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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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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Facing a similar challenge to this Ohio polyurethane 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.
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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North Carolina Annular Grouting
The Job
This North Carolina annular grouting project is located in Havelock, North Carolina. Havelock is home to Marine Corps Air Station Cherry Point. US 70 passes through Havelock, providing a critical link between New Bern and the coastal beaches of North Carolina.
The Challenge
As part of North Carolina DOT work to upgrade the capacity and increase safety of US 70, a number of wet utilities were upgraded and relocated. This required a number of jack and bore crossings of the existing roadway to avoid disrupting traffic. NCDOT requires annular grouting for jack and bore crossings of wet utilities, for anything with less than a 100 year design life.
The Solution
This project had two crossings needing annular space grouting. One was 120 linear feet of 42″ steel casing with an 18″ ductile iron pipe water line. The second was 86 linear feet of 42″ steel casing with an 18″ ductile iron water line.
A CJGeo cellular grouting crew successfully filled each of the two casings with CJFill-Ultra Lightweight cellular concrete in a few hours in a single day. Carrier pipe buoyancy was not a concern due the low density of the grout.
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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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Electric Bore Annular Space Grouting
The Job
This electric bore annular space grouting project is located in Norfolk, Virginia. As part of significant work at the Port of Virginia’s Norfolk International Terminal, an electrical contractor installed seven jack & bore crossings of various roadways and railroad lines within the port.
The Challenge
There are seven bores, ranging from 85 feet to 362 feet. Each bore is 36″ steel casing, with eight, eight inch conduits. Most conduits are for electrical lines, some are reserve, and some are for communication and data.
The designer’s specification call for annular grouting of all the conduits, with a minimum 1000psi grout. There was no thermal conductivity requirement.
The Solution
CJGeo proposed a 60lb/cuft CJFill-Standard cellular grout in order to meet the 1000psi requirement. Buoyancy control was achieved through water filling of the conduits, along with a conduit & casing spacer design which presumed some buoyancy.
The customer filled each of the conduits with water prior to grouting. Due to the relatively low volume of grout per bore (ranging between 16 & 57 cubic yards), CJGeo used a local ready mix supplier for paste, and the wet batch generation method. CJGeo successfully performed the electric bore annular space grouting work over two days.
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Tunnel Adit Fill
The Job
This tunnel adit fill project is part of the Purple Line project outside of Washington, DC. Specifically, the adit is located at the pedestrian connection between the Purple Line project and WMATA’s Bethesda station on the Red Line.
The Challenge
Plans call to connect the Purple Line to the Red Line using an adit constructed during the original construction of the Red Line. The adit is approximately 30 feet wide by a 35 foot tall arch. During preparation to blast from a shaft dropped adjacent to the station, a fault was identified passing through the adit.
The construction and design teams were concerned about stability of the adit during blasting operations as the Purple Line access tunnel was excavated towards it. The team determined that filling the adit to plug and stabilize it during blasting would be the most risk appropriate move.
Filling the adit would fulfill the design challenge of stabilizing the rock during blasting. However, it created the following challenges:
- the tunnel adit fill material would need to be removed after blasting was completed
- the adit is approximately 100 feet below grade
- there is very limited space up top
- material couldn’t segregate, and had to be pumped approximately 250 feet in addition to the 100 foot drop
The Solution
The tunnel engineer of record recommended CJGeo to the contractor. The EOR is familiar with CJGeo’s cellular concrete generation and placement expertise, and thought that cellular concrete would be the lowest risk way to fill the adit, while facilitating excavation and removal afterwards.
CJGeo took five days onsite to fill the adit, in lifts up to eight vertical feet. Due to the potential dead load from the rock cover, 400psi CJFill-Standard was the material of choice. By using our colloidal mixing dry batch process, the material set off quickly, ensuring that it would not consolidate during cure as lower energy mixing methods can suffer from.
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Facing a similar challenge to this tunnel adit fill 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.
Maryland Concrete Lifting
The Job
This Maryland concrete lifting project is located in Frederick, Maryland. The project is for the MARC system, on tracks also used by CSX.
The Challenge
MARC’s Brunswick Line includes a spur to Frederick, which utilizes a freight track that also serves multiple industrial sites, including quarries and concrete plants. As it winds through an industrial area towards the Frederick station, the line crosses multiple arterial roadways. As Frederick grows, traffic is increasing significantly with both cars and industrial truck traffic.
At two crossings, bellies have developed in the precast modular grade crossings. Water collects at the low spots, which then reduces bearing capacity of the base, causing deterioration of the adjacent asphalt pavement. This deterioration causes spalling of the panels, and ride quality problems for motorists.
The Solution
CJGeo’s rail grouting experience includes dozens of precast modular grade crossing stabilization projects. Working with the rail system’s on-call MOW contractor, a CJGeo polyurethane grouting crew grouted each of the two crossings in a day, each.
CJGeo uses CJGrout 48NHL, which is specifically formulated for high dynamic load applications. 48NHL provides multiple factors of safety from a compressive strength perspective, but is slightly elastomeric, which makes it much more durable than mudjacking or traditional cementitious pressure grouting grouts sometimes used to stabilize modular grade crossings on a temporary basis.
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Facing a similar challenge to this Maryland concrete 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.
