206 paper 351 - smart construction 1

8/8/2019 206 Paper 351 - SMART Construction 1

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Mr. Gusztav Klados, Senior Tunnel Project Manager, SMART Project Office, No.67, Jalan 3/93, TamanMihraja, off Jalan Cheras, 55200 Kuala Lumpur, Malaysia; tel: +603 9206 3000; fax: +603 9285 3723;[email protected]

Mr. David R.Parks, BSc(Hons), CEng., PEng., FICE, Chief Resident Engineer, SMART Project Office,No.67, Jalan 3/93, Taman Mihraja, off Jalan Cheras, 55200 Kuala Lumpur, Malaysia; tel: +603 92063000; fax: +603 9285 3723; [email protected]

STORMWATER MANAGEMENT AND ROAD TUNNEL(SMART)

OVERVIEW, TBM SELECTION AND CONSTRUCTION

This paper highlights the following main points:

1. Project overview2. Geological profile3. Site investigation4. Selection of TBM equipment5. Special features in the TBM to handle the geological conditions.6. The extensive geophysical and soil investigation together with real time instrumentations on site.7. Evaluation of TBM performances in difficult excavation conditions.8. Difficulties encountered tunnelling in highly variable karstic limestone conditions



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PROJECT DESCRIPTION

Kuala Lumpur, the business and commercial hub of Malaysia has oflate often been inundated by the floods from the Klang River asdevelopment has canalized the river. Over the years the intensity ofthe floods increased with each incidence, causing financial lossesand inconvenience to the city folk. With cars submerged and trafficgrinding to a standstill, the city was in urgent and immediate need offlood mitigation. (Figure 1)

The innovative SMART Project provides a stormwater diversionscheme including floodwater storage and a 10km, 11.8m diameterbypass tunnel, sufficient to save the city from flooding in theforeseeable future. With no major flood event likely to occur overmost of the year the tunnel a dual use was engineered, with doubleroad decks built into the central three kilometre section, relieving

traffic congestion by providing 2×2 traffic lanes for cars connectingthe city centre to the southern gateway, the KL – Serembanhighway.

The flood water is diverted at the confluence of the Klang andAmpang rivers into a Holding Pond. From there the water passesthrough the tunnel into the Taman Desa Attenuation Pond and via abox culvert discharges into the Kerayong River. (Figure 2).

The government accepted the innovative proposal of two Malaysiancompanies, MMC and GAMUDA, to reduce the cost of the schemefor the Government. The firms proposed to build the road tunnelsection at a cost to be recovered by a toll collection Concession

from the Government thus providing a dual purpose usage andoffsetting the overall Government costs as a Concession.

Main Project Components

The paper focuses mainly on the 9.7km, 11.8m internaldiameter stormwater tunnel but the project alsocomprises of a number of other major structuresassociated with river diversion, intake to the tunnel, roadstructures and outfalls. The main project componentsare as follows:• River Klang Offtake Structure• River Klang Diversion Weir• Holding Pond excavation• Tunnel Inlet Structure• 9.7km, 11.8m int. dia. Tunnel• Emergency Escape Passages• North Ingress/Egress Road Box ramps• North Junction Box• North Ventilation Shaft• South Ventilation Shaft• South Junction Box• South Ingress/Egress Road Box ramps• Tunnel Outlet Structure• Attenuation Pond

Figure 1: Flood in the city and Sg. Besi traffic

Figure 2: Location of tunnel in Kuala Lumpur



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• Twin Box Culvert• River Kerayong Outfall Structure

The overall scheme provides storage for some 3,000,000m³ of water and allows water to be transferredthrough the system whilst utilizing the upper and lower road decks for traffic at the same time. Threeoperational modes are envisaged.

Organisation of the SMART Project

The project owner, the Government of Malaysia is represented by JPS the Public Works Department, DIDthe Drainage and Irrigation Department and by LLM, the Highway Authority.

The project design and supervision Consultants are Sepakat Setia Perunding (SSP) in association withMott MacDonald.

The project promoter is the MMC - GAMUDA Joint Venture.

MMC - GAMUDA Joint Venture also set up the Concession holder company for the road operation calledSyarikat Mengurus Air Banjir & Terowong Sdn Bhd (or SMART Sdn Bhd).

The EPC Contractor is the MMC - GAMUDA Joint Venture.

Geological Profile

The tunnel traverses the Kuala Lumpur limestone formation at shallow depth (Figure 3). The maturekarstic formation is covered by loose silty sand, peat or, at some places , mine tailings, the remnants ofthe extensive but now historic tin mining in the region.

The quaternary alluvial deposit is generally 4 - 5m thick. However in karstic areas the unpredictable

rockhead may suddenly drop 20-30m due to eroded solution and cliff features. The mean UCS value is

-10.00m

0.00m

KERAYONG

10.00m

20.00m

30.00m

40.00m

1 : 6 5 0

1 : 1000

LEGEND:-

OVER BURDEN

ROCK BED

STORAGEPOND

SG.SG.Klang JALAN DESA PANDAN

FROM SG. KLANG TOKPG. PANDANALONG JALAN

ALONG JALAN TUN RAZAK CHAN SOW LINAL0NG JALAN KL - SEREMBAN

HIGHWAYSALAK

I/C

Figure 3: Sub surface conditions for the SMART tunnel

50 MPa. The maximum value is 120 MPa but the limestone has not been found to be very abrasive.

The groundwater table is 1.5-2.0m below the surface. The permeability of the rock is generally lowalthough groundwater movement through the soft alluvial overlay and karstic features can be extensiveand lead to water drawdown hundreds of metres away from a disturbed area. Drastic differences inrockhead are an expected feature in karstic areas or at fissure zones.(see Figure 4 ).



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Considering the alignment from north to south thetunnel runs in alluvium and mine tailings for about2,5kms. and mixed conditions for a further 1.5km.

This is followed by a central section of some 5.5kmpredominantly in limestone with karstic features thelatter 1.5km being with shallow rockhead cover. Thelast 200 m is in residual soils of the Kenny HillFormation. The full cover of the tunnel ranges between0,8-1,8 diameters. Typically, the rock cover isexpected to be 3-7m but in areas of karstic depressedrockhead, a full face of soil or a mixed face of soil androck are expected.

The area is very sensitive to groundwater drawdown.The reduction of groundwater level is known to triggersinkhole incidents in karstic areas, sometimes a

considerable distance from excavations. The alluvial cover produces differential settlements in proportionto the thickness of the cover on the undulating rockhead. Hence only tunnel excavation methodspreventing the drawdown of the groundwater were considered.

For shaft excavations experience has shown that ground treatment prior to excavation is essential incontrolling ground water to eliminate movement which may trigger a sinkhole some distance from theworks. Initial excavations to rockhead identified deeper features where piling was necessary to supportthe excavation. These areas were extensively ground treated to control ground water before excavationby drill and blast methods continued.

Site Investigation

The original soil investigation carried out to determine the profile of the rock head, was found to beinadequate to evaluate and understand better the highly variable karstic limestone and facilitate thechoice of optimum excavation techniques. The following additional soil investigations were carried out:

a) Three stages of soil investigation totalling to more than 334 boreholes over a 12 km project length.

b) Microgravity Survey conducted over sections where there is significant drop in rock head andpresence of cavities.

c) Resistivity Tests and Seismic Tests are also being carried out. Such tests cover most of thealignment and focus on areas of particular concern and risk identified in the earlier site investigationwork.

Sensitive Structures and Instrumentation

a) Settlement predictions along the tunnel alignment have been plotted as a settlement trough based onO’Reilly & New i. Extensive instrumentation has been identified and installed on site as groundmonitoring markers, building settlement markers, standpipes and tiltmeters

b) With the alignment traversing an urban environment with urban infrastructures such as highways,railway lines, existing bridges and adjacent buildings a number of sensitive structures were identified.

c) These sensitive structures have intensive instrumentations coverage as well as ground treatments tostabilize the ground where the TBM transverses. In total there are 1300 no of instrumentations on site(see Figure 5).

Figure 4: Exposed karstic rockhead at a tin mine



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Figure 5: Instrumentation Layout around NVS

d) Risk analysis was carried out categorising the buildings based on their type of foundation, structuralcondition and use. Risk mitigation measures were defined based on this risk.

Tunnel Lining

The tunnel segmental lining was designed by Mott MacDonald and consists of an 11.8m internal diameterprecast lining with 500mm thick segments. The ring is in effect a universal taper of 2x55mm, giving overall110mm taper, but the rings are used as left and right tapers to keep the keystone above the axis level forease of erection. The ring is made up of 6 standard plates, 2 counter keys and a keystone. The rings are1.7m long and weigh 82 tonnes. (Figure 6)

Figure 5: Instrumentation of North Drive after NVS

Criteria for Selection of TBM

The original proposal for excavation of the south section from the North Ventilation Shaft was used drilland blast tunnelling and cut and cover methods. At a very early stage in the project this was consideredimpractical and imposed unacceptable risks and disruption to the public. Accordingly, it was decided to



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use a second TBM. Both EPB and Slurry TBMs were considered. The following criteria influenced thedecision to select a TBM:

a) The alignment had very tight radius curves of 250m radius to allow land acquisition to follow roadreserves and stay within the public right of way.

b) The overburden is shallow with only 10m to 20m cover.

c) The control of ground water with a pressurized system to maintain required face support pressure inorder to prevent triggering of sinkhole incidents.

d) The machines have to work in a predominantly limestone environment. Several sections are expectedto have either filled karstic caverns or sudden drops in rockhead. Both machines have to be able towork in mixed face conditions.

TBM Features

With the majority of the tunnel in karstic rock conditions and the need to control groundwater, it wasconsidered appropriate to select slurry TBMs with an air bubble based control. The air bubble systemregulates the face pressure more accurately than the pump speed based systems. The pressure controlwas deemed to be very important in enabling tunnelling with very low overburden and high water table.

The control of groundwater drawdown in a rock filled excavation chamber which would also haveunsuitable material to seal the screw conveyor was deemed to be unachievable with the EPB technologyeven with constant conditioning of the material in the excavation chamber.

Two identical Mixshields were purchased from Herrenknecht, Germany. The first TBM was deliveredwithin 12 months and the second machine within 15 months of order. The cutterhead configurationselected was for mixed face conditions. The double rotational head had to be able to effectively excavatemedium rock and soft soil or mixed face conditions.

Special emphasis was placed on the spherical main bearings. It allowed the cutterhead to tilt in thedirection of the curve to be negotiated, thereby reducing the differential ram loads on the segmentallining. The cutterhead had also to be shoved out by a maximum of 400 mm through the drive unithousing. (See Figure 7) This feature allowed the pull-back of the head for cutter change and inspection inrock face conditions without moving the front shield.

The machine is equippedwith two air locks and asmaller material lock tofacilitate near continuouscompressed air work tochange tools on thecutterhead. Themachines are equippedwith two probe drillingrigs to investigateconditions ahead of themachines althoughexperience to date hasseen only occasional useof them. This is due tothe limited value providedover such a large face

area and the fact that the very ground conditions which are being investigated are the conditions wherethe rods may become jammed thus disrupting TBM progress.

Figure 7: Major components of Mixshield TBM



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Cutterhead tilt monitoring device is fitted on both machines. This device indicates the location of thecentre of load on the cutterhead. It also shows and indicates if the machine goes through large cavities

or is in mixed face conditions.

TBM Operations and Countermeasures

Difficult excavation by the TBM was envisaged due to the potential risk of settlements from soft materialoverlaying the limestone, the existence of karstic limestone and ground cavities. Loss of bentonite intofeatures would lead to loss of face pressure and resulting collapse of ground surface. Alternatively overpressurization can lead to surface heaving and bentonite loss to ground surface areas through karsticfeatures in the ground. These not only cause disruption and mess at the surface but are often followed bycollapse of the ground surface as the cutterhead slurry pressure must be reduced to avoid losingbentonite to the surface.

In order to overcome the potential risks and mitigate the loss of bentonite, whilst controlling face

pressures, there are a number of countermeasures that have been adopted to manage the risks involvedin tunnelling through these ground conditions. These include:

a) Confinement pressure, was computed for various scenarios of cavities formation in terms of sizeand location in front of the drive face using the Mohkam Model .

b) Specifying correct TBM parameters for each of the following scenarios i.e. tunnelling throughhomogeneous ground conditions, mixed ground conditions of rock and alluvium/peat, interface conditionsand in filled cavities.

c) Carrying out extensive site investigations involving geophysical methods, boreholes, piezometersetc. Geophysical surveys have been calibrated and correlated to SI results and used to cover areasbetween SI boreholes. This provides the coverage needed to anticipate possible cavities ahead of theTBM drive. Samples of results showing cavities with low density portrayed by different colour usingResistivity and Seismic Survey are shown in Figures 8 and 9.

d) Intensive settlement monitoring on the surface to monitor any surface settlement or heave,together with controlling the face pressure during TBM excavation in various ground conditions.

e) Intensive visual monitoring of the surface in a wide area to observe signs of distress caused bylocalised settlement of karstic features. These settlements are not picked up by conventional monitoringsystems

f) Adjustment of slurry composition to cope with varying ground compositions and characteristicstogether with slurry volume control to compensate face loss.



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Figure 8: Resistivity Image

Figure 9: Cross hole Seismic Tomography Image



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g) In sensitive zones, the possibility to drill and grout from the ground surface ahead of the TBMusing three different types of grouting namely: compensation grouting, compaction grouting and rock

fissure grouting methods. These grouting methods differ in sequencing of the works and grout mix.h) Probing and grouting can be carried out from within the TBM although grouting from the surfaceoffers cost and scheduling advantages as it is considerably less disruptive to TBM progress and likely tobe more successful.

Tunnelling Difficulties

In karstic limestone conditions, the face pressure (confinement pressure) is considered critical.Equilibrium of hydrostatic and earth pressures with the face pressure, utilising slurry support, will bemaintained so long at the cavities in front of the TBM are filled with water or soil. As such, encounteringfilled cavities at the front face has controllable risk. If there is no loss of slurry and no heave on thesurface then the calculated face pressure reflects the actual pressure requirement. This is shown by the

determination of face pressure support and subsequent observations during tunnelling.Cavities that are not filled or partially filled pose a serious risk. Such cavities will potentially cause the lossof slurry pressure and could lead to face collapse and ground settlement. The contingency is that theSeparation Plant has 1000m 3 of fresh bentonite and 1000m 3 of used bentonite available for filling anyunfilled cavities. Where water filled cavities connected to extended karstic systems are encountered, themost likely event is the reduction of confinement pressure. This only constitutes a risk if at the same timethe rockhead is dropped and the crown is in soft ground. Under these conditions the density of slurry canbe increased to a maximum of 13kN/m 3.

Similar risks can occur if the TBM hits a loosely filled well or funnel of loose material like in mining areas.In such events, the TBM will have to reduce face pressure to hydrostatic pressure and grout from thesurface.

Road Deck

Within the central 3 km of tunnel the dual purpose facility of double deck roads is sited between the Northand South Junction Boxes. These Junction Boxes provide the bifurcation arrangement where thestormwater and road systems merge together with provision of the road and flood gate systems thatprovide the control and safety of the operation of the scheme.

The road decks are constructed in two pours. Firstly the lower deck and secondly sidewalls and upperdeck. (Figure 10) The original design was modified and precast planks, 100mm thick carrying the lowerreinforcement cage, introduced similar to the ‘Omni’ system used in bridge decks. To achieve programmethe work progresses at the same time that tunnelling proceeds. To achieve this special considerationswere needed to develop the formwork so TBM trains could still supply segments and materials to the TBMwhile deck construction proceeded.



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Cross Passages

Within the road tunnel, Access to escape passages are provided approximately every 250m to a place ofsafety in the event of an emergency. These passages are constructed between the lower and upper roaddecks, each being considered a point of safety in the event of an emergency in the other. This provision,together with a tailor-made ventilation system designed to handle a 100MW fire, ensures public safety.

The passage configuration also contains a switch room, telephones, fire fighting provisions and watertightdoors that are sealed during the flooding operation.

The construction of the passages was preceded by extensive grouting from the surface to preventgroundwater drawdown. Drill & blast method with shotcrete temporary support and spot rock bolting wereused. Sprayed on waterproofing will be used to mitigate the difficulties of placing a conventionalmembrane on complicated 3D surfaces.

Progress to Date

The initial North TBM Tunnel drive from the North Ventilation Shaft to the North Junction Box wascompleted by the sub contractor, Wayss & Freytag. The 743 ring drive holed through on 11 December2004 and was relaunched on the second drive towards the Holding Pond on 5 March 2005. As of midJune 2005 the drive was 26% complete and had reached Ring 770.

The South TBM Tunnel drive from the North Ventilation Shaft through the South Ventilation Shaft and onto the South Junction Box was completed by MMC – Gamuda. The 1072 ring drive holed through on4 June 2005 completing 44% of the drive. At the time of writing, the TBM is undergoing refurbishmentand is intended to be moved across the shaft for relaunch in mid July 2005

The entire dual use tunnel section has been completed. The lower road deck in the 740m long dual usesection of the North Drive is 100% complete and 44% of the upper road deck has been completed. Thelower road deck in the South Drive is 42% complete together with 20% of the upper road deck.

Figure 10: Road Deck Configuration in Tunnel



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Overall the SMART project progress is on schedule with 51% having been completed by the end of endMay 2005.

Summary/Conclusion

The Stormwater Management and Road Tunnel scheme has demonstrated that with some innovativethinking dual usage of major infrastructure works are feasible from an engineering perspective.

Despite concerns regarding the variable nature of the karstic limestone in Kuala Lumpur beforeembarking on the project, the choice of TBM has been vindicated and the project has shown thattunnelling in this type of ground is possible, although considerable care is needed to maintain optimumTBM parameters and slurry properties.

With careful interpretation the use of seismic and resistivity geophysical survey methods to investigate theground conditions from the surface have provided useful additional information to replace the original

intention to supplement the site investigation with probing ahead of the TBM. This has proved to be auseful tool that could be developed further.

Large scale shaft excavations have also been achieved with minimal settlement using carefully designedground treatment strategically located to control groundwater in geological features and avoid sinkholes,a common event in this type of ground. Settlement monitoring, although a major tool in checking surfaceand building movement, needs to be supplemented with a surface based team to visually inspect theground above the TBM in case sinkholes develop.

i O’Reilly, M.P. and New, B.M., Transport and Road Research Laboratory, Crowthorne, England “ Settlementsabove tunnels in the United Kingdom—through magnitude and prediction ” Tunnelling’82 Institute of Mining andMetallurgy, UK

206 paper 351 - smart construction 1

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