Werren, Baird, Denechere, and Fons 1

THE CORE-LOC® ARMORING TECHNIQUE EXPERIENCE ON RECENT PROJECTS

David J. Werren1, William F. Baird1, Michel Denechere2 and Michel Fons2

Abstract : This paper discusses recent experience with the application of the Core-Loc® armor unit. Practical issues associated with implementation of Core-Loc® as the armor unit on breakwaters are discussed, including stability, place-ment technique, packing density, the toe and the crest details.

INTRODUCTION The Core-Loc® armor unit is the result of many years of research at the U. S. Army Corps of Engineers (USACE) Waterways Experiment Station (WES), Coastal and Hydraulic Laboratory (CHL), (Melby and Turk 1996, 1997, Turk and Melby 1998) that has involved two- and three-dimensional hydraulic model studies, measurement of internal stresses using load cell based procedures and analysis of the distribution of stress in the unit using finite element methods. The Core-Loc® unit is intended to be placed in a single, armor layer on a breakwater or revetment and may be considered as an advanced or refined version of an Accropode®

unit. Core-Loc® units have also been designed to repair damaged Dolos breakwaters (Turk and Melby, 1997). 1 Principal, W. F. Baird & Associates, 2981 Yarmouth Greenway, Madison, WI 53711 USA.

dwerren@baird.com 2 Principal, W. F. Baird & Associates, 1145 Hunt Club Rd., Suite 500, Ottawa, ON K1V 0Y3

Canada. bbaird@baird.com 3 Core Loc® International, Pole 1, 3,cour du 56, av. M. Dassault Tours 37200 France.

michel.denechere@coreloc.com 4 Sogreah Maritime, Patents and Trademarks Division, 6 rue de Lorraine - 38130 Echirolles, BP

172 Cedex 9, Grenoble, 38042 France.

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Physical model tests have shown that superior hydraulic stability is achieved with the symmetrically-tapered octagonal flukes, and stress analyses have demonstrated improved strength characteristics compared to the Accropode®. Consequently, the Core-Loc® unit has significant economic advantages compared to other concrete armor units with equivalent performance. This paper discusses practical issues related to the construction and placement of Core-Loc® units and addresses some overall breakwater design and construction issues. Ten projects have recently been completed or are under construction with the involve-ment of the authors. These projects involve approximately 330,000 cubic meters of concrete and over 120,000 Core-Loc® units varying, so far, from 0.5 to 9 cubic meters in size. BACKGROUND The Core-Loc® Concrete Armoring Unit was developed by the USACE, Coastal Hydraulics Laboratory. The Principal Investigators were Dr. Jeffrey Melby and Mr. George Turk. The USACE undertook considerable research and development on the unit including a number of generalized model studies in order to develop design information. In addition, the USACE took out patents and trademark protection to license the technology around the world. The USACE then contracted with a number of private organizations to manage the various licenses required under the patents and trademarks. The purpose of this licensing arrangement was to assure that the technology was applied appropriately, as well as to charge and collect a royalty for the use of the units. This royalty money then flows back to the USACE to provide additional funds for research both on the Core-Loc® and other similar concrete armor units. As a part of the licensing process, two of the sub-licensees (W. F. Baird & Associates and Sogreah) established a company to manage the licensing and quality assurance activities of Core-Loc® in their territories. This new company is called Core-Loc Interna-tional, or CLI for short. CLI has been structured to include a repository of information about Core-Loc®, both in the design and construction phases, to assist designers and contractors in the implementation of Core-Loc® projects. It is the belief of the authors and the stated objective of CLI that future coastal structures need to be developed from a dynamic and managed knowledge base accessible to all designers. “Knowledge-based solutions” benefit from past experience and provide the best performing coastal structures at the most practical cost. CLI will make this best current practice information available on its website: www.coreloc.com. SPECIFIC ISSUES LEARNED ABOUT CORE-LOC ®

One of the key project elements experienced by the authors has been the importance of the preparation of the underlayer, or filter stone, prior to receiving the Core-Loc® units. Although model studies and field experience show good performance of the Core-Loc®units placed over a range of prepared underlayer tolerances, it is found that the placement of the single layer of Core-Loc® units is much easier, and higher production is achieved, if adequate care is taken to prepare the underlayer with minimal variation from the specified line and grade. The generalized specification for Core-Loc® is that any one survey line should not vary more that one-sixth of the “C-dimension” of the Core-Loc®, nor

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should the surface vary more that one-tenth of the “C-dimension” for an average of three consecutive survey lines. We have generally found that contractors who meet or improve upon these tolerances achieve better production rates during the placement of the Core-Loc® units. Experience on the projects to date has shown that there are two approaches to placing the Core-Loc® units. While the preferred method is to place the units each with a random orientation on an organized grid pattern, they can also be placed with random orientation in a random placement pattern on the slope. The latter is particularly useful in areas of small placement where the establishment of a grid and the purchasing of global positioning equipment to assist in an organized grid placement is cost prohibitive. A diver is required to assist with placement of all underwater portions. It is found that placing the units underwa-ter on an organized grid with carefully controlled locations, reduces the effort and time required by the diver to both assist and verify that the unit is placed correctly. Therefore, it has been concluded that grid placement is preferred over the random-placement approach, except in those areas where the work can be observed (such as above water), or if the units themselves are very small, and the grid pattern is difficult to achieve because of its small size. In any event, even with the random placement, an attempt should be made to achieve an organized placing pattern such that each row of units is placed staggered above the previous row, and without Core-Loc® units in the same row touching each other. The USACE guidelines addressing the packing density of the Core-Loc® units have been found to provide both stability in hydraulic model studies as well as good interlocking in prototype experience. Most of the structures constructed to-date have had packing densities of between 0.57 and 0.60. It is generally easier to achieve a higher packing density with smaller units during the prototype construction. Packing density needs to be very carefully monitored both in the hydraulic model studies and in the prototype construction. If the units are being placed on a regular-grid placement where the position of each unit is known, the packing density can be easily controlled. However, if random placement is used, the packing density needs to be checked very frequently to assure that there are no areas of the structure that have been placed to a sub-standard density. A significant amount has been learned about optimizing both the toe and crest details of Core-Loc® breakwaters. There are a number of options for the toe construction using the Core-Loc® unit. One option is that in the first row the units sit on two lower flukes in what is known as a “cannon position”. It is found that contracting and placing crews like to place the lowest unit in this position because it is relatively easy to control and visually verify that it is placed correctly. A number of variations can be made following this first row “cannon position” placement. The first option is to begin random orientation of units immediately above the cannon-placed units in the first row at the toe. The second option is to place one or two regularly-oriented units specifically above the cannon units to interlock them prior to placing the randomly-placed units on the slope. Again, it has been found in prototype experience by several contractors that, the placing crews prefer to place the units in a regular pattern near the toe because it assists the diver during the placing operation and provides a rapid visual verification that the units are well interlocked (and that the density has been met.) It is, however, more difficult to orient large units in deepwater conditions. Model studies have been completed with both randomly-oriented units and with an

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organized cannon-placement method. Both configurations have been found to provide very stable structures. It is our opinion that the most critical factor with respect to toe placement is that the toe units extend low enough to the sea floor, and are not placed on a rock-berm or rock-support partly up the slope. This is because it is difficult to place the first units against an armor stone slope at the toe and assure that they are well nested and solid. The concern being the overlying units are relying on the lower or first row units not shifting or moving. If these units are placed on large armor-stone buttresses, there is a potential that during the first storm event these units may shift and settle into a lower position within the armor stone, allowing the units on the slope to shift downslope. With respect to crest details, it is very important to consider how the crest of the breakwater will be finished. On several projects, the Core-Locs® have been finished against a fixed crown-wall structure. Initially, there was a concern that trying to establish a fixed- or oriented-grid pattern against a fixed-structure such as a crown wall would create problems. However, it has generally been found that there are enough opportunities to adjust the units above the waterline such that a tight fit between the crown wall, and the front slope can be achieved. In areas where access to the top of the breakwater is not required, the Core-Loc® units have generally been extended across the top of the breakwater and down the lee side breakwater at least to the low waterline. The primary issue found in this application is that the units in the crest of the breakwater are more difficult to place than those on the slopes of the breakwater. This is due to the fact that while placing the Core-Loc® on the slope of a structure, gravity assists the placing operation and a good interlock can be achieved. On a horizontal surface such as the crest, there is no gravity assistance. There is a natural tendency for the units to want to sit in a cannon position, and they can either be placed too loosely (i.e., not meeting the required packing density) or too tightly by stacking them as found in a casting yard where they are nested together very tightly. The best experience has been to undertake several test sections and work with the contractors to achieve a placement pattern that provides good unit-to-unit contact without excessive consumption of concrete. The casting of Core-Loc® units is generally found to be both straightforward and has been without problems in all projects completed. The forming process uses a two-piece mold with a vertical seam. It has been found that using a two-piece mold with wheels on the mold allows the forms to be removed from the units without the use of a crane or equipment. A wide range of experience has been observed with respect to the speed of the casting process. In general, it has been concluded that very successful production operations can be achieved by obtaining one pouring of a Core-Loc® unit per-day per-mold. PROJECT EXPERIENCE The following projects illustrate the representative experience of Core-Loc® along with a range of examples with experience about specific details discussed above. Although these projects show a number of possible alternatives with respect to Core-Loc®, because of the significant learning curve for each of the projects, we caution that there may be methods depicted for these individual projects which would not be recom-mended on future projects of a similar nature.

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Khaboura, Oman This project consisted on an offshore breakwater with a pile-supported structural pier servicing a small fish-loading facility behind the breakwater. This structure was designed by Baird & Associates and Cansult for the Ministry of Agriculture and Fisheries in Oman. The toe of the structure was located in a water depth of -3.5m below datum. There were design issues related to the ongoing erosion of the surrounding seafloor, so the structure was designed for eventual downcutting of the seafloor and deeper-water conditions at the structure. In addition, because of the relatively short length of the breakwater, the Core-Loc® units were sized assuming the head condition, or a Kd of 12 rather than the published Kd of 16 for trunk section. Given the small size of the structure, it was concluded that utilizing two separate sizes of Core-Loc® was not justified. This was one of the first Core-Loc® projects implemented and it was left to the contractor whether they wanted to use a random-placement pattern or use a grid orientation. The number of test sections were built and the contractor elected to proceed utilizing a random-placement method.

Photograph 1 Photograph 2 Photograph 1 shows the construction of the offshore breakwater. The pile supported access way in the center of the photo, and a temporary construction access road of rock fill on the right-hand side of the pile-supported trestleway. As noted above, random placement was utilized for the Core-Loc® in this project. A total of 2, 500 Core-Loc® were utilized in the project each being 3.0 cubic meters in size. In this case, the casting was achieved by the utilization of seven molds, in a controlled casting yard. Because of the controlled conditions for casting units, the molds were used two times per day, with very good success. Placement of the units in the structure was relatively slow, at a rate of approximately four-to-six units per hour once the crane operator and diver became experienced with the procedure (photograph 2). The placing crew followed three basic rules in the placement process: 1) the units must always rest on the prepared under-layer surface and not be supported strictly by the adjoining Core-Loc® units; 2) each Core-Loc® unit when placed had to interlock and constrain the units below it; and 3) the placing density was checked frequently by calculating the area of coverage and the number of units placed and that the density met the placement density specification of 0.60. Placement of the units started by placing the toe rows, and then building a pyramid or triangular section on the face of the slope from the toe. Placing then worked from the toe up the 45° degree slope of previously placed units to a level above the water surface.

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Photograph 3 Photograph 4

Photograph 3 shows the finished face of the Khaboura breakwater structure. Although the placement pattern was random, it was noticed that after some time a more regular pattern of placing appeared as a result of the experience of the placing crew. Generally it was found that once the crew established a certain degree of comfort and experience in the placing operation they preferred to place the units in a more regular pattern although they were encouraged to maintain a random orientation in the individual units placed. Dhalkut, Oman This project was designed by Scott Wilson and was also for the Ministry Agriculture and Fisheries in Oman. This is a fisheries harbor, with a secondary objective of providing a harbor refuge for small coastal patrol vessels. The site is located in a very remote location, at the southwestern end of Oman near the border of Yemen. The project is subject to a depth-limited breaking wave climate; a severe wave climate is experienced each year as a result of the annual monsoon. In total in this location over 64,000 Core-Loc® units were used, ranging in size from 3.9 to 9 cubic meters. The slopes on the outboard face of this structure were 1.5:1, except at the head of the structure where a slope of 2:1 was utilized along with the 9 cubic meter Core-Loc® units. This project was tested at HR Wallingford in the UK (Lee, Allsop, and Baird, 2000.) We are considering with future model studies whether or not there are any stability advantages in decreasing the slope at the head of the breakwater. Certainly there are some advantages in maintaining the steeper slope. A number of design issues came up during the design of this project. These included exposed rock at the head of the breakwater structure. The seafloor at the head consisted of generally smooth rock floor and it was determined in the model study that this could lead to an instability in the Core-Loc® units on the inside of the head of the structure at the toe. In addition to the exposed rock and extreme wave conditions, the structure had to be designed such that it could be built over two construction monsoon seasons. This meant that the structure had to be partially completed and survive the monsoon during the construction period. The contractor worked with HR Wallingford to develop a monsoon closedown procedure utilizing Core-Loc® to protect the temporary facility. Photograph 4 shows the 6.75 cubic meter forms during the casting process. The two-piece form units, split vertically, with form half-supported by a wheel assembly can be seen. The forms are extracted by applying pressure at the nose of the horizontal fluke and removed relatively easily from the finished Core-Loc® unit.

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Photograph 5 Photograph 6

Photograph 5 shows a completed 9 cubic meter Core-Loc® unit. It can be seen from the

photograph that a very high quality has been achieved during casting of the unit with very little loss of water from the form at the joint and no honeycombing or visual surface damage on the finished Core-Loc® unit.

In photograph 6 the prepared underlayer slope, as the initial Core-Loc® units were placed on the structure, can be seen. The units being placed in this photograph are 3.9 cubic meters. The very high quality of the underlayer preparation provided significant assistance to the contractor in achieving rapid placement of the Core-Loc® units. Again, as with Khaboura, the contractor elected to utilize random placement of the Core-Loc® units on the structure rather than following a specified grid pattern.

Photograph 7 shows the head of the completed Dhalkut breakwater consisting of 9 cubic

meter units at a 2:1 slope. The crest of this breakwater is at approximately +10 meters CD in elevation and the toe at the outside of this breakwater is approximately -8 meters CD for a total structure height of 18 meters. Although the breakwater was initially tested at a 2:1 slope and found to be stable, it is the opinion of the authors that perhaps this structure would be

Photograph 7

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as stable on a 1.5:1 slope as on a 2:1 slope. This is an area in which CLI will be doing additional research; however, it is our initial observation that decreasing slopes do not necessarily provide increased stability, as is suggested by the Hudson equation when utilizing Core-Loc® units. The Core-Loc® units obtain a significant degree of their interlock and stability by the weight of the overlaying units providing the force of interlock.

As mentioned, the other concern and design difficulty at this site was the exposed rock seafloor at the head of the structure. Initially, excavation of a trench into the rock was considered. However, because of environmental concerns related to the local lobster fishery, blasting of the rock was extremely difficult and limited to a very few weeks per year. Therefore, a toe detail was developed, in which the Core-Loc® units extended to the seafloor and rested on a row of cannon-placed Core-Loc® units. These cannon-placed units rested on a thin bedding layer immediately above the smooth rock seafloor. In front of the cannon units was a wide berm of armor stone units a single-layer thick placed around the toe of the structure. This armor stone berm was then choked, by divers using grout bags, and prepared to receive a tremy grout. Once the outer edge of the armor stone layer was choked, concrete was pumped in filling the voids in the entire armor stone berm, and filling the first Core-Loc® unit to about two-thirds their depth in concrete. This provided a single massive toe, with the first row of Core-Loc® protruding slightly above the tremied mass.

The transition between the1.5:1 outboard slope and the 2:1 slope of the finished head of

the structure can be observed. In this transition area, the size of the units also make a transition from 6.75 to 9 cubic meters. Although this transition represents a significant increase in the size of the units, it is very difficult to observe the transition in the field as the units have achieved an excellent interlock even through a size and slope transition. It has been generally found that changes in size of units up to 100-percent can be easily achieved at a transition area as the Core-Loc® units provide exceptional interlock capabilities through various size ranges. The breakwater was constructed at a lower elevation initially allowing a wider width for

construction ac-cess. All construc-tion was done as a land-based opera-tion. Photograph 8 shows the completed break-water structure at Dhalkut.

Photograph 8

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Sohar, Oman The port at Sohar is a large commercial port designed by Halcrow. This is a project for the Ministry of Communications of Oman. In total, over six kilometers of breakwaters were constructed consuming over 150,000 cubic meters of concrete. The Core-Loc® sizes ranged from 0.5 to 3 cubic meters. In total, over 80,000 Core-Loc® units were utilized in the structure. This structure was originally designed by Halcrow to utilize the Stabit armor unit. The Core-Loc® units were proposed as an alternative, and eventually accepted by the Owner and Halcrow. The contractor was Daewoo Construction of Korea. The contractor submitted the Core-Loc® alternative as a cost-savings measure, and significant cost savings were achieved.

Photograph 9 Photograph 10 Because of the large number of units required for this project, a very organized casting procedure was required. In photograph 9 an elevated roadway prepared by the contractor to assist in the casting process can be seen. Utilizing standard concrete trucks on the elevated roadways, the concrete was discharged directly from the truck into the forms without pumping. Each form was used once-per-day. After pouring, the forms were stripped approximately 12 to18 hours later and prepared for the next day’s pouring. The casting yard was prepared on the concept of three Core-Loc® per-casting-station. At a casting station, the forms were located and the current day’s pour was made. This allowed room for two additional Core-Loc® units; one was the previous day’s pour and the third unit was from two days prior. The third unit was removed on the third day, and the forms, once stripped from the freshly poured unit, were moved into the third position. This allowed a total-curing time of between 2 to 3 days for each Core-Loc® unit before it was initially moved. The units were lifted from the casting area using a forklift with padded forks.

Photograph 10 shows the vibration process after pouring, as well as the storage area of the Core-Loc®. It was found with a particular mixed design, using Type V Cement, at Sohar that after the initial vibration and filling of the units, some plastic settling of the concrete occurred, which generated bleed-water at the edge of the forms. It was found that by re-vibrating the forms after a period of 30 to 60 minutes, depending on the temperature conditions, that the plastic settling and the water problem could be eliminated. The end

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result was a very high quality consistent Core-Loc® with an extremely low number of units rejected due to manufacturing defects.

Again because of the large number of units involved the system of form-removal and curing of the units was highly organized. Compressed-air lines serving the casting area allowed the rapid application of curing compound immediately upon removal of the forms. Because adequate storage room was available, the Core-Loc® units were stored on the project's site, without stacking.

Photograph 11 Photograph 12

For this project a specific project placing grid was utilized. A placing grid was prepared

in AutoCad based on the underlayer drawings. This placing grid established an X, Y, position for each of the 80,000 Core-Loc® units to be placed. At the beginning of each work shift, the day's work was programmed into the Global Positioning System (GPS) that was used to control the placement of the units (Photograph 11). In addition, a placing chart showing all the locations was taken out to the work crew doing the work. In this way, the work crew could track the location of each unit placed in the previous day’s work, the units to be placed during the current workday, and the actual work completed that day. Each of the coordinates for each unit was preprogrammed into the data collector. Each unit also had a specific and unique number. As the operators entered the unit number, the grid coordi-nates would be displayed along with the actual position of the crane and the target location for the units. This system proved to be extremely effective allowing very rapid placement of the units. Photograph 12 shows a prepared underlayer slope with the Core-Loc® placement advancing.

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Photograph 13 Photograph 14

Photograph 13 is a view of the northerly breakwater taken from the entrance to the harbor. In this picture the placing crane can be seen working from a barge placing Core-Loc® units on the front face of the breakwater. This operation is being undertaken by only the crane operator, and one spotter-assistant who is working on the front face of the structure. It is not possible for the crane operator to see the placing position even though the units are above water. However by using the GPS placing system, this operation achieved very rapid placing rates, with excellent results.

Photograph 14 shows the tower crane that was utilized at the head of the breakwater. The tower crane was utilized because the head of the breakwater was designed to extend into the dredged entrance channel into the port. Therefore, the toe of the structure extended into -16 meters CD of water, and resulted in very long slopes with a long reach. The tower crane proved to be an effective tool in reaching the long slopes to place the Core-Loc®.

Photograph 15 shows a view of the southerly breakwater structure. The Core-Loc® units are fit up against the crown-wall structure and although placed on a regular pattern, it was found that the units were relatively easy to maneuver in the last two to three rows in order to achieve a tight fit against the crown-wall structure. In this view, Core-Loc® units on this breakwater are three cubic meters.

Photograph 15

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Saham, Oman The Saham Fishery Harbor was another project for the Ministry of Agriculture and Fisheries in Oman. The designer of this project was Scott Wilson. As this is a relatively small fishing port in protected waters, the size of the units ranged from 1.3 to 2.0 cubic meters. In total, approximately 16,000 cubic meters of concrete were utilized, with a total of approximately 12,000 Core-Loc® being cast. In this case, the contractor elected to utilize random placement of the Core-Loc® units. This was largely due to the fact that the water depths were relatively shallow, and after the initial first two or three rows of the Core-Loc®, at low tide the Core-Loc® units could be seen from the surface.

Photograph 16 shows a view of the Saham Fishery Port under construction.

Photograph 16

Photograph 17 shows a problem that occurs with specified random placement. Although the concept of random placement had been discussed in detail with both the placing crew and the contractor, it is difficult to convey the full intent of random placement. This photograph was taken after an initial placement of Core-Loc® had been attempted. The placing crew thought they were achieving a good interlock of units in this fashion. After explaining that this did not provide a good interlock and was something to be avoided with Core-Loc® units, the placing pattern was subsequently modified. This type of placing pattern should most definitely be avoided and does not provide the stability that needs to be achieved with Core-Loc® units.

Photograph 17 Photograph 18

Photograph 18 shows the finished crest of the Saham breakwater. Because this was a relatively low crested but wide structure, some difficulty in finding the best method to place the units at the crest was encountered. As noted previously, the difficulty is that gravity does not assist the interlock between the units, and the units must be placed in a manner that prevents rocking during an overtopping event. This takes some degree of work between the contractor and the on-site representative crew to establish the best methodology to place

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the units in order to achieve good interlock without using excessive consumption of concrete by nesting the units back-to-back. CONCLUSION The Core-Loc® armor unit has been used on many projects. With each project, new experience is gained that will assist new Core-Loc® projects achieve both stability and ease of construction. In general, it has been found that the prototype construction has proceeded extremely well and the unit has demonstrated that it can be readily adapted to site-specific issues that arise. Contractors have reported that the casting and placing process has gone well, and the unit has met their needs and expectations. Clearly, there is a significant amount yet to learn. The establishment of a dynamic knowledge base, accessible to designers, is believed to be of critical importance by providing the most up-to-date and current design practice. This database will be available in a web-based environment at www.coreloc.com. While Core-Loc® is not for every project, it has demonstrated that it is both a robust and economical solution when appro-priately used. REFERENCES Lee, T.H. Allsop, N.W.H. and Baird, W.F., The Laboratory Results of Core-Loc perform-

ance at Sohar Breakwater, Sultanate of Oman, Korea-China Conference on Port and Coastal Engineering, September 2000, Seoul, Korea.

McHale, J., O’Loan, D., Denechere, M. and Fons, M., First Application in Europe of the CORE-LOC™ Technique at Tory Island, Republic of Ireland Coastlines, Structures and Breakwaters September 2001, London. Marine & Natural Resources, Ballyshanon, Ireland – Kirk Mc Klure Morton, Belfast, Ireland – Sogreah, Echirolles, France.

Melby, J.A. and Turk, G.F. 1996. Core-Loc Development as Related to Historical Corps Concrete Armor Unit Performance. Proceedings of Advances in Coastal Structures and Breakwaters, London, England, April 27-29, 253-267.

Melby, J.A. and Turk, G.F. 1997. Core-Loc™ Concrete Armour Units: Technical Guide-lines, U.S. Army Corps of Engineers, Waterways Experiment Station, Technical Report CHL-97-4.

Turk, G. and Melby, J.A. August 1997. Preliminary 3-D Testing of CORE-LOC™ as a Repair Concrete Armor Unit for Dolos-Armored Breakwater Slopes, Technical Report REMR-CO-18.

Turk, G. and Melby, J.A. 1997 Dynamic Structural Response of Core-Loc™. The REMR Bulletin, Vol. 14, 3.

Turk G.F., Melby J.A., 1998 Impact structural response of Core-Loc™. Proceedings 26th Coastal Engineering Conference V.2, ASCE, Reston, VA, 1846-1856.

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THE CORE-LOC® ARMORING TECHNIQUE EXPERIENCE ON RECENT PROJECTS

David J. Werren1, William F. Baird1, Michel Denechere2 and Michel Fons2

KEY WORDS armor breakwater concrete construction Core-Loc®

knowledge base revetment single layer stability