results. The UC and UU tests, in which a specimen is not consolidated, give very scattered and unreliable test results. From the comparison between undrained shear strengths for design determined by each test with correction factors, it is found that the strength of the DS test is smaller than those of K0CU and CU tests. This fact is derived from the relatively larger strength anisotropy of the Pleistocene clay. The undrained shear strength increase ratio with depth Δsu/Δz for design is obtained as 2.09 kPa/m, considering strength anisotropy.