Thermoplastic Lined Tunnels

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1 Thermoplastic Lined Tunnels General For tunnel structures under ground used to store and transport potable, drinking and waste water it is an essential requirement to protect the inside surface. The protection of the inside surface is necessary to ensure water proofing, good flow characteristics, high chemical resistance. Past experience has shown that unprotected concrete surfaces as well as chemical based linings such as coatings, sprayed linings are not providing the life duration which is required for such investment intensive life lines for cities and industrial installations. Lining with thermoplastic material which is based on mechanical bonding in the concrete substrate is providing much superior properties for such applications. This report will discuss the main benefits of such linings and various methods of construction. The main application areas where such lining should be applied are waste water tunnels and pipes potable water tunnels and pipes drinking water tunnels and pipes storage tunnels for drinking and potable water Advantages of Thermoplastic Lining Thermoplastic lining based on already widely used material such as High density polyethylene (PEHD) is applied to the concrete substrate during the construction of the system. This provides major advantages over other lining systems. Immediate implementation of the lining material ensuring better bonding capabilities and faster construction cycles (coatings can only be applied after concrete is completely dry and clean which will increase construction time) Mechanical anchoring by means of anchor studs which are applied on the thermoplastic liner during manufacturing provides high bonding strength between the lining material and the concrete (high pull out strength and ground water pressure resistance) Thermoplastic lining provides further major advantages for such kind of applications such as: Full leak tightness The material has excellent mechanical properties including high elongation behaviour. These properties provide in the application the benefit that cracks of the concrete structure will not create a leak of the lining material. Cracks of the concrete substrate will be bridged. The picture shows destructive tests performed on CPL lined concrete pipes where this behaviour of the lining material is demonstrated. Prepared by Albert Lueghamer Page 1 of

2 Very good chemical resistance Unprotected concrete structures are heavily deteriorated by chemical attack resulting in many cases that the structures are collapsing or heavily leaking. Similar behaviour is also happening on coated concrete structures whereby the lifetime is slightly higher than for unlined system. Especially in regions where environment temperatures are consistently higher than 25 C chemical resistance of concrete structures play a significant factor for the life time of the system. Picture of unlined concrete structure Thermoplastic materials such as PEHD are chemically resistant against diluted solutions of salts, acids and alkalis if these are not strong oxidizing agents. Good resistance is also given against many solvents, such as alcohols, esters and ketones. Scheme and picture of CPL lined tunnel systems This ensures that thermoplastic systems are not deteriorated by any chemical attack of long periods and will therefore play a significant factor for the long life duration of tunnel systems. Very good abrasion resistance Unlined concrete surfaces do not have very good resistance against abrasion. In operation this will create pretty fast deterioration of the installed system. Reduced flow capabilities, build up of sediments in the tunnel have been detected in many occasions. Prepared by Albert Lueghamer Page 2 of

3 Abrasion tests have verified that various material types do provide very different properties. As the best materials, thermoplastic materials such as PEHD have by far the highest abrasion resistance. Long-term analyses based on actual testing also identified that PEHD lined surfaces are suitable to withstand life durations more than 100 years. Very good resistance against root growth Unlined or uncoated surfaces do not provide resistance against penetration of roots. Especially joint sections in tunnel and piping systems underground are showing such problems. The growth of roots into piping system will cause reduction of the static condition of the installed underground system and is causing significant reduction of flow capabilities. Cracks which are leading to leaking require significant efforts in maintenance, causing high operation costs and downtime periods in operation. Prepared by Albert Lueghamer Page 3 of

4 PEHD lined structures ensure a further benefit to the system and life duration because of their proven resistance against root growth. Lining of the joint section and the advantage that PEHD lined structures are welded in all joint areas avoid any penetration of roots also in these areas. Good surface smoothness Plastic lining provides the further bid advantage of very smooth surface characteristic. The above given properties and benefit of plastic ensure also that the surface properties remain consistent which ensures that the installed system can be operated with consistent flow conditions over a long period of time. A further advantage is that cleaning of the system does not require a lot of effort. Prepared by Albert Lueghamer Page 4 of

5 The Lining System Concrete Protective Liners (CPL) manufactured out of various thermoplastics are the best solution for lining of concrete structures. The CPL s are available in various sizes and configurations to provide for each application a cost effective solution. The Product Range: - Custom-made CPL ( 2,0 mm up to 5,0 mm) in PEHD (product sizes are manufactured according customer requirements to fit best the installation sequence) - Concrete Protective Liners (CPL) 4000mm x 2000mm x (3 12)mm (PEHD, PP, PVDF, ECTFE) - CPL with anti-skid surface 4000mm x 1800mm x (3 5)mm (PEHD, PP) - CPL polyester fabric backed 4000mm x 1800mm x (3 5)mm (PEHD, PP) - CPL with signal layer 4000mm x 2000mm x 5mm (PEHD, PP) - CPL with aluminium barrier 4000mm x 1350mm x 5mm (PEHD, PP) - Various installation profiles (PEHD, PE80-el, PP) - Welding rods (PP, PE80, PE80-el, PVDF, ECTFE) - Welding equipments and welding robots The SURE GRIP CPL System meets the requirements of national and international standards. National approvals are qualifying this system for the application in tunnels for the transport and storage of drinking and waste water. Prepared by Albert Lueghamer Page 5 of

6 A major benefit of thermoplastic lining is that all joints are welded whereby the welding provides similar properties and strength as the lining material itself. Various welding methods are suitable to fit the requirements for fast pre-fabrication, easy welding on site providing high joint reliability and quality. Fusion Result Application Area Material Recommendation Hot Gas Fusion pre-welding HDPE,PP 2-5 mm PVDF ECTFE Extrusion Welding 2,5-12 mm HDPE,PP PVDF Hot Wedge Welding up to 3 mm HDPE Butt Fusion up to 12 mm HDPE,PP PVDF,ECTFE Application and Installation of CPL in Pipes/Tunnels For the application of thermoplastic lining in tunnel systems various installation methods are applied depending on the construction method of the tunnel system and the diameter of the tunnel. In this report the main two methods are discussed. Installation of lined precast pipes Cast in situ installation of CPL in large tunnels Prepared by Albert Lueghamer Page 6 of

7 1.) Installation of lined precast pipes For tunnels up to 2,0m diameter the micro tunnelling method is mostly used. With this method precast (pre-stressed) pipes are installed. These pipes are manufactured in Precast Fabs whereby the lining is implemented during the casting process. This allows fast installation cycles on site. The lining material used for such applications is in most cases PEHD in light colours. The light colours such as white, yellow, light green or light blue enable ease visual control and the benefit that later on inspection by TV cameras is improved. Optionally also co-extruded liners are available which provide the advantage that damages during installation can be detected very easy. Repair of such damages is performed by extrusion welding after installation is finished. The PEHD CPL is prefabricated using butt fusion or extrusion welding method into the required hose suiting the inside diameter of the precast pipe. Liner thicknesses of 2,5 mm up to 6,0 mm are in most cases used in this application area. The high flexibility of the lining material offers the advantage that the prefabricated liner can easy be handled and installed on the casting machine. The casting machine and casting cycles remain unchanged by applying a lining material. The installed PEHD lining provides all the benefits of thermoplastic lining in conjunction with the mechanical strength of the concrete pipe. Prepared by Albert Lueghamer Page 7 of

8 These lined pipes are installed on site using the Micro - Tunnelling method. For the joint connections between the installed pipes special cover strips are used. According customer requirements 3 different joint types are available. Connection profile on both sides and cover strip Pipe A Pipe B Pipe AWith connection profile one side Pipe A Pipe B With cover strip only Pipe A Pipe B After installation of the pipe the joint sections between the pipes are welded using extrusion welding. For larger diameters welding robots are offering fast and controlled fusion. In the enclosed Annex A a reference report about executed projects in the field using above described installation method of lined piping system is given. Prepared by Albert Lueghamer Page 8 of

9 2.) Cast in situ installation of CPL in large Tunnels For tunnels with larger diameters (>2m) in most cases the tunnels are constructed with NATOM- Method or standard tunnel construction method. Such tunnels are constructed for applications for the transport and storage of water up to diameters of 10m. surrounding structure initial ground support concrete segmental lining seccondary lining agru CPL primary lining Tunnel with already installed concrete segments It is essential for such systems to line the inside surface to ensure: full water proofing high chemical resistance (mainly needed for waste water transport) high abrasion resistance physiological non toxic ground water pressure resistant (to avoid any penetration of ground water into the tunnel system) Depending on the application full lining and partial lining of the inside tunnel surface are practised system methods. The thermoplastic lining is applied in the tunnel system using specially designed hydraulic formwork systems. These hydraulic formwork systems in lengths up to 40m are designed to hold and tension the CPL during the casting sequence. Prepared by Albert Lueghamer Page 9 of

10 For casting modified concrete (easy flow able) is used. According casting distance and thickness of the cast structure the concrete mix is defined. Automatisized formwork systems and trained personal can reach installation capacity of CPL of up to 900 m²/day. Prefabrication of the CPL outside of the tunnel in a designated area close to the job site to the needed panel size according to the formwork layout ensures high quality of the installed CPL-lining and reduced amount of joints which must be done in the tunnel. As for such linings in many cases thin liners ( s = 2,5 up to 3,5 mm) are used for the prefabrication the hot wedge welding method is applied. This method enables very high production capacity of prefabricated CPL liners, which are produced according the formwork dimension. CPL rolls supplied to site Preparation of CPL for welding Hot wedge welding of CPL Joint section on inside surface provides also smooth surface Prepared by Albert Lueghamer Page 10 of

11 The hot wedge welding method produces an overlap joint using an automatizised fusion equipment Which enables easy and effective testing of the joint quality by a pressure test. Movement of the pre-fabricated liner and transportation to the formwork is done in a rolled shape which requires less space. Using umbrella movers the liner will then be lifted to the formwork and fixed on the formwork using mechanical gripping units on the formwork. After fixation of the liner the distance between the existing tunnel surface and the CPL is casted. Normally after hours later the formwork will be removed from the casting section in the tunnel and moved into the next section. The installed lining will be joined together using extrusion welding. Through large enough dimensioned access shafts the prefabricated panels, concrete and formwork systems are transported into the tunnel system. Umbrella lifter to install the prefabricated CPL liner on the formwork system the CPL panel is dimensioned exactly according the circumference of the lining surface and the length of the formwork. Prepared by Albert Lueghamer Page 11 of

12 The lining can be applied for tunnels in various shapes and configurations whereby the procedure of installation is similar to use hydraulic formwork systems. These formworks are specially designed and set up to hold the CPL panel during the casting sequence. Tension of CPL during casting and Optimised removal of the formwork from the cast section are essential criteria for good implementation of the CPL lining into the tunnel. Connection points like incoming link pipes, manholes and shafts are feasible to do with this lining system. The final installed system provides a full integrated and leak tight lining with high life time properties reduced maintenance costs and therefore increased system performance provide the customer a perfect solution. Picture of PEHD CPL lined tunnels in large diameters. Light colours are used to ensure easier visual inspection by TV cameras. Prepared by Albert Lueghamer Page 12 of

13 Also for open trench installation using the cast in situ method the application of CPL liners on inside the tunnel surfaces is practicable. In Annex B various references for underground and above ground installed tunnel systems with CPL lining applied on the inside surface are shown. The protection of concrete structures used for the transport of water and wastewater with thermoplastic lining materials such as PEHD based on Concrete Protective Liners have shown and proven fast and easy installation. Lined surfaces with thermoplastic materials ensure significant improved system performance and reduced maintenance requirements. - End of Report - Annex A Annex B Reference report of installed lined precast pipes underground (Elbedücker Project in Germany) Reference report of cast in situ installations of CPL in large diameter tunnel systems underground and in open trench installations ( DTSS Project in Singapore and lining of waste water tunnel in Stuttgart / Germany). For more information please contact AGRU Kunststofftechnik in Austria Technical Department e- Mail: anwt@agru.at, Tel (0) or visit our web site Prepared by Albert Lueghamer Page 13 of