Sliding Surface Liquefaction Research Articles

Investigation of the characteristics and long-runout movement mechanisms of the Luanshibao landslide on the eastern margin of the Qinghai-Tibet Plateau

The Luanshibao (LSB) ancient landslide is a typical long-runout landslide that occurred on the eastern margin of the Qinghai-Tibet Plateau. To examine the long-runout mechanism of the LSB landslide, a detailed field investigation and a series of saturated soil triaxial and ring shear tests were carried out. The field investigation results revealed that the flat and broad Maoyaba (MYB) basin provides the required topographic conditions for the long-runout movement of the LSB landslide. The shallow deposit of the MYB basin is mainly composed of saturated weathered granite sand, which plays a key role in resulting in the high mobility of landslides. The results of the triaxial tests reveal that the soils show the characteristics of shear contraction first and then dilatation under static loading, and cyclic mobility occurs under cyclic loading. The results of the ring shear test reveal that the pore water pressure of the sample has undergone three stages of increase-decrease-increase. Finally, the pore-water pressure ratio increases to a constant of approximately 0.79, and the shear resistance decreases significantly. Grain crushing results in pore-water pressure generation and the liquefaction of saturated weathered granite sand for long shear displacement. It is proposed that sliding surface liquefaction is the main reason for the formation of complex surface landforms and the long-runout movement of LSB landslides.

Structural properties of shear zone materials of the Neogene soft-rock landslides in the northeastern margin of the Tibetan Plateau

Seven landslides among the 110 landslides on the northeastern margin of the Tibetan Plateau in China were selected to analyze the structural development processes within the shear zones. In addition, the platy clay mineral content and mineralogical composition of the shear zone were also investigated. The samples obtained from the vertical profiles were quantitatively studied from top to bottom with respect to their material composition, pore structure, and water properties to understand the changes in the cementation and frictional properties of the shear zone. The results indicate that the structure is progressively modified by fractures, cleavage, and plasticization. Even though there is no sliding surface liquefaction, clayey particles are observed to exhibit slipping and rearrangement. The illite–montmorillonite mixed-mineral layer accumulates near sliding surface in the core zone, and the platy clay minerals are arranged along shearing direction for long shear displacement.

Mechanism of two rapid and long-runout landslides in the 16 April 2016 Kumamoto earthquake using a ring-shear apparatus and computer simulation (LS-RAPID)

Around hundred landslides were triggered by the Kumamoto earthquakes in April 2016, causing fatalities and serious damage to properties in Minamiaso village, Kumamoto Prefecture, Japan. The landslides included many rapid and long-runout landslides which were responsible for much of the damage. To understand the mechanism of these earthquake-triggered landslides, we carried out field investigations with an unmanned aerial vehicle to obtain DSM and took samples from two major landslides (Takanodai landslide and Aso-ohashi landslide) to measure parameters of the initiation and the motion of landslides. A series of ring-shear tests and computer simulations were conducted using a measured Kumamoto earthquake acceleration record from KNet station KMM005, 10 km west of Aso-ohashi landslide. The research results supported our assumed mechanism of sliding-surface liquefaction for the rapid and long-runout motion of these landslides.

A model for grain-crushing-induced landslides—Application to Nikawa, Kobe 1995

A novel method is developed, motivated by one of the mysteries of the Hyogoken-Nambu (Kobe): the Nikawa landslide. To this end, prompted by the hypothesis of “sliding-surface liquefaction” advocated by Sassa [Development of a new cyclic loading ring shear apparatus to study earthquake-induced-landslides. Report for grant-in-aid for development of scientific research by the Ministry on Education, Science and Culture, Japan (project no. 03556021), 1994, p. 1–106; Keynote lecture: access to the dynamics of landslides during earthquakes by a new cyclic loading high-speed ring shear apparatus. In: Proceedings of the sixth international symposium on landslides, 1992. In: Landslides, vol. 3. Balkema: Rotterdam; 1995. p. 1919–39], a dynamic analysis of the early stages of an earth slide is presented considering two mechanically coupled sub-structures: (a) the rapidly deforming shear band at the base of the slide and (b) the accelerating sliding mass modeled as a rigid body. The proposed model for sliding is based on: (i) the concept of high pore-water pressure generation by grain crushing along the sliding surface (proposed by Sassa et al. in 1995), (ii) an experimental model developed by Hardin [Crushing of soil particles. J Geotech Eng 1985;111(10):1177–92] for crushing of soil particles under compression and shear, expressed with a set of developed equations governing the mechanism of breakage, and (iii) the hysteretic stress–strain Bouc–Wen-type constitutive model coupled with the Coulomb friction law. An attempt is made to adjust the model parameters to Sassa's experimental data in ring-shear tests. The method leads to a reasonable prediction of the large displacement of the Nikawa landslide. A sensitivity analysis is also carried out for the influence of key model parameters (e.g. shape, crushing hardness, void ratio, grain size distribution, effective normal stress) on the pore-pressure rise due to particle breakage.

Influence of shear speed and normal stress on the shear behavior and shear zone structure of granular materials in naturally drained ring shear tests

“Sliding Surface Liquefaction” is a process causing strength loss and consequent rapid motion and long runout of certain landslides. Using a new ring shear apparatus with a transparent shear-box and digital video camera system, shear-speed-controlled tests were conducted on mixed grains (mixture of three different sizes of sand and gravel) and mixed beads to study shear behavior and shear zone development process under the naturally drained condition in which pore pressure is allowed to dissipate through the opened upper drainage valve during shearing. Higher excess pore water pressure and lower minimum apparent friction were observed in the tests where grain crushing was more extensive under higher normal stress and higher shear speed. Along with the diffusion of silty water generated by grain crushing, smaller particles were transported upward and downward from the shear zone. Concentration of larger grains to the central and upper part of the shear zone was confirmed by means of visual observation together with grain size analysis of sliced samples from several layers after the test. On the other hand, smaller particles were accumulated mostly below the layer where larger grains were accumulated. The reason why larger grains were accumulated into the shear zone may be interpreted as follows: grains under shearing are also subjected to vertical movement, the penetration resistance of larger grains into a layer of moving particles is smaller than that into the static layer. Therefore, larger grains tend to move into the layer of moving grains. At the same time, smaller particles can drop into the pores of underlying larger grains downward due to gravity.

Landslide disasters triggered by the 2004 Mid-Niigata Prefecture earthquake in Japan

Synopsis During the 2004 Mid-Niigata Prefecture earthquake, thousands of landslides were triggered. Among them five catastrophic landslides were introduced in this paper. In addition, the influence of rainfalls in prior to the earthquake and the urgent response to prevent disastrous failure of landslide dams were also discussed and presented. Higashi Takezawa and Terano landslides occurred within past landslide masses and dammed the river at the toe of the landslides, causing great damages to the properties. Detailed field investigation was performed on these two landslides. To examine the triggering and movement mechanisms, samples were taken from these landslides. By using a ring shear apparatus, real earthquake wave loading test and cyclic loading tests were performed on these samples. The test results revealed that those sand samples from both landslides can suffer from sliding surface liquefaction phenomenon with very lower final apparent friction angles, while the silt sample from Terano landslide showed no liquefaction failure, indicating that landsliding during this earthquake time was triggered within the sand layer above the silt layer in the past landslide masses. Finally, the movement of Higashi Takezawa landslide was simulated.

Dynamic properties of earthquake-induced large-scale rapid landslides within past landslide masses

During the 2004 Mid-Niigata Prefecture earthquake, thousands of landslides were triggered, among them two large-scale rapid landslides (Higashi Takezawa and Terano landslides) occurred within past landslide masses and dammed the river at the toe of the landslides, posing great risks for the society. Detailed field investigation was performed on these two landslides. To examine the triggering and movement mechanisms, samples were taken from these two landslides. By using a ring shear apparatus, real earthquake wave loading test and cyclic loading tests were performed on these samples. The test results revealed that those sand samples from both landslides can suffer from sliding surface liquefaction phenomenon with very low final apparent friction angles, while the silt sample from Terano landslide showed no liquefaction failure, indicating that the sliding surfaces of these rapid landslides must have been formed within the sand layer in the past landslide masses.

Landslide risk evaluation and hazard zoning for rapid and long-travel landslides in urban development areas

Risk evaluation for earthquake-induced rapid and long-travel landslides in densely populated urban areas is currently the most important disaster mitigation task in landslide-threatened areas throughout the world. The research achievements of the IPL M-101 APERITIF project were applied to two urban areas in megacities of Japan. One site is in the upper slope of the Nikawa landslide site where previous movements were triggered by the 1995 Hyogoken-Nambu earthquake. During detailed investigation, the slope was found to be at risk from a rapid and long-travel landslide induced by sliding surface liquefaction by earthquakes similar in scale to the 1995 event. A new plan to prevent the occurrence of this phenomenon was proposed and the plan was implemented. Another area is the Tama residential area near Tokyo. A set of field and laboratory investigations including laser scanner, geological drilling and ring-shear tests showed that there was a risk of sliding surface liquefaction for both sites. A geotechnical computer simulation (Rapid/LS) using the quantitative data obtained in the study allowed urban landslide hazard zoning to be made at individual street level.

Mechanism of a long-runout landslide triggered by the August 1998 heavy rainfall in Fukushima Prefecture, Japan

Heavy rainfall from 26 to 31 August 1998 triggered many landslides in Nishigo Village of southern Fukushima Prefecture, Japan. The Hiegaesi landslide, a long-runout landslide with travel angle of 11°, which occurred in loamy volcanic-ash/pumice layer and was deposited in a nearby rice paddy, was investigated. In an observation pit dug in the middle part of the landslide deposit, the sliding zone just above the deflected rice plants was observed, and it was confirmed that grain crushing occurred in the sliding zone. The triggering and sliding mechanisms of this landslide then were investigated by ring-shear tests in laboratory. For the triggering mechanism, one saturated naturally drained test (test A: torque-controlled test) and one saturated undrained test (test B: speed-controlled test) were conducted on the samples taken from the source area of the landslide. Even in the naturally drained test opening the upper drain valve of the shear box, a temporary liquefaction occurred. In the undrained test, excess pore-pressure was generated along with shearing, and “sliding-surface liquefaction” phenomenon was observed. The effective stress and shear resistance finally decreased to near zero. These results can explain the observed phenomenon of small friction resistance like a flow of liquid when the sliding mass slid out of the source area. For the sliding mechanism of the landslide in the rice paddy, saturated undrained test (test C: speed-controlled test) was performed on soil sample above the deflected rice plants. The apparent friction angle obtained in this test was 8°. In addition, the residual friction angle measured after test B and test C was the same value of 41°. Combining with the observation on the shear zone in the ring-shear box after test C, it is concluded that, during the sliding in rice paddy, the undrained shear strength of the soil layer itself mainly influenced the high mobility of the landslide, probably because the friction between rice plants and soils is greater than the undrained shear strength inside the soil mass.

Geotechnical Simulation Test for the Nikawa Landslide Induced by January 17, 1995 Hyogoken-Nambu Earthquake

By employing an undrained cyclic loading ring-shear apparatus, a series of tests to reproduce the dynamic behavior of the Nikawa landslide induced by the January 17, 1995 Hyogoken-Nambu earthquake, is conducted. The test sample is Osaka-group coarse sandy soil taken from the landslide. The initial stress condition acting on a soil element in the sliding surface is applied to the sample. Based on the seismic records monitored at the JR Takarazuka Station, the input seismic wave is synthesized to reproduce the seismic stress acting on the sliding surface. The test results show that the soil failed due to the dynamic loading of the earthquake. The most important results are the excess pore water pressure generation and the acceleration of shear displacement continuing after the main shock. Combined with the grain crushing at the shear zone and the volume reduction in the drained constant-speed ring-shear test, the mechanism of this landslide is interpreted as, shear displacement causing grain crushing in the shear zone and volume reduction, and then resulting in a localized liquefaction phenomenon, “sliding-surface liquefaction”. This geotechnical simulation test provides a reasonable interpretation of this highly mobile landslide.

Liquefaction Behaviour of Osaka-group Coarse Sandy Soils

An investigation of the shear behaviour of Osaka-group coarse sandy soils by employment of the undrained speed-controlled ring shear test and the undrained strain-controlled triaxial compression test was conducted. A wide range of initial states of sand are covered to investigate a full spectrum of the shear behaviour including liquefaction and the newly proposed sliding-surface liquefaction. A comparative analysis by both soil tests suggests the followings ; (1) as to loose specimen at almost same relative density, the different types of liquefaction were generated (the triaxial compression test yielded conventional liquefaction and the ring shear test generated the sliding-surface liquefaction), (2) a clear shear plane appeared in the dense specimen for the triaxial compression test played an important role in excess pore pressure generation due to grain crushing.Next, the stress condition which marks the onset of collapse and the consequence of liquefaction after long shearing were examined using the ring shear test. It was revealed that the collapse behaviour took place in effective stress path reaching a certain stress ratio for normally consolidated specimens by the undrained ring shear test. And the steady state line from the ring shear tests which is obtained after the termination of grain crushing is located below that from the triaxial compression tests. It is interpreted as an ultimately obtained steady state, and it is called “ultimate steady state line.”

Mechanism of Rapid Long Runout Motion in the May 1997 Sumikawa Reactivated Landslide in Akita Prefecture and the July 1997 Harihara Landslide-Debris Flow, Kagoshima Prefecture, Japan

Two disastrous long runout rapid landslides caused big disasters in Japan, 1997. One is a reactivated type landslide which traveled over 1.5 km in Akita Prefecture. Another is a rapid landslide-debris flow which killed 21 persons living on a debris fan in Kagoshima Prefecture. The authors took samples in both landslides and simulated the stress condition at the initiation of landslide motion by the stress control ring shear apparatus. The test results suggested that the sliding surface liquefaction of the saturated andesitic debris in both landslides played a key role for the rapid long runout landslide motion. One of the remarkable test results is that the andesitic debris showed a low apparent friction angle of about 5 degrees after failure even in the drained state of shear box and during gradual increase of pore pressure. Excess pore pressure generation in the shear zone after failure was much greater than the pore pressure dissipation, and the permeability in the shear zone was much decreased due to grain crushing by shearing.

Earthquake-Induced-Landslides: Distribution, Motion and Mechanisms

ABSTRACT Landslides triggered by the 1995 Hyogoken-Nambu earthquake were reviewed based on air photo interpretation for their distribution. Landslides were almost linearly distributed along the line of aftershocks. Most landslides showed limited motion probably affected by less saturated soil condition due to the very dry season. The Osaka group layer, however, retained the ground water and rapid landslides took place there. The Nikawa landslide and the Takarazuka landslide were investigated as case histories. The undrained cyclic loading ring shear test suggested that this landslide showed a rapid motion due to the high pore pressure generation caused by grain crushing along the sliding surface. It can be called “sliding-surface liquefaction”. The trench investigation for the Takarazuka landslide and the previous undrained loading ring shear test for the Sale landslide suggested that the high mobility of the Takarazuka landslide was caused by the undrained loading onto the saturated layer. The sliding surface was formed inside the saturated layer below the ground surface, and the landslide mass moved scraping the surface soil layer above the saturated layer.