Construction Supervision

Summary

As of June 30, 2003, total length of Main Tunnel excavation reached to 2,765.1m (progress 71.70) from the Tunnel Portal.

Fifty four (54) niches (13 emergency & call niches and 41 Firefighting Niches) were completely excavated inside the Main Tunnel.

The Main Tunnel Concrete Lining completed up to the end of this month totaled to 2,039.4m (progress 52:88%)

As of June 30, 2003, the length of Evacuation Tunnel excavation reached to 2,634.3, (progress 64.30%) from the Tunnel Portal.

Main Tunnel 

• Excavation

In the month of June 2003, the rock encountered in the Main Tunnel was generally good. Geologically, the condition was stable on Class B. On some portion, it was classified as class A this month.

However, the excavation progress for the month of June 2003 is still less than the rate needed per month. Total excavation length for this month was 142.10m, giving a total length of 2,765.10m Sta. 4+408.1 (Progress: 71.70%) from the tunnel portal.

• Niche Excavation:

Fifty-four (54) Niches – Thirteen (13) Emergency Call Niches and Fourty-one (41) Firefighting Niches – in the Main Tunnel were already excavated. Excavation of niches continues according to the designed niche distribution plan.

• Lay-by Left No.1, 2, 3, 4 and Right No.1, 2, 3(connected to EP Outlet), 4

The excavation of Lay-by Left Nos. 1, 2, 3 and Lay-by Right Nos. 1, 2, 3 in the Main Tunnel, which has a total length of thirty-two (32) meters each, were completed during the previous months as per original plan. Excavation of Lay-by Right No. 4 (connection to VA Clean Air Supply Section) was completed this month.

• Main Tunnel Rear Works (Concrete Works)

The pouring of Class D concrete for the Foundation Beam of the Lining Concrete continued this month from Station 3+739.5 to 3+871.5 with a total length of 132m on each side.

Installation of Mole Drain Pipes, together with filter cement aggregate, on both sides of the tunnel continued simultaneous with the foundation beams.

Cutting of Rock bolt heads and installation of geo-textile covers were done on areas with rock bolts.

Installation of EVA Waterproofing Membrane was also continued following the covering of rock bolts. Until the end of this month, a total length of 2,167m (Station 3+831.50) was completely covered with waterproofing membrane. The Engineer continued to require testing of the welded joint sheets using air pressure test, as per procedure stated on the method statement, before continuation of the installation.

Pouring of Concrete Lining was also carried out as per approved design segment. The Engineer carefully checked, during the joint survey with the contractor, the setting of the form for both bulkhead sides and the thickness as per design requirements.

The Concrete Lining for Standard Section of the Main Tunnel completed until the end of this month totaled to 1,915.40 meters. The Concrete Lining works for Lay-by Left Nos. 1, 2 and Lay-by Right No. 1, 2 in Main Tunnel, totaling a length of 124m, were also completed.

The Main Tunnel Concrete Lining completed up to the end of this month totaled to 2,039.40m (Progress: 52.88%).

For cross passages, only the concrete lining for the blocks connected to the Main Tunnel are being executed. Concrete lining completed until the end of this month includes the Pedestrian Cross Passage No. 1 (Station 2+000), No. 2 (Station 2+400) and Vehicular Cross Passage No. 1 (Station 2+800), and Pedestrian Cross Passage No. 3 (Station 3+190), totaling a length of 13.70m.

Cable Duct Bank Concreting:

This month of June 2003, the pouring of concrete for the cable duct bank with manholes, including two (2) lines of embedded conduit pipe with a diameter of 110mm each, were continuing from Station 1+699.0 and reached to Station 2+810.5, totaling a length of 1,110.50m.

Side Drainage/Catch Basin:

This month, the pouring of side drain and setting of pre-cast catch basins had been commenced from station 1+670 and reached to station 1+923m for side drain, totaling a length of 232m. The setting/installation of pre-cast catch basins started from no. 2 ~ 13, totaling 12nos. (station 1+945).

• West Side: (Right Side)

Side Drainage:

Casting on-site of side drainage on the west side of the Main Tunnel began at Station 1+770 and reached to Station 2+057.95 with a total length of 308.6m. The setting/installation of pre-cast catch basins were from no. 2 ~ 18, totaling 17nos. (station 2+070).  

EP No. 1 Concreting Works:

The pouring of Class D concrete for the Foundation Beam of the Lining Concrete this month completed a total length of 113.51m on the right side and 133.01m on the left side.

Installation of Mole Drain Pipes, together with filter cement aggregate, on both sides of the tunnel continued simultaneous with the foundation beams.

Installation of EVA Waterproofing Membrane for the connection of the Inlet and MT was completed. A total length of 103.7m was completely covered with waterproofing membrane. The Engineer also required testing of the welded joint sheets using air pressure test, as per procedure stated on the method statement, before continuation of the installation.

The casting of Lining Concrete continued this month from block no. 2 (station 0+012.92) to block no. 7 (station 0+047.42) with a total length of 34.50m. Preparation for concreting works for the connection of the Inlet (EP-block no. 1) and MT (block no. 151) has been under execution.

Evacuation Tunnel

At the end of the month of May 2003, small fracture zones were encountered with water flowing on the cutting face that was expected from MT joint dip direction. The water inflow, measuring 34.5L/sec, was experienced and disappeared after two (2) rounds during the month of June 2003.

On the Monthly Progress Meeting, the Consultant Chief Resident Engineer strongly mentioned to the contractor the necessity to recover the delay of ET from MT. Due to this discussion, the contractor proposed for the excavation of the Temporary Cross Passage No. 3 in front of VA Clean Air Supply Section, in order to excavate another cutting face (face no. 2) for ET and to catch-up with its delay from the MT. The Contractor excavated the Temporary Passage No. 3 at Station 4+259 simultaneous with the excavation of Evacuation Tunnel Face No.1 by the same ET group. The excavation for Face No. 2 also started this month.

Geologically, the rock condition encountered for both faces (face nos.1 and 2) this month was stable on Class B. On some portion, it was classified as class A this month.

The Face No.1 excavation length extended by 77.70m and excavation for Face No. 2 side yielded a length of 76.40m. Total excavation length for this month was 154.10m. The distance from the tunnel portal gives a total length of 2,634.30m (Progress: 68.30%). 

The Temporary Transformer Niches No. 1~11 were completely excavated as per approved plan submitted by the Contractor.

The Enlarged Pedestrian Cross Passageway Nos. 1, 2, 3 and 4 and the Vehicular Cross Passageway No. 1, 2 were also completed.

Ventilation Adit Tunnel

The breakthrough of the Main Tunnel and the Clean Air Supply Section of the Ventilation Adit on May 29, 2003 effected a 100% completion of the Ventilation Adit and early of this month of June 2003, the removal of under-break was totally completed.

• Concreting Works:

Cut and Cover Section / Connection Lining Concrete at Portal:

The Concrete Lining for Cut and Cover Section, with Portal Wall, and two (2) blocks of Normal Section of Lining Concrete connected to the Cut and Cover Section were completed with a total length 13.97m from Station 1+738.54 to 1+752.51.

Normal Section Lining Concrete:

Pouring of Class D concrete for the Foundation Beam of the Normal Section of Lining Concrete were continuing with a total length of 233.28m on both sides from Station 0-055.05 to 0+0161.22.  Block Nos. 17 ~40 were completed.

Installation of Mole Drain Pipes, together with filter cement aggregate, on both sides of the tunnel continued simultaneous with the foundation beams.

Cutting of Rock bolt heads and installation of geo-textile covers were done on areas with rock bolts.

Installation of EVA Waterproofing Membrane was started this month from station 0-056.0 ~ 0+088.5 with a total length of 161.5m. The Engineer continued to require testing of the welded joint sheets using air pressure test, as per procedure stated on the method statement, before continuation of the installation.

Pouring of Concrete Lining has also commenced after the reassembly of the sliding form was completed and has been carried out as per approved design segment. The Engineer carefully checked, during the joint survey with the contractor, the setting of the form for both bulkhead sides and the thickness as per design requirements.

The Concrete Lining for Normal Section of the Ventilation Adit completed until the end of this month totaled to 54meters block no.17 to 22 (0-055.05 ~ 0-001.05).

The Ventilation Adit Concrete Lining completed, including Cut and Cover Section together with its connection to the normal section, up to the end of this month totaled to 67.97m (Progress: 3.60%).

Major Events and Issue

Site Inspections

On June 14, 2003, representatives from the Government Complimentary Commission together with the Employer and the Engineer visited and inspected the Project.

Monthly Meeting

On June 11, 2003, a Monthly meeting was held at the Employers/Engineer’s Office between the Employer, the Engineer and the Contractor.

Safety Patrol and Meeting

On June 05, 2003, the Employer, the Engineer and the Contractors conducted a Safety Patrol on Package 1A and Package 1B Projects.

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