Liquefaction-Induced Flow Failure of Embankments and Residual Strength of Silty Sands

Ishihara, Kenji; Yasuda, Susumu; Yoshida, Yoshitada

doi:10.3208/sandf1972.30.3_69

Cited by 50 publications

(15 citation statements)

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“…It was found that the friction angle of the liquefied sandy material from the Ohzumi landslide is approximately 14°. It is noted that this value falls within the range of 13-17°, the range of friction angles that is typical for liquefied sands, according to numerous case studies (de Alba et al 1987;Ishihara et al 1990;Ishihara 1993;Stark and Mesri 1992;Olson and Stark 2003). Number of cycles to 5% axial strain Cyclic Stress Ratio, CSR The results of slope stability analysis presented in Fig.…”

Section: Assessment Of Slope Stability After Earthquakementioning

confidence: 86%

Analysis of the mechanisms of slope failures triggered by the 2007 Chuetsu Oki earthquake

Gratchev

Towhata

2011

Geotech Geol Eng

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The 2007 Chuetsu Oki earthquake (M JMA = 6.6) triggered more than one hundred slope failures in the northwest part of Niigata prefecture, Japan. A reconnaissance survey conducted by the authors revealed that although most of the failures were only a few meters deep, they still caused significant damage to roads, railways, and houses. It was also found that a vast number of shallow slides were concentrated along the coastal line of the Japan Sea, while only few, but relatively larger failures occurred in a mountainous part of the study area, which is located in a considerable distance from the earthquake's epicenter. This paper summarizes the reconnaissance observations, describes the geologic characteristics of the area covered by landslides, provides characterization of major types of the landslides, and examines the causes and mechanisms of typical failures. In addition, this paper seeks to investigate the mechanism of the Ohzumi landslide, the largest slide triggered by the Chuetsu Oki earthquake. For this purpose, a comprehensive analysis that included field investigation and laboratory testing of soils samples was performed. Results of field investigation suggested that the failure plane of the Ohzumi landslide formed in a saturated layer of sandy soil near a boundary with bedrock. Data from undrained cyclic loading triaxial compression tests indicated that the sandy material was highly susceptible to generation of high excess pore-water pressures during earthquake loading. On the basis of the obtained results and the outcome of seismic response and slope stability analyses, the authors posited an explanation on the mechanism of the Ohzumi landslide.

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Section: Assessment Of Slope Stability After Earthquakementioning

confidence: 86%

Analysis of the mechanisms of slope failures triggered by the 2007 Chuetsu Oki earthquake

Gratchev

Towhata

2011

Geotech Geol Eng

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“…When assessing liquefaction potential and related cyclic failures in sloping grounds, the soil element is subjected to the static shear stress maintained all the way through, before, during, and after an earthquake shaking, though it may decrease as a result of changes in the configuration occurring in the earth structures due to seismic shaking (Ishihara et al 1990). Then, in the analysis, measured shear resistance under a certain given number of cycles is compared against the seismically induced driving shear stress.…”

Section: Approachmentioning

confidence: 99%

Study on seismic behavior of nonplastic silt by means of ring-shear apparatus

2008

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Study on seismic behavior of nonplastic silt by means of ring-shear apparatusAbstract The influence of static shear stress on undrained cyclic behavior of nonplastic and low-plasticity silts has been studied by means of undrained cyclic torque-controlled ring-shear tests. The cyclic and post-cyclic behavior of silty soils assumed on sliding surface were investigated to assess the liquefaction potential and cyclically induced deformation of silty slopes. Six different initial static shear stresses corresponding to slope angles from 0°to 25°w ere examined. To better understand undrained cyclic behavior of silt governed by a change in clay content, three different mixtures were achieved by mixing of nonplastic silt with 0%, 10%, and 20% of commercially available clay. These tests were conducted to simulate field conditions prior to earthquake with initial static shear stresses corresponding to slopes and those with no initial static shear stresses of level grounds. The gradual loss of mobilized undrained cyclic shear resistance after failure and pore water buildup in relation to a number of cycles was observed. The undrained response of the soil to cyclic shear stress loading with the constant amplitude revealed the significant effect of the initial static shear stress on the excess pore water pressure generation and post-failure shear resistance. Test results showed that an increase in the initial static shear stress at the given initial effective normal stress is associated with an increase of mobilized shear resistance at its peak state; however, the actual resistance to liquefaction diminished for both nonplastic and low-plasticity silts. During both cyclic and post-cyclic stages of loading, distinctly different types of shear deformation were identified. In order to evaluate mobility of landslides, a modified conventional brittleness index for seismic loading, I BS ¼ S peak À S u À Á S peak À S initial À Á , was proposed and used to characterize unlimited deformation of silts.

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“…In the present study, the relation between the cone tip resistance and undrained shear strength of soils is examined based on the data of undrained shear strength of soils estimated from each site of ‰ow failure and the results of Dutch cone penetration tests conducted during the post-earthquakeˆeld reconnaissance investigations. The details of the case history studies reported by Ishihara et al (1990aIshihara et al ( , 1990b) are summarized in Table 2. The main focus of the past studies was to estimate the undrained shear strength of soils from post-earthquake stability analysis, and to correlate it with the cone tip resistance observed along the depth of`collapsed' debris of sliding soil mass.…”

Section: Case History Studies On Cone Penetration Testsmentioning

confidence: 99%

“…The undrained shear strength ratio, Sus/s? vo, of soils mobilized at this site is estimated to be about 0.12, based on the following simple expression (Ishihara et al, 1990a),…”

Section: Tsukidate Landslidementioning

confidence: 99%

“…To evaluate the occurrence of ‰ow deformation during earthquakes, the procedures for estimating undrained shear strength of soils are necessary and have also been examined, based on laboratory triaxial tests and also on case history studies involvingˆeld penetration tests, (Seed, 1987;Seed and Harder, 1990;Ishihara et al, 1990a;Idriss and Boulanger, 2007; and others). One of the recentˆndings was that, in the presence of a soil layer with signiˆcantly lower permeability overlying the liqueˆable layer, there would be situations where the upward pore water seepage during earthquakes could lead to localized loosening of the liqueˆable soil, resulting in the undrained shear strength mobilized in theˆeld being much lower than that observed in laboratory tests, (Idriss and Boulanger, 2007).…”

Section: Introductionmentioning

confidence: 99%

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