Search

The Kyoto Landslide Commitment 2020 (KLC 2020;Sassa [3]) has officially been launched since the online launching session of KLC 2020, 5 November 2020 in the midst of COVID19 pandemic (Sassa [4], [5]) In the field of capacity building, SE RIBC offers courses for postgraduate students in landslide mechanics, dynamics and stabilization, and landslide risk mitigation Since 2011, UB FMG has been a full member of the International Consortium on Landslides (ICL) and has gradually been intensifying its contributions to the ICL worldwide efforts for landslide risk reduction and international promotion of landslide research Since 2009, ITGIS has been a full member of the International Consortium on Landslides (ICL) and has been gradually intensifying its contributions to the ICL worldwide efforts for landslide risk reduction and international promotion of landslide research [Extracted from the article] Copyright of Landslides is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission However, users may print, download, or email articles for individual use This abstract may be abridged No warranty is given about the accuracy of the copy Users should refer to the original published version of the material for the full abstract (Copyright applies to all Abstracts )

Influenced by the recent global climate change, extreme rainfall events have become more frequent worldwide and resultant hydro-meteorological hazards are creating more deaths and devastations. One of the most remarkable disasters of rain-induced rapid long-travelling landslides (RRLL) in Sri Lanka took place at Aranayake, 70 km east of Colombo in 2016 (JICA Survey Team 2016) (JICA Survey Team in Survey results of Aranayake Disaster, 2016). The fluidized landslide mass ran over an about 2 km distance claiming the lives of 125 people. This tragic event has thus highlighted the importance of sophisticated early warning and disaster management mechanism even more than ever, because the presence of these hidden unstable soil masses as well as their run-out distances are very difficult to predict, and once they start sliding, it is almost impossible to stop them. Both the National Building Research Organisation, Sri Lanka (NBRO) and the International Consortium on Landslides (ICL) have jointly compiled a research proposal within the framework of SATREPS, standing for “Science and Technology Research Partnership for Sustainable Development,” a Japanese government program that promotes international joint researches, and it passed the final round of selection on May 16, 2019. Thus, the new 5-years SATREPS project for Sri Lanka with regard to “Development of early warning technology of Rain-induced Rapid and Long-travelling Landslides (Project RRLL)”, starts in 2020. This article reports on the outline of the project including its goals, plans of plots for developing individual technologies for the early warning system, etc.

Rational estimation of debris flow velocity is one of the key issues in debris hazard mitigation. Among the various procedures, back-calculation of debris flow velocity is one of the most frequently used approaches. Back-calculation includes determination of super-elevations and channel properties, and velocities are calculated using the forced vortex equation. Super-elevation and bend radius are biasing parameters in the back-calculation scheme. Therefore, an iterative approach based on simplified assumptions is developed to avoid the direct and subjective determination of bend radius. Besides, as only the highest mud prints are visible after the disaster, this misreads the actual super-elevation. To seek better ways to fix this anomaly, a series of three-dimensional numerical curved flume tests using smoothed particle hydrodynamics are carried out. Estimated velocities from highest flow marks underestimate the actual velocities near the source, while they converge on the actual velocities as the distance to source increases. A best-fit line is then proposed to adjust the mud-marks-derived velocities to the real velocities. The assumption taken during development of the iterative approach for determining bend radii is also justified from the numerical simulations. The law of similarity allows application of these findings to real debris flow disasters. Thus, two real debris flow disasters in Japan are examined for validation of the developed procedure and adjusted velocities are proven to be consistent with verbal evidences and previous analyses.

A nonlinear p – y element was provided which can simply model the behavior of a pile group foundation subjected to lateral loading. Its elasto-plastic side soil is expressed as a Winkler-type distributed model. Despite the simplification involved in modeling such a complex phenomenon the proposed nonlinear soil model can reproduce the system behavior as computed by more rigorous 3D finite element methods. The numerical results are also compared with those from available physical model data to confirm that our simulations can predict the behavior of pile groups with good accuracy.

Fault surface ruptures constitute a great risk to human lives, buildings and infrastructure. Despite this few building codes contain risk reducing provisions. Experiments provided results for establishing design rules in terms of possible dislocation and failure strains. Dry and wet soil behave substantially different. A brief discussion on counteracting effects of the wet soil on the interaction between a buried structure and the surrounding ground is included.

The study of earthquake engineering requires an understanding of various processes by which structures are seriously damaged. For this, archiving available data in a systematic way will be quite necessary. Taskforces of both Japan Society of Civil Engineers (JSCE) and Japan Geotechnical Society (JGS), with a mission of establishing remedial measures for fault-inflicted damage to civil infrastructures, have been investigating previous examples of fault-related damages. Some of their important activities were further expanded as a subject of EqTAP project (Development of Earthquake and Tsunami Disaster Mitigation Technologies and Their Integration for the Asia-Pacific Region). This paper introduces some examples from the JSCE/JGS/EqTAP Data Archives, which can give some hints for rational remedial or design measures for civil-infrastructures whose constructions across faults were/are unavoidable.

Most laterally loaded piles are flexible in the sense that they are not deformed over their entire lengths. Instead, pile deflections become negligible below an ‘active pile length’ L a . This L a is an important parameter that governs the overall behavior of a rigidly capped pile group. In the present approach, piles closely grouped together beneath a superstructure are viewed as a single equivalent upright beam whose stiffness matrix determines L a . This idea is verified for different cases of pile spacing, and is further extended for nonlinear behavior of soils surrounding grouped piles.

A method to cover a tunnel lining with a soft and thin coating is discussed herein as a possible measure for mitigating seismic damage to tunnels. Long-term earthquake observations at different tunnel sites within a variety of alluvial soil deposits have demonstrated that a circular tunnel is liable to deform in such a way that its two diagonal diameters crossing each other expand and contract alternately. Narrowing down vibration modes, in order to discuss this particular and the most important mode, any of the essential items of the soil–tunnel system, namely the soil, the coating and the tunnel lining, has only one degree of freedom, allowing the coating effect to be simply evaluated in terms of a limited number of key parameters. Copyright © 2001 John Wiley & Sons, Ltd.

A method to cover a tunnel lining with a soft and thin coating is discussed herein as a possible measure for mitigating seismic damage to tunnels. Long-term earthquake observations at different tunnel sites within a variety of alluvial soil deposits have demonstrated that a circular tunnel is liable to deform in such a way that its two diagonal diameters crossing each other expand and contract alternately. Narrowing down vibration modes for discussion to this particular and the most important mode, any of the essential items of the soil-tunnel system—namely the soil, the coating and the tunneling lining—had only one degree of freedom, allowing the isolation effect to be simply evaluated in terms of a limited number of key parameters.

A simplified expression is derived for the dynamic stiffness of grouped piles subjected to lateral loading. A computer program, based on the Thin Layered Element Method, is used for this purpose. The results of the program are compared with rigorous solutions. The simplified expression of the dynamic stiffness of grouped piles, where the mass, damping and stiffness parameters are frequency invariant, will be particularly useful for an equivalent linear analysis of the interaction between nonlinear soil and grouped piles in real time.

A soil medium at the side of an embedded structure is treated as mutually uncoupled horizontal layers of a unit thickness. A plane strain condition is assumed within each individual layer such that the medium responses do not vary along the thickness. According to previous work by the authors and also a new formulation given herein, the impedance of the above layer at the structure can be produced by frequency-independent simple mechanical models for all three modes of foundation responses. Similar frequency-independent models are also presented for the impedance at the foundation base. These models are made of two different basic elements and a mass interconnected in series. Their arrangements directly indicate the wiring of electric circuits which generate signals corresponding to the transient soil–structure interaction responses. To all intents and purposes, electric circuits do not loose time in responding to the inputs. Therefore, they allow us to simulate the soil–structure interaction response in shake table model tests, which are commonly conducted at relatively high excitation frequencies for earthquake simulation.

Long term earthquake observations at different tunnel sites within a variety of alluvial soil deposits have clearly demonstrated that a circular tunnel is liable to deform in such a way that its two diagonal diameters crossing each other expand and contract alternately. Based on this knowledge, the soil-tunnel interaction for this particular vibration mode is investigated. The soil surrounding a tunnel is assumed to be a homogeneous elastic medium, and two extreme boundary conditions on the soil-tunnel interface are considered; the condition of fixed tangential strain and the shear stress-free condition. The former case suggests a firm bond between the tunnel lining and the soil, whereas the latter case is associated with an artificial slippery soiltunnel interface.

During the dynamic response of multiple partially or fully embedded structures, the subgrade medium at the sides of the structures not only generates the soil-structure interaction forces but also transmits the motions from one structural body to others. With Winkler's hypothesis, these forces and motions are formulated in the time-domain in a simple form utilizing the frequency-domains formulations. The validity of the developed formulations is examined using small-scale-model test results obtained for piles in a synthetic ground. A numerical example is provided to demonstrate the approach proposed and the formulations developed. The simplified time-domain formulations are found to be numerically efficient and yet capable of predicting the behaviour reasonably well.

A rational dynamic soil‐pile interaction model is presented. The model is developed adopting Winkler's hypothesis with a special attention to the conditions in which the strong nonlinearity is induced in the vicinity of the pile shaft under dynamic loading. It is formulated in a simple system of frequency independent mass, springs, and dashpots. Therefore, the model enables us to conduct the time‐domain nonlinear analysis in a relatively simple manner. Since the model can reproduce the dynamic effects by itself, its parameters are defined from the static behavior of a soil‐pile system or reasonable p‐y curves developed under the static condition. With a special consideration of a gap formed at the soil‐pile interface, the proposed model and procedure to define its parameters have successfully predicted the dynamic pile response observed in the field dynamic pile load tests. The nonlinear condition and dynamic condition are coupled with each other to produce the complex soil action to the pile shaft motion.

The Authors have recently proposed an idea to define the parameters of a logical nonlinear Winkler soil model. In the current paper, the capability of the model will be verified to evaluate the response of grouped piles beneath a superstructure. The results are then compared with those from available physical model data and 3D FE analysis to confirm that our simulations can predict the behavior of pile groups with good accuracy.

1 Graduate student, Institute of Industrial Science, University of Tokyo Tokyo 153-8505, Japan, kazmi@iis.u-tokyo.ac.jp 2 Professor, Institute of Industrial Science, University of Tokyo Tokyo 153-8505, Japan, konagai@iis.u-tokyo.ac.jp 3 Researcher, Institute of Industrial Science, University of Tokyo Tokyo 153-8505, Japan, kyokawa@iis.u-tokyo.ac.jp 4 Master course student, Disaster Management Policy Program (Seismology), Building Research Institute, Tsukuba Tsukuba 305-0802, Japan, cigdemtetik@hotmail.com

Nonlinear conditions are implemented in the time domain formulation for the dynamic response of pile foundations previously developed by the writers. Both single and group piles subjected to vertical dynamic load are considered. In the present study, the nonlinear effects in the vertical response are assumed to result from slippage of the pile from the soil. In order to demonstrate the capability of the present formulations and to see the effects of nonlinearity on the dynamic response of pile foundations, pile foundation responses are computed for both harmonic and transient load. Various interesting observations are made based upon the computed results.

A procedure for the time‐domain analysis of axial pile group response is developed. A pile‐soil‐pile interaction force is formulated in the time‐domain based on a previously developed dynamic, frequency‐domain Winkler model for a pile group. The response of the pile shafts in a group can be computed for one pile at a time individually in the time‐domain. The transfer matrix approach in the time‐domain, previously developed for a single pile, is applied with a minor modification to the pile group response analysis. Steady‐state responses of pile groups subjected to harmonic excitation are calculated using both the present time‐domain analysis and the previously developed frequency‐domain analysis. Good agreement between the results obtained by these two analyses validates the present approach. Numerical examples are provided for pile groups subjected to dynamic transient loading.

A new photoelastic experimental method for displacement measurement on rough surfaces of opaque materials was developed. In the method, a surface of a test specimen, such as that made of weak rock, mortar or soil, is coated with photoelastic transparent polymer, and the surface of the polymer coating is fixed by a rigid transparent plate. Accordingly, displacement on the surface of the test specimen is transformed into shear strain in the photoelastic coating. The shear strain induced in the coating can be easily detected by analyzing dispersive photoelastic fringes which appear when a polarized laser beam parallel to the surface of the specimen passes through the coating. This method can be expected as one of the simplest and useful methods for detecting minute deformations of opaque specimens.

Adopting a Winkler assumption, a simple mechanical soil model is developed for the flexural response analysis of dynamically loaded piles. The model is defined by examining a frequency-domain analytical expression of the dynamic response of a massless cylinder in an infinite previously developed medium. The expression is based on the plane strain assumption. Using this soil model, the time-domain transfer matrix is developed for the flexural response of a single pile. The steady-state harmonic response of a single pile is computed by both the present approach and a previously developed frequency-domain solution. Good agreement between the two computed results validates the present approach. The dynamic response of single piles subjected to the lateral impulse load is computed for piles in both homogeneous and inhomogeneous soil, in order to demonstrate the capability of the present approach. It is confirmed that the developed soil model and pile response formulation are very efficient in numerical computation.

In order to clarify soil-pile dynamics, a new experimental method using an electromagnetic induction type shock wave source was developed. In the experiment, a ground model was made of water-cured urethane polymer, and a pile of urethane was buried in this gel-like ground. An impulse with duration time of 0.5ms was given to the pile head by the shock wave source. This device consists of an aluminium circular plate and a flat solenoid coil close to this plate. A capacitor discharge through the solenoid serves as the energy source. Using this device makes it possible not only to estimate exact response characteristis of soil-pile systems pretty well but also to follow sharp wave fronts by photoelastic experiments.