NCDOT abandonment grouting
The Job
This NCDOT abandonment grouting project is located outside of Chapel Hill, North Carolina. The abandonment grouting is the final step in a gravity main replacement project. The scope requires filling 3,023 linear feet of 24″ RCP gravity sewer with NCDOT-approved flowable fill.
The Challenge
This gravity main runs entirely in a cross-country backwoods right of way. Along the alignment, there are a few road crossings, which require the NCDOT approved material.
Because the new pipe is in the same right of way, there are multiple locations where new and old pipe alignments cross. This breaks it into a collection of smaller runs, as opposed to one continuous run of pipe.
The Solution
If this was one continuous run of pipe, it would be a great candidate for dry batch generation cellular grouting. The 352CY project volume would only take about two hours to fill.
However, being broken into multiple, shorter runs in the middle of the woods, meant that wet batch equipment was more appropriate from an access and productivity perspective.
CJGeo mobilized a wet batch crew to the site, and it took them two days to complete the work. There were a total of 11 runs of pipe and six placement points. The longest run was 1113 linear feet, the shortest only 56.
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NCDOT pipe abandonment
The Job
This NCDOT pipe abandonment project is located outside of Wilmington, North Carolina. It is part of a large highway improvement project to improve capacity in the rapidly expanding southern coastal North Carolina area.
The Challenge
NCDOT requires grout fill for most abandoned pipes within their right-of-way. Traditionally this is done using flowable fill mixes. Using flowable fill for short abandonment is generally pretty simple.
However, this project has more than 100,000 linear feet of pipe ranging from 6″ to 36″ to fill. Most flowable fill mixes won’t go more than a couple hundred feet in best cast conditions. The utility contractor was looking at having to dig up to five hundred access points to place flowable fill. That’s incredibly time consuming and costly.
The Solution
The utility contractor reached out to CJGeo about performing the abandonment grouting on this project, using low density cementitious material (cellular concrete).
Due to the highly variable pipe diameters and run lengths, CJGeo proposed a mix of wet batch and dry batch cellular concrete generation.
Wet batch was used for the lower volume runs. Dry batch is best suited for large volume runs. Over the course of a few months, CJGeo mobilized multiple times to fill runs as long as a mile at a time.
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Ohio Annular Space Grouting
The Job
This Ohio annular space grouting project is located in Akron. It is part of the Northside Interceptor, being constructed by Granite Construction. The total project budget is about $215 million, to construct 6,660 linear feet of 16.5′ diameter segmental liner tunnel.
While the main tunnel is single pass, there are multiple tie-ins to the structure, some of which are open cut, and another which is a microtunnel. The microtunnel is 530 linear feet of 48″ pipe.
The Challenge
Plans call to grout the annulus between the carrier pipe and microtunnel casing with 600psi at 28 day material. A lean concrete mix to achieve this compressive strength would be significantly heavier than water. This can cause significant headaches managing carrier pipe buoyancy, as the heavier the grout, the greater the uplift during grouting.
The Solution
CJGeo proposed a 55lb/cuft CJFill-Standard mix to meet the compressive strength requirement, while minimizing carrier pipe buoyancy. Because the proposed material is less dense than water, filling the carrier pipe with water during the grouting process keeps the carrier pipe in place.
A CJGeo dry batch cellular grout crew placed 119 cubic yards of 55lb/cuft CJFill-Standard over two hours to fill the annular space in a single lift. Cellular concrete is also referred to as foamed concrete fill.
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Indiana Pipe Abandonment
The Job
This Indiana pipe abandonment project is located in Anderson. Anderson is in central Indiana, near Indianapolis. The project is a water main relocation out of a park.
The Challenge
Plans call for safe loading the pipe being replaced. It’s important to fill abandoned utilities to prevent them from being groundwater conduits, or eventually failing completely. This can cause significant amounts of settlement, and transport soils long distances, neither of which is desirable.
The Solution
Using traditional flowable fill would have required close to 10 access points to place material into the pipe. This would have torn up a bunch of the park that the pipe ran though, and taken quite a bit of time.
CJGeo proposed filling the pipe from a single access point near the middle, using CJFill-Ultra Lightweight cellular grout. The beauty of cellular grout for abandonment is that it’s pumpable thousands of feet. In this case, the first run was 770 linear feet. The second run was 488 linear feet.
It would be possible to grout the entire run in a single stretch, however there was already an excavation at this point to blind a connecting pipe, and there was a nearby fire hydrant.
CJGeo sent a dry batch plant to the site, and the grouting work took less than an hour of pumping to completely fill the pipe.
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New York Pipe Abandonment
The Job
This New York pipe abandonment project is located in Newburgh, New York. Newburgh is on the Hudson River, about an hour upstream of New York City.
The Challenge
As part of a sanitary sewer upgrade project, 5,399 linear feet of gravity sewer ranging from 6″ to 24″ was specified for grout filling. The highest volume run was a 1,022 linear feet continuous run of 24″ pipe. The longest run was 1,469 linear feet of 18 inch” pipe. Each run did have intermediate manholes, but most manholes were a few hundred feet apart.
The Solution
Traditionally, the customer would have dumped flowable fill in the manholes in an attempt to completely fill the lines by gravity. However, many of the manholes were off road, and some of them were hundreds of feet apart. This makes gravity discharge of flowable fill into manholes unreliable for ensuring complete fill.
CJGeo proposed performing the abandonment grouting using 30lb/cuft CJFill-Ultra Lightweight cellular grout. Since cellular grout will flow much further at nominal pressures, CJGeo was able to place through multiple manholes at once, which significantly reduced access requirements.
Due to the relatively low volume on this project, continuous wet batch was the best method for generating the cellular grout for this project. Wet batch uses slurry delivered by ready mix truck, with Aerlite-iX added downstream of CJGeo’s slurry pump.
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Indoor Pool Abandonment
The Job
This indoor pool abandonment project is located in West Virginia, at Concord University. A swimming pool built in the 1970’s was no longer in use, and had sat empty for years. As part of a renovation, the pool had to be filled in order to pour a slab and prepare the room for other uses.
The Challenge
Like many buildings in the mountains, the original site sloped. A retaining/basement wall passes through the building close to the deep end of the pool, whose sloped floor roughly follows the original grade of the site. The structural engineer had to concerns about backfilling the pool:
- increasing lateral loads on the adjacent basement wall if a heavy, granular material was used for the fill material
- causing settlement by filling the pool with material heavier than the water it was designed to hold, and which the underlying soils had seen for years
The original bid had two options: filling the pool entirely with 57 stone, or filling it entirely with 2lb/cuft EPS blocks.
The Solution
Geofoam blocks would have addressed both the axial and lateral load challenges. However, EPS would take a few weeks to import, cut, and place. 57 stone would have been least expensive, but increased lateral and axial loads beyond those of water.
CJGeo proposed a value engineered alternative to fill the bottom 70% of the pool with 25lb/cuft CJFill-Ultra Lightweight low density cellular fill (LDCF), topped with 57 stone, and then a new floor slab. The structural engineer, architect and owner all accepted the proposed change. The general contractor was excited to save weeks out of their schedule.
A single CJGeo dry batch cellular concrete crew performed the work over two days. The first lift, of 400 cubic yards took about two hours to place, and was roughly 6 feet deep. The second lift, around 350 cubic yards, also took about two hours to place. The day after CJGeo wrapped up, the general contractor was able to start placing the 57 stone on top of the CJFill-Ultra Lightweight fill.
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WWTP Tunnel Curtain Grouting
The Job
This WWTP tunnel curtain grouting project is located in Syracuse, New York. It is located immediately adjacent to the southern shore of Onandaga Lake in an area that is historical infill.
The Challenge
A 700 foot long, 17 feet deep utility tunnel runs through the treatment plant site. Inside are numerous site utilities, including large diameter waste lines, along with many smaller diameter chemical and treatment lines.
Over time, the tunnel walls have developed leaks, accentuated by the highly variable fill material outside of the structure. When it rains, water enters the tunnel, which has roughly three feet of cover.
The Solution
As part of a large project at the plant, plans call for curtain grouting the length of the tunnel with polyurethane grout. Curtain grouting can be done two ways:
- through the structure walls, using holes drilled through the structure, or
- from the surface, using tubing inserted down along the exterior face of the wall
In this case, the interior walls of the tunnel were not uniformly accessible due to the number of utilities mounted on the wall. CJGeo designed a grouting program using the sacrificial tubes from the surface method. The advantage of this method in this case was that the density of utilities on the inside face of the structure didn’t affect the ability to uniformly introduce grout along the outside surface of the structure.
A CJGeo chemical grouting crew placed nearly 1300 gallons of single component polyurethane resin on this WWTP curtain grouting project. The work took about three weeks start to finish. The general contractor had removed the backfill and installed a new waterproofing membrane over the tunnel lid and extending down the walls about one foot on each side.
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Penstock Void Grouting
The Job
This penstock void grouting project is located near Hopkinton, New Hampshire. It is located at a small hydroelectric power plant that has been in service for more than 40 years.
The Challenge
This hydro-electric plant’s two original parallel penstocks are wooden. Sometime after original construction, 6.5′ ID steel liners were installed inside the original wooden penstocks.
Typically, when pipes are slip lined, the annular space between the ID of the original pipe and OD of the liner is grouted. However, in this case, the annulus was left open.
The steel pipes are nearing the end of their service life, and require rehabilitation. Plans called for installing a shotcrete liner. Specs called for a cementitious grout with 30 minute working time placement behind the steel pipes prior to spraying shotcrete.
The Solution
The marine contractor performing the shotcrete lining reached out to CJGeo about performing the annular space grouting with cementitious grout. CJGeo’s engineering & operations teams evaluated the project documents and site conditions and determined that there was a very high risk of grout escaping the annulus and making it to the adjacent waterway. This was due to the unknown condition of the original wood penstock, minimal cover over the pipes, and unknown, but potentially open graded backfill material.
CJGeo proposed an alternative, using CJGrout 22SHV geotechnical polyurethane grout to perform the penstock void grouting. CJGeo’s alternative material proposal was accompanied by load calculations from our geotechnical professional engineer confirming that despite strength significantly less than the specification requirement, that CJGrout 22SHV provided multiple factors of safety beyond the actual loads the annulus would see.
Upon approval by the owner’s consulting engineering team, CJGeo mobilized a confined space polyurethane grouting crew to the site. Over two days, the crew successfully grouted the annular space between the steel and wood penstocks. The following day, the contractor began installing reinforcement and prepping the steel pipe surface for shotcrete application.
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Ohio Polyurethane Grouting
The Job
This Ohio polyurethane grouting project by CJGeo was for a short line railroad near Scio, Ohio. The railroad received numerous complaints from motorists about a settled grade crossing. The settlement of the precast grade crossing was great enough to also require a speed restriction for rail traffic.
The Challenge
When this precast grade crossing settled, the clips holding the rail to the crossing panels broke. This allowed significant differential settlement between the various panels. The differential settlement was up to two inches.
In order to install new clips, the panels generally have to be within 3/8-inches of the adjacent panels’ elevation. If any debris has accumulated between the rail foot and bearing surface of the precast panels, which in this case were Oldcastle’s StarTrack.
The Solution
Having repaired multiple precast crossings for this short line, they reached out to CJGeo about performing this Ohio polyurethane grouting project. CJGeo proposed CJGrout 40NHL geotechnical polyurethane grout to the railroad. CJGrout 40NHL is formulated for high dynamic loading environments, and is excellent for different settlement correction of thick pavements.
CJGeo mobilized a polyurethane grouting crew to the site. Due to relatively low traffic on the line, the customer was able to provide an eight hour window for the repair, and the DOT allowed a complete road closure, as the settlement affected both lanes, with the centerline being the worst spot on the crossing.
CJGeo crews used mechanical assistance to address some of the worst differential settlement. Cleaning the accumulated debris between the rail foot and panels was key to facilitating complete correction of the differential settlement. After CJGeo wrapped up the polyurethane grouting, the railroad’s maintenance-of-way crew installed new clips, replaced the boots, and patch the adjacent asphalt.
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Flooded Shaft Grouting
The Job
This flooded shaft grouting project by CJGeo is located outside of Washington, DC at a data center site. As the 60″ microtunneling machine was entering the retrieval shaft, a piece broke off of the secant pile wall, and tore the seal. This resulted in water infiltration of around 600 gallons per minute into the shaft. The machine was recovered, but the shaft filled with nearly 15 feet of water in a matter of hours.
The casing crown has roughly 20 feet of cover, and is about 15 feet below the ground water level. The ground in the area is a mix of clays and sands. The tunnel is primarily in the underlying fractured rock. For the last 30 feet of tunnel before the secant pile receiving shaft, the tunnel is in a mix of weathered rock and sandy clay.
The Challenge
Having used CJGeo in the past to address high volume leaks into shafts, the tunneling contractor reached out to CJGeo for this flood shaft grouting problem. The primary constraints were:
- time – the project was already behind schedule
- water management – any groundwater was considered contaminated
Typically, grouting a leak such as this would be as simple as throwing bigger pumps into the shaft, dewatering it, then grouting the leak from inside the shaft. However, because of the costs associated with treating potentially very high volumes of water at this site, this wasn’t an option.
The Solution
CJGeo proposed, and then successfully performed, a two stage grouting program. Primary grouting was done using CJGrout 35NHV61 geotechnical polyurethane on a Saturday. The CJGrout 35NHV61 was installed immediately behind the secant pile wall through three holes drilled from the surface to intercept the over cut. Grout injection through these holes resulted in grout return to the retrieval shaft. Off gassing also showed up at the launch shaft. This indicates that the rapid inflow of water during the flooding event had washed out some of the mud in the over cut.
After completion of the plural component primary seal injection, CJGeo dye tested the primary grouting program. This was done through Tube-A-Manchette grout pipes installed along the tunnel alignment, further out from the shaft. No dyed water returned to either shaft.
The following day (Sunday), CJGeo performed permeation grouting using colloidal silica through the TAM grouting tubes. This secondary grouting program served two purposes:
- seal any rock fractures that weren’t penetrable by the higher viscosity plural component polyurethane grout
- replace any overcut mud washed out during the initial flooding event
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