The Longest Bi-directional Roadway

Tunnel in Korea, Baehuryeong Tunnel (Arial, 20pt)

Dongbu Corporation (Times New Roman, 11pt)

(# 전체 분량: 그림/표를 포함하여 10-12 페이지 내외, 영문으로 작성, 제출시한: 16. 12. 16, 그림/개념도의 경우 해상도가 높은 것을 사용할 것)

1. Introduction (Arial, 13pt)

(Times New Roman, 11pt) The Baehuryeong Tunnel, which connects Chuncheon and Hwacheon in Gangwon-do is a bi-directional, two-lane, single tube tunnel with a length of 5,057 m (See Figure 1).

The construction began in 2006, the excavation was finished and the construction of ventilation facilities is in progress, which is on schedule to be completed by 2012. After the completion of construction, it will be the longest bi-directional roadway tunnel in Korea.

Since the project area has a rugged topography and the tunnel is located over 400 m below, the vertical shafts were difficult to construct. Compared to a twin-tube tunnel, a bidirectional single tube tunnel has two major disadvantages with regard to a ventilation system and easy escape during fire. For these reasons, a service tunnel and the transverse ventilation system were selected.

The service tunnel is designed with a length of 5,173 m for the first time in Korea.

Figure 1. Plan of Baehuryeong Tunne (Arial, 10pt)

2. Geology (Arial, 13pt)

(Times New Roman, 11pt) The geology of the Baehuryeong Tunnel site is mainly composed of gneiss and granite as shown in Figure 2 and 3. The Baehuryeong fault develops parallel to the tunnel axis. Since the influenced zone of this fault is within 60 m, the Baehuryeong Tunnel is designed to separate from the Baehuryeong fault with the distance of more than 100 m.

Figure 2. Geological map of Baehuryeong Tunnel (Arial, 10pt)

Average compressive strength, total hardness, and quartz contents of rocks in the Baehuryeong Tunnel site are 13.5 MPa, 119~145, and 24~31 %, respectively. More than 70 % of the rocks in the Baehuryeong Tunnel site have the value of RMR > 75.

3. Design  (Arial, 13pt)

(Times New Roman, 11pt) The design specification of the Baehuryeong Tunnel is composed of bi-directional, twotraffic lanes with the speed limit of 80 km/hr, traffic lane width of 3.5 m, and hard shoulder width of 1 m for the Chuncheon direction and 2.5 m for the Hwacheon direction. Table 1 summarizes the design specification of the Baehuryeong Tunnel.

Since the Baehuryeong Tunnel has a plan to expand as twin tunnels operating four lanes, the service tunnel will be expanded as a two-traffic-lane tunnel with the length of 5,057 m.

Table 1. Design specification of Baehuryeong Tunnel (Arial, 10pt)
Length	Longitudinal slope	Ventilation system	Road layout	Comments (Times New Roman, 10pt)
5,057 m	S = +1.38 %	Transverse	•Two traffic lane : 3.5 m×2 •Hard shoulder : 1.0 m+2.5 m •Central median strip : 0.5 m	•Roadway width : 11.0 m •Service tunnel (TBM 5.0)

3.1 Tunnel cross section (Arial, 11pt)

(Times New Roman, 11pt) The Baehuryeong Tunnel with a width of 13.7 m was excavated by the drill and blast method. The service tunnel, bored ahead of the tunnel by TBM with an excavation diameter of 5.0 m, was used as a pilot tunnel to determine the geological conditions. Figure 4 and 5 show the typical cross section for the main tunnel and the service tunnel, respectively.