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 say.
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 in the past, 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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RCP Joint Sealing
The Job
This RCP joint sealing project is located near Charlottesville, Virginia. The polyurethane grouting work was subcontracted to CJGeo as part of an on call contract for stormwater structure and dam maintenance with a municipality.
The Challenge
Pavement distress of an asphalt roadway over a small dam prompted an inspection of the triple barrel 48 inch RCP structure passing through the dam. Upon inspection, significantly less water was flowing through the pipes than was flowing through the downstream spillway.
On each of the three pipes, water was flowing out of the endwall around the RCP inverts. There was relatively little cover on the pipes. This would make open cut replacement relatively simple. However, the roadway is the primary access to a neighborhood. Thus, a trenchless grouting repair to address the joint failures and piping was optimal.
The Solution
CJGeo worked with the on-call contractor, and owner’s dam engineering consultant to design a grouting program that not only addressed the piping and joint leaks, but also the voids in the fill material between the pipes and roadway.
Over the course of two days onsite, a CJGeo polyurethane grouting crew grouted each of the three pipes using CJGrout 35NHV61 geotechnical polyurethane. 35NHV61 is provides adequate bearing capacity for typical roadway loading, performs identically in flowing water and dry environments, and is certified for potable water contact.
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Michigan Polyurethane Grouting
The Job
This Michigan polyurethane grouting project is located near Saginaw, Michigan. The work was done to stabilize the settling basement floor of a sugar beet processing facility.
The Challenge
This facility is nearly 100 years old, and has been settling for as long as anyone currently working there can remember. Over time, as the facility has been expanded, various things have been done to address the settlement. All of the repairs have been to accommodate the settlement, such as adding beams below floors, mass reinforced concrete of footings, etc, but nothing done with the problematic soils below the facility.
Due to nature of sugar manufacturing, process liquids with high sugar content discharging onto the floor is relatively common. Some of this sugary water inevitably flows through joints in the floor, saturating the subgrade with sugary water.
Sugar kills the curing of cement-based grouts, so traditionally cementitious grouting was not an option here. Cementitious grouting is also incredibly difficult to perform as food-grade clean process.
The facility and their consulting structural and geotechnical engineers reached out to CJGeo to see if polyurethane grouting was a good option to address the approximately 10′ of soils below the floor with inadequate bearing capacity.
The Solution
CJGeo’s operations and engineering team evaluated the geotechnical and structural information and determined that a polyurethane and chemical grouting program would be appropriate.
The plan to address the underlying soils and water exfiltration from the basement involved two primary grouting programs. First, compaction grouting using a potable water certified plural component geotechnical polyurethane grout, CJGrout 35NHV61.
The next step of this Michigan polyurethane grouting project was to underseal the floor with single component chemical grout. The goal here was to effectively coat the bottom side of the slab to reduce the ability of process water to exfiltrate the basement and resaturate the underlying soils.
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Bridge Approach Grouting
The Job
This bridge approach grouting project is located near Lexington, Virginia. It is on Interstate 81, which has some of the highest truck traffic in Virginia. The Virginia Department of Transportation maintains this section of Interstate 81.
The Challenge
Settlement over time caused voids under three lanes of approach slab at an overpass structure. During precipitation events, the voids became saturated, and then act as diaphragm pumps. The high dynamic loads from the heavy truck traffic effectively pump the fines out of the saturated base materail.
Over time, this resulted in extensive deterioration of the adjacent asphalt pavement, along with distress of the concrete approach slabs.
The Solution
Working with the local bridge maintenance group and their on-call maintenance contractor, CJGeo proposed a polyurethane bridge approach grouting program to restore stability to the slabs. Previous repair attempts had used flowable fill to attempt to fill the voids below the pavement. This generally doesn’t work very well, and proved to not be suitable in this case, either.
Primarily constrained by maintenance of traffic concerns, CJGeo undersealed all three lanes of the approach over two nights. Grouting was done using CJGrout 40NHL, which is optimized for heavy loads, wet environments, and is capable of lifting settled pavements.
Because 40NHL cures to 95% within a few minutes, by the time the injection holes are patched, treated slabs and soils are ready for traffic as usual.
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Virginia Polyurethane Grouting
The Job
This Virginia polyurethane grouting project is located in Blacksburg, Virginia, at Virginia Tech. The work was done to support continued occupancy of the structure, after voids as deep as two feet were located below the floor slab.
The Challenge
A small area of the ground floor slab on grade settled, primarily adjacent to the basement, which is only under about 20% of the building footprint. The basement contains mechanical equipment, and ties to a large crawlspace used as a ventilation duct.
Upon initial discovery, the university’s on-call geotechnical and building envelope consultant performed exploratory drilling to determine the extent of voids. Several auger bores for exploration of the backfill material identified poor control during installation as the most probable cause of settlement.
The Solution
CJGeo was the most responsive bidder on the owner’s solicitation, which called for filling the voids below the floor with CJGrout 20SDB geotechnical polyurethane. 20SDB is specifically formulated for maximum expansion, high mobility, and very low exotherm.
One particular challenge was the amount of glass gravity drain piping below the floor. Because much of the building is lab space, when it was built, the most chemical-tolerant pipe available was glass. So, it was very important that the polyurethane grouting work not damage the relatively fragile pipes.
CJGeo timed its work around spring break to avoid any disruption to classes, research, and offices. The work took six days onsite, and a total of just under 10,000 pounds of CJGrout 20SDB.
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Outfall Leak Grouting
The Job
This outfall leak grouting project is located near Emporia, Virginia. The work is located at two different stormwater ponds at an industrial scale solar facility. The facility is owned by Dominion Energy.
The Challenge
This facility has a mix of both dry and wet ponds. At two wet ponds, leaks developed along the outfall pipes, which prevented them from holding water long term. During a precipitation event, water would build up, but then afterwards, slowly drain out by piping alongside the outfall pipes. In order to turn over the facility to the owner, the contractor needed to address the leaks to ensure the ponds functioned as designed.
The Solution
Due to the small diameter of the pipes, they weren’t accessible from the inside. CJGeo proposed grouting along the pipe alignments using single component expanding chemical grout. The pipes are reinforced concrete.
To facilitate this, CJGeo drove sacrificial injection tubes along both sides of each of the two pipes. No grout returned to the inside of the pipes, which confirms that the root cause of the problem was poor control of the backfill, as opposed to problems with the pipe joints. When bedding isn’t properly installed, and backfill properly compacted, water can flow outside of stormwater pipes, which is what was happening here.
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Facing a similar challenge to this outfall leak grouting project? 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.
SOE Leak Grouting
The Job
This SOE leak grouting project is located in Alexandria, Virginia. It is part of the RiverRenew project, which is a large CSO tunnel and drop shaft project. This location is immediately adjacent to the Woodrow Wilson Bridge, and the Potomac River.
The Challenge
At a drop shaft location, the contract installed two parallel slurry walls between an existing combined sewer box culvert and a drop shaft to the new tunnel. During excavation of the pit, two high volume leaks, each around 125GPM opened up below the existing conduit.
The customer installed road plates to stabilize the area, and pumped flowable fill behind the road plates. This provided short term stability to the area, but did not address the high velocity flow of water through an unanticipated open graded sand seam that was causing the leaks.
The Solution
CJGeo mobilized a grouting crew capable of performing both high volume geotechnical polyurethane grouting and acrylic permeation grouting at the same time for this SOE leak grouting work. The first step was to install CJGrout 35NHV61 to fill voids which had washed out immediately behind the road plates.
After grouting the bulk voids and slowing the velocity of the leaks, CJGeo installed acrylic grout up to 20 feet behind the slurry wall face. The only way to reliably stop water flow through sands is to bind them together with a very low viscosity grout. The acrylic grout installed on this project has a viscosity less than 10 centipoise. This allows it to uniformly permeate the sands, react into a cooked egg white consistency, and make the treated sands impermeable.
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Facing a similar challenge to this SOE leak grouting project? 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.
Apartment Floor Lifting
The Job
This apartment floor lifting project is on a military facility in Washington, DC. During turnover of a unit, the property management company discovered signs of significant settlement affecting the interior floor. There was a significant crack showing through vinyl flooring, and up to 1.5 inch gaps below the baseboard in a carpeted room.
The Challenge
The primary challenge for the general contractor on this project was repairing the floor as quickly as possible. The unit was only going to be unoccupied for about two weeks between tenants. The contractor not only had to repaint, install all new floors, but also had to address this settlement.
The Solution
The general contractor reached out to CJGeo to assess the feasibility of raising the floor using polyurethane grouting. Having worked together in the past, the general contractor knew that CJGeo’s polyurethane grouting process is significantly faster than traditional mud jacking or concrete replacement.
A single CJGeo polyurethane grouting crew took less than a day to complete this apartment floor lifting repair. The total area grouted was around 750 square feet. Using CJGrout 28FDL, the grouting process corrected all of the settlement. Because polyurethane grouts are about 95% lighter than traditional grout and backfill materials, the likelihood of the grout material inducing future settlement is virtually eliminated.
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Facing a similar challenge to this apartment floor lifting project? 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.
