HDPE Pipe Joint Sealing
THE JOB
A large sinkhole opened up in the parking lot of a manufacturing facility. The sinkhole was adjacent to a cast-in-place stormwater drop inlet structure. The structure was 14VF deep and was fed and discharged by 54″ HDPE pipes, requiring HDPE pipe joint sealing.
Facility maintenance personnel had been monitoring the sinkhole and noted that it was growing rapidly. Inspection of the pipe revealed that there were joint failures at the first joint out from the manhole and deterioration of the parging. The parging between the HDPE and concrete pipe had failed to the point of significant amounts of soil washing out during rain events.
THE CHALLENGE
The repair could not disrupt traffic in the parking lot or other facility operations. It also had to provide a long-term solution to the failed pipe joints.
Along with gently filling the voids around the HDPE pipe without deflecting or damaging it, the repair material had to have enough expansive force to thoroughly seal the small cracks and leaks in the parging between the HDPE pipe and concrete structural walls.
THE SOLUTION
Chemical grouting using both prepolymer chemical grouting and plural component polyurethane grouting.
Chemical grouting was chosen for injection through the joints of the HDPE pipe. Prepolymer chemical grouting uses single component polyurethane grouts with exceptionally long gel times. This virtually eliminates localized expansive pressure, which could further damage the HDPE pipe, which was already out of round.
The plural component structural foam was used for void filling the large sinkhole that extended from the bottom of the structure to the surface.
Prepolymer chemical grout was injected through the joints in the HDPE pipe. This successfully sealed the bell and spigot joints without causing further deflection of the pipes.
The large sinkhole void was grouting using plural component polyurethane grouting. Due to void size, CJGrout 20SDB is the best material due to its low exotherm. Structural foams are important in situations where there are very large voids in areas subject to traffic loading.
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Dam Outfall Pipe Seep Grouting
THE JOB
This dam outfall pipe seep grouting is located in Fairfax, Virginia at Northern Virginia Community College. A 36″ RCP outfall pipe for a dam terminated at an end wall. As part of a dam rehabilitation, small seeping leaks at the end wall/pipe joint needed to be stopped. The leaks had to be stopped so the wall could be resurfaced.
The engineer specified chemical grouting.
THE CHALLENGE
Access to the area was quite difficult. It was more than 150 feet from the closest vehicle access, which was only accessible by 4×4 vehicles down a steep slope.
While unknown during the planning of the chemical grouting repair, what was thought to be 36″ RCP was actually a larger diameter RCP that had been lined with steel casing pipe. An interior poured-in-place concrete liner had been installed afterward.
THE SOLUTION
Super low viscosity prepolymer chemical grout was selected. This was for two reasons: 1) the ability to easily pump more than 150LF from the lay-down area. 2) the ability to seek out and stop leaks through very tight cracks in the structures.
Prepolymer chemical grouts are water-reactive, so can be injected into active water flows. The grout expands when it comes into contact with the water, which seals the leak.
The initial grouting plan was to install the chemical grout through the pipe wall starting beyond the first joint. However, because the pipe had been cased, placement had to be done through the end-wall structure only. Multiple injection holes were drilled through the end wall structure, and the chemical grout was pumped through the end-wall structure.
Extensive catalyzation was used to first seal the leaks at the end wall and then chase the water flow pathways up along the outside of the pipe. The job was messy due to the forced proximity of the injection points and the leaks. But all the leaks were successfully stopped.
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Stormwater Pipe Repair
The Job
This stormwater pipe repair project is located at a chemical manufacturing plant in Petersburg, Virginia. The facility manager discovered a large sinkhole adjacent to a secondary containment structure holding a 10,000 gallon tank. The sinkhole appeared to extend far under the footprint of the containment structure. The structure is approximately 20 feet by 40 feet.
The Challenge
The containment structure, which was cast-in-place concrete, was coated with a coating designed specifically for the chemical makeup of the tank’s contents. Therefore, drilling holes through the floor of the structure to fill voids below it wasn’t possible.
The Solution
CJGeo proposed polyurethane grouting to seal joints. A CJGeo crew spent one day onsite installing CJGrout 35NHV61 to seal the joints and fill the sinkholes. The grouting process reestablished uniform support to the structure.
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SSP Tunnel Reline Back Grouting
THE JOB
This tunnel reline back grouting project is located in Somerset, Pennsylvania. The roof of rails to trails tunnel started to collapse. In the worst area, a 150 cubic yard cavity opened up at the tunnel crown. Previous rock bolting slowed but did not stop the collapse. Due to the unsafe conditions, the tunnel was closed. Trail users had to use a 1.5-mile bypass to go around the tunnel.
GeoBuild & Gannett Fleming teamed up for the design-build repair of the tunnel. After choosing a structural steel plate lining system for the repair, they turned to CJGeo to provide a back grouting solution. The tunnel is approximately 850 feet long, and 30′ in diameter, with an annular volume of approximately 2300 cubic yards.
Tunnel History
The original tunnel is bare rock surfaces. Over time, various lining materials were placed, starting with timbers. Sometime after the timber lining installation, the concrete lining was installed. The concrete lining was up to 2′ thick in places. A contributing factor to the deterioration of the concrete liner was water accumulating in the timber lining, freezing, and expanding behind the concrete lining.
The daylighting of an adjacent live railroad tunnel also posed challenges for the safety of the pedestrian tunnel. The haul road for disposal of the daylighting spoils passed over the top of the pedestrian tunnel.
The biggest limit on this tunnel reline back grouting job was access. The tunnel was located 2 miles from the nearest paved road, down a single-lane bike path. Once at the site, a 20-ton weight limit bridge stood between the staging area and tunnel. This effectively ruled out using low slump grout as the grouting material. Low slump grout is the typical grout recommendation from the SSP liner manufacturer, Armtec. Minimizing cost was also important; the customer was a non-profit trail maintenance organization.
Cellular concrete was also considered as an option for this tunnel reline back grouting application. Cellular concrete is up to 80% atmospheric air by volume. This would cut down by 80% the number of trucks needed to deliver grout to the site. However, cellular concrete is also exceptionally flowable. Given the tunnel size, there were nearly 20,000 linear feet of the joint which would have to be watertight in order to use cellular concrete. Another limit of cellular concrete on this project was the very high potential for fouling the drainage system.
The Challenge
While contemplating using polyurethane grouting to seal the joints in the SSP liner to facilitate cellular concrete grouting, we thought “why not grout the whole thing with polyurethane.” For this project, polyurethane grouting offered a number of key benefits:
- Logistics; the entire 2300 cubic yard annulus would only require three truck loads of material delivered to the site. This alleviated concerns about bridge capacity & truck traffic on the bike path.
- Speed; CJGeo’s in-house polyurethane grout placement capacity exceeds 100 cubic yards per hour.
- Fast cure; the selected polyurethane grout completed expansion & cured within three minutes. This alleviated concerns about leaks through the joints in the SSP. It also allowed for deep, successive lifts.
- Strength; the selected material had a bearing capacity of 3700PSF, despite only weighing 2PCF.
- Cost; while the raw material cost was higher for polyurethane grout than cellular concrete, the savings from speed, insensitivity to joint leaks & logistics made polyurethane grouting the economical choice.
The Solution
CJGeo placed 120,000 pounds of CJGrout 20SDB polyurethane grout in two weeks to complete the tunnel reline back grouting. In addition to the annulus, approximately 250 cubic yards were placed in the roof collapse cavities. Polyurethane grout was also used for bulkheading the ends of the annulus. CJGeo’s use of polyurethane grout was an unquestionable success.
Because the chosen polyurethane grout only weighs 2 pounds per cubic foot, it wasn’t necessary to perfectly balance injection across sides. This facilitated continued traffic through the tunnel for other activities associated with the relining.
The infrared inspection was used to confirm complete fill during the tunnel reline back grouting, in conjunction with a visual inspection of joints & extrusion of polyurethane grout through vent holes.
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8 foot diameter CMP joint sealing
THE JOB
This CMP joint sealing project is located near Fredericksburg, Virginia. An 8′ diameter stormwater structure required CMP joint sealing in order to pass an exfiltration test by the municipality for acceptance. The filter assembly has sections of 8′ diameter corrugated metal pipe. Arranged in a rectangle with distribution and, six filter chambers, and a collection end.
In order to pass the water exfiltration test, 38 joints within the distribution and filter chambers had to be sealed.
THE CHALLENGE
Many of the pipe ends were snagged during installation. A compressed construction schedule also forced the connection of the filter to the stormwater drainage system prior to the CMP joint sealing. The structure charged multiple times before the joint sealing work. This introduced extensive amounts of silt and trash to the filter. CJGeo cleaned the structure prior to the application of the sprayed joint sealant.
THE SOLUTION
CJGeo cleaned and ventilated the structure in order to dry it. 24 hours of negative pressure ventilation thoroughly dried the structure, allowing for proper surface preparation of the filter structure. After drying and surface preparation, all 38 joints in the 8′ diameter CMP were sealed using a polyurethane-polyurea hybrid foam.
Sprayed application of polyurethane-polyurea hybrid allows for conforming the joint sealant to joints that are too misaligned or deformed to seal using traditional neoprene gasketed bands clamps. Slightly misaligned joints are very common in culvert construction; our CMP repair processes are inherently adaptive for sealing misaligned joints.
The CJGrout 60FDC uses a spray application process, with a combination of supplied air and negative pressure ventilation. CJGeo self-performed confined space permitting, entry, and monitoring for this CMP joint sealing project.
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Box Culvert Abandonment
THE JOB
This box culvert abandonment project is located in Alexandria, Virginia. The existing single barrel box culvert had insufficient hydraulic capacity, and the discharge end was causing erosion adjacent to occupied structures. The contractor was building a new double barrel structure adjacent to the original one. After the new structure was in place, the 350 foot long original structure had to be filled. Access to the box culvert was only available from one end, and there were multiple sources of active water infiltration into the box culvert.
THE CHALLENGE
VDOT standards specify a minimum compressive strength of 50psi for pipe & culvert abandonments. The proposed mix design needed to meet or exceed 50psi.
The customer wanted lump sum pricing. Therefore, all sources of infiltration (potential leaks during grouting) had to be completely sealed prior to abandonment material placement.
The laydown area was about 100 feet from the opening.
Solution:
25PCF wet cast density CJFill-Ultra Lightweight mix met the minimum compressive strength requirement and constructibility challenges.
Pumping 100 feet to reach the placement location, and then up to an additional 350 feet to the far end of the culvert wasn’t a problem.
Prior to abandonment grouting, CJGeo polyurethane grouting crews used CJGrout geotechnical polyurethane to:
- plug out of service tie-ins
- seal penetrations for a 48″ HDPE pipe crossing through the existing box
- grout various leaks at joints & cracks
THE SOLUTION
CJGeo successfully performed the box culvert abandonment using CJFill-UL. CJGeo self-performed all polyurethane grouting for making the structure watertight placed all sacrificial placement pipes and generated and placed the cellular concrete to complete the box culvert abandonment.
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Box Culvert Leak Sealing
THE JOB
A new double box culvert was constructed. The original single box culvert needed to be abandoned in place. Access to the box culvert was only available from one end. Box culvert leak sealing was required because there were multiple sources of active water infiltration into the structure, and old tie-ins that hadn’t been completely plugged.
THE CHALLENGE
To contain the grout within the box culvert, it had to be watertight before being abandoned. More than 10 water infiltration/potential cellular concrete exfiltration locations were identified. Additionally, to avoid inducing settlement, the abandonment grout was only 25lb/cuft. Because it could float, there couldn’t be any water in the box culvert during the abandonment grouting work.
CJGeo selected plural component polyurethane grouting for sealing all potential cellular concrete exfiltrations. Sites included RCP pipes terminating in stone beds, a 48″ HDPE culvert extension punched through the walls of the box culvert, and multiple holes in the ceiling covered with steel plates.
Some of the infiltration points were actively leaking water, so the selected material had to set in, and stop active water flows.
THE SOLUTION
A CJGeo polyurethane grouting crew performed the box culvert leak sealing repairs using CJGrout 35NHV. 35NHV is a normal reaction speed, hydro-insensitive geotechnical polyurethane specifically formulated for void filling applications and water intrusion repair. The cost of sealing the leaks in the culvert to make it watertight was significantly less than the potential losses due to leaks during grouting.
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25VF stormwater manhole sealing
THE JOB
Leaks throughout the joints on a 25VF, 48″ precast stormwater manhole were leaking. This caused a large sinkhole to open up at the surface, adjacent to the structure, requiring manhole sealing. Homeowners on either side of the easement were concerned about the stability of the area and reached out to the municipality. The estimated cost for excavating the structure to repair it from the outside exceeded $50,000.
THE CHALLENGE
Due to the depth of the manhole, a confined space entry had to be used. Additionally, the grout had to tolerate high moisture levels in the adjacent soil, and economically fill the extensive voids. Due to the presumed large size of voids, the grout had to also below heat.
High-density geotechnical polyurethane grouting fills the sinkholes adjacent to the structure and seals all points of infiltration.
THE SOLUTION
CJGeo polyurethane grouting crew sealed all of the infiltration points and filled the sinkholes in a single day. No excavation was required. The cost of the manhole sealing was less than 20% of that of open excavation.
The CJGeo crew used CJGrout 35NHV, which is specifically formulated for use around buried structures. It has a moderate reaction speed to helps reduce the number of injection holes. It’s hydroinsensitive, meaning even when injected directly into standing water, it reacts the same as in a dry environment. Hyrdoinsensitivity is important for water intrusion repair applications.
After drilling 5/8″ holes through the structure’s walls, 35NHV is injected through mechanical packers. There were two cutoff criteria for this project:
- 35NHV geotechnical polyurethane extruding through the full circumference of each joint in the precast structure
- grout coming to the surface from the bottom of the sinkholes
CJGrout 35NHV sets within two minutes, and reaches 95% cure within 15 minutes.
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HDPE reline annular space grouting
THE JOB
A utility contractor installing 500LF of 48″ HDPE reline pipe through a 63″ CMP culvert required annular space grouting done at very low installation pressure yet able to ensure complete filling of the washouts outside of the CMP. This HDPE reline annular space grouting project is located in Baltimore, Maryland.
THE CHALLENGE
Due to traffic control limitations, only one end of the pipe was accessible for grouting. Therefore, all grout installation was done with up to 200LF of pumping to get to the bulkhead and then up to 500 feet of travel through the annulus via sacrificial grout tubes. Bulkhead leaks usually result from extensive voids outside of the host pipe. This pipe’s invert corrosion posed unique challenges for containing the annular space grout. CJGeo proposed cellular concrete for the annular space grouting. Cellular concrete is highly flowable. High flowability ensures low installation pressure, reduces flotation of lightweight carrier pipes, and ensures complete void filling outside of the host pipe. Using cellular concrete for annular space grouting was specified by the HDPE slip lining pipe manufacturer.
THE SOLUTION
CJGeo successfully performed this HDPE reline annular space grouting project over two days, in two lifts. Multiple lifts reduce the heat of hydration and carrier buoyancy. The cellular concrete-filled all of the voids outside of the host pipe. The peak pressure at the pump did not exceed 15PSI throughout the project. Therefore, the project was successfully completed without floating, deflecting, or damaging the HDPE slip line pipe.
CJGeo placed 30PCF wet cast density CJFill-Ultra Lightweight, with a 125psi compressive strength for this project. With a 24 hour penetration exceeding 50psi, 30PCF cellular concrete reduces buoyancy with its low unit weight, provides adequate strength, and rapid stability.
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North Jersey Annular Space Grouting
THE JOB
This North Jersey annular space grouting project is located in Paterson, New Jersey. A 30″ brick sewer in New Jersey started to unravel during an open excavation point repair. The municipal engineer directed the utility contractor to use welded HDPE pipe to reline the sewer instead of finishing the open cut point repair.
THE CHALLENGE
The HDPE slip lining contractor had four requirements for grouting:
- No more than 10psi grouting pressure, as measured at the bulkheads
- A mix which minimized carrier buoyancy
- Three day turnaround from notification to completion
- 200psi strength at 28 days
THE SOLUTION
CJGeo proposed 38PCF wet cast density cellular concrete for the annular space grouting. Cellular concrete is highly flowable. High flowability ensures low installation pressure. 38PCF cellular concrete reduces exerts 60% less buoyancy force compared to traditional weight grout. 38PCF cellular concrete reaches approximately 250psi at 28 days, when generated through the ready mix supply chain.
CJGeo mobilized to the site with two days’ notice. The CJGeo cellular concrete crew used continuous generation to generate and place the 38PCF cellular concrete to complete this North Jersey annular space grouting project. Peak pressure at the bulkheads never exceeded 5psi. All 500LF of the annulus was grouted in a single day, between four different manholes (three sections).
Confirmation of fill was uniform material venting at each bulkhead.
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