Laboratory Investigation on Reactivated Residual Strength

Carrubba, Paolo; Fabbro, M. Del

doi:10.1061/(asce)1090-0241(2008)134:3(302)

Cited by 28 publications

(18 citation statements)

References 13 publications

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“…When landslides reach the dormant state, the shear strength could be recovered (Gibo et al, 2002;Nakamura, 2002;Carrubba & Del Fabbro, 2008), and it is expected that the recovered shear strength is time dependent. As shown in Fig.…”

Section: Recovery Of Shear Strength With Consolidation Periodmentioning

confidence: 99%

Mechanism of the slow-moving landslides in Jurassic red-strata in the Three Gorges Reservoir, China

Miao

Wang

Yin

et al. 2014

Engineering Geology

119

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Landslides in Jurassic red-strata make up a great part of geohazards in the Three Gorges Reservoir (TGR) in China. Most of them begin to move slowly with the accumulated displacement increasing stepwise, which corresponds to seasonal rainfall and 30 meters of reservoir water level fluctuation (145 m to 175 m on elevation). We analyzed the movement of 21 slow moving landslides in Jurassic red-strata in TGR, and found that all these landslides involved in two differing processes; one is the sliding process with different shear speeds of soils within the sliding zone (landslide activity), and the other one is in steady state with different durations (dormant state). This means that the soil within the sliding surface may experience shearing at different shear rates and recovery in shear strength during the dormant period. To clarify the mechanism of this kind of movement, we took soil samples from the sliding surface of Xiangshanlu landslide, which occurred on August 30, 2008 in Jurassic red-strata in TGR, and examined the shear rate dependency and recovery of shear resistance by means of ring shear tests. The results of tests at different shear rates show that the shear strength is positively dependent on the shear rate, and can be recovered within short consolidation duration after the shearing ceased. By increasing the pore-water pressure (PWP) from the upper layer of the sample, we also examined the 2 initiation of shearing which can simulate the restart of landsliding due to the fluctuation of groundwater level caused by rainfall or changes in reservoir water level. The monitored PWP near the sliding surface revealed that there was delayed response of PWP near the sliding surface to the applied one. This kind of delayed response in pore-water pressure may provide help for the prediction of landslide occurrence due to rainfall or fluctuation of reservoir water level.

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Section: Recovery Of Shear Strength With Consolidation Periodmentioning

confidence: 99%

Mechanism of the slow-moving landslides in Jurassic red-strata in the Three Gorges Reservoir, China

Miao

Wang

Yin

et al. 2014

Engineering Geology

119

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“…This is the case if we presume that the initial decrease in friction of 1) an aged, normally consolidated soil is comparable to the decrease in friction of 2) an overconsolidated clay that has a) been sheared to a residual friction and b) been allowed to regain some strength under fixed displacement. While the strength gain is time dependent, for experiments on 2) with healing times of 100–200 days the drop in friction coefficient with slip is low ( f p − f r ≈ 0.05), but occurs over smaller displacements, with initial slip‐weakening rates in the range w = 0.3–0.8/cm [ Stark et al , 2005; Carrubba and Del Fabbro , 2008; Stark and Hussain , 2010]. A freshly sedimented seafloor, like that presented in section 2 with accumulation rates of the order of 1 mm/yr, would represent a potentially well aged, normally consolidated slope.…”

Section: Rupture Nucleation By Local Increases In Pore Pressurementioning

confidence: 99%

“…However, while marine sediments are ideally considered as normally consolidated, given typical sedimentation rates on these slopes (∼mm/yr or less) strength may develop due to the long lifetime of interparticle contacts. Such behavior is indicated by increased sample stiffness following long periods of fixed loads in consolidation tests [e.g., Karig and Ask , 2003]; by the development of increasingly peaked stress‐strain profiles under triaxial loading conditions for normally consolidated samples previously held under loads for increasingly long times [e.g., Bjerrum and Lo , 1963]; as well as evidence of strength regain in ring‐shear tests after a period of fixed displacement [e.g., Stark et al , 2005; Carrubba and Del Fabbro , 2008; Stark and Hussain , 2010]. Such strength would be lost upon sufficient disruption of contacts (i.e., the sediments are considered sensitive), and if weakening is sufficiently strong, localized deformation may be expected as for overconsolidated sediments.…”

Section: Introductionmentioning

confidence: 99%

Nucleation of slip‐weakening rupture instability in landslides by localized increase of pore pressure

Viesca¹,

Rice²

2012

J. Geophys. Res.

108

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[1] We model landslide initiation as slip surface growth driven by locally elevated pore pressure, with particular reference to submarine slides. Assuming an elastic medium and friction that weakens with slip, solutions exist in which the slip surface may dynamically grow, without further pore pressure increases, at a rate of the order of the sediment shear wave speed, a situation comparable to earthquake nucleation. The size of the rupture at this transition point depends weakly on the imposed pore pressure profile; however, the amount of slip at the transition depends strongly on whether the pore pressure was broadly or sharply elevated. Sharper profiles may result in pore pressures reaching the total slope-normal stress before dynamic rupture is nucleated. While we do not account for modes of failure other than pure slip on a failure surface, this may be an indication that additional modes involving liquefaction or hydraulic cracking may be factors in the initiation of shallow slope failure. We identify two length scales, one geometrical (h, depth below the free surface) and one material (', determined by the frictional weakening rate) and a transition in nucleation behavior between effectively "deep" and "shallow" limits dependent on their ratio. Whether dynamic propagation of failure is indefinite or arresting depends largely on whether the background shear stress is closer to nominal peak or residual frictional strength. This is determined in part by background pore pressures, and to consider the submarine case we simplify a common sedimentation/consolidation approach to reflect interest in near-seafloor conditions. Citation: Viesca, R. C., and J. R. Rice (2012), Nucleation of slip-weakening rupture instability in landslides by localized increase of pore pressure,

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“…Stark et al (2005) observed that the magnitude of recovered shear strength increases with increasing soil plasticity, but the recovered strength was lost with small shear displacement. Carrubba and Del Fabbro (2008) conducted Bromhead (1979) ring shear tests, similar to those performed by Stark et al (2005), for aging times of up to 30 days and found more strength gain in Montona flysch than in Rosazzo flysch. Strength recovery is negligible in clayey soils after a 3 day rest period, but it is lost after a small shear displacement (Bhat et al, 2013b, c, d).…”

Section: Introductionmentioning

confidence: 94%

Strength Recovery of Landslide Soils from the Residual State of Shear

Bhat

Yatabe

Bhandary

2014

Soil Behavior and Geomechanics

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A preexisting shear surface of a reactivated landslide has been subjected to repeated sliding and recession. During the sliding, the shear strength of shear zone has been reduced to the residual state, but the strength may be recovered from the residual state to some extent during a rest period. In this study, three landslide soils collected from the different large-scale landslide sites in Nepal and Japan are tested in a ring shear apparatus for the discontinued shear rest periods of 1, 3, 7, 15, and 30 days. Test results show that recovered strength measured in the laboratory is slightly noticeable after a rest period of 3 days, but recovered strength is lost after a very small shear displacement. This paper mainly focuses on the strength recovery behavior in highly plastic and less plastic soils from the residual-state of shear. The probable causes of the strength recovery are also discussed.

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Laboratory Investigation on Reactivated Residual Strength

Cited by 28 publications

References 13 publications

Mechanism of the slow-moving landslides in Jurassic red-strata in the Three Gorges Reservoir, China

Mechanism of the slow-moving landslides in Jurassic red-strata in the Three Gorges Reservoir, China

Nucleation of slip‐weakening rupture instability in landslides by localized increase of pore pressure

Strength Recovery of Landslide Soils from the Residual State of Shear

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