Hiroshi Fukuoka

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, 10xa0km 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.

Sonographically detected malignant transformation of a simple renal cyst

Abstract The clinical course is reported of a simple renal cyst which developed into a septated renal cyst, and finally to a cystic renal cell carcinoma. A 49‐year‐old man, who had been diagnosed as having a renal cyst, was found by repeated ultrasonography over 6 years to have solid components developing within the cyst. Radical nephrectomy was performed, and pathological examination confirmed cystic renal cell carcinoma (RCC). This case clearly shows a natural history of malignant transformation from a simple renal cyst, and emphasizes that careful follow‐up of renal cysts, especially of complicated renal cysts, is mandatory for successful treatment of RCC.

Landslides: review of achievements in the second 5-year period (2009–2013)

The international journal Landslides: Journal of International Consortium on Landslides was established in April 2004. The aims of Landslides are to promote landslide science, technology, and capacity building, and to strengthen global cooperation for landslide risk reduction within the United Nations International Strategy for Disaster Risk Reduction (ISDR). The achievements of the first 5xa0years from the beginning of 2004 (Vol. 1, No. 1) to the mid-2009 (Vol. 6, No. 2) were reviewed in 2009 (Landslides 6:275–286, 2009). This article presents the review for the second 5-year period from mid-2009 (Vol. 6, No. 3) to the end of 2013 (Vol. 10, No. 6), focusing on the journal’s significance and its impact. We include an analysis of the classifications of articles in Landslides.

Shear behavior of waste rock materials in drained and undrained ring shear tests

The denudation processes in abandoned mines pose environmental and social problems. Insufficient remediation and cleanup modify the physicochemical properties near the mine sites. In addition, large amounts of sediment and debris can flow downward due to heavy rainfall. Here, the shear characteristics of mine deposits are presented rather than their chemical contaminants, which include heavy metals. Drained and undrained ring shear tests were performed on waste rock materials that were collected from pyrophyllite mine deposits in the mountainous region of Korea. These samples were classified as gravelly sandy soils (i.e., with an effective grain size of D10 = 0.3 mm and a uniformity coefficient of cu = 5). The following three tests were performed: (i) shear stress measurement with shearing time for a given shear velocity (i.e., 0.1 mm/sec), (ii) shear stress as a function of shear velocity, and (iii) shear stress as a function of normal stress. The fully saturated samples were subjected to different normal stresses (i.e., 25 and 100 kPa) and shear velocities (i.e., 0.01, 0.1, 1, and 100 mm/sec). The waste materials exhibited a strain-softening behavior regardless of the drainage and shear velocity condition. In addition, the shear stress was strongly influenced by the shear velocity and increased with increasing shear velocity and normal stress in the post-failure stage. Using grain size distribution analyses, we show that significant grain crushing occurs in the shear zone during shearing. Under relatively high shear velocity conditions (i.e., >;100 mm/sec), the grain crushing effect is more significant and results in rapid mass movements.

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.

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.

Formation process of two massive dams following rainfall-induced deep-seated rapid landslide failures in the Kii Peninsula of Japan

Extreme heavy rainfall due to Typhoon Talas on September 2–4, 2011 in the Kii Peninsula, Japan, triggered numerous floods and landslides. This study investigates the mechanism and the entire process of rainfall-induced deep-seated landslides forming two massive dams in the Kuridaira and Akatani valleys, respectively. The mechanism of the rapid deep-seated landslides is examined through a series of laboratory experiments on samples from sliding surfaces by using undrained high-stress dynamic-loading ring-shear apparatus. The test results indicate that the failure of samples is triggered by excess pore water pressure generation under a shear displacement from 2 to 7xa0mm with a pore pressure ratio ranging from 0.33 to 0.37. The rapid movement of landslides is mainly attributed to high mobility due to the liquefaction behavior of both sandstone-rich and shale samples. Geomorphic settings and landslide mobility are major contributing factors to the dam formation. Additionally, shear displacement control tests show that a certain amount of shear displacement between 2 and 7xa0mm along the sliding surfaces of the gravitationally deformed slopes might have led to the failures. Importantly, computer simulation with LS-RAPID software using input parameters obtained from physical experiments is employed to interpret the entire formation process of the abovementioned two landslide dams. The simulation results are examined in accordance with the observed on-site geomorphic features and recorded data to explain the possibility of sliding processes. The results further point out that local failures are initiated from the lower middle part of the landslide bodies where the geological boundary exists. This condition most probably influences the landslide initiation in the two case studies. This research is therefore helpful for hazard assessment of slopes that are susceptible to deep-seated landslides and other sequential processes in areas with geology and geomorphology similar to that of the Kii Peninsula.

Shear and viscous characteristics of gravels in ring shear tests

The shear and viscous characteristics of a material are strongly dependent on the material’s properties, such as cementation, density and grain size distribution, as well as the testing conditions, such as drainage and shearing speed. More complex shear behaviors can occur when the tested materials have diverse grain sizes. The shear and viscous characteristics of gravels are examined in terms of drainage and shear velocity under the constant normal stress using a ring shear apparatus, in which the materials used can be sheared under a large deformation. In this study, the materials used are commercial aquarium gravels with mean diameter of 6 mm. Test results show that the materials typically exhibited strain-hardening behavior when subjected to low shear velocity (i.e., ≤ 0.01 mm/sec) and strain-softening behavior when subjected to high shear velocity (i.e., > 0.1 mm/sec) in the ring shear torque measuring system. As expected, higher shear velocities correspond to higher shear stresses, regardless of the drainage condition. For a given shear velocity (V) ranging from 0.01 to 1 mm/sec, a gradual decrease in shear stress is observed in the drained condition; however, a relatively constant shear stress is observed in undrained shear stress. It is clearly exhibited that the vertical displacement is large in the drained condition but relatively unchanged in the undrained condition. The grain crushing is significant for both drainage conditions when the materials experienced a large deformation. There are two regions: (a) non-dominant grain crushing and (b) dominant grain crushing (with a large amount of sand and fine contents) as a function of shear velocity. For both drainage conditions, a large shear resistance occurred when the shear velocity reaches 1 mm/sec. Through the contraction-particle rearrangement-grain crushing process during shear, when V ≥ 1 mm/sec, it appears that the shear stress is easily reached to the residual state of shear. The amounts of fine contents from grain crushing are much larger in the drained condition than in the undrained condition. In the extreme case that grains are highly crushed, it may result in a high mobilization of materials in natural hazards.

Drainage and Shear Velocity Dependent Shear Characteristics of Abandoned Imgi Mine Waste Materials in Ring Shear Tests

This paper presents the ring shear characteristics of abandoned Imgi mine waste materials (Busan Metropolitan City, Republic of Korea) as a function of drainage and shear velocity with the help of ring shear tests. The soil samples are mainly composed of gravelly sands with little percentage of fines. Normal stress, drainage (drained/undrained condition) and shear velocity (0.01–100 mm/s) were applied under the unlimited shear deformation. The test results show that the peak and residual shear strength were influenced as a function of shear velocity. The shear stresses increase with increasing shear velocity. The shear stresses measured from drained condition is much larger than those from undrained condition at the same shear velocity. It is due to the fact that a progressive grain crushing and sedimentation may occur strongly in the drained condition. Grain crushing is also significant with shear velocity: the higher the shear speed, the larger the crushed fines. Thus, high mobile characteristics of failed masses should be examined in terms of grain crushing and pore water generation.