Lightweight Pipe Backfill
The Job
This lightweight pipe backfill is part of the City of Alexandria’s RiverRenew project, its largest in history. The project includes installation of new interceptors, and a large CSO/conveyance tunnel.
The Challenge
A pile-supported, concrete-encased interceptor needed to be backfilled. Due to the pile support capacity, the maximum allowable density of the load reducing backfill was 90lb/cuft.
The Solution
To bring the average backfill density to 90lb/cuft, CJGeo proposed filling between the SOE & concrete encasement with 30lb/cuft CJFill-High Permeability (HP). CJFill-HP has very high permeability, so reduces buoyancy when saturated when compared to other lightweight fill materials. CJGeo successfully filled between the concrete encasement and SOE with 145CY of CJFill-HP. The placements was done in a single, 6′ deep lift in less than an hour.
To facilitate the fast placement speed, CJGeo used a mobile batch plant to generate the CJFill-High Permeability cellular grout onsite. Onsite generation blends dry, bulk cement onsite with water, using custom batch plants which also make generate the preformed foam on site. The cement slurry is around 110lb/cuft, and the preformed foam is around 2.5lb/cuft. CJGeo’s batch plants utilize colloidal mixing, which ensures the highest quality cement paste, and therefore the highest quality finished product possible.
The use of very low density material then allowed the client to backfill on top of the structure with normal unit weight material while maintaining the average 90lb/cuft density through the full depth of the fill column. Aerix Industries supplied the preformed foam.
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Valve Vault Infiltration Grouting
The Job
This valve vault infiltration grouting project is part of the Purple Line project in Maryland. A large diameter water line was relocated, with the tie-in done inside a 10′ diameter vault that was about 20′ deep. The vault structure, which is precast, and set inside a line plate shaft, was leaking at multiple joints and at a poured in place pipe penetration closure.
The Challenge
The vault structure wasn’t concentric in the shaft. This left little room to pour the closure around the pipe penetrations. One of the penetrations leaked, causing the structure to completely fill with water. Per specifications, it needed to be dry.
Most of the shaft was backfilled with 57 stone. Highly permeable backfill material can make water control grouting particularly difficult. When grouting to seal relatively tight leaks in a structure, the less permeable the adjacent soils the better. All grouts want to take the path of least resistance, and with highly permeable backfills, that often means traveling out into, and permeating, the backfill material instead of into tight cracks and water passageways.
The Solution
CJGeo proposed grouting the infiltration points with CJGrout-35NHV61. 35NHV61 is a hydroinsensitive, plural component geotechnical polyurethane, certified for potable water contact. 35NHV61 is a moderately mobile grout, selected to minimize mobility into the 57 stone backfill and reduce material loss during grouting.
CJGeo mobilized a three person crew to the site, and performed the valve vault infiltration grouting over a few hours.
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8′ CMP Joint Grouting
The Job
A spec warehouse was planned for a vacant piece of land which had 1700LF of 8′ CMP running through it. The pipe was 10 years old. Because the site was vacant, there was no maintenance. Nearly every joint showed signs of soil infiltration, and there were massive sinkholes along the entire alignment. Given the depth, size, and short work window, the contractor sought out a CMP joint grouting repair alternative to replacement.
The Challenge
To avoid replacing the entire run of pipe, the joints had to be sealed. There were 80 pipe joints and 12 pipe to structure joints to seal. The pipe crossed under a roadway, and then crossed the site at an angle. The downstream end of the pipe transitioned to new 96″ RCP.
The Solution
In preparation for the repair, CJGeo had to educate the town, contractor, owner & consulting engineers that polyurethane grouting is an effective CMP repair method.
CJGeo mobilized a polyurethane grouting crew to the the site. Over the course of a week onsite, the crew performed all of the CMP joint grouting.
CJGeo used CJGrout 20SDB geotechnical polyurethane. 20SDB is a high mobility geotechnical polyurethane, so seeks out and fills even the smallest of voids outside of pipes. Because it’s highly mobile, it doesn’t deflect or damage the CMP that needs repair.
The manholes also had significant defects. Made of non-parged sewer brick, they leaked extensively. To address the widespread infiltration through the structures, CJGeo sprayed the interior of each structure with CJGrout 60FDC. 60FDC is a hybrid polyurethane/polyurea spray coating. For durability, the 60FDC was coated with polyurea. The 20SDB, 60SDB & polyurea coating were all installed using the same equipment, significantly reducing costs.
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Atlanta cellular concrete
The Job
This Atlanta cellular concrete installation is part of Atlanta Watershed Management’s Niles Avenue Sewer Improvements project. The project took approximately 2500LF of microtunneling to install a new 18″ sewer main.
The Challenge
A 72″ microtunnel was chosen, which required approximately 1200CY of annular space grouting. Operations were challenged by the pandemic hitting in the middle of the project.
The Solution
CJGeo proposed 30lb/cuft CJFill-UL cellular grout for the annular space grout. This allowed the contractor to avoid mechanical buoyancy control during grouting operations during single lift grouting. Buoyancy control of the carrier was one of the driving factors for using CJFill-Ultra Lightweight for this Atlanta cellular concrete project. Because the tunnels had a good amount of slope on them, grouting in multiple stages would have been impractical. Flowable fill would have floated the carrier pipe, even if it was full of water.
Over two mobilizations, CJGeo generated the cellular concrete grout onsite using preformed foam from Aerix Industries and placed it via shafts which were up to 40 feet deep. CJGeo chose wet batch generation due to the project volumes.
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66″ Water Main Abandonment
The Job
This 66″ water main abandonment is part of the The Purple Line’s construction. The Purple Line is a light rail line project in suburban Maryland. It will increase connectivity within Maryland’s suburbs of Washington, DC. The project involves extensive utility relocation to facilitate installation of large embankments and the extensive infrastructure required for a double track rail corridor dropped into the middle of an already exceptionally congested/dense corridor.
The Challenge
As part of the project, a large MSE wall was built over approximately 3000LF of 66″ PCCP water main. To avoid any future maintenance problems under the rail alignment, a new line was put in adjacent to the embankment. The old line had to be completely full of grout.
Due to construction sequencing, the embankment installation happened before the water line relocation.
The Solution
CJGeo worked with the utility relocation contractor to design a grout mix and grouting program that provided sufficient bearing capacity to eliminate concerns about future stability. The ultimate design for the mix was a 100psi CJFill-Ultra Lightweight cellular grout. Because the embankment was already in place, the entire 3000LF stretch was accessible from just two access points.
CJGeo used a 200CY/hour dry mix batch plant onsite to generate and pump the cellular concrete up to 1500LF to place the material. This 66″ water main abandonment took four days to complete, and didn’t disrupt any of the adjacent construction activities.
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Garden State Parkway grouting
The Job
This Garden State Parkway grouting project is located near Middletown, New Jersey. As part of ongoing large diameter culvert rehabilitations and replacements, four new bored stormwater crossings and the original culvert they replaced needed to be grouted. The tunnels ranged from 120″ down to 74″, for a total of 312CY, and the abandonment required 405CY.
The Challenge
Grout needed to meet the minimum strength requirements of the owner, and ideally needed to be light enough to facilitate single lift annular space grouting.
The Solution
CJGeo’s preconstruction team worked with the general contractor to design a grouting program which facilitated single lift abandonment of the original culvert, and single lift grouting of the four various annular space runs. CJGeo utilized onsite dry batching to generate 30lb/cuft CJFill Ultra Lightweight cellular concrete.
CJFill is a type of Low Density Controlled Low Strength Material, or LD-CLSM. The “low density” comes from using preformed foam, in this case Aerlite-iX, as a substitute for aggregate. This significantly reduces the unit weight, which exponentially increases pumpability. In this case, all 405 cubic yards of abandonment grout were placeable at once.
Because CJFill LD-CLSM is significantly lighter than water, each annular space grouting run was doable in a single lift. Filling each carrier pipe partially with water was all it took to facilitate this.
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CBBT Sheet Pile Pregrouting
The Job
This sheet pile pregrouting project is located in the Chesapeake Bay. The Chesapeake Bay Bridge Tunnel’s Parallel Thimble Shoal Tunnel Project is constructing a second tunnel parallel to the original to reduce traffic congestion. All launch & receiving work is on man-made islands in the Chesapeake Bay. The islands are dense with utilities, equipment and operations facilities associated with the existing tunnel, which is in continuous use.
The Challenge
During previous phases, installation of sheet piling for tunneling activities and other driven elements induced consolidation of the loose sandy fill on the islands. This was causing settlement of duct banks, pavements and other structures, which were remedied by CJGeo using polyurethane compaction grouting.
In this case, sheet piles had to be driven immediately adjacent to the roadway. This is in order to excavate the receiving pit for the tunnel boring machine. The construction team was concerned about inducing settlement of the adjacent roadway. They reached out to CJGeo about performing compaction grouting under the footing for the original tunnel’s portal wall. This was after the wall had been demolished down to grade.
The Solution
CJGeo performed compaction grouting utilizing an NSF-certified potable water contact plural component CJGrout 35NHV polyurethane grout. Cutoff criteria was 0.10 inches of movement of the foundation or adjacent roadway. Upon completion of the compaction grouting by CJGeo, sheet piling installation started. There was only nominal movement of the foundation and roadway.
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8″ Pipe Abandonment
The Job
This 8″ pipe abandonment project is located outside of Washington, DC. As part of continuing waterline replacements, a utility contractor in Fort Washington, Maryland, needed to abandon 10,600LF of 8″ water main. The utility and DOT both require grouting of all utilities 6″ and larger taken out of service.
The Challenge
In order to minimize the number of placement points, the grout needed to be exceptionally mobile.
The Solution
CJGeo proposed a 30lb/cuft CJFill-Ultra Lightweight (CJFill-UL) cellular grout, and worked with the client to design a grouting plan that would allow grouting all 10,600LF of pipe from just three access points. CJGeo performed the grouting over a period of two days, with no additional excavation required from the customer other than their original tie ins/disconnects.
By cutting the pipe at three locations, it was split into roughly equal segments. Each of around two thousand six hundred feet. 30lb/cuft CJFill-Ultra Lightweight is easily pumpable this distance without yield loss.
To do this same work with flowable fill would have required approximately thirty five access points. This would be to split the pipe into roughly thirty six segments around three hundred feet, each. Even then, pumping flowable fill three hundred feet through eight inch pipe is very difficult. By using CJFill-Ultra Lightweight for this pipe abandonment project, the general contractor saved about two weeks off of their schedule, and tens of thousands of dollars.
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Facing a similar challenge to this 8″ pipe abandonment project that CJGeo performed using cellular grout? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.
Union County Annular Space Grouting
The Job
This Union County annular space grouting project is located in North Carolina, near Charlotte. Due to a rapidly increasing population, Union County, North Carolina installed a new raw water intake. It required a nearly 11 mile long raw water line to supply a water treatment plant.
The Challenge
There are dozens of road crossings along the alignment. 17 crossings are jack & bore, and require annular space grouting per NCDOT requirements. Given the length of the project, there weren’t any ready mix providers who could cover this entire annular space grouting in North Carolina project.
The Solution
CJGeo has multiple NCDOT approved mix designs, for CJFill-UL. CJGeo sourced material from two different ready mix providers. Each annular space on all crossings was grouted per NCDOT requirements. CJGeo has approved mix designs with the North Carolina Department of Transportation that cover the entire state. From the Outer Banks to Asheville, Raleigh/Durham, Wilmington & Charlotte, CJGeo has you covered.
The density for this work was 30lb/cuft CJFill-Ultra Lightweight. 30lb/cuft CJFill-Ultra Lightweight breaks above NCDOT’s minimum 125psi at 28 day unconfined compressive strength requirement for annular space grout. Because the project volume on this job is relatively low per crossing, CJGeo used ready mix for the raw slurry. Ready mix typically isn’t best for large placements. But for small, spread out placements like this project, is a great fit.
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24″ Water Main Abandonment
The Job
This 24″ water main abandonment project is located in Fairfax, Virginia. Fairfax County is part of the rapidly expanding Northern Virginia region. As part of a large transportation project, 2000 linear feet of 24″ water main were being relocated out of a highway right-of-way.
The Challenge
Due to phasing, the old water main was located under the existing roadway and could not be accessed, except for at one point near the center of the run. So, the abandonment grout had to meet VDOT’s minimum strength requirements for flowable fill, and be pumpable up to 1100LF at low pressure. VDOT’s minimum 28 day unconfined compressive strength requirement is 30psi.
The Solution
CJGeo grouted each run of pipe using 30lb/cuft CJFill-Ultra Lightweight low density controlled low strength material. Each CJFill-UL placement took fewer than two hours, and required no additional traffic control, disruptions to other construction activities, or help from the utility contractor after they installed the bulkheads.
The 28 day compressive strength of 30lb/cuft CJFill-Ultra Lightweight cellular grout is 150psi. This significantly exceeds VDOT’s minimum compressive strength for controlled low strength material (flowable fill).
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Facing a similar challenge to this 24″ water main abandonment project that CJGeo completed using CJFill-Ultra Lightweight cellular concrete? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.
