Box Culvert Void Filling
The Job
This box culvert void filling project is located near Fredericksburg, Virginia. The Virginia Department of Transportation owns and maintains the structure, which conveys a stream under a rural divided highway. As part of a rehabilitation project, extensive cracking in the structure (a double barrel six foot by six foot box), was being patched with repair mortar, and some cracks epoxied.
The Challenge
At the start of project, the general contractor discovered extensive voids outside of the structure. These voids were allowing significant amounts of the stream flow outside of the box culvert (piping). This was cause for concert regarding the specified repair mortar application and epoxy injection.
The general contractor reached out to CJGeo about filling the voids with grout prior to the patching and repair operation.
The Solution
CJGeo proposed grouting all the voids outside of the box culvert with CJGrout 35NHV61. 35NHV61 is a hydro-insensitive, structural polyurethane grout. Its NSF61 potable water certification makes it excellent for work on drainage structures.
The owner, Virginia’s Department of Transportation, required water testing before, during and after grouting. This water testing specifically looks for MDI. All of the water testing, which was performed by a third party environmental laboratory, found zero MDI in any of the water samples.
It took three days onsite to complete the grouting. Some hairline cracks that were still damp after the bulk box culvert void filling work. CJGeo grouted these cracks with a hydrophilic chemical grout to make them completely dry.
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Stormwater Sinkhole Repair
The Job
This stormwater sinkhole repair project is located at a data center near Dulles, Virginia. Within a few months of construction, a depression started over a utility intersection within a street intersection inside the fence. Time showed that asphalt patching wasn’t going to solve the problem, so a geotechnical engineering firm was brought into investigate the sinkhole.
The Challenge
The first step taken was video inspection of all the gravity utilities in the area. None of them were showing any signs of leaks of water or soil. Utilities within the zone of influence of the sinkhole include:
- stormwater (deepest & largest)
- fire protection
- two fiber duct banks
- three electrical duct banks
Given the shear number and crossing alignments of utilities, and lack of leaks, the presumption was that backfill consolidation over the underlying stormwater structure was the most likely cause of the settlement.
The Solution
Due to the presumed cause of inadequate compaction, the geotechnical engineer recommended polyurethane compaction grouting to the owner. Compaction grouting with polyurethane grout is significantly faster, less disruptive, and less likely to displace adjacent structures than cementitious compaction grouting.
CJGeo proposed using CJGrout 20SDB for this stormwater sinkhole repair project. 20SDB is well suited for filling bulk voids, and has very little expansive pressure, so minimizes the chances of fouling or damaging the adjacent critical utilities.
A CJGeo polyurethane grouting crew was able to complete the repairs over two days onsite.
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Maryland compaction grouting
The Job
This Maryland compaction grouting project is located on East West Highway, in Chevy Chase. A few years after finishing construction of a new mixed use building with underground parking, the public sidewalks began to settle.
The Challenge
A local consulting geotechnical engineer was the first call by the building owner. After reviewing the construction drawings, and visiting the site, the geotech recommended performing a few hand augers. The hand augers were to:
- confirm the sidewalk construction matched the plans
- check for bulk voids below the sidewalk
- confirm the backfill material
- see just how loose the backfill material was.
The hand augers confirmed that the sidewalk was indeed pavers over asphalt, over a thin concrete mud slab. There were sporadic voids below the mud slab, up to six inches deep. The backfill material was poorly controlled soil, and was relatively loose.
The Solution
Due to the backfill material being relatively loose, and the building being new enough that the soils hadn’t consolidated on their own, the geotechnical engineer recommended polyurethane compaction grouting to the owner. Compaction grouting with polyurethane grout is significantly faster, less disruptive, and less likely to displace adjacent structures than cementitious compaction grouting.
CJGeo proposed using CJGrout 20SDB for this Maryland compaction grouting project. 20SDB is well suited for filling bulk voids, and has very little expansive pressure, so minimizes the chances of fouling or damaging drainage board.
A CJGeo polyurethane grouting crew was able to complete the repairs over two days onsite.
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SOE Closure Manchette Grouting
The Job
This SOE closure Manchette grouting project is located in Alexandria, Virginia. It is part of the RiverRenew project, a large CSO project.
The Challenge
As part of this project, a diversion structure and drop shaft were being installed to pull flow off of an existing sewer tunnel. The box tunnel is around 8′ wide. The SOE will facilitate installation of the diversion chamber. Excavation within the SOE called for closing the gap between slurry wall panels. This is to be done under the existing structure with steel lagging.
However, the closure is below ground water table. The “marsh” deposits soils require stabilization prior to excavation. The conceptual design from the owner called for permeation grouting tied into an underlying clay layer. The clay layer is approximately 50′ below existing grade.
The Solution
CJGeo proposed performing the permeation grouting to cut off ground water flow and stabilize the soils for excavation using an acrylic grout. Due to the relatively deep required depth, traditional percussion driven installation tubing wasn’t possible.
To ensure accurate placement at depth, CJGeo used the TAM grouting method. TAM grouting, or Tube-a-Manchette, uses special grout casing installed by drilling to grout through.
CJGeo performed this SOE closure Manchette grouting work over a period of two weeks.
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Massachusetts Lightweight Fill
The Job
This Massachusetts lightweight fill project is located at Boston’s Logan International Airport. It is part of Logan Forward continuing improvements to the airport.
The Challenge
As part of this project, the general contractor installed two cast-in-place barrier walls. The space between the barrier walls is between four and nine feet. The walls are curving, have non-vertical faces, and bear on a curving, non-horizontal existing podium slab. The gap between the walls needed to be filled in order to pour a housekeeping slab spanning between the walls.
This work is all on an existing podium structure. So, the fill density between the two walls had to be as low as possible.
The Solution
CJGeo proposed filling between the two walls with CJGrout 20SDB. 20SDB has a similar density and compressive strength to typical expanded polystyrene (EPS, or Geofoam) blocks. However, unlike geofoam blocks, 20SDB:
- is pumped, so doesn’t require trimming, and fits to any shape
- expanded onsite, so logistics are significantly simpler
- cures within a few minutes, so is still quick
- not affected by petroleum products
A CJGeo polyurethane grouting crew took a single shift onsite to install the 64 cubic yards of CJGrout 20SDB. The general contractor began installing the topping slab the next day.
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Detroit Michigan Annular Space Grouting
The Job
This Detroit Michigan annular space grouting project is located near Van Dyke Avenue & 8 Mile Road. The project owner is Great Lakes Water Authority, and the project is part of the PCI-4 rehabilitation.
The Challenge
As part of the rehabilitation of this large diameter sewer, three different liner systems had to be installed. The longest section of single liner type is approximately 800 linear feet. The concrete sewer’s inner diameter is approximately 17.5 feet. The outer diameter of the liner that the installer subcontracted the annular space grouting to CJGeo on is approximately 16.5 feet.
Based on the theoretical average inside diameter of the existing sewer, the annulus is almost exactly one cubic yard per linear foot.
The Solution
The pipe runs at full charge at least once per day, so there was a high likelihood of accumulated water in the annulus. To displace this water and ensure consistent bearing of the pipe, CJGeo proposed 75lb/cuft CJFill-Under Water. While this density of CJFill cellular grout significantly exceeds the 300psi at 28 day compressive strength requirement, it facilitates displacing solids from the annulus.
To help manage buoyancy, once the first lift was in place, the wet cast density of the cellular concrete on this Detroit Michigan annular space grouting project was reduced to 45lb/cuft CJFill-Standard. Reducing the wet cast density significantly reduces uplift, which allows taller lifts.
CJGeo used an onsite dry mix batch plant to generate the cellular concrete and pump it up to five hundred feet in the sewer line.
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New Jersey polyurethane grouting
The Job
This New Jersey polyurethane grouting project is located in Creskill, New Jersey. As part of a full gut renovation of the library, the architect specified lifting settled areas of the floor. The floor settlement was affecting approximately 3200 square feet, with settlement up to two inches.
The Challenge
The library building is a slab on grade, with relatively light design loads. The floor is approximately four inches thick, and reinforced with welded wire mesh. The original design to correct settlement was to use mud jacking. Mud jacking works well, but is rather slow, and tends to be very messy. Mud jacking uses cement-based grout pumped under high pressure below concrete to fill voids and push the concrete back up. A downside is that the grout is quite heavy, and the additional weight it adds to already compromised soils can cause additional future settlement.
The Solution
CJGeo proposed using CJGrout 28FDL geotechnical polyurethane grout as an alternative to the specified mud jacking process. CJGeo’s value engineer proposal was based on the following benefits of polyurethane grouting over traditional cementitious grouting:
- speed – polyurethane grouting tends to be significantly faster than cementitious grouting
- cleanliness – polyurethane grouting is a very clean process, including dustless drilling, mechanical connections to the slab, and material that scrapes off with a putty knife if it leaks from below a slab
- density – traditional mud jacking grout is approximately 50 times heavier than in place CJGrout 28FDL. This reduces the likelihood of future resettlement by minimizing the additional load that grout places on the underlying soils.
The architect and structural engineer accepted CJGeo’s value engineering proposal for this New Jersey polyurethane grouting repair. A crew of three CJGeo polyurethane grouting experts completed the repair in less than a day. Because polyurethane cures within a few minutes, the general contractor was able to move on to the next steps in the project very quickly.
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Michigan Pipe Abandonment
The Job
This Michigan pipe abandonment project is located in Grand Rapids, Michigan. As part of the Coldbrook Pumping Station decommissioning project, 2250LF of 48″ pipe, and 2300LF of 60″ pipe were specified for grout filling.
The Challenge
The primary challenge for the general contractor on this project was the sheer volume of abandonment grouting. The project also had a significant amount of smaller diameter pipe, but it was in shorter runs, so was easy for them to self-perform with flowable fill.
The Solution
CJGeo proposed using 25lb/cuft CJFill-Ultra Lightweight cellular concrete. CJFill-Ultra Lightweight can be pumped thousands of feet per placement. This eliminates the need for most intermediate access points. Placement points on this project were in the driveway of a fire station, next to a new riverwalk project, and also on the grounds of the pumping station.
CJGeo mobilized a dry batch cellular grout plant to the site, and made around 200 cubic yards per hour of CJFill-Ultra Lightweight to finish this Michigan pipe abandonment project. Each run was up to 2500 feet long at a time. The abandonment work took five days onsite. By utilizing on site dry batching, a snow storm and cold overnight temperatures did not affect the work.
After the crew was completed with this work, they moved to Detroit to perform annular space grouting on a 17′ diameter CSO outfall structure.
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Pregrouting for Hand Mining
The Job
This large CSO project in Alexandria, Virginia required pregrouting for hand mining. The hand mining was to install a new pipe below an existing influent tunnel, which is on piles. The hand mined tunnel was to connect two a secant pile shaft to a slurry wall pit, which are roughly 25′ apart.
The Challenge
The challenges on this project included:
- no drilling allowed without pre-probing
- 3′ thick secant pile walls
- unknown exact pile support layout of influent tunnel
- fully saturated soils
- potential debris in backfill under existing influent tunnel
The Solution
CJGeo proposed performing the permeation grouting using acrylate. Acrylate is exceptionally low viscosity, so well suited to the organic, fine-grained soils. Previous permeation grouting on the project was done with acrylamide. However, acrylamide is neurotoxic and carcinogenic, so the owner was happy to learn about acrylate, which has very similar properties, but is not neurotoxic or carcinogenic.
To avoid drilling, CJGeo developed a pushed/driven probe grouting installation. This approach uses 1/2″ diameter steel tubing driven to depth, and then grouted through during extraction.
The 3′ thick secant pile walls didn’t pose too much of an issue, clearance holes were drilled with hand-held percussion drills.
Drilling wasn’t allowed. The owner and design team were concerned about potentially hitting and damaging the pile foundation. Because there was the potential for debris, there would be no way to distinguish debris from a pile until it was potentially too late. By using groutable probe rods, CJGeo avoided all of this risk.
The fully saturated soils had relatively low permeability, and the site was constrained on two sides by the existing SOE structures. Performing permeation grouting when below the water table you’re limits the placement rate by the ability to displace the existing groundwater. Because of the water-tight walls on two sides of this pregrouting for hand mining application, take was slower than originally anticipated.
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New Jersey Pipe Abandonment
The Job
This New Jersey pipe abandonment project is located in northern New Jersey. First, the general contractor installed a new force main by micro tunneling. After the the new micro tunneled force main was in service, the existing force main had to have grout filling. The pipe is 24″, and about 6300 feet long.
The Challenge
The pipes ran underneath an existing roadway, so digging access points for flowable fill installation would have been expensive, time consuming, and disruptive to traffic. The general contractor recommended CJFill Low Density Controlled Low Strength Material (LD-CLSM) as an alternative to the controlled low strength material that the township typically uses.
In addition to the old force main abandonment, a wet well structure also required abandonment. The original plan was to use flowable fill, however there were concerns about inducing settlement if the fill material was heavy.
The Solution
CJGeo proposed using 25lb/cuft CJFill-Ultra Lightweight cellular concrete. CJFill-Ultra Lightweight can be pumped thousands of feet per placement. This eliminates the need for most intermediate access points.
CJGeo mobilized a dry batch cellular grout plant to the site, and made around 150 cubic yards per hour of CJFill-Ultra Lightweight to finish this New Jersey pipe abandonment project. Each run was up to 2500 feet long at a time. The abandonment work took two days onsite. After the abandonment grouting was done, the CJGeo crew did the wet well abandoning work with 25lb/cuft CJFill-Ultra Lightweight.
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