*Corresponding author. Tel.: #49-5741-4008-28; fax: #49-5741-4008-84.E-mail addresses: kvmaubeuge@naue.com (K.P. von Maubeuge), mhb@bow.de (M. Heibaum)

Geotextiles and Geomembranes 18 (2000) 263}271

echnical Note

Installation and monitoring of a geosyntheticclay liner as a canal liner in

a major waterway

Kent P. von Maubeuge!,*, Juergen Witte!, Michael Heibaum"!Naue Fasertechnik GmbH & Co. KG, Wartturmstrasse 1, Luebbecke, Germany

"Bundesanstalt fuer Wasserbau, Kussmaulstrasse 17, Karlsruhe, Germany

Received 25 November 1998; received in revised form 15 July 1999; accepted 17 August 1999

Abstract

Sealing materials are of major importance in hydraulic engineering applications. They ensurethe stability of hydraulic structures and prevent or reduce seepage losses out of the waterway. Inwaterways, mainly natural clay liners and in some cases also asphalt and concrete liners havebeen used. In the new turnout Eberswalde, Germany, a needlepunched geosynthetic clay liner(GCL) was installed in a navigated waterway as a canal liner by order of the Federal Water andShipping Administration (Fleischer and Schreier, 1998). GCLs are thin composite materialscombining bentonite clay (usually natural sodium bentonite) and geosynthetics (usually geotex-tiles) and are generally used to replace or augment compacted liners. To avoid the closure of thewaterway for ship tra$c, an installation method was chosen which allowed continuous shiptra$c. The GCLs were installed in two segments, both halfway under water, and a sand ballastmat provided the necessary con"ning stress prior to the rock ballast covering, and acted mainlyas a protection layer for installation stress due to the placement of the rock rip rap. Continuousmonitoring was carried out to prove the e$ciency of the sealing system. ( 2000 ElsevierScience Ltd. All rights reserved.

Keywords: Canal liner; Geosynthetic clay liner; Underwater installation

0266-1144/00/$ - see front matter ( 2000 Elsevier Science Ltd. All rights reserved.PII: S 0 2 6 6 - 1 1 4 4 ( 9 9 ) 0 0 0 3 1 - X

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Fig. 1. Schematic cross-section of the extension pro"le.

1. Introduction

The turnout Eberswalde is located in the area of the reach of the River Havel RiverOder-Waterway (HOW) from 65.9 km to 66.9 km near the town Eberswalde, Ger-many. In order to avoid further damages on the side slopes and the canal lining, thecanal could only be navigated either on one side or the other. Through the additionalnew turnout the former waiting periods have been reduced and thus the shippingtra$c can be improved in the current narrow pass of the HOW between Marienwer-der and Nieder"now.

In the area of the reach the waterway had a hollow pro"le which had an existingwater depth of 3 m in the section of the new turnout and a water level width of 35 m.Before the extension the canal had been sealed with a 30 cm thick compacted clayliner (CCL). The canal water level normally lies at NN#37.25 m.

The extension of the turnout was carried out as rectangle-trapezoid-pro"le ona length of 1 km. On the southern side, the slope was formed as embankment with aninclination of H:V 3:1 (18,43), on the northern side an anchored sealed sheetpile wallwas installed for the ships to land. Fig. 1 shows a schematic cross-section of theextension pro"le with a water level width of 48 m and a water depth of 4 m. As newcanal lining, the needlepunched GCL BF-2 was installed which was covered witha special needlepunched geotextile sandmat (Table 1). The needle-punched sandmatperformed as a con"ning layer on top of the GCL and allowed a uniform swelling andacted mainly as a load distribution layer for the rock rip}rap of 15}45 cm average size.Because of the dynamics caused by the current and the landing and manwuvring ofthe ships, a grouting of the rip}rap was carried out on a 6 m wide strip directly besidethe sheetpile wall. To ensure a tight connection of the canal lining with the sheetpilewall, an additional `sealing wedgea was installed.

The soil subgrade mainly consists of sand and boulder clay. The surface of theboulder clay changes very strongly even along small distances. Partly the boulder clayreaches to the height of the extended canal bed, and partly it is lower than 12 m under

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Table 1Generic description of used GCL BF-2 and sandmat SM-1!

Genericsymbol Product name

Nominalmass/area[g/m2]

Bentonitemass/area[g/m2]

Uppergeosynthetic

Lowergeosynthetic

Method ofconstruction

BF-2 Bento"xBFG 5000

5,500 5,000 NW,bentoniteimpregnated

W NP

SM-1 Terra"x B 609 8,900 8,000 sand NW NW NP

!SM"sandmat; NW"Nonwoven needlepunched; W"Woven; NP"Needlepunched.

the canal bed. The density of the sand rises with an increasing depth, however, in theupper 3 to 6 m only a low density can be assumed.

In this area the groundwater #ows with a relatively high gradient from north tosouth, i.e., approx. perpendicularly to the waterway. According to the results of thegroundwater measurements taken prior to the extension, the groundwater level isNN#34 m on an average, i.e. a little more than 3 m under the normal level of theHOW. For this reason, a canal lining is necessary to prevent leakage from thewaterway. There is no dam since the adjacent ground lies over the canal water level.

2. Lining of the canal

Originally the Waterway and Shipping O$ce Eberswalde in Eastern Germanyplanned for the construction of the turnout Eberswalde a compacted clay liner witha thickness of 20 cm, covered with a geotextile and rock rip}rap with a maximumdiameter of 15}45 cm.

If there is the intention to use a new sealing system for navigable waterways, it hasto be compared with the state-of-the-art systems, namely the clay liner made ofconditioned natural clay. The clay has to be within the following limits: clay fraction*30%, sand fraction )10%, undrained shear strength 15 kPa)c

6)25 kPa. And

the following general demands have to be ful"lled:

f A su$ciently low permeability. Because of the di!erent thicknesses of the variousliner systems, one has to compare the permittivity or the discharge of water. Forclay liners, the permeability has to be below 1]10~9 m/s. With the minimumthickness of 20 cm and a water head of 5 m the discharge through a clay linertherefore is below 2.5]10~8 m3/s/m2. Thus considering a GCL with a thickness of1 cm, one has to ask for a permeability of 5]10~11 m/s.

f There has to be a su$cient resistance against impact forces. When rip}rap isdropped upon the GCL, the sealing must not be perforated.

f A #exibility that guarantees that no leakage or weakening will develop due todeformations of the subsoil. Deformations of the subsoil are inevitable since duringthe construction process the subsoil will be saturated "rst.

K.P. von Maubeuge et al. / Geotextiles and Geomembranes 18 (2000) 263}271 265

Fig. 2. Schematic cross-section of the underwater installed geosynthetic system needlepunched GCL BF-2sealing element with needlepunched sandmat SM-1 protection layer.

f High resistance against bentonite erosion is necessary to maintain the impervious-ness.

The selected and approved sealing system was a needlepunched GCL BF-2, unrolledon the subgrade and directly covered with a needlepunched sandmat, and coveredwith rock rip}rap. For the "rst time, such an underwater installation over the entirewaterway was carried out in Germany. Previous tests had proven the e$ciency of theGCL/sandmat sandwich system:

f permeability tests under site conditions,f deformation tests followed by permeability tests,f erosion stability tests simulating 10 year wave action,f damage during installation tests,f shear tests,f permeability tests on the overlaps, andf peel tests on fully hydrated GCLs covered only with the sandmat.

From July}December 1997, the GCL BF-2 was installed as the single sealingelement, and the geosynthetic sandmat as a temporary ballast mat and the protectionlayer (Fig. 2). A special underwater installation device was used (Fig. 3). The need-lepunched GCL and the needlepunched sandmat were rolled up on a steel core (Fig. 4)with a displacement of 50 cm. This enabled a su$cient overlap of the GCLs and aninstallation of the sandmat and the sealing element in one operation. The selectedneedlepunched GCL BF-2 had a bentonite impregnated cover nonwoven and a car-rier woven. This special GCL did not need any on-site overlap treatment with

266 K.P. von Maubeuge et al. / Geotextiles and Geomembranes 18 (2000) 263}271

Fig. 3. Underwater installation device for the composite product GCL BF-2 and sandmat SM-1.

bentonite. The carrier woven once in contact with the bentonite impregnatednonwoven acted immediately as a seal. Hence a continuous bentonite layer in theoverlap area was ensured. A homogeneous swelling of the GCL was ensured by theuniform load of quartz sand "lling (8 kg/m2) of the needlepunched sandmat SM-1.Moreover, the sandmat performed as a protection layer against the load duringinstallation of the rock rip}rap. Shear and peel strength tests proved that the integrityof the needlepunched GCL, even after swelling over several weeks with the sandmatas only surcharge, was maintained so that the entire construction of the shipturnout and at the same time the installation of the GCL lining could be carried outunder a closure of only one side of the canal and ship tra$c on the other side. Theperfected installation technique with a 30 m long trolley arm (Fig. 3) with its verticallattice mast and hydraulically driven spreader bar made an exact installation up toa water depth of 5 m possible. Divers continuously controlled the correct position ofthis GCL/sandmat sandwich method. On the northern shore of the canal, the GCLand the sandmat were installed perpendicularly from the new sheetpile wall up to 1 mover the canal axis. The southern shore consisted of an embankment with aninclination of H:V 3:1 (Fig. 5) in which the GCL and the sandmat ended in ananchoring trench.

Time restrictions asked for a short installation period and it was clear that theoriginal clay liner could only be installed within the required time frame if hardly any

K.P. von Maubeuge et al. / Geotextiles and Geomembranes 18 (2000) 263}271 267

Fig. 4. Lowering of the GCL BF-2 and sandmat SM-1 into the water for underwater installation from thesheetpile wall side.

Fig. 5. Installation of the GCL BF-2 and sandmat SM-1 from the sloped side of the HOW canal.

268 K.P. von Maubeuge et al. / Geotextiles and Geomembranes 18 (2000) 263}271

problems occurred during the construction phase. Additionally the proposed installa-tion method o!ered cost savings and had technical advantages:

f Less soil excavation } a 20 cm thick clay liner requires more subsoil excavationwhich must be treated and deposited.

f The proposed needlepunched GCL BF-2 has a hydraulic permeability of2]10~11 m/s which is at least 50 times lower than the original compacted clay,whereas the thickness of the clay is only 20 times larger (Von Maubeuge and Eberle,1997). The permittivities are therefore approx. 2.5 times less with the selected GCL.

f The needlepunched GCL BF-2 can survive a two-dimensional elongation of ap-prox. 20% without an increase of the permeability. Compacted clay liners show anincrease of permeability already at smaller strains.

f The use of natural sodium bentonite with a very high swelling capacity allowsa self-sealing performance.

f The single installation operation of the GCL and the sandmat is an operationaladvantage. The covering with the rock rip}rap could follow soon after, and theconstruction period was extremely reduced, and the waterway could be opened forfull ship tra$c sooner than expected.

The joint of the GCL and the sheetpile wall required more attention. This connec-tion needed careful execution in order to prevent seepage along the sheetpile wall. Forthis reason, it was planned to protect the direct area of the sheetpile wall with anadditional clay wedge of a length of 1.5 m and a thickness of at least 50 cm which wasinstalled beneath the GCL. In order to ful"l the requirements of the `AdditionalTechnical Contract Conditions for Hydraulic Engineeringa for slope and bottomprotection, the natural clay being available for the installation would have had to beimproved with a great deal of time and machinery. Therefore, it was decided to usea new developed sealing clay. It was a sealing matrix based on sand, clay, polymersand water, being prepared in high-reving mixers. The lowest hydraulic conductivitycoe$cient indicated in the tests was at least 1]10~9 m/s at installation. Besidesa su$cient hydraulic conductivity, appropriate mixing relations should guaranteea su$cient permanent plasticity in the installed status. Therefore, the site wasconstantly monitored and random samples were taken.

3. Monitoring of the sealing

Since geosynthetic clay liners are new in hydraulic waterway applications, moreinterest was given to post seepage measurements.

During the construction, special emphasis was placed on careful execution andmonitoring of the construction to avoid faults during installation at the lining itself, atthe protection layers (sandmat and rock rip}rap) and in the area of the connection ofthe lining. The quality of the installed sealing clay was controlled by means of takingregular samples and testing them in the laboratory of the Waterway Engineering

K.P. von Maubeuge et al. / Geotextiles and Geomembranes 18 (2000) 263}271 269

Institute. Even for single samples of the GCL, several tests in addition to the usualquality controls were conducted on the hydraulic conductivity and the shear perfor-mance. Additionally, measurements were planned to check the hydraulic conductivityof the liner after the construction works had been "nished.

The measurement of the soil temperature is one successful method to provethat seepage has not permeated through the liner. The temperatures of waters nearthe surface are subject to a typical development of temperatures depending onthe season. With an increasing depth, the low heat conductivity of the soilcauses a growing displacement of the phases compared to the development of thewater temperature. Moreover, the range of variation of temperature decreaseswith increasing depth. Thus there is a di!erence in temperature of soil and water.Surface water leaking into deeper soil areas causes a heat transport and thus achange of temperature in the area in which #ow occurs. The soil temperature adaptsto the temperature of the leakage water. Anomalies of temperatures being encoun-tered in the soil can therefore indicate leakage water from the canal due to existingleaks in the sealing. Two systems were chosen to carry out the temperaturemeasurements: Temperature gauges in di!erent depths in a vertical steel pipe (Dorn-staK dter, 1997) and continuous measurement by horizontal glass "bre cables (Au#egeret al., 1998).

Fleischer et al. (1998) reported that "rst measurements in February 1998 had beensuccessful and had shown leakage rates at the connection of the old clay liner and thenew installed system. The sealing clay connection to the sheetpile wall which wasadditionally equipped showed no anomalies so that the sealing was considered asintact, but additional tests are planned because this connection is considered as themost likely one to show leakage.

Several other places are equipped with this temperature measurement system sothat long-term measurements can prove the e$ciency of the new system.

4. Summary

In the "rst known application of an underwater installation of a GCL in directcombination with a geosynthetic sandmat, the installation operation proved to besuccessful. Continuous quality control on the material as well as on-site-monitoring ofthe installation proved the technical e$ciency and showed that underwater installa-tion of needlepunched GCLs is possible. The monitoring of seepage rates by means ofsoil and water temperature measurements was successful and will be continued.Compared to other possible placement methods, overall risks with the describedinstallation method were at a minimum (Heibaum, 1999). It occurred during thesemeasurements that the connection areas to old sealing structures were the problemzones, a reason why an additional wedge sealing was chosen at the cuto!-walls.Overall the GCL/sandmat sandwich system outperformed the traditional CCL solu-tion technically and economically, but more, the system could be installed within therequired time frame.

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References

Au#eger, M., DornstaK dter, J., Fabritius, A., Strobl, Th., 1998. Fibre optic temperature measurements forleakage detection } applications in the reconstruction of dams. ICOLD 66th Annual Meeting: Rehabili-tation of Dams, New Delhi, India.

DornstaK dter, J., 1997. Detection of internal erosion in embankment dams. Comptes Rendues du 19emeCongre`s des Grands Barrages, Florence, pp. 87}101.

Fleischer, P., Schreier, S., 1998. Einsatz von geosynthetischen Tondichtungsbahnen als Kanaldichtung.Binnenschi!ahrt Nr. 19, October 1998, pp. 40}45.

Heibaum, M., 1999. Application of geosynthetic clay liners in German waterways. Rencontres geH osyn-thetiques '99, Bordeaux, France, October, in press.

Von Maubeuge, K.P., Eberle, M.A., 1997. The use of geosynthetic clay liners for sealing applications in thewaste industry. In: Proc. of the 1st Australian}New Zealand Conference on Environmental Geotechnics} Geoenvironment '97. Melbourne, Australia, pp. 283}297.

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