Construction Supervision

Summary

As of May 31, 2003, total length of Main Tunnel excavation reached to 2,623m (including 7 Laybys) from the Tunnel Portal.

Forty nine (49) niches (12 emergency & call niches and 37 Firefighting Niches) were completely excavated inside the Main Tunnel.

Concreting of the Foundation Beam and concrete Lining Works at the Main Tunnel were carried out. As of May 31, 2003, concrete lining construction reached to 1,943.40 meters, progress 50.39%.

As of May 31, 2003, the length of Evacuation Tunnel excavation reached to Sta. 4+123.2, giving a total length of 2,480.20m (progress 64.30%) from the Tunnel Portal.

Six (6) Cross passageways were completely excavated across the Evacuation and Main Tunnels.

Ventilation Adit excavation was completed.

Ventilation Adit Portal’s Cut and Cover Section was constructed during this month.

Main Tunnel 

• Excavation

In the month of May 2003, the encountered fracture zone with water flowing in the Main Tunnel occurred since last month and was observed gradually moving on the left side face until disappearing early this month. With its dip direction, it was assumed that the fracture zones with water flowing would be encountered in the Evacuation Tunnel.

This month, the Main Tunnel group reached and broken through the top heading excavation of the Main Tunnel from the Ventilation Adit at Station 4+194.8.

Also, unforeseen rock deformation was experienced again when nearly reaching the connection with the VA Exhaust Section. Cracks appeared on the existing shotcreted walls along the spring line on both sides of the Main Tunnel. The Chief Resident Engineer gave an instruction to chip out the crack areas, re-shotcrete and install rock bolts. The Engineer carefully observed the NATM result on those areas until it became stable and no more deformation was monitored.

Geologically, the rock condition encountered this month was stable on class B under supporting type I.

 The excavation progress for the month of May 2003 is less than the rate needed per month. The MT full-face excavation length extended by 118.0m and top-heading excavation from the Ventilation Adit side yielded a length of 34.8m. Total excavation length for this month was 152.80m. The distance from the tunnel portal gives a total length of 2,623.00m (Progress: 68.01%).

• Niche Excavation:

Fifty-one (51) Niches - Twelve (12) Emergency Call Niches and Thirty-nine (39) 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 and Right No.1, 2, 3

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 Left No. 4 was completed this month and the excavation of the Lay-by Right No. 4, which is connected to the Clean Air Supply Section of the Ventilation Adit at Station 4+259.0, is currently going on.

• 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+588.5 to 3+739.5 with a total length of 151m 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 1,995.5m (Station 3+659.50) 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 1,819.40 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 1,943.40m (Progress: 50.39%).

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 May 2003, the pouring of concrete for the cable duct bank, including two (2) lines of embedded conduit pipe with a diameter of 110mm each and manhole walls, has been commenced from Station 1+699.0 and reached to Station 2+443.5, totaling a length 746.9m.

• West Side: (Right Side)

Side Drainage:

Casting on-site of side drainage on the west side of the Main Tunnel began at Station 1+910.5 and reached to Station 1+929.5 with a total length 19m. 

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 94.6m on the right side and 107.9m 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 was started from Station 0+010 to 0+30.5 with a length 20.5m using the sliding form for concrete lining and from Station 0+030.5 to 0+034.5 using the new staging assembled on site. Until the end of this month, a total length of 24.5m was completely covered with waterproofing membrane. The Engineer also require testing of the welded joint sheets using air pressure test, as per procedure stated on the method statement, before continuation of the installation.

The assembling of Sliding Form for Lining Concrete of the Electrostatic Precipitator No.1 was completed and was used for casting Lining Concrete on Block No. 2 with a length of 6.0m this month at Station 0+012.92 ~ 0+018.92.

Evacuation Tunnel

For the month of April 2003, small fracture zones were encountered on the cutting face over the whole month on the cutting face. On 28th of this month, May 2003, the water that was expected from MT joint direction occurred at Round No. 778. The water inflow, measuring 34.5L/sec, was experienced until the end of this month. Generally, the rock was classified as class B, which was under supporting system type I.

The Contractor executed the excavated of Vehicular Cross Passage No. 2 at Station 3+910 simultaneous with the excavation of Evacuation Tunnel by the same ET group. 

The tunnel length excavated this month was 140.00m (Station 3+983.2 ~ 4+123.2), giving a total length of 2,480.20m  (Progress: 64.30%) from the tunnel portal.

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

Early of May 2003 in the Ventilation Adit, the contractor completed the excavation of Temporary Connection Tunnel through MT at Station 0+090 of the Ventilation Adit

The top heading excavation for MT resumed through the access road at temporary connection tunnel and the excavation stopped at Station 4+249.8 on May 25, 2003 after the breakthrough of the MT connection to VA side.

The encountered geological condition was stable on class B and some other portions were classified as class A.

This month of May 2003, due to the poor condition of equipment of the contractor, the excavated length was only 34.80m, from Station 4+215.0 to 4+249.8.

On 29th of May 2003, the VA Clean Air Supply Section connection with the Main Tunnel was also broken through after blasting of Round No. 850 of the MT. The breakthrough effected a 100% completion of the Ventilation Adit, together with the 135.11m extended length, from Station 1+1752.51 to 0-135.11. 

• 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 Lining Concrete connection 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 was started on the bottom part of VA.  A total length of 18m from Station 0-055.05 to 0-037.05, Block No. 17 ~18, was completed.

The Sliding Form, which was used by the contractor for the Cut and Cover Section was dismantled and was transferred inside the tunnel to be reassembled. After the steel lining sheets were removed from the gantry frame, the frame was moved to the bottom part, at the enlargement section, of the Ventilation Adit.  Reattachment of steel lining sheets to the gantry frame has been started this month.

The Staging Form for Waterproofing Membrane was also re-assemble at the Enlargement Section area.

Major Events and Issue

Site Inspections

Site visit of SITOC on May 31, 2003

Monthly Meeting

Monthly Meeting on May 15, 2003 held at Engineer & Employer North Office

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