By Yoo Heui-Jin
In general, people are not familiar with the vertical tunnel. It is derived from the vertical shaft in the mine that is used for reaching mineral deposits. In the mine, it is a passage for carrying ore, construction materials and mine workers. At the same time, it is also used for supplying air and power or for draining water.
In the construction industry, it has been used as ventilation shafts, water pressure tunnel for hydroelectric power plant, pumping-up power plant and atomic power plant. Sungpoong Construction Co., Ltd.(website: www.sp-ok.com) based in Jecheon, Chungcheongbuk-do Province, has been a leader in the construction industry specializing in vertical tunnel with unique technologies for design, construction work and maintenance in Korea. The Korea Post recently interviewed President Kim In-pil for his company introduction and plan for expanding his business into world market this year.
Question: What made you to start vertical tunnel business?
Answer: After working at a bakery in Jecheon for several years in my late 20s, I established a civil engineering company in March 1989, which took part in projects of developing and repairing mines in the region in early stages. Since transportation of ore from mines on high mountains to lower grounds where crushers are located cost much, we devised a vertical shaft as a solution. Under the circumstance of weak excavation technology, we realized the necessity of a vertical shaft in constructing tunnels and power plants that plays the part of a safe ventilation shafts. And we have been concentrating efforts on developing technologies for excavating tunnels.
Q: What are examples of vertical tunnel construction projects?
A: The company constructed more than a dozen major vertical tunnels in Korea. Building on technologies accumulated in constructing the Jukryeong Tunnel in the Jungang Express Way, it built the vertical water pressure tunnel at the Cheongsong Pumping-up Power Plant. It is an example of a construction project that shortened construction period and removed problems in constructing vertical tunnels. Adopting the Raise Climber (RC) method, the company built a tunnel between Miryang and Eonyang without constructing a separate access road. It is noted as a project of adopting eco-friendly construction method that installed a ropeway using helicopters in order not to damage the national park. At the pumping-up power plant in Yecheon, we constructed the longest vertical tunnel in Korea ( Depth: 534 meters). Despite numerous risk factors, we could successfully build the tunnel owing to unique technologies and expertise.
And recently the company completed the excavation work of ventilation shafts in the Inje Tunnel on the express way between Dong Hong-cheon and Yangyang. In building tunnels in total length of 10.965 kilometers on the road that connect the Seoul metropolitan area with East Coast, we used the RBM 73RVF-C, a state-of-the-art excavation equipment, for drilling vertical shafts. In addition, we completed the project of constructing ventilation shaft in a Geumseong tunnel on the express way between Chungju and Jecheon and also for Handuk Iron Mine‘s Sinyemi mine(Depth: 598 meter, Diameter: 8meter) and are currently working for Sanseong tunnel(Depth: 210meter, diameter: 9.4meter) at Busan.
Q: What are methods of excavating vertical tunnels?
Major excavation methods are Top-Down excavation and Pilot-Enlargement excavation method. The Top-Down excavation refers to a method of fetching muck up by excavating a tunnel from upper part to lower part without pilot drift. The pilot-enlargement excavation is a way of carrying down muck through pilot hole after enlarging such holes, which is more efficient than the Top-Down method. And Pilot-Enlargement excavation can be made in two methods – Raise Climber(RC) and Raise Boring Machine(RBM) methods.
RC method needs an enough working space at the bottom(lower area of the shaft). First install guide-rail with anchor on the wall inside of the shaft. Second, install Raise Claimer on the rail. Third, workers go upside to the top of the shaft by Raise Claimer. Last, drilling, loading, blasting by explosive, ventilation, scaling process is performed repeatedly in this order. Raise Boring Machine method is upward excavating method when working space is enough both upper and lower area of the shaft. Machine-room shall be installed at upper area of the shaft and reaming-room shall be installed at lower part of the shaft. RBM in the machine-room drills downward with Tri-con Bit(311millimeter). After penetrating to the bottom, assemble Reamer Head and then enlarge the hole(2.4-3.1meter)upward to the top.
While the RC method is disadvantageous when rocks or roof falls or water gushes out, the RBM excavation is easier when water gushes out. The RC excavation can immediately cope with change in ground and requires less early investment. In contrast, the RBM excavation is an advanced method as it is safer and accuracy of vertical shaft is higher with shorter construction period as it is mechanical excavation rather than manual one though it needs larger early investment.
After choosing one of the excavation methods, we install gantry crane at the top of the pilot with NATM method for safety and start excavating with Enlargement machine, Bucket machine, Injecting shotcrete device, Vertically moving slip form all in our unique expertise and know.
Q: Would you introduce your excavation equipment?
A: We have made unreserved investment in excavation equipment to enhance efficiency in construction work with long-range perspective. Our latest excavation equipment, RBM 73RVF C, can easily address various quality of rocks, and it is 14% more efficient than conventional hydraulic equipment, being a frequency convertible AC electric motor-driven machine. And it allows us to carry out competitive construction work by providing higher accuracy, higher safety and shorter construction period. We also have 2 RC equipment, STH-5L and STH-5D, 2 sets of enlargement machines and 3 sets of gantry cranes needed for constructing vertical shafts. We hold 31 vertical tunnel-related patents at the moment and are exerting our best efforts to develop new methods and equipment.
Q: Please explain your future business plan.
A: In early stage, we aimed at sustaining business for 10 years, and we concentrated resources on developing technologies for 10 years thereafter. Now we intend to contribute to social development in coming 10 years. We cannot be satisfied with the present situation. The domestic construction market is undergoing a long recession and is saturated. Leveraging our experiences and expertise, we are developing overseas markets. Having established a joint venture in April 2011 in Libya, we are expanding business to civil engineering area from waterworks and sewage installation. Currently, we are tapping the possibility of entering the market for building vertical tunnels of hydraulic power plant with the concerned authorities of Nepal, Iran, Pakistan, Indonesia. Furthermore, via meeting with ambassadors of Myanmar, India and Iran, we expressed our earnest desire to enter their market for the construction of infrastructure with our expertise and knowhow accumulated for 30 years. We are poised to compete with about 10 competitors around the world in the segment of vertical tunnel however, we are quite certain that we will fly high to world construction market not only in vertical tunnel area but also in civil engineering in the years to come.