The Hong Kong Branch of the Institute of Materials, Minerals and Mining (IOM3) organised an overseas trip regarding “Exploring Underground Works in Taiwan”, which was a three day trip from 1-3 October 2015 consisting of various workshops, research centre and technical site visits, conferences and field studies, and was attended by 24 participants.
Day 1 – Taipei MRT CK5701 Tunnel Project, National Center for Research on Earthquake Engineering and Chinese Taipei Tunnelling Association
A technical visit hosted by Continental Engineering Corp (CEC) at the Taipei MRT CK5701 Tunnel Project. The project is part of the additional Xinzhuang line to the Taipei Metropolitan Rapid Transit System. The Manager of Taiwan Business Division of CEC, Mr Garry Kuo, with the site representative of CEC, the Project Manager Mr Jack Lee and the Site Manage Mr Hung-Ming Tsai, intruded the Contract CK5701J to the participants. The construction site is located at Sinjhuang District of New Taipei City. The Client and the Architect of this project are the Northern District Project Office of Department of Rapid Transit Systems of Taipei and CECI Engineering Consultants Inc. respectively. The contract sum is about 6 Billion NTD (approximately 1.58 Billion HKD). This project involves the construction of an about 367.7 metres long tunnel and associated construction of a repair workshop. The visit consisted of viewing the site formation, shaft construction and tunnelling works. As part of the excavation works, extensive retaining structures were required to stabilize the ground around the shaft and tunnel. The geology of the retained soil was mostly consolidated clay, thus shoring and tie-back anchors supporting the slurry walls were constructed, and ground anchors of approximately 55 m length were installed to stabilize the hillside slopes, prior to the excavation of the shaft and tunnel. The lateral support system was observed to be more heavily strutted compared to ones found in Hong Kong as Taiwan had to account for the additional seismic loading. In anticipation of the dense temporary support system, only small plant were used for excavation; as such a long programme was intended for the construction works. The tunnel construction is separated into two main methods of construction: i) cut and open construction for sensitive clay soil and ii) with application of NATM tunnelling for rock section.
Participants at Taipei MRT CK5701 Tunnel Project Site
Taipei MRT CK5701 Tunnel
Mr Guy Bridges (middle), President of IOM3(HK), presenting souvenir to Mr Garry Kuo (R), Manager of Taiwan Business Division of CEC, and Mr Jack Lee (L), Project Manager of CEC
Participants then visited the National Center for Research on Earthquake Engineering (NCREE) in Taipei. Upon the visit to the research laboratory, the Director of NCREE, Prof. K.C. Chang, gave a detailed introduction of the objective of the NCREE, which is to provide earthquake research and testing services that are tailor to the needs of Taiwan. NCREE was also responsible for research works on early earthquake warning system, planning for emergency responses, and providing structure health monitoring. After the informative presentation, Dr. Pei-Yang Lin from National Taiwan University specializing in earthquake study showed the participants around the earthquake testing laboratory, detailing how various equipment worked such as the shake table, reaction wall and strong floor and Multi-Axial Testing System. Afterwards we were also shown the isolation system on the second floor of NCREE, which functions to decouple a superstructure from its substructure, therefore protecting a building’s structural integrity against earthquake. Dr. Lin described how the isolation system could be placed in the basement or second floor; basement had the advantage of accommodating elevators which is often used in malls, while second floor would allow for maximum land usage since no additional land is needed to accommodate for building movement.
Earthquake Research Center
Participants on the Seismic Isolation Floor of the National Center for Research on Earthquake Engineering
Afterward, we were invited to the Chinese Taipei Tunnelling Association (CTTA) for a meet-and-greet conference. The secretary of CTTA opened with the objectives of their respectful association, and then a sharing session was followed. Some of the discussion shared between the fellow members of CTTA and the participants included the design and construction of tunnel lining differences between Taiwan and Hong Kong, as well as site constraints in Taiwan tunnelling works.
(L to R) Mr Tim Leung, Mr Guy Bridges, Mr Ping-Cheng Hou, Prof. Tai-Tien Wang, Mr Winston Yung-Tuane Ni and Mr Andy Raine (middle) sharing experience at the forum
Participants with the CTTA Representatives at the forum
Day 2 – Suhua Improvement Works – Exhibition Centre – Suao Tunnel Section – Guanyin Tunnel Portion – Renshui Tunnel Portion
On the second day, the participants travelled from Taipei to Yilan to visit the Suhua Improvement Works. The visit commenced with a warm welcome by Mr Fong-Yuan Li, Chief of Suhua Improvement Engineering Office, Directorate General of Highways, MOTC, and informative presentation and introduction in the exhibition centre. The exhibition hall acted as an information centre for the local residents, which detailed the objective, methodology and progress of the construction of the improvement works. The tour guide informed the participants the purpose of the project is to provide a safer access for those who travelled on Suhua Highway, which is a major trunk road linking between Northern Taiwan and Eastern Taiwan. Some of the site constraints on the project include high ground water level and areas where very weathered rock were encountered. Furthermore, since a portion of the improvement works passed through the Taroko National Park, it was also required for them to monitor and adjust their work if the environment was negatively impacted.
Mr Fong-Yuan Li, Chief of Suhua Improvement Engineering Office, presenting Suhua Improvement Works at the exhibition hall
Participants at the exhibition hall of Suhua Improvement Works
After the detail explanation in the exhibition centre, the participants visited the Suao Tunnel Section. The construction manager explained to the participants that the Suao Tunnel is located near residential area and schools, thus drill and blast was not recommended. In addition, the geology of the Suao Tunnel composed of mostly highly weathered rock with high ground water level, which posed difficult site conditions. The method of construction for the tunnel excavation involved first excavating a central smaller drift and casting a central column, then using that as a support to assist excavation of the two adjacent main tunnels. The central smaller drift also facilitated the construction and allowed a review of the geological conditions as they excavated, allowing adjustments to be made if necessary.
Participants at the south portal of Suao Tunnel
Mr Guy Bridges (R), President of IOM3(HK), presenting souvenir to Mr Fong-Yuan Li (L), Chief of Suhua Improvement Engineering Office
The participants then visited the Guanyin-Yufeng Tunnel Portion, where some of the construction safety measures have been implemented. Part of the scope of work for Guanyin-Yufeng tunnel was to provide a ventilation duct along the top portion of the tunnel. In addition to regular ventilation uses, the duct would also assist in the emergency condition by extracting smoke and providing automatic temporary fire protection responses. It is because this section of the tunnel is the longest and most remote, these safety measures are critical to the tunnel functionality to accommodate future emergency services.
Participants at Guanyin Tunnel
For the last stop, the participants visited the Renshui Tunnel Portion, of which one main tunnel was to service two future carriage ways, and an additional emergency access tunnel that runs parallel to the main tunnel were being constructed. For this tunnel portion, the geology of the tunnel consisted of gneiss in the entrance of the tunnel, then marble with schist were found as the tunnel advanced. Since the geology of the rock were hard and weathered, and the tunnel is not located near sensitive buildings (i.e., residential areas), drill-and-blast method is used for the excavation. The participants witnessed a blast that was undertaken in the adjacent emergency access tunnel, and understood that a good ventilation system is critical for the safety for the workers as a measure to control dust and fumes resulting from blasting.
Tunnel portal of Renshui Tunnel
Participants at Renshui Tunnel
Day 3 Taroko National Park – Suhua Improvement Works
On the third day of the visit, the participants conducted a field study in Taroko National Park, where the Suhua Improvements would pass through.
The participants stopped by the Changchun Shrine, where both the steep mountains and Liwu River were seen. Marble and gneiss were observed along the exposed area of the visitor tunnels to the Shrine. Furthermore, water marks were seen along the side of the valley. From the observations and the information on the tourist centre, it is understood how Taroko was formed. Taroko Rorge started with calcareous sediments deposited along the rivers of the Eurasian continent, which eventually formed limestone after lithification. The limestone then underwent metamorphism from the pressure and heat and recrystallized into marble. This marble, eventually covered by other strata, was uplifted when the Philippine Sea Plate and the Eurasian Continental Plate collided. The exposed marble and strata were then eroded by rainwater and river, however due to the hardness of marble, only the softer material were eroded away, forming the famous steep valley and cliffs today. An interesting fact the participants learned was the Eurasian Continental Plate is still being pushed up continuously and Taroko Gorge rises at a rate of five to ten centimeters a year.
Participants at Taroko National Park
Taroko National Park
Highway No. 8 inside Taroko National Park is located between the steep valleys. As such, much soil stabilization works of different scales were observed along the highway. The participants were able to observe ongoing large scale repair works inside the national park during the tour. From the reports, the landslide location occurred near a fault line where weathered rock and discontinuities in the rock mass were found. Combined with continuous heavy rainfall, it caused a landslide resulting with 670,000 m3 of debris, which damaged at least 250 m of the highway. The large boulders, which were still observed today, provided additional challenges to the repair works as they needed to be blast into smaller pieces prior to removal.
During the travel back to Taipei, the participants reflected on the reasons Suhua Improvement Works were needed. As the visit was scheduled after the passing of the recent typhoon Dujuan that landed on the East coast of Taiwan, the damages were easily seen. Travelling on Suhua Highway was already difficult due to the narrow and winding road located near cliffs, but was even more risky with additional tree and boulder falls. From a transportation point of view, since the road serves as a major link between Northern Taiwan and Eastern Taiwan, any sort of landslide near the highway would increase in travel time and endanger the road users. Furthermore, the narrow road with minimal emergency access would be challenging to carry out most emergency responses. Therefore, from the transportation and safety point of view, the participants understood the need and urgency of the Suhua Improvement works.
We were very grateful for IOM3(HK) for providing this wonderful opportunity for us. Furthermore, we thank you all the hard work Mr. Tim Leung, the Council Member of IOM3(HK), and the coordinators had put to make this trip interesting and fruitful.
Author: Melissa Waye, Hong Kong Branch, 25 Nov 2015