Retrofit Mrt

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Workshop "Underground Structures in Hot Climate Conditions",8-9 December 2009, Ministry of Transport, Riyadh, Saudi Arabia

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2.TUNNEL MAITENANCE PROGRAMS

The maintenance program should be designed to include prevention of deterioration and damage;prompt detection of deficiencies; and early accomplishment of maintenance and repairs to preventinterruptions of transportations or limitation/restrictions of tunnel use as presented in Figure 1 (Chinh2004).

Figure 1. Effect of maintenance on structural condition of tunnels

The main elements of tunnel maintenance programs are the inspection and the maintenance and Stepby Step Inspection, analyzing, and recommendation for tunnels is shown in Figure 2 (ITA 1991).

Inspection

Inspections of tunnel are classified as follows (Shuaib 2006): initial inspection; routine inspection;damage inspection (emergency inspection); in-depth inspection; and special Inspection.

Maintenance

Maintenance of tunnels is the scheduled work that is required to preserve the tunnel condition.T h e maintenance is divided to routine maintenance like sealing concrete; preventive maintenancesuch as filling cracks; and major maintenance like water leakage and crack repair.

Figure 2. Step by Step Inspection, analyzing, and recommendation for tunnels

Preventive maintenance of structures system should include: washing/cleaning; inspection;maintenance; and testing of the following elements (Shuaib 2006a):

Tunnel lining structures Tunnel finishers /claddings


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Ventilation tunnel emergency way Anchors and mechanical supporting

Drainage system in tunnel Roadway structures in road tunnel Structural system of railway

Preventive maintenance of equipment systems in tunnels are subdivided into mechanical system andelectrical system. The preventive maintenance of these systems must be complied with specialistrules and manufactures suggested preventive maintenance procedures.

3 TUNNEL INSPECTION PROGRAM

Tunnel inspection program is a multi stage process, which may be categorized in the followingdifferent tasks which may occur during routine inspection works (US-DOT 2005).

Inspection Management.

Inspection and Condition Assessment.

Reporting.

Report Distribution and Archiving.

4 CAUSES OF TUNNEL DEGRADATION

This section outlines major causes of deficiencies in structural elements within a tunnel. Thesedefects must first be evaluated to determine the cause and the severity of the deterioration, in order toselect the best repair method. Many concrete linings in highway tunnels have an additional tunnelfinish which may hide the extent of the deterioration. Therefore, a repair analysis will need toaccount for the replacement or repair of the finish as well. Deterioration in tunnels may be caused byany of the various factors listed below (US-DOT 2004).

Water Infiltration

Cracked and separated joints Lack of tightness Design or construction mistakes Corrosion of embedded metals Thermal loads Effects

Steep fill slopes above tunnels

Changing of geologic conditions Poor Workmanship Deterioration of mortar Degradation in concrete strength Longitudinal loads on tunnels

Longitudinal spreading of foundations Longitudinal differential settlement Swelling soil and invert damage Spall of tunnel crown joints. Loss of support due to erosion Seismic load and shape distortion

Chemical action on lining Damage to surface finishes Clogging drainage due to fines Cracks in track/road slab Inclined tension cracks at the base Differential movement at crown

Ingress of dissolved gases Damage in repair system

Some defects in tunnels are presented in in Figures 3, 4, and 5 (Conclinic 2007).

Figure 3. Water leakage in tunnels and underground structures


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Figure 4. Concrete deterioration due to carbonation, alkali-aggregate reaction, and sulfate attack

Figure 5. Longitudinal cracks in tunnels and underground structures

5. REPAIR CONCEPTS OF TUNNELS

Method of repair could vary due to the fact that there are different causes for the degradation. Theapplied repair methods must be durable, easy to install, capable of being performed quickly duringnon-operating hours, and cost-effective. Factors affecting the repair method are the deteriorationseverity, and the structural impact of the defect. The cause of the defect should be determined before

and remedial works, otherwise the same problem may repeat itself.

Repair priority definitions may be classified as follows (Chinh 2004);

Critical: if it requires immediate action Priority: when interim or long-term repairs should be undertaken on a priority basis Routine: for that can be undertaken as part of a scheduled maintenance program.

Repair of defect in a tunnel could be divided in the following steps (ACI 224.1R 2007):

Evaluation of damage/defect Relating observation to causes

Selecting appropriate methods andmaterials

Preparation of drawing and specification Selection of a contractor

Execution of the work Quality control and acceptance

5.1 REPAIR FOR WATER INFLITERATION

5.1.1 Cause of Water Infiltration

Water infiltration is the main cause of deterioration of the tunnel structure. Tunnels can developleaks due to inadequate connection/joint design, substandard construction, and deterioration of the

waterproof lining. Most tunnels are designed with drainage mechanisms around the exterior of thelining or embedded within the joints. As ground water flow patterns change over time a due to the


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accumulating effects of basements of surrounding buildings, drains become clogged with sediment,the water is bound to find its way into the tunnel through joints or structural cracks. Another scenariois that a tunnel which was designed to be above the water table, is subjected to hydrostatic forces thatit is unable to resist and subsequently water infiltration becomes a problem.

5.1.2 Repair of Water Infiltration

Water infiltration repair must be investigated in the following zones (US-DOT 2005) :

The surrounding ground Interface between ground and lining Tunnel Lining Structures The lining intrados Internal useful spaces of the tunnel

Remedial works for water infiltration inside tunnels could be a short term solution, a long term

solution and partial or full replacement of the tunnel lining. To determine the most cost efficientmethod of repair for a particular situation, a specific cost analysis should be performed that considersthe costs over the life of the tunnel (ITA 1991).

5.1.2.1 Short Term Repair

This is a temporary or permanent solution by redirecting the infiltrated water to the drainage systemuntil further investigation can be performed and a more long term solution implemented. Thisincludes drainage toughs and using pipe network as shown in Figure 6 (Chinh 2004).

Figure 6. Short term repair of water infiltration

5.1.2.2 Long Term Repair

Many factors are involved in determining which long-term method should be used. These factors are:site specific; cause of water infiltration, and water volume. A detailed study should be performed onmajor leaks to determine source, amount of water leakage, and exact location of the leak. Some ofthe long term repair methods are given below as shown in Figure 7 (Conclinic 2007),

Insulated panels Waterproofing membrane Crack/joint injection

Soil/rock grouting (back-wall grouting) Crack/joint repair (ACI 503.7 2007) Segmental joint repair


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Figure 7. Long-term repair of water infiltration by waterproofing, and injection methods

5.1.2.3 Structural Replacement

Lining reconstruction has advanced to a point where repairing numerous localized areas of the linerbecomes cost prohibitive. Reconstruction could include shotcrete or pumping plasticized concretewithin a form liner. In addition, using an exterior drainage system in a tunnel below the ground waterelevation is normally not effective over the long term because of the ability for water to penetrate

very small cracks that develop between drains. Some of the available systems for extensive liningreconstruction are mentioned below as shown in Figure 8 (Watson 2003) and (Conclinic 2007).

Shotcrete applications Joint control Water tight concrete

Figure 8. Shotcrete , and joint control by re-injection system

5.1.2.4 Joint Leakage Repair

Existing Repair systems for water leakage repair includes the following items:

(1) Types of Repair Materials

Water-based epoxy Poly Urethane grout Cementit ious grout Acrylic grout Combined cementitious polymer grout

(2) Types of Repair Methods

Injection system (Epoxy, PU) Surface treatment system

(cementitious) Surface filling systems (Polymer cementitious)


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(3) Problems of Repair Systems

Low adhesion to the wet surface (epoxy, urethane) Improper hardening in a wet condition Water absorption (Urethane) Lack of movement of the substrate cracks by thermal change and vehicles (epoxy, cement)

Polyurethane fume has failed as injection material for case of sea water or high sulfate salts in theground water (Kang et al. 2008), while acrylic grout is a durable leakage repair system as shown inFigure 9 (Conclinic 2007).

Figure 9. Failure of polyurethane and success of acrylic for leakage repair system

6. CONCRETE REPAIR OF TUNNELS

Concrete deterioration in tunnels and concrete lining may be caused by various factors including:water Infiltration, corrosion from embedded metal, thermal effects, loading conditions, and poorworkmanship. As concrete deteriorates, proper repairs shall help to avoid further degradation of thestructure.

6.1 Corrosion Protection of Concrete

Concrete protection could be satisfied through construction areas and electrochemical/cathodic areasas shown below (ACI 224.1R 2007).

Design improvement (increase of cover thickness) Material improvement (permeability using fly ash, slag, and silica fume) Material improvement (Inhibitor using anoding or cathodic protection) Concrete surface block (Painting, lining, sheet coating, and polymer mortar) Rebar surface block (Coatings using fusion bonded epoxy and zinc coating) Cathodic Protection

- Sacrificial Anode Method (No impressed current, low initial cost and reliable)- Impressed Current Method

Corrosion protection of concrete Cathodic protection by sacrificial anode method consists of thefollowing items (Conclinic 2007) as shown in Figure 10.:

Zinc mesh is used as a sacrificial anode Glass Fiber Reinforced Polymer (GFRP) jacket for structure rehabilitation Conductive mortar is used as a electrolyte solution Corrosion sensors is used as a corrosion potential monitoring


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Figure 10. Corrosion protection of concrete by sacrificial anode

6.2 Crack Repair of Concrete

Concrete and reinforced concrete lining crack repair is classified (US-DOT 2004) as shown inFigure 11 (Conclinic 2007):

Injection/grouting techniques Routing and sealing techniques Packing techniquesThe selection of techniques or any combination is based on:

Dimension, condition of crack Condition of concrete area need to repair Required target

Figure 11. Concrete crack repair by injection, sealant, and packing

6.3 Spall Repair of Concrete

Concrete and reinforced concrete lining crack repair is classified as shown in Figure 12(Conclinic 2007) and (Newman 2001).

Shallow spall with no reinforcement steel exposed Shallow spall with reinforcement steel exposed Deep Spall with reinforcement steel exposed

6.3.1 Repair of shallow spall with no reinforcement exposed is given below (Emmons 1994).

Removal of loose or deteriorated surfaces Clean the concrete surface Sawcut on a 20-degree angle around the spalled area Placing polymer repair mortar to original concrete depth

6.3.2 Repair of shallow spall with reinforcement steel exposed is as follows (Newman 2001).


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Removal of loose or deteriorated surfaces Clean the concrete surface and the exposed steel rebar Sawcut on a 20-degree angle around the spalled area Coating rebars with anticorrosion agent compatible with the repair mortar Placing polymer repair mortar to original concrete depth Applying protective coat to the surface

Figure 12. Repair of shallow spall with reinforcement steel exposed

6.3.3 Repair of deep spall with reinforcement steel exposed is as given below (Chinh 2004).

Removal of loose or deteriorated surfaces Clean the concrete surface and the exposed steel rebar Sawcut on a 20-degree angle around the spalled area Coating rebars with anticorrosion agent compatible with the repair mortar Placing polymer repair mortar to original concrete depth Applying shotcrete with additional welded wire fabric mesh WWF.

6.4 Seismic Strengthening of Tunnels

Tunnels were considered the safest structures under earthquake loads, the recent studies haveestablished that some damages have been observed in different tunnels and underground structuresduring and after ground shaking []. Deformation modes and behavior of circular and non-circulartunnels during earthquake are presented in Figure 13 (Hashash et al. 2001).


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Figure 13. Behavior of tunnels during earthquake

Seismic response of underground structures consists of three major steps as follows (El-Nahass et al.2006).

1. Definition of the seismic environment and parameters2. Evaluation of ground response to shaking3. Assessment of structure behavior due to seismic loads

Application of advanced composite material can help in strengthening and retrofit of tunnels forseismic resistance upgrade. Carbon and glass reinforced polymer (CFRP) and (GFRP) are used forsuch purposes for its high tensile strength with light weight. The application of theses material isshown in Figure 14 (Conclinic 2007).


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Figure 14. Application of fiber reinforced polymer for strengthening of culverts

7. DECISION MAKING IN REPAIR

Tunnel management system (BMS) should provide a Decision Support System (DSS) which helps indecision making for repair and rehabilitation of tunnels. Decision making is the study of identifyingand choosing alternatives based on the values and preferences of the decision making to choose theone that best fits with our goals, objectives, desires, values, and so on. General decision making

process is as follows (Shuaib 2009).

Establish goals

Identify alternatives Define criteria Assign decision matrix Establish priority score matrix Select a decision making tool Preference ranking of alternatives Sensitivity analysis Final recommendation

7.1 Decision Matrix

Decision matrix combines both alternatives and criteria in one matrix to transfer the problem frompractical field to mathematical field as shown in Figure 15 (Shuaib 2009).

CriteriaC1 C2 . CN

( w1 w2 wN)Alternatives ______________________________

A1 a11 a12 . a1NA2 a21 a22 . a2N

. . . . .AM aM1 aM2 . AMN

Figure 15. Decision matrix model


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where, (Ai) is the alternatives, such as; repair using: Carbon Fiber Reinforced Polymer (CFRP), FiberReinforced Polymer (FRP), Adding concrete element, adding steel plate and replacement of thetunnel or part of it. (i) = 1,2,3,.Mand (M) is the total number of alternatives. (Cj) is the criterionon which a comparison is to be held between different alternatives such as; construction cost,construction duration; traffic detouring cost; maintenance cost; ease of construction; future flexibilityand aesthetic appearance. (j) = 1,2,3, N; where (N) is the total number of criteria. (wj) is theweight and importance of each criterion, which is estimated by the decision maker group such as:the owner, the consultant office and public community representatives where ;

N wj= 1.0 (1)

j=1

(aij) is a measure or score of performance for each alternative subjected to each criteria. This measurecould be a quantitative type or a qualitative type. Qualitative types should be transformed to anestimated quantity to handle decision making mathematically.

7.2 Priority Score Matrix

Each criterion has a different unit for measuring of (aij) such as US $, day,elct. The decisionmatrix should be formalized by normalization of each column of the matrix to find the modifiedscores (bij) and to produce the dimensionless priority score matrix. Each column of the prioritydecision matrix should satisfy (Eq. 2 ) (Shuaib 2009).

M (bij) = 1.0 (2)

i=1

7.3 Decision Making Methods

There are several decision making methods such as: the weighted sum method (WSM); the weighted

product method (WPM); the analytical hierarchy process (AHP); the ELECTRE method; andtechnique for order preference by similarity to ideal solution (TOPSIS) (Shuaib 2009).

(I)- Weighted Sum Method (WSM)

NPi = (bij) * wj for i= 1,2,3 M (3)

j=1

(II)- Weighted Products Method (WPM)

NPi = (100*bij)

wj for i= 1,2,3 M (4)

j=1

8. CONCLUSION

Tunnel management systems should be established carefully to increase the service life of tunnels.Degradation of new tunnels starts from the first day of service of tunnels. Scheduled maintenance oftunnels is required to preserve the tunnel condition. Water infiltration and water leakage representthe major reasons for deterioration of tunnels. Efficient drainage system and waterproof of the tunnelshall reserve tunnels. Regular repair of concrete and concrete lining are very essential for tunnels.Corrosion protection and corrosion protection system could retard deterioration of concrete inunderground structures. The use of fiber reinforced material can help efficiently in strengthening andseismic upgrade of tunnels us. Decision making in repair and strengthening of tunnels is complicatedissue but it could be modeled mathematically to use multi criteria decision methods for choosing themost preferable alternative for repair of tunnels and underground structures.


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REFERENCES

American Concrete Institute (ACI) Committee 503.7. (2007). Specification for crack repair by epoxyinjection. ACI, Farmington Hills, MI.

American Concrete Institute (ACI) Committee 224.1R. (2007). Causes, evaluation and repair of cracks inconcrete structures, ACI, Farmington Hills, MI.

Chinh, B.C. (2004). Maintenance and repair of underground works in Vietnam. ITA 30th General assembly,

Singapore.

Conclinic, Co. (2007). Total Solutions of Repair & Retrofit of the Facilities. www.conclinic.co.kr.

El-Nahas, F., Abdel-Motaal, M.A.& Khairy, A.T.H. (2006). Engineering of tunnels duringearthquake.Workshop on Safety in Tunnels and Underground Structures. Riyadh, KSA.

Emmons, P.H. (1994) . Concrete repair and maintenance illustrated, R. S. Means Company, Inc., Kingston,MA.

Hashash, Y.M.A., Jeffrey J. Hook, J.J., Schmidtb, B. & Yaoa, J.I. (2001). Seismic design and analysis of

underground structures. Tunnelling and Underground Space Technology , 16: 247-293.

International Tunnel Association, ITA. (1991). Report on the damaging effects of water on tunnels during theirworking life. Tunnelling and Underground Space Technology , 6: 11-76.

Kang, S., Cho, I. & Kim, S. (2008). Effect of isocyanate index on the physical properties of rigid polyurethanefoam under sea water. J. Korean Ind. Eng. Chem., 19: 427-431.

Newman, A.P.E. (2001). Structural renovation of buildings, methods, details, and design examples,. McGraw-Hill, New York.

Shuaib, M.F. (2006) Maintenance program and condition rating of existing highway bridges, InternationalConference on Bridge Management Systems _Monitoring, Assessment, and Rehabilitation, Housing &Building National Research Centre, Cairo, Egypt.

Shuaib, M.F. (2009). Decision making in repair of highway bridges with applications in the gulf area. 11th

Conference of Arab Structural Engineers , King Fahd University-Dhahran, KSA.

U.S. Department of Transportation, Federal Highway Administration. (2005). Highway and rail transit tunnelinspection manual. FHWA, Washington, D.C.

U.S. Department of Transportation, Federal Highway Administration. (2004). Highway and rail transit tunnelmaintenance and rehabilitation manual. FHWA, Washington, D.C.

Watson, P.D., (2003). Spall repair by low-pressure spraying.Field Guide to concrete repair applicationprocedures, ACI International, ACI RAP 3.

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