method statement mae moh tunnel

บรษท เอนจเนยรง มาสเตอร จ ากด

ENGINEERING MASTER CO.,LTD. เลขท 10/4 หม1 ต.ทาขาม อ.ชนแดน จ.เพชรบรณ 67150 โทรศพท/แฟกซ : 056-767089 E-mail : [email protected] ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

No.TG_ITD.Doc.MS01-001

Document Revision : R1

Date : 19 May 2009

Release / Amendment No. Date

Page No. P a g e | of 23

METHOD STATEMENT FOR

MAE MOH TUNNEL EXCAVATION

1. General The Mae Moh tunnel excavation and construction will be executed and prepared for the insertion of belt conveyor line. The belt conveyor will be constructed to support the material handling system from the 7th Phase overburden removal operation in the Mae Moh Mine.

2. Scope of Works The scope of work will be: a) Tunnel excavation in claystone by non-blasting method (Using of continuous Miner), which is 2.25 meters

crown radius, 4.50 meters width, 3.50 meters height , 110.12 meters length. b) Construction of Reinforced concrete Portals and Head walls, including the slope stabilization works which

consist of Retaining Wall construction at existing embankment and concrete ditch. c) Installation of necessary ground support to the tunnel excavation which consists of steel ribs, tensioned

grouted rockbolts, shotcrete and also concrete floor lining. d) Associated ventilation and lighting work.

3. Referrence Documents Document No. : TG_ITD.DS01 Rev. : R1 Description : Calculation for Mae Moh Tunnel Supports Design.

Document No. : TG_ITD.DWG01 Rev. : R1 Description : Reference Design Drawings for Mae Moh Tunnel Excavation & Construction.

Document No. : TG_ITD.DWG02 Rev. : R1 Description : Site and Tunnel Facilities Layout

Document No. : TG_ITD.DWG03 Rev. : R1 Description : Water Reservior , Sedimentation Pond and Temporary Waste Disposal area Drwaings and details

Document No. : TG_ITD.DWG04 Rev. : R1 Description : Typical Tunnel Excavation Profile.





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Document No. : TG_ITD.DWG05 Rev. : R1 Description : Layout for Slope Protection at poratal Area. Document No. : TG_ITD.DWG06 Rev. : R1 Description : Typical Soil Nail , Rockbolt and Drainhole Installation. Document No. : TG_ITD.DWG07 Rev. : R1 Description : Steel Rib Drawings and Details for Mae. Document No. : TG_ITD.Doc.MIX01 Rev. : R1 Description : Proposed Concrete and Shotcrete Mix Designs. Document No. : TG_ITD.Doc.WPRO01 Rev. : R1 Description : Work Procedure Flowchart Diagram. Document No. : TG_ITD.Doc.REP01 Rev. : R1 Description : Inspection and Report Forms. Document No. : TG_ITD.Doc.EQ01 Rev. : R1 Description : List of Equipments. Document No. : TG_ITD.Doc.MAT01 Rev. : R1 Description : Material Specifications. Document No. : TG_ITD.Doc.SPEC01 Rev. : R1 Description : Specifications for Mae Moh Tunnel.

4. Major Materials and Supplies Item Description Use

1 Steel Ribs WF-150x150 Support from (Sta. 0+003) to (Sta. 0+064) 2 Rock bolt and accessories Rock support as applicable 3 Cement ASTM C150 Type I Concrete and Shotcrete mix component 4 Coarse Sand Concrete and Shotcrete mix component 5 ¾” Aggregate Concrete mix component





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6 3/8” Aggregate Concrete and Shotcrete Mix component 7 Steel wire mesh Rock support and Slope protection 8 Grout Capsules (Cementitious) Rock bolt anchorage 9 Admixtures (Rheobuild 718 or Plasiment R ) Concrete Superplasticizer 10 Admixtures (Meyco SA160) Shotcrete Accelerator 11 Reinforce steel Reinforcement of concrete 12 1 ½” Ø PVC Pipe Class 13.5 Drain Pipes 13 Geotextile , polyfelt TS40 Filter for drain pipes

5. Major Equipment s and Tools Item Description Brand/Model/Spec. Quantity Activity

1 Continuous Miner KOMATSU CM200 (Modified)

1 Rock (Tunnel) excavation

2 Rear Dump Truck 4-7 tons Capacity 2 Spoil Disposal 3 Air Compressor AIRMAN PDS655 , 650 cfm. 2 Compressed air supply 4 Air Receiver Tank 3.0 m3 Capacity 2 Compressed air buffer 5 Power Supply or

Generator 150 kVA. Per each Portal 2 Reserve Power supply

6 Water Pump Centrifugal Pump 2”Ø 2 Water supply 7 Water Pump Submersible 2”Ø 2 Dewatering 8 Front-End Wheel

Loader KOMATSU , JH36 or WA150 1.2 m3 Capacity

1 Mucking, Tunnel service

9 Front-End Wheel Loader

FURUKAWA FL30 , 0.5 m3 Capacity

1 Batching Plant service

10 Concrete Transit Truck

2.5 m3 Capacity 2 Shotcrete/Concrete delivery

11 Ventilation Fan 900 mm.Ø , 30 kW. 2 Ventilation 12 Dry-Mix or Wet Mix

Shotcrete Machine MEYCO - GP or MEYCO - Altera

1 Shotcrete Application

13 Dosing pump Multi-Piston Pump 25mm. 2 Accelerator dosing unit 14 Truck Crane 5 tons Capacity 1 Handling service 15 Concrete Plant 12 m3/hr Capacity 2 Concrete batching 16 Trailer Long bed 1 Equipment mobilization 17 Pick up 4 Wheels Drivel Pickup 2 Service car





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6. Works Sequence The works sequence shall be as shown in the working flowchart diagram below.

WORK FLOWCHART DIAGRAM

7. Work Execution / Methodology The Mae Moh Tunnel shall be Horse shoe shaped, with a crown radius of 2.25 meters., 4.50 meters width, 3.50 meters height . To be excavated in sedimentary rock formations composed mainly of claystone , In order to prevent the vibration caused from the blasting which may damage or interrupt the existing belt conveyor lines around that area, the Non-blasting tunnel excavation method has to be employed by using of the Continuous Miner in conjunction with Rear dump truck. After every certain 4.0 meters length of tunnel has been excavated, the support system shall be applied immediately in order to prevent the danger and accident from rock squeezing and falling down. The support system shall be consisted of Steel ribs, Tensioned grouted rockbolts, and Shotcrete.

Mobilization

Site / Tunnel Facilities Surface Excavation by ITD

Portal Construction

Tunnel Excavation Each 4.0 m. per round

- Continuous Miner (Excavator) - Rear Dump Trucks (Disposal)

Slope Stabilization at Portal Areas

- Retaining Wall - Concrete Ditch

- Drainholes

Tunnel Supports Each 4.0 m. - Steel Rib supports - Floor Lining - Rockbolt - Shotcrete

Survey & Setting out Survey & Setting out

Survey & Setting out

Survey & Setting out





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7.1 Preparation Prior to starting the excavation and construction works, the necessary plants, equipments, materials and supplies needed to start the works will be at the site. The necessary temporary facilities will be on site, as close to the work area as possible. (Appendix3) The main facilities consist of Electric power supply, Water supply, Compressed air supply and Ventilation system, connected to the tunnel as shown in Picture 1. Electrical power supply will be from EGAT, with standby diesel driven engine generators provided on site to serve as back-up power source. The capacity of the generator will be enough to sustain normal tunnel construction activities. Industrial water supply will be from the local water main or from deep wells drilled in the vicinity of the platform. In either case, the water will be transported from the source to a water reservoir (plastic sheet lined – sump located in front of the portal) ready to deliver the water through 2 inch diameter galvanized steel pipe lines to the plants and tunnel for any application. Compressed air supply will be provided by diesel driven engine air compressors set up at the portal area. Air receiver tanks will be installed, delivery lines will be 2 inch diameter galvanized steel pipe lines in the tunnel. A Main valve shall be installed after the air receiver tank to control or shut off compressed air supply in cases of repair or emergency. Isolation valves shall be installed at the intervals of 50 meters also for repair and emergency purposes.

CROSS SECTION

VENTILATION DUCTCABLE RACK

COMPRESSED AIR PIPEWATER SUPPLY PIPE

LIGHTING

PREPARATION OF TUNNEL FACILITIES

CONTINUOUS MINER

PICTURE 1

The ventilation system will be supplied from the 1 unit of 900 cm.Ø, 30 kW. Electric motor drive axial-contra rotation type ventilator installed in front of each portal (Appendix 12) The fresh air will be delivered to the work face through the 800 cm.Ø flexible vent ducts.





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7.2 Survey and Setting out The Mae Moh tunnel location, centerline and alignment, gradient, and elevation will be established by survey, starting from the portals, in accordance with the design as indicated in the layout plan and typical cross sections of the reference drawings. Survey equipment s to be used will be the tunnel profiler, computer – aided type, Tunneling software on board, to ensure accuracy of the survey execution. Data processing of the survey results will be done by downloading the survey data to a computer, which will also be the compatible software on board.

7.3 Tunnel excavation and Construction

7.3.1 Portal Construction Prior to start tunnel excavation, the reinforced concrete portal structure consist of foundation, collar, and retaining wall have to be constructed in accordance with the design as indicated in the reference drawings ( Apendix 1, 6, 9) The construction procedures are as followed:

- Ground excavation to match to all the designed location, dimensions and elevation prepared for 5 cm. thick sand compaction on the floor base.

- After sand compaction is finished then start to fix the reinforce steel follow the specified drawings at the foundation and floor and also in the meanwhile install the formworks ready for concrete placing and compaction.

- Continue the reinforcement steel fixing up to the side wall, collar and retaining wall. - Install the complete formworks ready for concrete placing. - The concrete will be mixed by using the submitted 280 ksc. mix design (Appendix 9) form the batching

plant which are installed in front of portal areas, the concrete will be delivered to that concrete works by the prepared concrete transit trucks.

- Execution and completion of concrete placing and compaction then wait for 3 days before the removal of the formworks. The concrete works shall be done under inspection of the resident engineer.

7.3.2 Tunnel Excavation

After the portals construction has been completed, the tunnel excavation can be started. As mentioned before, the continuous miner will be employed for tunnel excavation. There are two alternatives for the selection of the continuous miner type, the 1st alternative is electrical drive and the 2nd is diesel engine drive, depends on the most convenience conditions.





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FORWARD

PROFILETUNNEL EXCAVATION , ADVANCING FORWARD ( BY CONTINUOUS MINER + TRUCKS )

REAR DUMP TRUCK CONTINUOUS MINER

PICTURE 2.

BACKWARD

PROFILETUNNEL EXCAVATION AT THE FLOOR BACKWARD

REAR DUMP TRUCKCONTINUOUS MINER

PICTURE 3.

The working principle of the machine are as described, the numbers of cutting teeth on the cutting drum of continuous miner will break the rock to be the form of cuttings, fall down into the tray below which are two sets of sweeping impeller to put the cut rock to the next built-in belt conveyor underneath, then it be conveyed up through the belt conveyor and load down to the rear dump truck behind. The rear dump truck will transport that material to dump at the disposal area. The 1st Step : Excavate progressing forward on the upper part which is the same level with the previous concrete floor, to keep the machine stable as shown in Picture 2. The 2nd Step : Excavate progressing backward and down to the designed level as shown in Picture 3.





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Mucking : The final stage of excavation is mucking, that will be done by using the front-end wheel loader . The wheel loader will load the remaining spoil from excavation to the dump trucks for transportation to designated disposal areas.

7.3.3 Tunnel Supports

7.3.3.1 Steel Ribs As the soonest time as possible after each certain 4.0 meters section of the tunnel has been excavated the steel rib supports need to be installed to sustain the tunnel stability in accordance with the design as indicated in the reference drawings ( Appendix 2, 8). Prior to install the steel ribs, that needed to start from rock scaling at the tunnel roof and side wall as shown in Picture 4.

PROFILEROCK SCALING PRIOR TO THE STEEL RIBS INSTALLATION AND SHOTCRETE

DUMP TRUCK

PICTURE 4

Then the prepared components of steel ribs will be installed, equipped by the front-end wheel loader as the assisting equipment as the following procedures : o Put the timber pieces (100mm.x100mm.x1200mm.) roughly at 0.5 meter spacing, direction parallel

along the tunnel on the compacted sand floor and fix the timber pieces roughly around the tunnel section (roof and side wall) with the grouted DB12 steel bar into the prepared drilled holes.

o Put the Basing Piece WF-150x150 of steel set on the timbers at 1.0 meter spacing in transverse direction of the tunnel.

o The Arc Crown Piece WF-150x150 of steel set will be lift up to the approximately position, meanwhile the workers take the Column Pieces WF-150x150 to the position. The 1 Arc crown Piece and the 2 Column Pieces will be connected and tighten together with the 6 sets of M20x60x1.75 bolts and nuts per each column.





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o To set the alignment of steel sets by the survey instruments and positioning the steel sets to the exactly position in accordance with the plan from reference drawings, by the workers and under the assistance of the wheel loader as shown in Picture 5.

KOMATSU

Lifting Point Lifting PointLifting Point

PROFILESTEEL RIBS INSTALLATION BY USING OF THE WHEEL LOADER AS THE ASSISTING EQUIPMENT

CROSS SECTION

WHEEL LOADER

PICTURE 5

Up-Lifting Force = 5 TonsBefore Joint Weldingat the Rectangular Edge

CROSS SECTIONINSTALLATION OF STEEL RIB

Hydraulic Pump Set

Attachable Bearing Pad

Hydraulic Jack

Fixed by 8 nr. of M12x50x1.5 Bolts&Nuts

Crown Arc Piece

Column Piece

Basing Piece

Connecting End PlatesFixed by 6 nr. of M16x60x1.75 Bolts&Nuts

Pop Post

PICTURE 6

o After all pieces of steel set are in the exactly proper position then lift the upper steel set up with the 2 units of hydraulic jack at 5 tons lifting force to make the steel set tightly fastened to the timber pieces as shown in Picture 6 and then fix the column pieces with the basing piece by welding at the contact joint finally.

o Some timber pieces may be still loose with the steel sets, they could be tightly fastened with the timber wedging later but prior to wire mesh installation and shotcrete application.

o Five rows of bracings will be installed by arc welding in accordance with the design as indicated in the reference drawings.





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7.3.3.2 Concrete Floor Lining The following step after steel ribs support will be concrete floor lining, the reinforcement shall be RB8x200x200 wire mesh in accordance with the design as indicated in the reference drawings ( Appendix 9) The construction procedures are as followed:

o Prepare the 5 cm. thick sand compaction on the floor base. o After sand compaction is finished then start to fix the wire mesh (RB8x200x200) follow the

specified drawings ready for concrete placing and compaction. o The concrete will be mixed by using the submitted 320 ksc. mix design form the batching plant

which are installed in front of portal areas, the concrete will be delivered to that concrete works by the prepared concrete transit trucks.

o Execution and completion of concrete placing and compaction as shown in the picture 7, then wait for 12 hours before continuing with the preparation works for initial shotcrete. The concrete works shall be done under inspection of the resident engineer from project owner.

PROFILECONCRETE PLACING ( CONCRETE FLOOR LINING WORK )

CONCRETE TRANSIT TRUCK

PICTURE 7

7.3.3.3 Initial Shotcrete (1st Layer)

Once the designed excavation for steel rib installation is achieved, the initial shotcrete layer will be applied (Appendix 9). Thickness of shotcrete will be75 mm. to cover the excavated surface and prevent the deterioration of the rock when exposed to the air and also strengthen up tunnel wall to keep security until the permanent supports will be completed. The wire mesh (RB6x150mm.x150mm.) will be installed at the middle of 1st layer shotcrete thickness prior to shotcrete application. The wire mesh will be fixed with the dowel bars (DB12) which have been previously installed into the 10mm. drilled hole (drilled by Rotary Hand Drill) and be kept stable by





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friction, at 0.75 meter spacing and leave the certain designed space between wire mesh and rock surface with the limited concrete spacer.

MEYCO

PROFILEINITIAL SHOTCRETE APPLICATIONS

CONCRETE TRANSIT TRUCK SHOTCRETE MACHINE DUMP TRUCK

NOZZLE

INITIAL SHOTCRETE LAYER

PICTURE 8.

Shotcrete application will be dry mix, mixed by using the submitted 280 ksc. Dry mix design from the batching plant which are installed in front of portal areas, the concrete will be delivered to that shotcrete workface by the prepared concrete transit trucks. The equipments setting up is shown in Picture 8. The mix will be conveyed to the surface of application by a dry mix shotcrete machine which operated by electric motor drive in co-operation with compressed air (operating pressure is 3.0-3.5 bars , but the compressed air shall be supplied from the 650 cfm. @ 7.0 bar Air compressor) to convey the mix passed through the flexible 2”Ø hoses to a nozzle. The liquid, alkali free accelerator will be mixed with water in the designed content and introduced from the dosing pump through the separated rubber hose and finally connected to the nozzle. The mixture of water and liquid accelerator can be regulated to achieve the proper W/C ratio by the regulating valve at the nozzle, so that the quantity of accelerator dosage in the mix design is attained by the relation with W/C ratio. (Accellerator @ 2.0% by Cement weight at tunnel side wall , @4.0% by Cement Weight at Tunnel roof). Shot crete application will start at the toe of the tunnel wall and progress toward the crown on both sides of the tunnel. The nozzle shall be held at a distance of 1.0 meter to a maximum of 1.2 meters from the application surface. To minimize rebound, the nozzle will not be held perpendicular to the surface of application. During application, the nozzle will be moved in circular motion, to ensure even distribution of the shotcrete and compaction. The shotcrete works shall be executed under inspection by the resident engineer from project owner.





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7.3.3.4 Tensioned grouted Rock bolt Rockbolting is the next step from steel ribs support installation. The 4 numbers of tensioned grouted rockbolt will be installed for each one tunnel section at 1.50 meters spacing from center to center. The rock bolt shall be 2.50 meters long made from 25mm.Ø deformed bar (DB25) grade SD40 (Appendix 7.) The following will be the procedure for the fore tensioned grouted rockbolt installation : 1. The type of rockbolt patterns for support, will be set out and marked by survey as indicated in the

typical sections of the design drawings. 2. Holes for rock bolts will be drilled, following the bolting pattern set out and marked by survey,

using the Air leg Drill Hammer as shown in Picture 9. Hole diameter will be 38-40 mm. and length will be 2.50 meters as shown in the design drawing or as instructed by the geologist or geotechnical engineer.

3. After drilling the holes for rockbolts, cleaning and flushing with water will be done to remove loose rocks fragments and/or sludge resulting from the drilling. The holes will also be checked for length. The blocked holes will be cleaned to the depth or re-drilled.

PROFILEDRILLING THE HOLES , PREPARING FOR THE INSTALLATION OF TENSIONED GROUT RCKBOLTS

CONCRETE TRANSIT TRUCK

AIR LEG DRILLHAMMER

PICTURE 9

4. Once the holes for rockbolts has been cleaned, then prepare the quick set cementitious grout

capsules (32 mm.Ø), Pierce the plastic around the capsule using the tool provided by the manufacturer which is included in the packaging.

5. Place the quick set cementitious grout capsules in a container with water, and leave it to be water-saturated until no bubbles can be seen.

6. Insert the saturated cartridges in the borehole using a suitable round wooden stick to squeeze the cartridges against the borehole and ensure they do not slip out, the enough capsules will be





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inserted into the hole to ensure that the whole length of the bolt is grouted in accordance with the design of the rockbolt anchorage as specified in the drawings.

7. Insert the rock bolt (25mm.Ø x 2.50m.) by using the Air leg drill hammer for pushing forward until the full bolt length is installed. This will produce the mortar mix 0.3 W/C ratio ensuring a complete annular mortar filling.

8. After 10 minutes, the cement paste will set and the accelerated hardening process will start. Complete setting will be achieved after 60 minutes.

9. Once the wire mesh will be installed before the fastening of the rock bolt face plate, conical washer and nut. The wire mesh will be fixed with the dowel bars (DB12) which have been previously installed into the 10mm. drilled hole (drilled by Rotary Hand Drill) and be kept stable by friction, at 0.75 meter spacing and leave the certain designed space between wire mesh and surface of application with the limited concrete spacer.

10. The face plate, conical washer and nut will be installed and fastened after pull test and 1st layer shotcrete is completed. And the tensioned grouted rockbolt installation shall be done under inspection by the resident engineer from project owner.

7.3.3.5 Final Shotcrete (2nd Layer)

After the tensioned grouted rockbolt is finished, the final shotcrete layer will be applied (Appendix 9). Thickness of shotcrete will be125 mm. to ensure that the shotcrete wall is strong enough against ground pressure applied to the tunnel wall. The wire mesh (RB6x150mm.x150mm.) will be installed at the middle of final shotcrete layer thickness prior to shotcrete application. The wire mesh will be fixed with the dowel bars (DB12) which have been previously installed into the 10mm. drilled hole (drilled by Rotary Hand Drill) and be kept stable by friction, at 0.75 meter spacing and leave the certain designed space between wire mesh and rock surface with the limited concrete spacer. Shotcrete application will be dry mix, mixed by using the submitted 280 ksc. Dry mix design from the batching plant which has been installed in front of portal areas, the concrete will be delivered to that shotcrete workface by the prepared concrete transit trucks. The equipments setting up is shown in Picture 10. The mix will be conveyed to the surface of application by a dry mix shotcrete machine which operated by electric motor drive in co-operation with compressed air (operating pressure is 3.0-3.5 bars, but the compressed air supply shall be delivered from the 650 cfm. @ 7.0 bars Air compressor) to convey the mix passed through the flexible 2”Ø hoses to a nozzle. The liquid, alkali free accelerator will be mixed with water in the designed content and introduced from the dosing pump





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through the separated rubber hose and finally connected to the nozzle. The mixture of water and liquid accelerator can be regulated to achieved the proper W/C ratio by the regulating valve at the nozzle, so that the quantity of accelerator dosage in the mix design is attained by the relation with W/C ratio. (Accellerator @ 2.0% by Cement weight at tunnel side wall, @4.0% by Cement weight on tunnel roof). Shot crete application will start at the toe of the tunnel wall and progress toward the crown on both sides of the tunnel. The nozzle shall be held at a distance of 1.0 meter to a maximum of 1.2 meters from the application surface. To minimize rebound, the nozzle will not be held perpendicular to the surface of application. During application, the nozzle will be moved in circular motion, to ensure even distribution of the shotcrete and compaction.

MEYCO

PROFILEFINAL SHOTCRETE APPLICATIONS

CONCRETE TRANSIT TRUCK SHOTCRETE MACHINE DUMP TRUCK

NOZZLE

FINAL SHOTCRETE LAYER

PICTURE 10

And the shotcrete works shall be done under inspection by resident engineer from project owner.

8. ventilation An adequate ventilation system will be set-up. Axial-contra rotation fans will be used and fresh air will be conveyed to the working face by flexible ducting. Since mobile diesel equipment will be used in the tunnel excavation, the ventilation system will provide of 50 l/s/hp. Gasoline powered or stationary diesel equipment will not be used inside the tunnel. Air quality determination will be done at the start of the work shift/s and during the work shift, to check the concentration of noxious gases, before starting or resuming work.

9. Illumination/ Lighting

As the tunnel excavation progresses, lighting will be provided at the advancing face and transit area. Mobile/movable with minimum 40 lux illumination, will be used in the working area, so that they can be easily positioned, transferred or removed for any purpose. In the transit area, fixed lighting with minimum of 10 lux





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illumination will be installed. The lighting will be at least 2 meters from the invert, and spacing will be every 10 meters. Fixed lighting will be maintained 50 meters away from the advancing face. All lighting fixtures to be used in the tunnel will be waterproof and maximum voltage for lighting will be 240 volts.

10. Dewatering

The tunnel will be excavated with a rising gradient, therefore, one side of tunnel will be self draining. The inflow water from another side tunnel will be de-watered by the 2”Ø submersible pump to deliver it through 2”Ø hose discharge to the drainage system around portal areas. The discharged water will be conveyed by the drainage system to a sedimentation pond (Appendix 8), to allow settling of silt and mud before further discharge of the water into natural drainage systems. The sedimentation pond will be regularly cleaned to ensure functionality. Sediment/silt from the cleaning of the sedimentation pond will be accumulated at the temporary disposal area of the platform to allow it to drain before transportation to the designated disposal areas.

11. Quality Assurance Before and during the execution of works, materials testing will be performed by either on-site or off site laboratories, as approved by the Employer’s Representative. Other specifications and test methods shall be approved and accepted by the Employer’s Representative on the site before use.

12. Monitoring The integrity of the tunnel during construction will be regularly monitored on short term and long term basis. Short term Monitoring Systems : 1. Geological mapping and geotechnical data collection after excavation shall be done to ascertain and confirm the support system to be applied. The Geologic data shall be interpreted and analyzed by the geologist and geotechnical engineer to be able to project the expected ground conditions for the each excavation round or cycles. 2. During drilling for rockbolting, cuttings and sludge from drilling shall be observed to obtain information on the geology and rock type immediately after the face at certain length, at the crown, walls and invert. If water ingress is encountered, flow rate shall be determined, and if necessary, pilot holes shall be drilled, to probe deeper into the rock face. Length of the pilot holes, diameter, etc. shall be determined by the geologist or the geotechnical engineer. Excavation methods and procedures may be modified according to the results or finding of these procedure.





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3. The applied shotcrete support shall be regularly checked for cracks and other abnormal conditions. Once these are observed, the appropriate measures to reinforce or repair the shotcrete shall be done immediately. 4. Quality control of the works shall be done strictly following the Inspection and Test Plan (Appendix 11.) Long Term Monitoring Systems : Long term monitoring systems shall consist of procedures that are programmed to be periodically done to monitor the tunnel integrity during and after the construction phase.

Convergence Monitoring Convergence monitoring stations (5 points) will be established at interval of 20 meters, One (1) week after excavation has passed. The monitoring stations shall be established by a computer aided Survey Instrument, since the instrument has the software and can be programmed to automatically locate the convergence points, and make readings. The frequency of monitoring will depend on the geology of the rock that is excavated and supported. If the monitoring shows movement, all measures shall be taken to reinforce the support systems at the particular location.

13. Health and safety

a. Tunnel Safety Excavation :

1. Excavation will be done only within the boundaries of the profiles as set out and marked by survey in accordance with the layout, plans, and sections in the reference design and construction drawings.

2. Effort shall be taken to minimize or eliminate over break and over excavation by controlling of the machinery.

3. All excavation done, will be supported within 12 hours from the time of excavation, to prevent the deterioration or weathering of the rock when exposed to air. An initial layer of shotcrete, 75 mm. thick shall be applied to cover the newly exposed rock resulting from mechanical excavation.

4. The excavations shall be regularly mapped by the geologist or geotechnical engineer to determine the type of rock, rock quality, geology, and other geotechnical information required, to be able to assess the type of support needed.

5. Electrical equipment and machinery to be used in the tunnel shall be properly grounded, and electrical components provided with the protection required. Only authorized personel shall be allowed to repair or work on the electrical components.





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6. Lighting will be provided at the tunnel face, the minimum illumination shall be 100 lux. These shall be properly mounted on stands that can be easily moved around and positioned as require at the working face. The lighting fixtures shall be waterproof and maximum voltage for the fixtures shall be 240 volts.

7. Transit area shall likewise be provided with lighting fixtures, and minimum illumination to be provided shall be 40 lux. The lighting fixtures shall be waterproof and shall have a maximum voltage of 240 volts.

b. Support Systems :

1. Rockbolt pattern and density will be installed in accordance with the typical plans, layout, and section of the reference design and construction drawings.

2. The geologist or geotechnical engineer shall evaluate all geologic and geotechnical information of the excavated area, and shall decide all the support system to be applied base on actual ground conditions (either the increase or decrease in rockbolt density and spacing between rockbolts, installation of wire mesh, use of steel ribs, shotcrete thickness, etc.). The geologist shall inform the site engineer of his evaluation and recommendations regarding the support system. The site engineer and foremen shall ensure that the support measures are applied.

3. When tensioned grouted rockbolt are employed, the whole length of the bolts shall be fully grouted. Pre-grouting of the rockbolts shall be the preferred method.

4. All rockbolt face plates, conical washer, hemispherical nuts, lock nuts, and stick out, shall be buried with the shotcrete.

5. Shotcrete quality shall be regularly checked by QC procedures. Application procedure shall be in accordance with sound construction practice. Thickness guides shall be installed to ensure that the correct thickness of shotcrete is applied. Water ingress will be isolated and the rock surface to be sprayed, cleaned of loose rock fragments, soil, debris, etc.

c. Electric power, Compressed air and Water supply systems

Electric power distribution lines, compressed air and water delivery pipes shall be properly laid out arranged in the tunnel. Power supply and distribution system The power lines shall be laid out separately from the air and water pipes and the necessary circuit breakers provided to automatically cut off power supply when abnormalities are detected. Electrically operated equipments and machineries shall be provided with circuit breakers and shall be properly grounded. Only





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authorized personal shall be allowed to work on repairs or maintenance of the power lines and equipments. Power cables will be properly laid out on cable trays, hangers, and racks provided.

Compressed air and water distribution system Air receiver tanks will be installed after the compressors prior to distribution to regulate the pressure in the delivery pipeline. The receiver shall be equipped with the necessary pressure release valves, pressure gauges, and drain valves. A main valve shall be installed after the air receiver tank to control or shut off compressed air supply in cases of repair or emergency. Isolation gate valves shall be installed at intervals of 50 meters also for repair and emergency purposes.

d. Personal Safety The safety of the worker shall be guaranteed at all times. Training and Information All personal who will be assigned in the tunnel and related work shall undergo safety orientation before being allowed to work in the tunnel. Aside from this, tunnel workers shall be required to undergo the Basic First Aid training course (Red Cross Standard) during the duration of their employment. They shall also be required to attend refresher courses to be scheduled by the Safety department. Safety reminders in English and Thai language shall be installed at strategic locations to keep the workers informed and remind them of safe rules, regulations, and procedures. Safety warning signs shall be installed whenever there is a hazard identified. All actions shall be taken to correct to eliminate the hazard at the soonest possible time. Personal Protective Equipment All personal assigned in the tunnel shall be provided with the basic safety protective equipment. These shall consist of but are not limited to the following:

Safety Helmet (approved for underground use) – for head protection Dust mask or respirator – for respiratory protection Ear plugs – for noise protection Rubber Boots – foot protection Safety gloves – hand protection Safety goggle- eye protection

When the nature of work requires additional personal protective equipments, these shall be identified and provided to ensure workers protection and welfare.





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Worker compliance in the use of the personal protective equipments shall be ensured by the Site supervisors, foremen, in coordination with the safety personal. Air Quality and Ventilation The minimum ventilation requirement of 300 l/s/m2 shall be maintained at all times. Air quality tests shall be done at the start of work shift and after blasting. In cases where the ventilation system has stopped, work inside the tunnel shall be suspended and the workers evacuated to the portal until such that the ventilation system has been re-started and the work area ventilated for at least 20 minutes. No one shall be allowed to work in the tunnel without proper ventilation. c. Emergency Response Procedures The emergency response plans and procedures as set forth in the Site Safety Plan shall be strictly implemented. Information dissemination shall be done and incorporated in the safety induction program. A First Aid station complete with a First Aid box containing essential medicines, equipments, medical supplies, shall be maintained at the platform area for administering first aid in case of accidents. The first aid station shall be regularly checked for supplies and equipments and provision or replenishment done. All other safety measures as stated in the Site Safety Plan will be implemented and compliance will be ensured. 13. Environmental Management The contractor’s environmental Monitoring and Management Plan and the Site Specific Environmental Plans will be strictly followed and complied with the ensure mitigation of any impact the work may have on the environment. Clearing and Grubbing As stated for the Tunnel Excavation, no additional clearing or grubbing is necessary for the duration of the works. Water from Tunnel Excavation The discharge water from the tunnel shall be isolated and diverted to the drainage net work at the platform area. The discharge water from the tunnel shall be made to pass through a sedimentation pond, where silt, mud, and other impurities will be allowed to settle, before the water is discharged to natural drainage systems.





Date : 19 May 2009



Dust Generated during Excavation and Mucking Dust generated during tunnel excavation and mucking shall be sprayed with water to suppress dust generation and the remaining shall be dissipated from the tunnel by means of the ventilation system. Hazardous Materials Storage and Handling Hazardous materials (oil, fuel, lubricants, etc.) shall be stored in designated areas that are fenced off and provided with containment structures or facilities in case of accidental spill. The storage areas shall be clearly marked out and fenced off. The necessary spill response kits and equipment shall be made available. Handling of these materials shall be in accordance with the manufacturer’s recommendations. Disposal Hazardous materials shall be disposed of at designated area. Temporary storage for waste shall be established to accommodate these materials until a permanent disposal area is designated. The temporary storage shall be provided with the necessary facilities to prevent contamination of the environment. Non - Hazardous Materials Storage and Handling Non - hazardous materials shall be stored according to the manufacturer’s recommendations. Accidental spills shall be immediately treated and cleaned up according to procedures recommended by the manufacturer. The storage area likewise has to be fenced out and clearly marked out. Disposal Disposal of these materials shall be in accordance with the manufacturer’s recommendations. Garbage Generated All temporary facilities (workshops, offices, dining rooms) shall be provided with garbage receptacles to receive garbage generated from these facilities. Garbage will be collected regularly and will be disposed in designated disposal areas and procedures.





Date : 19 May 2009



Toilets Toilets shall be provided at strategic locations within the platform area. The toilets shall be provided with a septic tank and continuous supply water. The toilets shall be maintained for cleanliness and sanitation. Temporary Spoil Disposal Areas Slopes of spoil disposal areas shall be maintained less than the determined angle of repose of the materials to ensure stability. Coffer dams along the boundaries of the spoil disposal areas shall be the accumulated spoil is not washed away into natural drainage systems during heavy rains. Drainage shall be properly maintained to avoid saturation of the spoil materials during rains and the necessary silt traps or ponds constructed along the drainage or the discharge channels into natural drainage systems. The disposal areas shall be monitored regularly so that they are filled only to the designed capacity. All other environmental plans and procedures shall be strictly complied with to mitigate any impact of the construction activities on the environment.





Date : 19 May 2009



APPENDIX

1. Calculation for Mae Moh Tunnel Supports Design 2. Reference Design Drawings 3. Site and Tunnel Facilities Layout 4. Water Reservior , Sedimentation Pond and Temporary Waste Disposal Area Drawings and

Details 5. Typical Tunnel Excavation Profile 6. Layout for Slope Protection at Portal Area 7. Typical Soil Nail , Rockbolt and Drainhole Installation 8. Steel Rib Drawings and Details 9. Proposed Concrete and Shotcrete Mix Design 10. Work Procedure Flowchart Diagram 11. Inspection and Report Forms 12. List of Equipments 13. Material Specifications 14. Specifications for Mae Moh Tunnel Excavation and Construction

method statement mae moh tunnel

Documents

rotary hand

release amendment

separated

electric motor

rear dump

alkali free

natural drainage

typical soil