New Zealand – Japan Workshop on Soil Liquefaction during
Recent Large-Scale Earthquakes

A/Prof Rolando P Orense (University of Auckland, NZ)

The 2010-2011 Canterbury earthquakes in New Zealand and the 2011 off the Pacific Coast of Tohoku Earthquake in Japan have caused significant damage to many residential houses due to varying degrees of soil liquefaction over a very wide extent of urban areas unseen in past destructive earthquakes. Although these earthquakes caused extensive damage to life and property, they also serve as an opportunity to understand better the response of soil and building foundations to such large-scale earthquake shaking. With the wealth of information obtained in the aftermath of both earthquakes, information-sharing and knowledge-exchange are vital in achieving liquefaction-proof urban areas in both countries. Data regarding the observed damage to residential houses as well and the lessons learnt and current research on the topic of liquefaction are essential for the rebuilding efforts in the coming years and in mitigating buildings located in regions with high liquefaction potential.

As part of MBIE-JSPS collaborative research programme, the Geomechanics Group of the University of Auckland and the Geotechnical Engineering Laboratory of the University of Tokyo co-hosted a workshop to bring together researchers to review the findings and observations from recent large-scale earthquakes related to soil liquefaction and discuss new research results and possible measures to mitigate future damage. This workshop was held at the Faculty of Engineering building, University of Auckland, New Zealand on December 2 – 3, 2013. This event, which was attended by more than 80 researchers, engineers and practitioners from the local industry, involved invited presentations from 20 soil liquefaction experts from Japan, the United States, Chile and New Zealand. The highlight of the workshop was the two discussion sessions, one at the end of each day, which focused on current soil liquefaction issues, such as soil/site characterisation, liquefaction susceptibility and triggering, liquefaction-induced ground deformations, effects on structures and countermeasures. The final workshop proceedings will be published by CRC Press / Taylor & Francis Ltd in mid-2014.

Photographs taken during the workshop are shown below.

Photo 1 Group photograph of participants

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Ongoing Study on Protection of Personal Houses from
Liquefaction Problems

Ikuo Towhata Professor, Department of Civil engineering, the University of Tokyo
Kazuo Konagai Professor, Institute of Industrial Science, the University of Tokyo
Takashi Kiyota Associate Professor, Institute of Industrial Science, the University of Tokyo

INTRODUCTION

Two years are going to pass after the M=9 gigantic earthquake in Japan that took place on March 11, 2011. Because the earthquake damage caused many new problems, attempts for reconstruction are still going on, and one of the very difficult problems concerns the liquefaction damage on personal properties. Because the authors had an opportunity to present their study during the 4th International Symposium on Forensic Geotechnical Engineering, Bangalore, India, in January, 2013, they re-write their paper for this issue of ISSMGE Bulletin. It is aimed to discuss what has been missing in the traditional kind of geotechnical earthquake engineering.

Traditional technology on mitigation of liquefaction problems started to develop in 1960s after two earthquake disasters in Alaska and Niigata. Many achievements have been made with rational or sophisticated approaches such as the use of SPT-N or CPT for subsoil investigations, collection of undisturbed soil samples for laboratory tests, and densification or grouting or installation of gravel drains for damage mitigation by using big construction machines. Consequently, the vulnerability of many structures have been drastically reduced in the recent times and the earthquake in 2011 caused few liquefaction problems in engineered important structures. It is, however, noteworthy that those measures are feasible only when sufficient financial resources are available.

During the earthquakes in 2010 and 2011, liquefaction affected such structures as river levees (Photo 1), embedded life lines (Photo 2), and personal houses (see the next chapter). Those structures are characterized by their limited budgets that are available for disaster mitigation. Levees and lifelines are too long for the overall reinforcement against subsoil liquefaction. Their construction cost per unit length does not allow the significant reinforcement either. Consequently, the disaster management philosophy in the past aimed to restore any seismic damage within a short period of time after a quake.

Photo 1. Liquefaction damage in Hinuma levee

Photo 2. Disconnection of sewage pipeline and deposit of sand after liquefaction (damage study in Tokyo Bay area, 2011)

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The Japanese Geotechnical Society has published “Geo-hazards During Earthquakes and Mitigation Measures -Lessons and Recommendations from the 2011 Great East Japan Earthquake-“. It covers the following contents and can be downloaded from:
http://www.jiban.or.jp/e/disaster-survey-information-of-2011-tohoku-earthquake-2/

1. Introduction
2. Impact of the 2011 Great East Japan Earthquake
3. Characteristics of Geo-hazards, Issues Arising and Recommendations
4. Issues for Future Examination and Research

Application of various geotechnical technologies, as typically illustrated blow, are proposed to prevent and reduce geo-disasters.

ISSMGE Bulletin – Volume 5 Issue 6 (pp.24-27)
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VISIT OF ATC3 COMMITTEE ON SLOPE INSTABILITY SITES IN BHUTAN

Ikuo Towhata, University of Tokyo, towhata@geot.t.u-tokyo.ac.jp
Mitsu Okamura, Ehime University, okamura@cee.ehime-u.ac.jp
Hirofumi Toyota, Nagaoka University of Technology, toyota@vos.nagaokaut.ac.jp

INTRODUCTION

Asian member societies of ISSMGE have been operating several technical committees of their own and among those committees is ATC3 that concerns geotechnical natural hazards. In the current 4 years of term, this committee is chaired by Ikuo Towhata and is working on slope problems. As a part of the ATC3 activities, three committee members made a visit to Bhutan from October 18th, 2011, to 25th, and carried out some studies in collaboration with the Department of Geology and Mines of Bhutan Government and DHI-Infra Ltd.

Figure 1 illustrates the general idea of the Kingdom of Bhutan which ranges from the lowland at its Indian border to the top of Himalaya. The size of Bhutan is 38,400 km2 in area and its population is 700 thousands. Because of the tectonic action between the Indian Ocean Plate and the Eurasian Plate, the geology in Bhutan is highly distorted and fractured, which makes mountain slopes highly vulnerable to instability problems. The precipitation rate is 3,000 to 5,000 mm in the southern lowland, 1,200 to 2,000 mm in the lower Himalayan slopes, 500 to 1,000 mm in the central mountain regions, and less than 500 mm in Himalaya. Most precipitation takes place during the monsoon season of June to September.

Fig. 1 Map of Kingdom of Bhutan.

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Ikuo Towhata, Professor, University of Tokyo Hiroyuki Goto, Assistant Professor, Kyoto University Motoki Kazama, Professor, Tohoku University, Sendai Takashi Kiyota, Assistant Professor, University of Tokyo
Susumu Nakamura, Professor, Nihon University, Fukushima
Kazue Wakamatsu, Professor, Kanto Gakuin University, Yokohama
Akihiko Wakai, Professor, Gunma University, Kiryu
Susumu Yasuda, Professor, Tokyo Denki University, Saitama
Nozomu Yoshida, Professor, Tohoku Gakuin University, Tagajo

INTRODUCTION

At 2:46 PM local time on March 11th, 2011, a gigantic earthquake of magnitude Mw=9.0 occurred and affected the eastern half of Japan. Because the seismological aspects of this earthquake have been reported at many web sites and publications, the present report puts emphasis on the damage aspects that have so far been revealed by the post-earthquake investigations. This report is a contribution made by many members of the Japanese Geotechnical Society.

The causative fault of this earthquake is located in the Pacific Ocean off east Japan where an oceanic tectonic plate has been subsiding under the archipelago (Fig. 1). In the area of Sendai City, that is one of the biggest cities in the eastern part of Japan, there had been warning about a possible big earthquake in the coming years. It was anticipated that a part of the plate subduction to the east of Japan would cause this extreme event. The reality was, however, more than anticipated, the size of the causative mechanism being 500 km in length in the NS direction and the width being 200 km.

Fig. 1 Location of causative mechanism and major damage areas (Fault model by National Research Institute for Earth Science and Disaster Prevention)

In modern times, two gigantic earthquakes have been reported in this part of subduction. The one in 1896 registered the seismic magnitude (M) of 8.2 to 8.5 and the associating tsunami killed 21,915 victims together with 44 missing. The other one in 1933 was of M=8.1 (Mw=8.4) and claimed 1522 victims with 1542 missing. Both earthquakes caused minor intensity of shaking. Another tsunami disaster in the same area was caused by the 1960 Chile earthquake of Mw=9.5 and 142 people were killed. Those experiences encouraged both public and private sectors to be prepared for future tsunami disasters by constructing high sea walls and conducting tsunami evacuation drills, in which the height of future tsunami was decided on the basis of previous tsunamis. Despite those efforts, the present earthquake produced much bigger tsunami over the entire coast of east Japan (Fig. 1). It is often said that the 2011 earthquake is of similar size and effect as the Jogan earthquake in AD 869 that hit the same area and produced huge tsunami damage.

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Suguru Yamada, Assistant Professor, University of Tokyo
Rolando Orense, Senior Lecturer, University of Auckland
Misko Cubrinovski, Associate Professor, University of Canterbury

INTRODUCTION

On 22 February 2011 ，a magnitude Mw 6.3 earthquake occurred with an epicenter located near Lyttelton at about 10km from Christchurch in Canterbury region on the South Island of New Zealand (Figure 1). Since this earthquake occurred in the midst of the aftershock activity which had continued since the 4 September 2010 Darfield Earthquake occurrence, it was considered to be an aftershock of the initial earthquake. Because of the short distance to the city and the shallower depth of the epicenter, this earthquake caused more significant damage to pipelines, traffic facilities, residential houses/properties and multi-story buildings in the central business district than the September 2010 Darfield Earthquake in spite of its smaller earthquake magnitude. Unfortunately, this earthquake resulted in significant number of casualties due to the collapse of multi-story buildings and unreinforced masonry structures in the city center of Christchurch. As of 4 April, 172 casualties were reported and the final death toll is expected to be 181. While it is extremely regrettable that Christchurch suffered a terrible number of victims, civil and geotechnical engineers have this hard-to-find opportunity to learn the response of real ground from two gigantic earthquakes which occurred in less than six months from each other. From geotechnical engineering point of view, it is interesting to discuss the widespread liquefaction in natural sediments, repeated liquefaction within short period and further damage to earth structures which have been damaged in the previous earthquake. Following the earthquake, an intensive geotechnical reconnaissance was conducted to capture evidence and perishable data from this event. The team included the following members: Misko Cubrinovski (University of Canterbury, NZ, Team Leader), Susumu Yasuda (Tokyo Denki University, Japan, JGS Team Leader), Rolando Orense (University of Auckland, NZ), Kohji Tokimatsu (Tokyo Institute of Technology, Japan), Ryosuke Uzuoka (Tokushima University, Japan), Takashi Kiyota (University of Tokyo, Japan), Yasuyo Hosono (Toyohashi University of Technology, Japan) and Suguru Yamada (University of Tokyo, Japan)

GEOLOGICAL AND TECTONIC SETTING

The Canterbury Plains, about 180 km long and of varying width, are New Zealand’s largest areas of flat land. They have been formed by the overlapping fans of glacier-fed rivers issuing from the Southern Alps, the mountain range of the South Island. The plains are often described as fertile, but the soils are variable. Most are derived from the greywacke of the mountains or from loess (fine sediment blown from riverbeds). In addition, clay and volcanic rock are present near Christchurch from the Port Hills slopes of Banks Peninsula. The city of Christchurch is located at the coast of the Canterbury Plains adjacent to an extinct volcanic complex forming Banks Peninsula. Most of the city was mainly swamp, behind beach dune sand, and estuaries and lagoons, which have now been drained (Brown et al., 1995). The simplified geographical and geological information are shown in Figures 1, 2 and 3.

Canterbury has abundant water, in the rivers which carry mountain rainfall to the coast, and in aquifers. Beneath the plains, layers of porous gravels are interspersed with impermeable finer sediments. Near Ashburton, bedrock is at a depth of 1,600 meters (Wilson, 2009). Unlike most urban water supplies, Christchurch’s water comes from aquifers beneath the city. The aquifers are recharged by rainfall and by river seepage. They have been tapped to irrigate farmland and for town water supplies

Download ISSMGE Bulletin – Volume 5  Issue 2 (pp.27-45)
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Suguru Yamada, Assistant Professor, University of Tokyo
Rolando Orense, Senior Lecturer, University of Auckland
Misko Cubrinovski, Associate Professor, University of Canterbury

INTRODUCTION

On 22 February 2011 ，a magnitude Mw 6.3 earthquake occurred with an epicenter located near Lyttelton at about 10km from Christchurch in Canterbury region on the South Island of New Zealand (Figure 1). Since this earthquake occurred in the midst of the aftershock activity which had continued since the 4 September 2010 Darfield Earthquake occurrence, it was considered to be an aftershock of the initial earthquake. Because of the short distance to the city and the shallower depth of the epicenter, this earthquake caused more significant damage to pipelines, traffic facilities, residential houses/properties and multi-story buildings in the central business district than the September 2010 Darfield Earthquake in spite of its smaller earthquake magnitude. Unfortunately, this earthquake resulted in significant number of casualties due to the collapse of multi-story buildings and unreinforced masonry structures in the city center of Christchurch. As of 4 April, 172 casualties were reported and the final death toll is expected to be 181. While it is extremely regrettable that Christchurch suffered a terrible number of victims, civil and geotechnical engineers have this hard-to-find opportunity to learn the response of real ground from two gigantic earthquakes which occurred in less than six months from each other. From geotechnical engineering point of view, it is interesting to discuss the widespread liquefaction in natural sediments, repeated liquefaction within short period and further damage to earth structures which have been damaged in the previous earthquake. Following the earthquake, an intensive geotechnical reconnaissance was conducted to capture evidence and perishable data from this event. The team included the following members: Misko Cubrinovski (University of Canterbury, NZ, Team Leader), Susumu Yasuda (Tokyo Denki University, Japan, JGS Team Leader), Rolando Orense (University of Auckland, NZ), Kohji Tokimatsu (Tokyo Institute of Technology, Japan), Ryosuke Uzuoka (Tokushima University, Japan), Takashi Kiyota (University of Tokyo, Japan), Yasuyo Hosono (Toyohashi University of Technology, Japan) and Suguru Yamada (University of Tokyo, Japan)

GEOLOGICAL AND TECTONIC SETTING

The Canterbury Plains, about 180 km long and of varying width, are New Zealand’s largest areas of flat land. They have been formed by the overlapping fans of glacier-fed rivers issuing from the Southern Alps, the mountain range of the South Island. The plains are often described as fertile, but the soils are variable. Most are derived from the greywacke of the mountains or from loess (fine sediment blown from riverbeds). In addition, clay and volcanic rock are present near Christchurch from the Port Hills slopes of Banks Peninsula. The city of Christchurch is located at the coast of the Canterbury Plains adjacent to an extinct volcanic complex forming Banks Peninsula. Most of the city was mainly swamp, behind beach dune sand, and estuaries and lagoons, which have now been drained (Brown et al., 1995). The simplified geographical and geological information are shown in Figures 1, 2 and 3.

Canterbury has abundant water, in the rivers which carry mountain rainfall to the coast, and in aquifers. Beneath the plains, layers of porous gravels are interspersed with impermeable finer sediments. Near Ashburton, bedrock is at a depth of 1,600 meters (Wilson, 2009). Unlike most urban water supplies, Christchurch’s water comes from aquifers beneath the city. The aquifers are recharged by rainfall and by river seepage. They have been tapped to irrigate farmland and for town water supplies.

Download ISSMGE Bulletin – Volume 5 Issue 2 (pp. 27-45)
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