De Vries, G.

Hopman, V.

Koelewijn, André

English

Hydraulic Engineering Repository

Conference Paper, Published VersionDe Vries, G.; Koelewijn, André; Hopman, V.IJkdijk Full Scale Underseepage Erosion (Piping) Test:Evaluation ofInnovative Sensor TechnologyVerfügbar unter/Available at: https://hdl.handle.net/20.500.11970/100277Vorgeschlagene Zitierweise/Suggested citation:De Vries, G.; Koelewijn, André; Hopman, V. (2010): IJkdijk Full Scale Underseepage Erosion(Piping) Test: Evaluation ofInnovative Sensor Technology. In: Burns, Susan E.; Bhatia,Shobha K.; Avila, Catherine M. C.; Hunt, Beatrice E. (Hg.): Proceedings 5th InternationalConference on Scour and Erosion (ICSE-5), November 7-10, 2010, San Francisco, USA.Reston, Va.: American Society of Civil Engineers. S. 649-657.Standardnutzungsbedingungen/Terms of Use:Die Dokumente in HENRY stehen unter der Creative Commons Lizenz CC BY 4.0, sofern keine abweichendenNutzungsbedingungen getroffen wurden. Damit ist sowohl die kommerzielle Nutzung als auch das Teilen, dieWeiterbearbeitung und Speicherung erlaubt. Das Verwenden und das Bearbeiten stehen unter der Bedingung derNamensnennung. Im Einzelfall kann eine restriktivere Lizenz gelten; dann gelten abweichend von den obigenNutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte.Documents in HENRY are made available under the Creative Commons License CC BY 4.0, if no other license isapplicable. Under CC BY 4.0 commercial use and sharing, remixing, transforming, and building upon the materialof the work is permitted. In some cases a different, more restrictive license may apply; if applicable the terms ofthe restrictive license will be binding.IJkdijk Full Scale Underseepage Erosion (Piping) Test: Evaluation ofInnovative Sensor Technology G. de Vries i, A.R. Koelewijn i and V. Hopman i iDeltares, P.O. Box 177, 2600 MH, Delft, Netherlands; PH +31(0)88-3357398; email: goaitske.devries@deltares.nl ABSTRACT The IJkdijk (Dutch for 'calibration levee ' ) is an unique Dutch facility where full scale levees are built and brought to failure with two explicit goals: to increase the knowledge on levee behaviour and to develop and test new sensor technologies for flood early warning systems under field conditions. In 2009 four experiments have been carried out, aiming at failure caused by underseepage erosion (Piping). Several innovative sensor technologies have been tested during these experiments. In this article the use of fibre optics is evaluated. To ensure a proper calibration of these experimental measurements, an extensive reference monitoring program has been carried out employing proven technology. The process of seepage erosion resulted in a huge amount of advanced sensor information. The results and predictive values of the measurements are analysed, compared and evaluated. INTRODUCTION The IJkdijk (pronounced as 'Ikedike ' and Dutch for 'calibration levee') is an initiative where knowledge on levees and sensor technology comes together. As part of the IJkdijk program, in Booneschans, the Netherlands, levees are built at full scale and brought to failure with two explicit goals : to increase the knowledge on levee behaviour and to develop and test new sensor technologies for flood early warning systems under field conditions. This should increase both the quality of the levee inspection process and the safety assessment of levees. The [mal goal is to develop a flood response toolbox aimed at ensuring the timely execution of appropriate measures. The IJkdijk project functions as an open innovation platform for testing sensor techniques and to improve dike technology, providing benchmarking to all contributors . By conducting experiments in a controlled environment and under pre-determined conditions, knowledge about the failure mechanisms of levees can be improved and the value of new technologies can be demonstrated. At present, more than forty companies and institutions from five different countries cooperate in this initiative. The full-scale piping tests were performed at the location of the IJkdijk in the Northeast of the Netherlands. Two large basins were created (size 30xl5m in area), each filled with a different type of sand, having a d50 of 150 !ill1 and 210 !lm respectively. Throughout this paper, these sands are denoted as 'fine sand' and 'coarse sand'. A clay levee with a height of3.5m and slopes of IV:2H was built on top of the sand by densification of smaller clay lumps. After construction a levee with a 15 m seepage length was obtained. Figure I shows a cross-section and longitudinal section of the full-scale tests . At the downstream side, a weir has been created to keep the downstream water level at a constant level (approx 0.15m above the sand layer). At the upstream side, the water level could be raised to a level of 3 m. A total of four tests has been carried out: 649 650 SCOUR AND EROSION 1. Fine sand, with reference monitoring and little disturbing innovative monitoring techniques (monitoring placed with a distance to the interface sand-clay); 2. Coarse sand, with reference monitoring techniques only; 3. Fine sand, with reference monitoring techniques only; 4. Coarse sand, with reference monitoring and little and medium disturbing innovative monitoring techniques (monitoring placed with and without a distance to the interface sand-clay). In this paper results from the first experiment are presented. c++ ·I·+-I·i· c·i·+ ·I·+-I·H-1 ·c·I·+·I·I·· ,-H·I·+·I+I-I·+ ·I·+·I·I··,-I·+·H·-I·I··,-H·H--I·i-·t·i··I-I-·I--I-l--1 c·I·+-I-+-I·+ ·'·I·+-I·+·I-' ·, ·I·+·t·t-t-j·-I· I-+- I-+·I ·i··c-I·+·I·+·I·i··'·I--'·1-+'!-i'-"I'+'!"I'-I-i-'c'i"c'I'+-I'i-'c'I'+-I'i Figure 1. Cross-section and longitudinal section of the full -scale tests. The innovative sensor technologies which have been tested during these experiments comprised measurements of deformations, vibrations and temperature by glass and plastic fibre optics, dynamic imaging by acoustics, waterleakage from self potential , deformation and well location with infrared cameras, and pore pressure, tilt and temperature from transducers integrated with MEMS technology. In this article the glass fibre optics measurements are evaluated against visual observations and pore pressure measurements from 'traditional' vibrating wire piezometers, laid in a dense grid at the interface of the levee and the sand layer. GTC Kappelmeyer has tested the leakage detection capability of fibre optic cables in conjunction with the Heat-Up (or Heat-Pulse) method (Dornstadter, 2010). TenCate Geosynthetics, Inventec, EDF and geophyConsult have been involved in the IJkdijk Piping project to provide a monitoring solution based on optical cable and on the GeoDetect® monitoring solution (Artieres, 20 I 0). PIPING The process, presented in Figure 2, is considered one of the most dominant failure mechanisms of levees in the Netherlands (Havinga and Kok, 2005). The process, visualized in Figure 2, starts with heave and cracking of the soft soil top layer at the land side of the levee, caused by high water pressures which are easily transferred through the permeable sand layer. The cracks in the top soft soil layer allow for seepage. In case the water level difference between river and land side (the hydraulic head) is large enough, sand grains may be transported along with the water flow , thereby creating a pipe underneath the levee. Continued erosion may finally lead to instability and failure of the levee. SCOUR AND EROSION 651 Several models and empirical relations are available to predict the occurrence of retrograde piping, of which the most well-known are the empirical rule of Bligh (1910) and the model of Sellrneijer (1988), of which the latter describes the process in most detail. However, in a recently performed safety assessment of Dutch levees using the model of Sellmeijer, a discrepancy emerged between calculation results and the opinion of levee managers. Scepticism existed on whether piping would actually result in failure of the levee and the validity of the model was questioned. A large research program was started to validate and possibly improve the model. This program and its results are more extensively described in Van Beek & Knoeff (2009) and Van Beek et al. (2010). a) Heave b) Seepage r;:=>' ~'----T'- .. ~ ----, ~ __ .,. __ ... _ ... __ .. __ ;X c) Pipe-formation d) Pipe-formation I ~ '-- -T--T - _ --' : I e) Progressive erosion f) Instability of the levee g) Breakthrough Figure 2. Process of retrograde erosion. INSTRUMENTATION Reference monitoring The piping formation, more specifically the growth of the pipe, can be monitored by the pore pressure meters. The pore pressure meters have been placed in 4 rows of 16 pressure meters each. These rows were placed at 0.2 m, 1.2 m, 3.8 m and 7.6 m from the downstream toe of the levee. A local decrease of water pressure is an indication for pipe formation . During the progressive erosion phase, an increase of water pressure is measured (because of the connection of the pipe with the upstream side). Figure 3 shows two contour plots of the hydraulic gradients as measured in the sand layer during pipe formation (phase d in Figure 2) and near the end of the progressive erosion phase (phase e in Figure 2). 652 SCOUR AND EROSION 1 Oct 2009, 6:25 pm (t=54.4 hours) 3 Oct 2009, 4:00 pm (t=1 00 hours) Figure 3. Contour plots of hydraulic gradients in sand layer. Figure 4 shows the levee half an hour after collapse, which took place on October 3rd , 2009 at 4:20 pm. Figure 4. The first IJkdijk piping test shortly after collapse. Heated fibre optic cables GTC Kappelmeyer has tested the leakage detection capability of fibre optic cables in conjunction with the Heat-Up (or Heat-Pulse) method (Domstadter, 2010) . The fibre optic cable was deployed both in sand and clay, parallel to the length axis of the levee. All cables were installed as single lines, except for one cable which runs in equidistant parallel loops in a mat, see Figure 5. SCOUR AND EROSION 653 Figure 5. left: cable deployed in clay; right: mat deployed in sand. For the Heat-Up method the fibre optic cable was heated up by sending an electrical current through the metallic cable coating (stranded steel wires). The fibre optic temperature measurements were conducted with an OTS 40P laser unit. All the instruments and the steering unit for the heating was place in a box on the crest of the dam. A mobile generator supplied the power for the heating. Six cables were placed in the test. Three were placed at a depth of 10 cm in the sand layer, one at 1.5 m, one at 7.5 m and one at 13.5 m from the downstream toe of the levee. The other three were placed about 10 cm above the sand-clay interface, in the clay, one at 5m, one at 8.5m and one at 10m from the downstream toe. Failure of the levee occurred at 3 October 2009, at 4:20 pm. The cables placed in the sand layer give more detailed information about the failure than the cables placed in the clay, see Figures 6 and 7. The cables show local shifts in temperature one hour before the failure of the levee occurs. The locations of these shifts (at the white and blue parts) correspond with the locations where an increase of the water pressures is measured during the progressive erosion phase (measured by the pore pressure meters, the reference monitoring). -T -t- , i l ' .~ t! [ f -;: X,< m) , Sa~d iay~r - 30.05UO'09 6:50' p~ , j-----____ ~i____'_____-:-_, ' _____ ~,_, _' _' __ '='X()' , . , • " " .. .. .. >- In Sand Layer - 03.10.2009 3:50 pm Figure 6. Test 1, results cables sand layer. 654 SCOUR AND EROSION Geotextile glass fibre optics TenCate Geosynthetics, Inventec, EDF and geophyConsult have been involved in the IJkdijk Piping project to provide a monitoring solution based on optical cable and on the GeoDetect® monitoring solution (Artieres, 20 I 0). The experiment in test I was to monitor the erosion process at the interface between the clayey levee and the erodible sandy subsoil. The optical cables were used without textile to avoid any perturbation. Having the geotextile in place would provide the added value of anchoring the optical cable to the soil to prevent slippage and act as a filter to delay micro-erosion's progress which may give levee owners more time to react (hence the ' little disturbing ' influence of the innovative monitoring techniques in this test). One multi mode optical cable was installed and connected to the instrumentation to measure a temperature profile. The optical cable was installed in the saturated sand at a depth of 10 cm below the sand surface, see Figure 8. The cable was installed parallel to the dike at six parallel lines at an increasing distance to the downstream toe, see Figure 9. Figure 8. Installation of the optical cable (blue) in the submerged sand layer. SCOUR AND EROSION 655 N 1 ' . ,, ' "50" 1 .-...... -.-.. ----- - ---- - .. - .............. . . Ii.::::''''''' 1 t (1, .... ~ 2:6m 1 d._·"'." 1 o 1, --='" 1 •. -----------.. -.. -----------.-.---------- ... ........ . -.... ~ E 1 d_. ·"'" 1 [~ ] 17 m s Pled ')val (plots M!ofl) • Pointc.haud d,., ..... Posi\lOllsurle cilble Figure 9_ Test 1, Location of the six optical cables - the dotted line is the toe of the levee. The plots of the raw temperatures measured by the optical cable indicate progressive erosion of the pipe from the upstream side to the downstream side of the dike on October 3rd, 2009 at 1:26 pm (see the green circle in Figure 10), i.e. about 4 hours before the levee failed. A post-failure analysis that is about to be included in real-time data analysis modules has revealed the presence of precursors several days before collapse (Artieres et aI., 20 I 0). m IJ~"llk.1 - leml>"'o>\Y' U d ec lm ~ !ed 10 1 pUh - :oc ~ O~~ 1&;:;:G;02 ' j"" ......--,r ___ "l ---Down~ l tream toe------.. . :=,== ;:=:c: ::; : ·· :: :::~;::::: . ::; : : ::: =;; . =: ~~;:: : ~ m IJl<dIJkIl1-Temp.r:rt ... r ~"d« IIn ~ \t'dtOlptlh-:l:OO!lf10103 10:Z6: 12 L - , ·-·--·-· .. :; · ~; ~· -.. - : · ·~- :" - : · :.: ~ - · - : ; ··· ~; .- · ~::r - ::·~·· •.• ~ .•.•••• ?~ .- . -" "" ~!",) Optical cable Optical cable Optical cable Optical cable Optical cable Temperature scale / colour I J~d jJ k ' l- T e m~ ,.a tu' ..s d . cll .. nlt ltolptlh-2003J1 (lJ'0313 :::6;12 L . , ... -.--.... -..•.. -...................... -~.- ........ -............ ~ 10-'- 1: '---1 ' rim) ~:;-------;:- - c-~ -:-=:i: 1 ~~ ~ : z ----- : · . -- 1 i=--~ ~ R,.I",,,,,,,] w i .:0:.1 3 Oct 2009 I 0:26 am 3 Oct 2009 I :26 pm Figure 10. Test 1, results of temperature measurements. 656 SCOUR AND EROSION In the fourth test, a 40 cm wide GeoDetect® strip embedding optical cables both for temperature and strain measurement was buried at 10 cm depth in dry sand well before the test in the three lines the nearest to the downstream toe, while in the other three locations only temperature was measured. Figure II shows some results from this other test. In test 4, failure took place at 5 December 2009, at 2:25 pm. IjkdlJk 114. Temperatules deelmated 10 1 ptlh . ;100'112}04 1 B::!4:~O , • t·, Yl m l ~ ,: o. ce os ,: ,i. P.,~ '''''''I ___ I TIC! o . : •• ~=--;: .. : .. ::~ : .. :: .... ~ : .- ~~ .,[ ... ) C: o. oio 0& ; , ": ,. It 1~ "'~ , ~ 1"'",1 ,i:l- ----.-.I ·r TIC] 05 .12.20096 am J I ' ...... _._. __ .............. _ ........................ _ ... _ ... , ~ --~--- - <--,----• ~ '<: r~ ,. ff .... j a'~ eO, c'" ~. ,~"" " '. 'h"'{"''''i 04.12.20096 pm c.: ". qr. ~, t': " """'1"''''; 05.12.20096 am Figure 11. Test 4, results of temperature (left) and strain (right) measurements. The upper right plot indicates a pipe right to the middle already on the afternoon before failure. The intermediate effects of the progressive failure process on the temperature below the levee early in the next morning is clearly shown in the lower left plot. The strain measurements give complementary information, even though they are less sensitive in this case as the geotextile fiber optic sensors were not placed close to failure zone for experimental reasons. CONCLUSIONS The process of piping is studied in full-scale tests at IJkdijk experiment site in Booneschans. The use of pore pressure meters as an early warning system for piping in levees is demonstrated. Water pressure measurements give an indication of the phase of piping attained in the test. Temperature measurements tum out to be effective for detecting signs of failure by piping, especially the progressive erosion phase is easily detected this way. As expected, the closer the optical fibers are located to the leaks, the better the predictions are, both for temperature and strain measurements. The cables placed in the sand layer give more detailed information about the failure than the cables placed in the clay because of the permeability of the sand layer. SCOUR AND EROSION 657 The results presented here show that temperature measurements near the top of a sand layer sensitive to underseepage erosion can be quite effective for the early detection of progressive erosion. Combined with the fact that such measurements may be performed at much lower costs than pore pressure measurements, this may become an efficient detection method in flood safety programs, especially if local last-minute measures can be taken to avoid failure ofthe levee. REFERENCES Artieres, O. (2010). "IJkdijk Piping experimentation - Report of the measurements made with the TenCate GeoDetect® system and separate optical fibers on the tests 1, 2, 3 and 4" Ten Cate / Inventec / EDF / aeophyConsult, Paris. Artieres 0., Beck Y.L. , Khan A.A. , Cunat P., Fry J.J ., Guidoux c., Pinettes P. (2010). "Thermal and stability monitori~g of earthdams with a fiber-optics based monitoring system", Proc. 2" Int. Conf on Dam Maintenance & Rehabilitation, Zaragoza, Spain, 28-30 September 2010. Beek, V. van and Knoeff, H. (2009). "SBW Piping: Hervalidatie piping, HP5 .5 Analyse en validatie full-scale proeven", Report no. 1200690-005-GEO-0006, Deltares, Delft. Beek, V.M. van, Bruijn, H.T.J. de, Knoeff, J.G., Bezuijen, A. and Forster, U. (2010) . "Levee failure due to piping: A full -scale experiment", Proc. 5th Inti. Conference on Scour and Erosion, San Fransisco (CD-ROM), ASCE, Reston, VA. Bligh, W.G. (1910). "Dams, barrages and weirs on porous foundations", Engineering News, 64(26):708-710. Domstadter, J. (2010). "IJkdijk - Experiment 1 and 4 - Fibre Optic Leakage Detection System Using the Heat-up Method", Final report, GTC Kappelmeyer, Karlsruhe. Havinga, FJ. and Kok, M. (2005). "Flood Risks and Safety in the Netherlands (Floris)", Ministry of Public Works, Delft . ISBN 90-369-5604-9. Koelewijn, A. (2009). "New Measurement Technology for Dike Monitoring", Deltares GeoAcademy Course on Geotechnical Instrumentation for Field Monitoring, 21 -23 April 2009, session S, Deltares, Delft .. Sellmeijer, J.B . (1988). "On the mechanism of piping under impervious structures", PhD Thesis, Delft University of Technology, 56 p. 

IJkdijk Full Scale Underseepage Erosion (Piping) Test: Evaluation ofInnovative Sensor Technology

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IJkdijk Full Scale Underseepage Erosion (Piping) Test: Evaluation ofInnovative Sensor Technology

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