Lightweight Fill Over Waterline
The Job
This lightweight fill over waterline project is located north of Baltimore, Maryland, in Edgewood. It is part of a modernization and widening of I-95. This includes replacement of multiple bridges crossing I-95, including Clayton Road. Clayton Road is a rural, two lane roadway. However, I-95 in this area is a very heavily traveled, critical piece of the east coast megalopolis infrastructure.
About half of the City of Baltimore’s raw water supply parallels I-95 in this area. It runs through a 108″ PCCP raw water main that originates at the Susquehanna River, a few miles north of the project site.
The Challenge
As part of replacing the Clayton Road bridge over I-95, the bridge clearance was increased. To facilitate this, the approach/departure embankments had to come up a few feet. On the west end, this was not a problem; there are no underlying utilities or compressible soils.
On the east end of the bridge, however, the 108″ PCCP raw water main passes under the roadway embankment, in an area where grades needed to come up by an average of three feet. The pipe cannot see any additional load.
The Solution
Two potential solutions for this challenge are using lightweight fill to balance loads, or install a pile-supported load transfer slab bridging over the pipe. Lightweight fill was the fastest and most economical option.
CJGeo mobilized a single dry batch plant to the site. Over the course of six days onsite CJGeo poured 2,000 cubic yards of CJFill-Ultra Lightweight load reducing fill. The fill mass is roughly 10 feet thick at the deepest. At 25lb/cuft, this balances the loads within the zone of influence of the pipe. The pipe sees no increase in loads despite up to 4 feet of additional elevation over it.
Due to CJGeo’s exclusive use of high shear mixing, the contractor was able to place aggregate base on top of the CJFill-UL the following day.
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Slurry Wall Gap Closure Grouting
The Job
This slurry wall gap closure grouting work is part of CJGeo’s continuing permeation and water control work at the RiverRenew project in Alexandria, Virginia. At an outfall structure that will pull wet weather flow from an existing CSO, which is a roughly 8’x8′ box culvert. It is currently suspended from a large beam and webbing. The beam spans a roughly 40′ wide excavation between two parallel slurry walls. The slurry wall gap is approximately 20 feet wide.
The Challenge
Excavation at this location has continued to uncover seams of highly permeable sand and gravel. The material is quickly recharging due to close proximity to the Potomac River. It also recharges with ground water flowing through the bedding stone below the box culvert from the uphill catchment area.
The Solution
Due to ground-level obstructions, drilling from the surface into the grouting zone isn’t possible. CJGeo designed a percussion-driven sacrificial tubing plan to install the grout. No sonic drilling needed.
The grout curtain is approximately two feet thick. It is fourteen feet deep. It is located about two feet behind the desired face of excavation.
All of the work was done from a mud mat installed by the contractor. Evaluated grouts included:
- colloidal silica grout, which would perform well from a permeation perspective, but likely be susceptible to washout. Colloidal silica would also potentially not perform well during lagging installation due to the friable nature of treated soils, and high groundwater head
- acrylic grout, which has performed very well onsite in previous work.
CJGeo mobilized to the site and completed the permeation grouting over a period of a few daytime shifts. This allowed the contractor to resume excavation within the structure.
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Fort Lauderdale Permeation Grouting
The Job
This Fort Lauderdale permeation grouting project is located next to Port Everglades. Port Everglades is a crucial piece of Florida’s infrastructure, with annual economic impact exceeding $30 billion dollars per year. The tunnel, which is being mined with a 72″ MTBM, crosses under Eisenhower Boulevard from the George T Lohmeyer Wastewater Treatment Plant towards the Broward County Convention Center.
The tunnel is more than 20′ below grade, below the water table, in limestone with pockets of silty sand.
The Challenge
On this project, the microtunneling contractor had two tunnel crossings. On the first, they elected to not pre-grout their break in & break outs through the SOE. This resulted in a significant water and soil inflow event during the first break in. This crossing, under the entrance to the cruise port and between two other pieces of critical infrastructure, would not tolerate any surface disturbances associated with a flooding event.
The contractor reached out to CJGeo about stabilizing the launch & retrieval shafts to ensure stability during the launch & retrieval processes, by performing permeation grouting.
The Solution
CJGeo proposed permeation grouting of the limestone with an acrylic grout to ensure stability of the launch & retrieval shafts. Permeation grouting with acrylic grout ensures uniform permeation, and displacement of groundwater. It also ensures that the soils are sufficiently bound together to not fail while cutting the launch & retrieval holes in the sheet pile.
CJGeo installed the sacrificial tubing for this installation from the shaft. Occasionally, sonic drilling is useful for pre-grouting, but in this case, it was more economical and less disruptive to go through the shaft walls.
CJGeo performed the permeation grouting work in a single shift at each shaft.
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Collapsed CMP Abandonment
The Job
This collapsed CMP abandonment project is located at a paper mill near Richmond, Virginia. The pipe drains a relatively large area of the site under the primary road into the facility. Onsite personnel noticed that flow through the structure diminished significantly with time.
The Challenge
The first thought was that the pipe had just filled slowly with sediment. To address this, the mill hired a jetting contractor to clean the pipe. The jetting equipment ran into an obstruction inside the 36″ corrugated metal pipe. The obstruction turned out to be a nearly complete collapse.
The mill hired a consulting civil firm to design a replacement crossing, who then reached out to CJGeo for options to abandon the collapsed pipe.
The Solution
The first thought from the consultant was to sonic drill down to the pipe at three locations, drop and grout 2″ PVC pipes in, and install cellular grout through the pipes.
CJGeo thought this could work, but had concerns about the environmental risks. The pipe has quite a bit of fall, so the low end would see quite a bit of head, which increases the likelihood of leaks out of the embankment. These leaks can be hard to predict, and if they occur, very difficult to contain.
CJGeo recommended abandoning the CMP with CJGrout 22SHV geotechnical polyurethane as a lower risk, faster alternative. The consultant agreed with CJGeo’s recommendation to use polyurethane grouting to reduce costs and environmental risks.
CJGeo mobilized a geotechnical polyurethane grouting crew to the site. It took a few hours to fill the pipe. Despite being significantly lighter than the water & muck in the pipe, the CJGrout 22SHV still displaced all of this material because it expands and is only moderately mobile.
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TBM Intervention Permeation Grouting
The Job
This TBM intervention permeation grouting project is located in Virginia. It is part of a highway tunnel installation project to increase capacity on a bridge tunnel.
The Challenge
During mining, the TBM, which is more than 40′ in diameter, began to pull pieces of sheet pile & wire rope through the face. To prevent further damage to the machine, tunneling was stopped. The machine encountered the debris approximately 250 feet short of the exit structure, underneath a constructed island.
The island is built out of relatively loose beach sand that’s commonly available in the area. The crown of the machine is approximately 25′ below grade, with the invert of the machine being about 70 feet below grade. Mean high tide is also about 25′ below grade.
In order to facilitate a hyperbaric intervention, the contractor needed a solid plug in front of and around the machine face. The criteria for the plug included:
- easily excavatable, to prevent issues for the TBM upon resumption of mining, and also to ensure that divers doing the hyperbaric intervention wouldn’t have issues removing grouted material in the case of grout entry into the machine face.
- low viscosity, to ensure uniform permeation into the soils in front of the machine, though they were relatively course (only 1% fines)
- readily available, in order to meet the incredibly short schedule requirement
The Solution
CJGeo proposed permeation grouting to create the plug using acrylic grout. Acrylic grout is:
- readily available through the mining supply chain
- very low viscosity, so well suited for permeating sands
- forms a stiff gel that’s stable, but still easily hand-excavatable
To perform permeation grouting up to 75 feet below grade, CJGeo proposed sonic drilling to install Tube-a-Manchette (TAM) pipes.
Due to the compressed timeframe, CJGeo subcontracted a sonic driller to install 86 different TAM wells, ranging from 25 to 75 feet deep. Once the first 10 TAM tubes were in place, CJGeo started placing acrylic grout through up to 10 simultaneous TAM pipes, using straddle packers and a PLC-controlled grouting system.
CJGeo was onsite within 10 days of the first call. Then, over 23 calendar days, CJGeo successfully installed more than 105,000 gallons of acrylic grout, at rates of nearly 15 gallons per minute.
The grouting facilitated the hyperbaric intervention. Following the intervention, the contractor resumed mining.
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Hobas Pipe Backfilling
The Job
This Hobas pipe backfilling project is located in Baltimore, Maryland. It is one of the last steps in an emergency storm drain collapse project.
The Challenge
The original design for this project was to slip line a roughly 100 linear foot length of 108″ brick sewer that had collapsed. There was a massive void above the pipe, which was going to be filled with CJFill-Ultra Lightweight after the new pipe was slid in. However, the soil collapsed and the repair turned into an open cut repair.
The pipe is more than 100 years old, and was installed in a rock trench, the walls of which were uneven and unstable. Extensive rock bolting and stabilization was installed to facilitate the installation of the pipe. In order to ensure uniform bedding and stability of the new pipe, Hobas and the EOR recommended backfilling the pipe to at least 1′ above the crown with self-consolidating fill.
150lb/cuft flowable fill would have resulted in tremendous uplift forces on the pipe, unless installed in impracticably thin layers.
The Solution
CJGeo proposed cellular grout as an alternative, in order to reduce the uplift while decreasing the number of lifts.
Due to water infiltration near the invert, the first lift was done using 65lb/cuft CJFill-Under Water. Once the first lift was in place, the placement was switched to CJFill-Standard.
All material was generated onsite from bulk cement using CJGeo’s colloidal dry batch generation process.
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USACE Pipe Abandonment
The Job
This USACE pipe abandonment project is located in Muncie, Indiana. The project was part of a locally-administered stormwater improvement project. Because the pipes pass through a US Army Corps of Engineers levee, abandonment of the existing culverts had to be performed to USACE specifications.
The Challenge
New pipes and an endwall wall had been in place for a few months. All paving restoration was done, and the original pipe discharged through the new endwall. Specifications for USACE pipe abandonment call for cellular grout with a minimum of 300psi unconfined compressive strength at 28 days, 100psi penetration resistance at 24 hours, and minimum wet cast density of 45lb/cuft (CJFill-Standard).
The Solution
The contractor reached out to CJGeo due our expertise in cellular concrete placements with tight specs and discerning owners.
CJGeo mobilized a wet batch cellular grout crew to the site, and filled the two pipes in about an hour. Aerix Industries supplied the Aerlite-iX preformed foaming agent. Wet batch method was best due to the relatively low volume of the placement. Both runs of pipe are 36″ CMP. The first run is 73 feet, the second run 103 linear feet, for a total of 47 cubic yards.
CJGeo successfully filled the two runs of pipe. Confirmation of fill was venting of uniform grout out of the 6 & 12 o’clock ports on each end of both runs.
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Tunnel Shaft Sinkhole Grouting
The Job
This tunnel shaft sinkhole grouting project is located in Newport News, Virginia. It is located outside the gate for Pier 2 at Newport News Shipbuilding, home to the deactivated USS Enterprise (CVN-65). As part of water and sewer upgrades in the area, multiple shafts were excavated to facilitate guided pilot tube bores.
The Challenge
At a shaft in the middle of an intersection, the dewatering well driller was unable to maintain circulation. This resulted in incomplete dewatering points. During excavation of the ring beam and liner plate shaft, the floor blew out after excavating through a fat clay layer. The fat clay is underlain by a highly permeable flowing sand.
When the floor blew out, the shaft, which is roughly 30 feet diameter, settled up to a foot on one side, and the shaft flooded in a few minutes. Multiple large sinkholes opened up around the perimeter of the shaft.
The Solution
The utility contractor, who was sinking the shaft, reached out to CJGeo for a solution. The only way to salvage the situation was to adequately dewater the site, which was even less possible due to the extensive voids around the shaft.
CJGeo visited the site, and made a few recommendations. First was to grade the site to direct the surface water away from the structure. There were multiple blocks of surface stormwater flowing directly into the area around the shaft. Second was to perform polyurethane compaction grouting around the entire structure to fill voids under the pavement and around the liner plates.
CJGeo mobilized a geotechnical polyurethane grouting crew to the site the following day. Using CJGrout 35NHV61, the crew filled approximately 70 cubic yards of sinkholes. Grout uniformly migrated through the liner plates, indicating that voids were continuous around the perimeter, and across the full depth of the shaft.
After CJGeo completed the grouting work, the dewatering contractor was able to successfully drop four wells around the shaft. By dewatering the underlying flowing sands, the contractor was able to resume excavating the shaft.
A few weeks after stabilizing the shaft, the two tunnels were successfully completed from the shaft. A CJGeo cellular grouting crew then grouted the annular space on both tunnels.
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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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