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Leaking of Dam – Geomembrane Water barriers
India Water Week 2016 New Delhi April 4 – 8, 2016
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Leaking of Dam – Geomembrane Water barriers The presentation will cover :Leaking Dams Causes & Effects Remedial Measures & Their Effects/Failures Application of geomembrane waterproofing system Case Study Performance over time
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DAMS ARE SUBJECT TO LEAKAGE In general, the following potential seepage pathways can be identified in Dams: Distributed seepage through the upstream face and dam body Concentrated seepage at joint locations Foundation seepage Abutment seepage Embankment seepage
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Distributed seepage through the upstream face and dam body:
This seepage consists of widespread, general seepage entering through relatively uniformly distributed point sources in the masonry facing system. The flow nets indicate that the majority of this seepage should be intercepted by the vertical drains or construction joints and conveyed to the gallery. However, the planimetric flow net indicates that a portion of the seepage originating through the masonry facing should flow past the drains and be discharged on the downstream face of the dam. Assuming uniform permeability of the dam body, approximately 70 to 80 percent of the seepage is expected to be collected by the drains or construction joints. The remaining 30 to 20 percent of the seepage is predicted to exit on the downstream face of the dam
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Water seepage reaching the downstream face can cause alarm in public opinion
‌‌ causing concern to the owner
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Concentrated seepage at joint locations (or cracks):
Significant seepage is known to be occurring as concentrated seepage at joints between monoliths. This seepage is non-uniform in nature, and, based on design and construction details for the original dam, the most likely cause of this seepage is flow that bypasses the copper water stops. Localized masonry deterioration in the joints could provide extremely short, direct flow paths from the reservoir to the construction joint drains that would produce high rates of seepage from relatively small flow channels.
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Upper Stillwater, USA
Furthermore, much water is wasted
Inspection gallery, Upper Stillwater, USA
Salto Caxias, Brazil
Inspection gallery, Kadamparai dam, India
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Foundation seepage: This seepage consists of seepage through the grouted rock foundation. Assuming that the grout curtain was tied into relatively impermeable rock at depth, nearly all of the seepage along this pathway should be collected by the drilled foundation drains located along the downstream side of the gallery. Significant seepage can occur at the downtream toe
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Abutment seepage: This ocurr in composite structures with a central gravity dam and abutments consisting of fill dams. The seepage pathway consists of seepage flowing through the embankment section and into or around the gravity section. This seepage path is very long and the anticipated quantity is extremely small in comparison to the other identified pathways.
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Embankment Seepage: It applies to composite dams, made of gravity section and embankment section This seepage is not associated with seepage issues for the masonry gravity dam.
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Conventional repair methods to provide watertightness and their failures
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NEW CONCRETE LAYER
The existing concrete face heavily deteriorated
Salt Springs CFRD dam – USA – 100 m
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SHOTCRETE
Camposecco, Italy 1993. Reinforced shotcrete layer installed to waterproof original deteriorated masonry
Reinforced shotcrete layer deteriorated and collapsed after a few years. Steel reinforcement corroded
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SHOTCRETE
Shotcrete failed due to freezing and thawing cycles
RESIN COATING
Failure due to UV exposure, backpressure, debonding, abrasion
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Application of Geomembrane waterproofing system
GEOMEMBRANES ARE THIN FLEXIBLE MATERIALS WITH VERY LOW PERMEABILITY
GEOMEMBRANES ARE MANUFACTURED IN A FACTORY. THEY HAVE BEEN USED IN DAMS SINCE 1959, NOW 56 YEARS
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Geomembrane + Geotextile = GEOCOMPOSITE Geomembrane
TERMINOLOGY
When a geomembrane is associated with a geotextile, laminated during the production process, it is called GECOMPOSITE Geotextile provides: dimensional stability, antipuncturing protection, drainage capability
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Development of PVC Geomembrane Water Proofing System
Established in Italy in 1963, CARPI is the oldest company and the leader in the world dealing with design, supply and installation of waterproofing geomembranes / geocomposites for dams, canals, hydro tunnels, reservoirs and hydraulic structures in general
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Geomembrane can tackle the following sources of uncertainities in dam construction
Geological conditions Unpredicted differential movements Seismic events Thermal behaviour, behaviour of lift joints Swelling processes in concrete Construction time Construction costs Possibility and costs of repair
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Miel 1, Colombia, 188 m, the highest RCC dam in the world, is waterproofed with an exposed PVC geomembrane which was part of the initial design. Total rate of leakage through the u/s face is only 2 l/s
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Exposed PVC geomembrane
Concepcion, Honduras, 70 m, 1990
Total rate of leakage through u/s face is < 1 l/s
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No repair of the unforeseen crack was required as the geomembrane covered it
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Geomembranes can resist large differential movements and rotations between monolith blocks in RCC dams Exposed geomembrane
Olivenhain RCC dam, USA, 100 m, 2003
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Uncertainty: seismic events Stresses can exceed the resistance of the element that provides watertightness to the dam (concrete facing, GEVC, clay core)
Geomembranes (PVC) resist seismic events because they have high (> 230%) elongation at break
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Olivenhain RCC dam, USA, 100 m, 2003
BENEFIT OF THE GEOMEMBRANE: on 16 June 2004, with reservoir at full supply level, a 5.5 Richter scale earthquake occurred at 100 Km from the dam. The blocks of the dam shaked and moved, but no damage has been reported and watertightness of the dam has been totally maintained, fully meeting the design and safety requirements
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Uncertainty: uplift
Geomembranes in RCC dams allow controlling uplift
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Uncertainty: swelling processes (AAR
Geomembranes stop water infiltration and decrease water content in dam body
Pracana dam, Portugal, affected by AAR. Geocomposite installed on active fissures, 1992
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Uncertainty: possibility and costs for repair
Geomembranes, especially those exposed, can be repaired easily, quickly, at low cost, and even underwater
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Underwater repair: entire upstream face Lost Creek, USA 1997 The dam cannot be totally dewatered as part of a cascade
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The CARPI concepts entail the installation of the drained waterproofing geocomposite from the crest down to the foundation.
Dam body
The geocomposite is then connected to the grouting curtain which is placed right upstream of the dam
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CASE STUDY Kadamparai dam (2005) First dam geomembrane project in India
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CARPI GEOCOMPOSITES HAVE BEEN USED FOR REHABILITATION OF STONE MASONRY DAMS: EXPOSED CARPI PVC GEOMEMBRANE
Pumped storage Before FIRST repair
Kadamparai dam, India, 2005 After repair
DAM GEOMEMBRANE PROJECT 38,000 lpm IN INDIA 80 lpm
Waterproofing works executed in 3 months (>17.000 m2)
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Kadamparai stone masonry dam, 67 m high, 478 m crest length (masonry section), was completed in 1984.
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At first impoudment it was observed a maximum seepage of 1,120 lpm
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The seepage through the drainage gallery gradually increased well above the allowable limit
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During 1990 to 1994, various ways and means have been tried to minimize leakage by doing from the crest vertical drilling and grouting at close intervals. These methods were unsuccessful and the seepage kept increasing (up to 38,000 lpm)
Leakage collection at downstream
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During 1999 racking and packing at selected locations was carried out on the upstream face of the dam, including chemical treatment in underwater conditions
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In fact the chemical treatment proved to be totally uncessfull because it became unbounded with the masonry and peeled off. Chemical grout came out through the drainage gallery by leaving more cavities inside the masonry body of the dam.
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Cementitious materials and fines were eroded and collected in the drainage gallery
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Next attempt was racking joints which have to be filled up with cement mortar and pointing had to be carried out. Even then the leakage rate was going up. During the process of racking and pointing it was found out that the mortar was without any cement content at some locations.
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The seepage through the drainage gallery gradually increased well above the allowable limit.
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In June 2003, Carpi Tech SA, a waterproofing specialist contractor from Switzerland, was invited to study the conditions of Kadamparai dam and to suggest remedial measures for watertightness
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Leakage in the drainage gallery, right abutment
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CARPI took over the site by end of November 2004 and started preparatory works which ended by December 2004 and materials were delivered at site in early January 2005
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Shotcrete with reinforcement was placed only along the ground line, to smooth the surface and allow installation of the geomembrane perimeter seal
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The base of each of the 12 vertical joints in the masonry has been drilled and then grouted to avoid water by-passing the perimeter seal of the geomembrane system
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Installation of the geomembrane system started in middle of January 2005 . Installation was performed from special travelling platforms suspended from the crest and which were imported from Italy
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Installation of vertical lower profiles started in mid-January 2005
The stainless steel profiles which fasten the geocomposite to the face of the dam, are adjusted to follow the shape of the upstream face and fastened by chemical anchors placed in the stone masonry
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The OFC (Optical Fiber Cable) for leak detection, has been placed along the perimeter seal, behind the geocomposite
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The ends of the OFC have been taken to the crest, in dedicated boxes, for future connection to the reading instrumentation
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A high transmissivity non-compressible geonet was placed along the perimeter seal to collect the drained water and convey it to the discharge point in the gallery
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A geotextile was installed on the upstream face, to protect the geomembrane against puncturing.
Geotextile, 2000 g/m2
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The anchoring profile at crest consists of a batten strip, placed over the surface smooothened with mortar. Ventilation pipes avoid formation of vacuum behind the geocomposite.
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The PVC geocomposite was laid over the antipuncturing geotextile Geocomposite 2.5 mm PVC + 500 g/m2 geotextile
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The rolls of geocomposite have been overlapped and welded together
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After welding all geocomposite panels together, the external tensioning profiles are placed over the geocomposite and connected to the lower profiles
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The tensioning profiles stretch the geocomposite and anchor it by vertical lines, imposing minimum stress to the material.
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The external tensioning profiles are covered by a PVC geomembrane strip which is heat welded to the parent geomembrane below
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The perimeter watertight seal is created, by placing chemical anchors, bedding mortar, geocomposite, gasket, stainless strip batten strip. Then the specified torque is applied to the bolts of the anchors
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Number 4 holes, 80 mm diam, have been drilled from upstream to the inspection gallery, to allow discharge of the water drained behind the geomembrane system
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Pipes discharge into the inspection gallery where it is also possible to read the piezometers
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Monitoring of the geomembrane system is enhanced by readings at piezometers, and by the optical fibre cable system that will allow locating the area of any unattended water from a possible leak Piezometer and data logging box installed in the gallery Optical fibre cable and data logging box installed at the crest
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The geomembrane system completely installed
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The works have been completed on April 8, 2005, 10 weeks after installation of the first profiles started. Impounding began on April 12, 2005
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The whole system installation covering more than 17,000 m2 including the monitoring system has been completed in 3 months, 6 weeks ahead of schedule
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Kadamparai dam fully impounded (July 2005)
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After 10 years of limited operation (well below the full level), with an experienced leakage of up to 38,000 lpm, now Kadamparai dam is again at full supply level. The rate of leakage is 80 lpm.
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INDIA POWER AWARD KADAMPARAI DAM
2008
FOR
Mr.Alberto M. Scuero, Director, CARPI TECH receiving INDIA POWER AWARD for the year 2008 from Dr.M.S.Swaminathan, Member of Parliament - Rajya Sabha, Agricultural Scientist.
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nearly 11 years of service, without any maintenance cost the system ensures water proof with leakage rate around 100 liters/minute.
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THANK YOU
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FIRST GEOMEMBRANE INSTALLATION IN A HYDROPOWER CANAL IN INDIA
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TANAKPUR HYDROPOWER CANAL NHPC NAINATAL DISTRICT,UTTARANCHAL STATE
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TANAKPUR CANAL, India 2008
LONGITUDINAL ANCHORAGE
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TANAKPUR CANAL, India 2008
February 7 2008 February 8 2008
February 15 2008
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TANAKPUR CANAL, India 2008
The first component of the tensioning profiles assembly was installed over the concrete before placement of the PVC geocomposite
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TANAKPUR CANAL, India 2008
The second component of the tensioning profiles assembly, installed over the PVC geocomposite, is waterproofed with a PVC cover strip
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TANAKPUR CANAL, India 2008
Watertight perimeter seal at beginning and end of lined section
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TANAKPUR CANAL, India 2008
February 29 2008
24,200 m2 of geomembrane installed in about 8 weeks
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TANAKPUR CANAL, India 2008 March 5 2008
High water velocity and turbulence at first filling
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TANAKPUR CANAL, India 2008
NO PROBLEM EVEN WITH GREAT TURBULENCE
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TANAKPUR CANAL, India 2008
Results in almost seven years of performance are on line with expectations.
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INDIA POWER AWARD 2009 FOR TANAKPUR POWER CHANNEL
Mr.V.Subramanian, Director, Carpi India waterproofing Specialists pvt ltd., receiving India Power Award for the year 2009 from Mr.Bharat Singh Solanki, Hon’ble Minister of State for Power, Government of India.
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THANK YOU