Hendy Setiawan

The Simulation of a Deep Large-Scale Landslide Near Aratozawa Dam Using a 3.0 MPa Undrained Dynamic Loading Ring Shear Apparatus

The translational block glide of deep and large-scale landslide near the Aratozawa dam that occurred in the middle of 2008 is of great importance for detailed study. Aratozawa landslide had resulted from landform deformation and the subsequent change of watershed geomorphology at the upstream part of the Aratozawa reservoir. The evidence of this phenomena was revealed during a site investigation in November 2012, as several natural reservoirs (lakes) formed in the cavities between ridges and the depression zone in main block slide. Aratozawa landslide located in the Ohu Mountains basically was triggered by the earthquake which had a peak ground acceleration of more than 1,000 gal. In addition, the possibility of reactivated landslides in surrounding terrains near Aratozawa dam has resulted in the hypothesis that the 2008 event was one sequence of the dynamic-geomorphological activity in this mountainous area within a period of hundred years. In this paper, the mechanism of the deep and large-scale landslide near Aratozawa dam is analysed through a physical laboratory experiment. Deep landslide simulation is conducted by applying high normal stress to address the assumed slip surface of 150 m depth in the Aratozawa case. The 3.0 MPa undrained dynamic loading ring shear apparatus with the high pore-water pressure controlled is used to meet the criteria of deep-seated landslide of Aratozawa. The effect of groundwater fluctuation and the inter-linkage with the reservoir in the Aratozawa dam was found to be the main concern besides the peak ground acceleration based on the 2008 landslide event. Results also show that there was no significant deformation in the Aratozawa dam area when the large Tohoku earthquake, magnitude 9.0, in 2011. Indication is, that the slide blocks, ridges and mass depression due to the 2008 event are already stable. However, the slope and soil mass movement are still possible in the future.

TXT-tool 4.081-1.1: Mechanism of Large-Scale Deep-Seated Landslides Induced by Rainfall on Gravitationally Deformed Slopes: A Case Study of the Kuridaira Landslide in the Kii Peninsula, Japan

In September 2011, heavy rainfall brought by Typhoon Talas triggered 72 large-scale deep-seated landslides in Nara and Wakayama Prefectures, the Kii Peninsula, Japan. Most investigated landslides on the gravitationally deformed slopes were preceded by pre-existing small scarps along or near the head of the slopes. This study seeks to clarify the mechanism of the huge rainfall-induced Kuridaira landslide by simulating the increasing of pore water pressure with undrained high-stress dynamic loading ring shear apparatus. The authors also examined how gravitational deformations of upland slopes contribute to the mass movement under shear deformation. Laboratory experiments were conducted on two samples of the sliding plane taken in a site investigation, namely sandstone-dominated materials and shale materials. The pore water pressure control tests and shear displacement control tests clearly indicated that the rapid landslide was initiated due to high excess pore pressure generation and significantly shear strength reduction in the progress of shear displacement. The critical pore pressure ratio (ru) was about from 0.33 to 0.36 while shear displacement at the starting point of failure (DL) had a threshold value ranging only from 2 to 6 mm. More specifically, the high mobility of the landslide was in tests on shale sample due to a significant loss of shear strength. In addition, the authors observed the landslide occurrence associated with the sliding surface liquefaction behavior for both samples. The evidence of liquefaction phenomena in the tests was in accordance with the findings in the field survey and previous studies.

Landslide Dynamics: ISDR-ICL Landslide Interactive Teaching Tools (LITT)Open image in new window

The International Consortium on Landslides (ICL) and ICL supporting organizations jointly established the ISDR-ICL Sendai Partnerships 2015–2025 which is the voluntary commitment to the Sendai Framework for Disaster Risk Reduction 2015–2030. As the core activity of the Sendai Partnerships, ICL has created “Landslide Dynamics: ISDR-ICL Landslide Interactive Teaching Tools”, which are always updated and continuously improved, based on responses from users and lessons during their application. This paper describes the aim, outline, the contents of Text tools, PPT tools for lectures and PDF tools including already published reference papers/reports, guidelines, etc. Core parts of two fundamentals of the Teaching Tools, namely 1. Landslide types: description, illustration and photos, and 2. Landslide Dynamics for Risk Assessment are introduced.

TXT-tool 3.081-1.5: Manual for the LS-RAPID Software

This paper highlights the LS RAPID software that has ability to simulate the initiation and motion of landslides. Fundamental equations and concepts in the LS RAPID model are briefly explained. Step by step procedure of the use of this software are presented, which started from setting of the topography, creating the possible sliding surface using the ellipsoidal parameter, delineation of the unstable mass, soil and water parameters input, triggering factors for the inducement of landslides, the conditions for calculation, running the landslide simulation and up to the output settings after the simulation. Several cases of landslides which were analyzed by LS RAPID are described further in the PDF Tool: Manual for the LS-RAPID software.

TXT-tool 3.081-1.6: Manual for the Undrained Dynamic-Loading Ring-Shear Apparatus

The development of the ring shear device was upgraded since 2010, particularly for the loading system. Previous version of the ring shear apparatus of DPRI series has a long loading frame consists of pillars and beam for the normal stress system. Recently, loading piston through the single central axis was applied for the normal stress in the newest version of ring shear apparatus. There are two version of this new apparatus, called the ICL-1 and the ICL-2. The ICL-1 version was developed since 2010 as a part of SATREPS project for ‘Risk identification and land-use planning for disaster mitigation of landslides and floods in Croatia.’ Meanwhile, the development of the ICL-2 was carried out since 2012 as a part of SATREPS project between Japan and Vietnam for ‘Development of landslide risk assessment technology along transportation arteries in Vietnam’. As for practical purpose, both version of the undrained dynamic-loading ring-shear apparatus were designed in a small dimensions (compare with DPRI series) but with high performances. Thus, shallow landslide as well as deep landslide can be simulated geotechnically using this apparatus. In this paper, the structure, control and loading system of the apparatus are described in detail. The testing procedures and data analysis of ring shear tests are also explained.

TXT-tool 3.081-1.3: A Hypothesis of the Senoumi Submarine Megaslide in Suruga Bay in Japan—Based on the Undrained Dynamic-Loading Ring Shear Tests and Computer Simulation

The Senoumi (stone flower sea), which is located in the Suruga Bay, has a distinctive bathymetric feature and a concave shape with the dimension approximately 30 km in width and 20 in length. The shape of Senoumi was believed as results of the intense tectonic activity in the plate border, the submarine slides and flows from the Oi River of Shizuoka Prefecture. This paper presents the study of Senoumi area as a submarine mega-slide by analyzing the shear behaviors of three samples through ring shear tests. One sample was drilled from the submarine floor by the Integrated Ocean Drilling Program (IODP), while two samples were taken from Omaezaki Hill near Senoumi area. The measured parameters from the ring shear tests then used as an input in the integrated model of landslide simulation (LS-RAPID) for the initiation and motion of earthquake-induced rapid landslide of Senoumi. We used the strong motion record of the 2011 Tohoku Earthquake at the observation point of MYG004 in Miyagi Prefecture. The results of this study indicated the importance of further investigation for the risk of large-scale submarine megaslide that may occur in the Senoumi area, including tsunami and the enlargement of submarine landslide into the adjacent coastal area particularly due to the mega earthquake in the Nankai Trough in the future.

TXT-tool 3.081-1.4: Initiation Mechanism of Rapid and Long Run-Out Landslide and Simulation of Hiroshima Landslide Disasters Using the Integrated Simulation Model (LS-RAPID)

On August 20, 2014 many landslides and debris flows occurred in Hiroshima city during the heavy rainfall. Ring shear apparatus (ICL-1) was used to simulate the failure of soils, the formation of sliding surfaces and the steady-state motion of Hiroshima landslide disasters. Samples were taken from source area in Midorii and Yagi district. The ring shear tests on Midorii and Yagi samples were carried out under the normal stress of 50 and 100 kPa that assumed the landslide depth from 4 to 8 m. The triggering factor such as pore-water pressure was calculated by using the Slope-Infiltration-Distributed Equilibrium (SLIDE) model that developed by Liao et al. (Landslides 7:317–324, 2010, Environ Earth Sci 55:1697–1705, 2012). The rainfall record monitored at the Miiri JMA station for each 10 min from 8:30 PM on August 19, 2014 was used to calculated pore-water pressure and landslide occurred when pore-water pressure reached 15.2 kPa. All test results were input to an integrated simulation model (LS-RAPID) as dynamic parameter of landslide. The combination of landslide ring shear simulator and integrated landslide simulation model provides a new tool for landslide assessment. The hazard area and time of occurrence in Hiroshima disaster were estimated by LS-RAPID. The estimated hazard area is similar with landslide moving area reported by Geospatial Information Authority of Japan (GSI). This research will contribute to understanding the mechanism of landslide and debris flow during heavy rainfall as a basic knowledge for disaster prevention.

TXT-tool 3.081-1.7: Undrained Dynamic-Loading Ring-Shear Apparatus and Its Application to Landslide Dynamics

Landslides are the mass of rock, debris and or earth that moves down a slope by gravity. Study on landslide dynamics, including the dynamic of loading and excess pore-pressure generation and dissipation, is necessary to understand the initiation and motion of rapid landslides. This paper presents the development of ring shear apparatus that can facilitate the simulation of landslides, particularly for the formation of shear zone and followed by long and rapid shear displacement. A series of different types of ring shear apparatus (i.e. DPRI-3, 4, 5, 6 and 7) were developed by Prof. K. Sassa and his colleagues at the Disaster Prevention Research Institute (DPRI) of Kyoto University. The application of this apparatus to study the earthquake-induced landslides and landslide-triggered debris flow in Japan are explained in this paper. In addition, the tests using a transparent shear box of the DPRI-7 for visual observation of the shear zone during rapid shearing are also described.

Detail Study of the Aratozawa Large-Scale Landslide in Miyagi Prefecture, JapanOpen image in new window

The deep large-scale landslide near Aratozawa Dam in Miyagi Prefecture of Japan was occurred in 2008 and still the initiation mechanism and motion behavior were not explained in detail up to now. This paper aims to report briefly the detail study of the Aratozawa landslide. We conducted several experiments to test the Aratozawa samples using the newest version of the undrained dynamic loading ring shear apparatus. As reported by Sassa et al. (2014), the ring shear apparatus was designed with the single central axis-based for the normal stress loading system, with the normal stress and pore pressure measurement capacities of up to 3.0 MPa. The friction coefficient, shear displacement at the start and end of shear strength reduction, mobilized friction angle and steady state shear resistance of the Aratozawa samples were obtained from the ring shear tests. Experiments results implied that the shear strength reduction in progress of shear displacement of the Aratozawa samples was caused not only by the earthquake but also by factor of the initial pore pressure (Setiawan et al. 2014, 2016). Further analysis has been conducted by occupying shear parameters of soil failure resulted from experiment as a critical inputs for the LS-RAPID geotechnical simulation. LS-RAPID landslide simulation model is used to observe the overall process of landslide phenomena started from initiation to moving process. The Aratozawa landslide was successfully simulated using LS-RAPID model which involves the pore pressure increase, seismic loading, and landslide volume enlargement during traveling process. However, factor of the reservoir and its relation to the groundwater and bedrock is still needed to analyze in further.