Geotechnical Division The Hong Kong Institution of Engineers 

 

 

REPORT ON TECHNICAL VISIT TO JAPAN 

17 – 22 JANUARY 2010  

 

 

 

 

 

 

 

 

 

 

 

By   Mr Jackie H L Cheng Mr Raymond W M Cheng Ms Angela H S Chow Ms Jennifer C K Ngai Mr Chris S C Tang Mr Steve M K Tang 

                       May 2010

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CONTENTS

Page No.

Title Page 1

CONTENTS 2

1 INTRODUCTION 3

2 VISITS TO RESEARCH INSTITUTE AND UNIVERSITY 3

2.1 PUBLIC WORKS RESEARCH INSTITUTE, TOKYO 3

2.2 NAGOYA UNIVERSITY, NAGOYA 5

3 VISITS TO CONSTRUCTION SITES 7

3.1 HANEDA AIRPORT EXPANSION SITE, TOKYO 7

3.2 NEW TOMEI EXPRESSWAY CONSTRUCTION SITE, FUJI 9

3.2.1 Introduction 9

3.2.2 Highway Bridge 10

3.2.3 Yuzawa Tunnel 11

3.2.4 Site Formation 11

3.3 VISIT TO MOUNTAIN FUJI SABO OFFICE AND YUI LANDSLIDE 12

PREVENTION SITE, FUJI

3.3.1 Countermeasures against Sediment Disasters of Mountain Fuji 12

3.3.2 Countermeasures against Volcanic Eruptions of Mountain Fuji 12

3.3.3 Yui Landslide Prevention 12

3.4 SLOPE STABILIZATION AND LANDSCAPE TREATMENT WORKS, 13

OKUTSU

4 JAPAN-HONG KONG SEMINAR ON UNDERGROUND CONSTRUCTION

TECHNOLOGY 14 4.1 GEO-RESEARCH INSTITUTE, OSAKA 14

5 CONCLUSION 16

6 ACKNOWLEDGEMENT 17

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1 INTRODUCTION The HKIE Geotechnical Division had organized a technical visit to Japan between 17 and

22 January 2010. The technical visit is one of the activities under the project “Study on State-of-the-art Technology and Experience on Civil and Geotechnical Engineering in Japan”, which is funded by the Professional Services Development Assistance Scheme (PSDAS) of the Hong Kong Government of Special Administrative Region. The visit aims at enriching Hong Kong engineers’ knowledge on the state-of-the-art technology and experience in civil and geotechnical engineering in Japan, especially on latest innovations for the construction of major infrastructures. The delegation comprised 38 members of the HKIE, led by Ir W K Pun, Chairman of Geotechnical Division, Ir Prof George Tham, Immediate Past Chairman, Ir Albert NL Ho, the PSDAS Project Chairman, and Committee members, Ir Ringo S M Yu and Ir Dr Eric S F Li.

The delegation was warmly received by the representatives of the Japanese Geotechnical

Society (JGS) in Tokyo and Geo-Research Institute (GRI) in Osaka. The technical visit for the delegation was arranged by JGS and GRI, which included visits to university, quasi-government research institutions, construction sites and consultant firms. Two itineraries had been arranged and the delegation briefly separated on two days to visit sites and institutions of different themes, with one focusing on infrastructure projects (Team A) while the other targeting at landslide mitigation measures and slope stabilization works (Team B).

The programme of the 5-day trip is summarized in the following table and details of the

technical visit will be described in the following sections.

Team Date Programme

A + B

17 Jan 2010 Depart Hong Kong to Tokyo

18 Jan 2010 Public Works Research Institute, Tsukuba City

19 Jan 2010 Haneda Airport Expansion Site, Tokyo

A 20 Jan 2010 New Tomei Expressway Construction Sites, Fuji City

21 Jan 2010 Nagoya University, Nagoya

B 20 Jan 2010 Landslide Prevention Sites at Yui River, Fuji

21 Jan 2010 Slope stabilization and mitigation works at Lake Okutsu

A + B 22 Jan 2010 Geo-Research Institute, Osaka Japan-Hong Kong Seminar on Underground Construction Technology 2010

2 VISITS TO RESEARCH INSTITUTE AND UNIVERSITY

2.1 PUBLIC WORKS RESEARCH INSTITUTE, TOKYO

On 18 January 2010, the delegation visited the Public Works Research Institute (PWRI) at

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Tsukuba City, which is 100 km from the metropolitan Tokyo. PWRI is one of the largest research institutions funded by the Ministry of Land, Infrastructure and Transport of the Government of Japan, although it is an independent administrative agency. As the core institution of civil engineering research in Japan, PWRI aims at efficiently developing public works technologies and quality social capital by conducting research and development concerning public works, technological instruction and promulgation of research results to the industry.

The Headquarter of the PWRI is located at the Tsukuba City and occupies more than

300,000 m2 land area. The Tsukuba Central Research Institute comprises six research groups with focuses on materials and geotechnical engineering, erosion and sediment control, road technology, construction technology, water environment, and hydraulic engineering. The PWRI has more than 345 research staff and has an annual budget of more than 13.2 billion yen (equivalent to HK$ 1.1 billion according to exchange rate in March 2010). PWRI receives about 25% of its revenue through collaboration in entrusted projects with the industry.

Professor Koseki of the Tokyo University led the delegation in visiting laboratories of

different research groups. The first visit was to the facility operated by the Tunnel Team of the Road Technology Research Group, which included a 700 m long full-scale test tunnel. The researchers briefed the delegation details of the research projects conducted in the tunnel, including testing of ventilation, trial study of lighting system, and study on the fire and smoke prevention system. The tunnel team also carries out research on tunnel lining, which includes 9.7 m diameter full-scale loading equipment for measuring stress and strain of loaded tunnel lining and occurrence of cracks in the lining.

The delegation was then led to the laboratory of the Debris Flow Team of the Erosion and Sediment Control Group. The team researches technologies to prevent and mitigate damage of debris flows and lahars, slope collapses and earthquake related damages. The laboratory has set up large scale physical model tests for simulating debris flow under heavy rainfall. Different dam models were added in the demonstration to investigate the collapse behaviour of the damming structures and the initiation of debris flow. The failure predictions are improved by understanding through physical models the change in slope displacement, soil water content and porewater pressure.

Plate 2.1.1 Group Photo of Delegates inside Plate 2.1.2 Physical Model of Debris Flow

a Full-scale Test Tunnel The delegation also visited the Dynamic Geotechnical Centrifuge Laboratory. PWRI’s

centrifuge is the second largest dynamic centrifuge in Japan, which has a rotating arm with effective radius of 6.6 m. Its maximum acceleration and payload capacity can reach 150 G and 400 tons G, respectively. Recent researches using the centrifuge mainly focused on

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simulating ground and earth structures, such as the behaviour of retaining walls subjected to large earthquake loads and behaviour of geosynthetics reinforced retaining walls. However, the centrifuge at PWRI cannot simulation field installation during the flight.

Plate 2.1.3 PWRI’s Centrifuge Plate 2.1.4 Full-scale Embankment Model

The delegation was led to the Earth Structure Laboratory of the Geotechnical Research

Group. The laboratory is housed inside a large span structure with a central pit measuring 20 m in length and 5 m in depth. The ceiling of the laboratory is equipped with sprinklers which can simulate up to an hourly rainfall of 100 mm. Full-scale model of earth structures such as river levees and road embankments can be formed in the pit and the seepage in the model can be produced by supplying water through water tank and rainfall infiltration.

2.2 NAGOYA UNIVERSITY, NAGOYA

On 21 January 2010, 20 delegation members visited the Department of Civil Engineering, Nagoya University. Nagoya University was established in 1871 and is now one of Japan’s pivotal comprehensive research universities, which plays an important role in shaping and influencing the future of today’s youth in Japan and overseas as well. The university has world-class researchers and four Nobel Prizes have been awarded to researchers of the University alumni.

Professor Masaki Nakano received and escorted the delegation to the Nagoya University Museum (NUM). The museum was opened in April 2000 for creating a broad interaction between the university and the public. The museum displayed the scientific results of both completed works and on-going research projects of the university; in particular, the research works of the four Nobel Prize Laureates in chemistry and physics.

Plate 2.2.1 Nagoya University Museum

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After visiting the NUM, the delegation was shown the Geotechnical Engineering

Laboratory, accompanied by the professors of the department and two post-graduate students from Mainland China. Professor Nakano introduced to the delegation various testing apparatus in the laboratory, such as the three dimensional triaxial testing apparatus based on hollow cylindrical specimen.

Plate 2.2.2 Geotechnical Engineering Laboratory, Nagoya University

Finally, Professor Akira Asaoka, the President of the Japanese Geotechnical Society met the delegation and gave a presentation on a numerical tool “Geo-Analysis Integration” (GEOASIA). GEOASIA is a soil-skeleton and water coupled finite deformation code developed by University of Nagoya. The numerical tool is designed to analyze the transient response of foundation and earth structure and could simulate behaviour of any soil types including sand and clay, in all states from deformation to destruction, and for all-round applications to both static and dynamic problems. The program utilizes the SYS Cam-clay model, which is an elasto-plastic constitutive model of the soil skeleton structure mechanisms (structure, overconsolidation, anisotropy). Professor Asaoka explained the ability of the SYS Cam-clay model of representing mechanical behaviours of all kinds of soil, from clay, with its pronouncedly non-linear material characteristics, through intermediate soil types, to sand, all within the same one logical framework. The soil constitutional model is specified by 17 parameters, which are determined from the results of conventional triaxial tests and oedometer tests.

The numerical tool adopts the finite deformation theory which takes into account the geometrical non-linear deformation from the primitive equation stage, in order to trace the geometrical shape deformation of foundations and structures. Consequently, the GEOASIA can be applied across a range of problems including consolidation deformation, slip failure, compaction of sand, liquefaction, and consolidation of sand after liquefaction, etc. The delegation was glad to learn from Professor Asoaka that GEOASIA would soon be released for the use of profession.

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Plate 2.2.3 Discussion of “GEOASIA” Plate 2.2.4 Photo of Delegation leaders with Professor Akira Asaoka 3 VISIT TO CONSTRUCTION SITES 3.1 HANEDA AIRPORT EXPANSION SITE, TOKYO

On 19 January 2010, the delegation visited the Haneda Airport Expansion site. Haneda Airport, which is situated at the northwest of Tokyo Bay, was used to be the international airport of Tokyo. It has been the principal domestic airport serving the Great Tokyo Area since the completion of Narita Airport. In early 2000s, the Japanese government had strengthened the Haneda Airport as the international routes in regional flights from Asia Region. Haneda Airport is the fifth busiest airport in the world based on passenger traffic in 2009. In order to meet the anticipated high demand of the air travel, the Japanese government launched the expansion project of Haneda Airport in 2007. The project mainly comprises construction of the fourth runway (D-runway) and the third terminal building for international flights. The technical visit mainly focused on the construction of the runway. The total expenditure for the expansion project was estimated to be about HK$50 billion and it is scheduled for completion by the end of 2010.

Plate 3.1.1 Overview of Haneda Airport Expansion Site

The alignment of the D-runway is constrained by its surrounding environment: the Tama

River to the south-west is the major shipping channel of Tokyo Bay to the north-east, as well as the flight restricted area of the airport itself. The proposed 3,120 m long fourth runway is constructed to the south-east of the existing airport. The southern part of the runway (about 1,000 m long) at the Tama River estuary is a decked structure minimizing the obstruction to water flow from the river, whereas the remaining part of the runway is constructed on reclaimed land. The project team gave a briefing on the technical background of the project.

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The decked platform is 1,100 meters long and 500 meters wide. It is a jacket-type

platform composed of approximately 200 steel jackets of 60 meters long and 45 meters wide. The platforms were supported on steel pipe piles driven through 40 m thick sediment of soft clayey soil over 15-19 m water. The upper portion of the platform was pre-fabricated and lifted into the pre-installed pipe piles. The accuracy of the driven piles was particularly tight to ensure smooth installation of the jacket-type platform. The steel piles were of 1.6 and 1.9 m in diameter and the top portion of the piles was lined with stainless steel. The deck was also covered with titanium cladding to reduce corrosion of the steel decking. In addition, the interior of the decking, which is mainly constructed with steel frame, would be ventilated with air condition for controlling the humidity as corrosion control measures.

Another technical challenge of the runway was the design of the expansion joint between

the decked structure and the reclaimed land. The expansion joint used at the connection is a roller shutter type made of steel plates system hinged together by pin connections. It mainly consists of a fixed plate on one side and a sliding rolling plate on the other side, with a maximum allowable transverse movement up to 1,200 mm. The joint allows differential movement at the connection due to temperature change or earthquake.

The long-term consolidation settlement of the reclaimed portion is another key design

consideration, which was estimated to exceed 900 mm in hundred years. To cope with this problem, cement treated soil (formed by pneumatic mixing) and air-foam treated soil (a lightweight soil with unit weight of about 10 kN/m3) were used as reclaimed materials, which could also enhance the stability of the seawall along the boundary of reclamation.

Tama River

D Runway

Tama River Haneda

Airport

Plate 3.1.2 – Layout of Expansion of Haneda Airport

(Courtesy of Tokyo Airport Authority)

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Plate 3.1.3 Stainless Steel Lining of Plate 3.1.4 Photo with Resident Site Staff

Bridge Section 3.2 NEW TOMEI EXPRESSWAY CONSTRUCTION SITE, FUJI 3.2.1 Introduction

On 20 January 2010, the delegation was separated into two teams, A and B. Team A visited the Fuji Office of the Central Nippon Expressway Company Limited (NEXCO). NEXCO manages the construction of the New Tomei Expressway connecting Tokyo and Nagoya. The new expressway will increase the traffic capacity between Tokyo and Nagoya and alleviate the congestion problems in original Tomei Expressway. It will also act as alternative route to Yui Coast, which can improve the reliability of the highway system.

The new expressway is routed closer to the mountainous area, which makes it more

resistant to the Tokai Earthquake that is predicted to occur in future. Moreover, the new expressway also features safer and more comfortable driving environment with more gentle curvature and gradient and wider shoulders compared to the existing expressway.

Figure 3.2.1 Features of the New Tomei Expressway (with courtesy of Central Nippon Expressway Co. Ltd.)

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3.2.2 Highway Bridge

A presentation of the project was given to the delegation in the Fuji site office and the two bridge sections used in the project were introduced, both of which could contribute to cost saving.

(a) Steel two-girder section - this section is widely used in the new expressway. The number of main girders could be reduced by adopting a prestressed concrete deck, as it is more durable and has a higher load bearing capacity. By using this girder section, the construction cost was reduced by 10% through reduction in steel girder manufacture, easier transportation and erection.

Figure 3.2.2 Steel Two-Girder Bridge Section (with courtesy of Central Nippon Expressway Co. Ltd.)

(b) Prestressed concrete box girder with struts - Another type of bridge section used is the prestressed concrete box girder with struts. By providing struts that supports the deck slab, the width of the main girder can be greatly decreased, hence reducing its self-weight, and the size of the pier and the foundation as well. Adoption of this bridge section reduced the construction cost by about 15%.

Figure 3.2.3 Prestressed Concrete Box Girder Section (with courtesy of Central Nippon Expressway Co. Ltd.)

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Plate 3.2.1 Flyover Construction at Yoshiwara Junction

3.2.3 Yuzawa Tunnel

The delegation was also led to visit the Chubu Odan No. 1 Yuzawa Tunnel. The Yuzawa tunnel is about 2.9 km long with a cross span of 9.5 m. It is excavated by using the drill and blast method. Each blast can progress the tunnel excavation by 1.5 m and a maximum of five blasts can be carried out daily. The delegation had the chance to inspect the temporary supports during the visit, including steel arches, patterned rock dowels and shotcreting), waterproof membrane, drainage measures and concreting of the permanent lining (Plate 3.2.2). Plate 3.2.3 shows the vertical drains beneath the waterproofing membranes, which collect seepage water from rock joints and discharge the water along the black drain pipe. Styrofoam rock dowel head protections are used to ensure that the rock dowels do not damage the waterproof membrane.

Plate 3.2.2 General View of the Chubu Odan Plate 3.2.3 Vertical Drains and Rock Dowel No. 1 Yuzawa Tunnel Head Protections 3.2.4 Site Formation

The last visit of the second Tomei Expressway was a large site formation (Plate 3.2.4) for

the future Shimizu Service Area of the new expressway. When completed, the area will provide travellers a service centre for drivers during their long hours drive.

Plate 3.2.4 General View of the Site Formation for the Future Shimizu Parking Area

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3.3 VISIT TO MOUNTAIN FUJI SABO OFFICE AND YUI LANDSLIDE PREVENTION SITE, FUJI

While Team A visited the construction sites of New Tomei Expressway, Team B went to the Mountain Fuji Sabo Office and the landslide mitigation measures constructed at Yui River. The office representative briefed members about the background of the SABO office. He highlighted three undertaking projects, namely countermeasures against sediment (debris flow) disasters of Mountain Fuji, countermeasures against volcanic eruptions of Mountain Fuji and Yui Landslide Prevention. 3.3.1 Countermeasures against Sediment Disasters of Mountain Fuji

The surface of Mountain Fuji was covered by metastable pyroclastic soil; where debris flow frequently occurs in early winter and late spring, especially in the area of Osawa Failure on the western side of the mountain. Osawa Failure was one of the biggest natural terrain failures in Japan, which extended from the peak at 2,200 m above sea level, and running 2.1 km. The debris spanned a maximum width of 500 m and 150 m deep maximum. The estimated volume of the collapsed soil was 75 million m3. The debris flow originated from Osawa Failure caused serious damage to downhill facilities and the largest lump of debris was found to be about 3 m thick. Mitigation measures, including Sabo dam, groundsill, sand pocket and excavated sediment trap, were constructed by the SABO office to prevent the debris flow from discharging into the Urui River at mountain toe. These mitigation measures successfully trapped debris flow in November 2000 and December 2004, respectively. 3.3.2 Countermeasures against Volcanic Eruptions of Mountain Fuji

The SABO Office took both soft and hard measures in mitigating the risk of volcanic eruption. The hard measures were basically the same as those adopted in mitigating the hazard in Osawa area. Soft measures included public relation activities to reach out local residents for emergency preparation to disastrous eruption, and preparation of systems that allowed sharing of information amongst the organizations concerned. In particular, a volcanic disaster-prevention map was produced to delineate the areas where craters could form and where lava streams, volcanic cinders, pyroclastic flows or the other eruption phenomena would occur. 3.3.3 Yui Landslide Prevention

The Yui area is located in Yui Town, Ihara-gun, Shizuoka Prefecture. The downhill side of Yui area is a key junction of transportation system connecting the east and the west of Japan. The main traffic artilleries passing through Yui include Japan Railway Tokaido Line, Route 1 and Tomei Expressway. Therefore, it is of paramount importance to take necessary measures to prevent slope failure in Yui area affecting the transportation system. Such stabilization measures included installation of ground anchors at the lower portion of the slope and diversion of groundwater from a collection chamber to a drainage tunnel, in order to control the groundwater level at the middle and the upper portion of the slope. The SABO office representative led the delegation to visit a 50 m deep collection chamber (Plate 3.3.2) and the monitoring system of Yui Landslide, which composes of raingauges, stream surveillance camera, and movement sensors for real-time monitoring. The system is operated on 7 x 24 basis such that immediate action could be taken in case of occurrence of landslide hazard.

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Plate 3.3.1 Yui Landslide Model Plate 3.3.2 Inspection of Collection Chamber

3.4 SLOPE STABILIZATION AND LANDSCAPE TREATMENT WORKS, OKUTSU

On 21 January 2010, Team B inspected the slope stabilization and landscape treatment works in the country park in Okutsu, Tsuyama. The visit was led by Ir Daniel Ho and Ir Tom Lee; which was arranged with a Japanese construction company who has extensive experience in slope upgrading projects in Japan.

In the past, landslides had frequently happened in the mountain range around Okutsu. To

deal with the landslide problem, the Japan Government carried out improvement works to the slopes since 2000. The slopes were classified into different groups according to their consequences of failure and priority was given to treatment of slopes adjacent to main roads, as compared with the ones situated along rural distributors or other remote areas.

During the visit, Team B paid particular attention to the treatment works of massive slopes

(say higher than 20 m). The typical treatment scheme includes cutting back of the hillside, installation of short soil nails (say 2 - 3 m long) on the upper part, and construction of a free frame system on the bottom part. The free frame system is composed of a lattice of reinforced concrete tie-beams intruded upon the slope surface (Plate 3.4.1). A layer of wire mesh is also installed on some of the slopes, in order to trap the debris originated from small-scaled landslides (Plate 3.4.2).

Plate 3.4.1 Free Frame System Plate 3.4.2 Wire Mesh on Slope Surface

Since the slopes to be treated were situated within country park around Lake Okutsu, their

landscape design had to create harmony with the natural environment. Soft landscape treatments (e.g. hydro-mulching) are commonly used to give the treated slopes a more natural appearance, so as to make them blend in with the surroundings. The plantation methods included fixing plantation in either flexible hessian bags or plastic pots. These are then

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anchored into the slope surface and short scrubs are used for greening the slope surface. The technique was found to be successful even on rock surface without soil layer. 4 Japan-Hong Kong Seminar on Underground Construction Technology 2010 4.1 GEO-RESEARCH INSTITUTE, OSAKA

In the morning of 22 January 2010, the two teams joined together again and attended the Japan-Hong Kong Seminar on “Underground Construction Technology 2010”. The Seminar was jointly organised by the Geo-Research Institute (GRI), the Hanshin Expressway Group (HEG) and the HKIE Geotechnical Division. About 100 Hong Kong and Japanese delegates including professional engineers from government, design consultants, contractors and academic institutions attended the Seminar.

Plate 4.1.1 Full House of Delegates Plate 4.1.2 Photo of Speakers and Organizers

The Seminar comprised 8 presentations under the theme of underground construction and

tunnelling projects. Ir W K Pun, the Chairman of the HKIEGD, was invited as a guest speaker to give a presentation on the subject “Construction projects and topics of geotechnical engineering in Hong Kong" in the Seminar, during which he shared with the delegates the geotechnical problems in Hong Kong and gave a introduction of tunnel projects in Hong Kong. At the beginning of the Seminar, welcoming remarks were given by Mr T. Hashimoto (the President of GRI) and Mr T. Nanbu from HEG. Eight presentations were given by guest speakers from Japan and Ir Pun respectively. A brief summary of the presentations are given in the following paragraphs. (a) Underground Structures in Hanshin Expressway

Mr Y. Adachi (Hanshin Expressway Engineering Co. Ltd.)

Mr Adachi presented the background and the technical details of major ongoing underground expressway projects of Hanshin Expressway Engineering Co. Ltd., including the Yodogawa Sagan Route near Osaka Bay, Inariyama Tunnel in Kyoto. He also shared with the participants their tunnel boring machine (TBM) technology in complex geological conditions composing of both soil and rock, as well as tunnelling projects under extremely severe site constraints, e.g. excavation under existing railway line, tunnel construction with river reclamation, and tunnel project with minimum clearance between two bored sections of only 1 to 3 metres, etc.

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(b) Introduction of Geo-Research Institute Group Mr J. Nagaya (Geo-Research Institute)

Mr Nagaya briefly introduced the company and some of the major researches and

development activities of the GRI Group. He also highlighted some of their recent research works, including a newly-developed wide-area web-server type automatic monitoring system, numerical analysis of ground deformation arising from excavation, embankment construction, groundwater flow, and earthquake, and development of investigation and construction management for environmental protection. (c) Introduction of Geo-information Database System

Mr K. Yamamoto (Geo-Research Institute)

Mr Yamamoto introduced the development of the “Kansai Geo-informatics Database” (GIbase). GIbase was essentially a collection of very large amount of borehole investigation data obtained under urban construction projects in Kansai region. As at June 2009, GIbase contains over 50,000 borehole data, with 23,600 of which were sunk in Osaka area. Development of GIbase not only promotes advancement in database technology, but also deepens the understanding of the underground conditions in Kansai region based on the analysis of the geological and geotechnical information revealed from the borehole investigation data. (d) Recent Bored Tunnelling (TBM) Technology in Japan

Mr T. Hashimoto (Geo-Research Institute)

Mr Hashimoto briefed the participants the recent bored tunnelling technology in Japan, such as a 70 m deep and steeply inclined tunnel bored for Nishi-Umeda pipeline, use of “Triple Multi-Face Shield Tunnelling” method for the construction of Osaka Business Park Station under an existing building and a trunk sewer, use of the world’s first “Shield Driven Double Track Subway Tunnel” with rectangular section for the Kyoto City Subway Network and Construction site, and the feasibility study of using large cross-section horseshoe shape shield tunnel for the Hirakata Tunnel of the New Meishin Expressway connecting Osaka and Tokyo. (e) For Effective Use of Underground Space

Mr S. Wada (Daiho Corporation)

Mr Wada highlighted the advanced tunnelling technology developed by Diaho Corporation, including the DK Shield (Muddy Soil Pressure) method, DOT (Double Circular) Shield Method, and DEPLEX (Eccentric Multi-shaft) Shield Method. In particular, the DEPLEX method was awarded the 1996 JSCE Technical Development Award. This method produces drilling machine that can bore any shape of section (e.g. circle, ellipse, arc-square, horseshoe shape, ring, etc.) by using multi rotary shafts with eccentric shaft rotors to drive the cutter heads. The key advantages of the method are smaller torque of cutter required, less abrasion of drilling bit, spacious working space inside the machine, and easier transportation, fabrication and disassemble of the machine on site, which make it the best choice for long distance boring of huge tunnel section. Since 1994, 10 tunnel projects had adopted the DEPLEX method, with section sizes ranging from 3.28 m to 9.6 m diameter for circular section and from H 2.35 m x W 2.95 m to H 3.98 m x W 4.38 m for square section. Mr Wada concluded his presentation by introducing a new pneumatic caisson excavation technique (New DREAM Method), which employs robots for deep excavation under high air pressure.

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(f) Hard Rock TBM Technology Mr T. Furusono (Nishimatsu Construction Co. Ltd.)

Mr Furusono demonstrated the broad experience of Nishmatsu Construction Company in

hard rock TBM technology by presenting the technical details of six tunnel projects, including rapid construction of Suzuka Road Tunnel in Japan (885.7 m per month) and Hong Kong Electric second cable tunnel in Hong Kong (592 m per month), large sections of Hida Road Tunnel in Japan (diameter of 12.84 m) and Dublin Port Tunnel in Ireland (diameter of 11.825 m), use of hard rock slurry TBM for Tseng-Wen Reservoir Transbasin Water Diversion Tunnel in Taiwan, and Odori Tunnel in Japan that was driven through fault zone with excessive water inflow. (g) Introduction of Technology of Slurry Shield Tunnelling Machine

Mr H. Onishi (Maeda Corporation)

Mr Onishi presented a railway tunnel construction project undertaken by Maeda Corporation, with particular emphasis on several special construction techniques, including u-turning of the shield tunnelling machine by using aero caster and use of cutter quick segment with special design of quick joint connection between tunnel lining rings.

The closing remarks of the Seminar were given by our chairman Ir Pun. He expressed our appreciation of the innovative tunnel boring technology and underground construction techniques in Japan. He also thanked for the effort of GRI and HEG in organizing the Seminar and wished for further interaction and collaboration with Japanese counterparts.

The participants and the delegation continued their interaction during the lunch time,

which provided opportunities to foster a stronger network for further collaboration. 5 CONCLUSION

The technical visit was well organized and informative; and successfully provided a useful platform for Japanese and Hong Kong practitioners and researchers to discuss and exchange knowledge on the state-of-the-art technology and experience on civil and geotechnical engineering in Japan.

The visit to the Public Works Research Institute and Civil Engineering Department of the Nagoya University impressed the delegation by its diversified research and development activities and the commitment of government and corporations to investing in research and development efforts. R&D programme initiated in Hong Kong cannot commensurate with the level of expenditure and commitment by the Japanese government and private corporations. It would no doubt enhance the capability in discharging of the Japanese industry in meeting future engineering challenges. A particular note on the approach by the Japanese research institutes is their investment on conducting large scale or full scale model tests, which are not common in Hong Kong.

The delegation was also impressed by the major construction projects in Haneda Airport

and New Tomei Expressway, in particular, their site tidiness and outstanding safety record. The workmanship in concrete and steel works was observed to be of an extremely high quality, which no doubt was attributed to the attitude of all personnel working on sites. Hopefully the exchange of knowledge and the networks that this technical visit established, could bring

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some of the excellent site practice in Japan to Hong Kong, which could definitely enhance the overall standard of the construction industry. During inspection of Yui landslide prevention project and slope works in Okutsu, the delegation gained Japanese experience in tackling natural terrain landslide hazards and upgrading existing unsafe slopes. Such experience would be most benefit to practitioners in Hong Kong in helping the implementation of systematic study and implementation of measures to mitigate natural terrain landslide risks, which is a core component of the post-2010 Landslip Prevention and Mitigation Programme in Hong Kong.

The Japan-Hong Kong Seminar in Osaka successfully promoted the exchange of advanced tunnel boring technology and prominent expertise in tunnel support. It also provided the delegation an invaluable chance to share their experience and vision on topics related to underground excavation with the Japanese counterparts. In particular, the delegation was impressed by the advancement of TBM technology in Japan, which enabled non-circular TBM being constructed and new tunnels being constructed close to existing underground structures. These techniques would be most relevant to Hong Kong environment. The exchange in the seminar would probably act as a catalyst for the introduction of some innovative tunnel boring techniques from Japan in the upcoming tunnel projects in Hong Kong.

The technical visit also allowed networking amongst the delegation and building up of strategic partnerships with the Japanese professional organizations. These partnerships enable us to continue acquiring the most current Japanese information in near future. The HKIE Geotechnical Division would arrange a symposium in September 2010; inviting Japanese academic and engineering practitioners to share their experience and insights on tunnelling technology in Japan. This could provide a good opportunity for Hong Kong practitioners, who had not joined the delegation visit, to keep abreast of latest developments and technology advancement in Japan.

6 ACKNOWLEDGEMENT

HKIE Geotechnical Division would like to express gratitude to the following organizations in arrangement of the technical visit, especially for their hospitality and logistic arrangement:

Public Works Research Institute Port and Airport Research Institute Central Nippon Expressway Company Limited Civil Engineering Department, Nagoya University Fuji Sabo Office Nisshoku Corporation Geo-Research Institute Hanshin Expressway Group

In particular, sincere appreciation is given to Mr. Hiroshi Yamada and Prof. Koseki,

representatives of Japanese Geotechnical Society, Dr Tadashi Hasimoto of Geo-Research Institute for their kind assistance in liaison with the above organizations.

Last but not least, the funding provided by the Government of the Hong Kong Special Administrative Region under the Professional Services Development Assistance Scheme

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(PSDAS) is gratefully acknowledged.