Secaucus Lightweight Fill
The Job
This Secaucus lightweight fill project is located just across the Hudson River from Manhattan. It’s part of a completely gut of an existing 100,000 square foot distribution and logistics building. While the ground in Secaucus is terrible, the real estate is valuable because of its close proximity to New York City, and also at the core of the dense, urban North Jersey market.
The Challenge
Since original construction in the 1970s, the floor of the building has settled nearly two feet. This is due to underlying compressible, organic soils. As the underlying soils consolidated, and the floor settled, two subsequent floors were poured on top of the existing floor. Varying thicknesses of recycled concrete and other base materials were used to level over the differentially settled previous floors in preparation for the new floor pours.
The goal of the full gut was to build a food grade space. This is to bring the building into a more profitable sector. To do this, minimizing the amount of future settlement was important. Reports from multiple consulting geotechs in the past recommended undercutting and lightweight fill placement as a viable option for achieving this goal. The CMAR reached out to CJGeo about designing and implementing an undercut and lightweight fill program. This was based on our experience on similar projects in the Secaucus area.
The Solution
CJGeo’s inhouse geotechnical engineer worked with the CMAR’s geotechnical consultant. We used RocScience’s Settle 3 program to design an undercut program that would bring anticipated settlement to no more than 1.5 inches. Given the global subsidence of the area, along with rising ground water levels and increasing flood chances, buoyancy was also a design consideration. The total system (floor, base stone & lightweight fill) had to have a minimum 1.1 factor of safety against uplift in fully inundated condition. As an added measure of safety, given the very large footprint of the fill, limited permeability soils immediately below the lightweight fill, and disruptions associated with any buoyancy, CJGeo recommended not factoring infiltration into reduced buoyancy.
The final design includes a 42 inch undercut, followed by placement of 32 inches of CJFill-Ultra Lightweight foamed concrete fill. CJGeo mobilized a single dry batch plant to the site, and placed approximately 8,500 cubic yards of CJFill-Ultra Lightweight material. Production was as high as 1100 cubic yards per day.
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Wet Well Lightweight Fill
The Job
This wet well lightweight fill project is located at HRSD’s Nansemond Treatment Plant, in Suffolk, Virginia. As part of an extensive capital improvement project, the Nansemond Treatment Plant is being upgraded to accept increased flows. The additional flow will be coming via the Hampton Roads Sanitation District’s Hampton Roads Crossing (HRX) project.
As part of the upgrades, a large wet well requires abandonment filling. The structure bears on deep foundation piles, and underlying soils are extremely poor. Therefore, the structure requires low density, self-consolidating fill instead of traditional flowable fill.
The Challenge
The Construction Manager At Risk evaluated multiple lightweight fill materials. Geofoam would provide the least additional load, but due to safety concerns from access into the structure, would not be practical. Foamed glass aggregate fell below maximum allowable densities, but would be difficult to place and compact in the tight space. Expanded shale would be too heavy, and very difficult to place and compact.
The Solution
CJGeo worked with the CMAR, along with the geotechnical and structural engineers to design a fill program which would minimize density, maximize safety, and be optimal for cost and schedule.
CJGeo mobilized a 200cy/hour cellular grout plant to the site, and placed 430 cubic yards of 25lb/cuft CJFill-Ultra Lightweight foamed concrete fill. To manage lateral loads on the walls during placement, two ten foot deep lifts brought the fill to finish elevation.
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NYC Cellular Concrete
The Job
This NYC cellular concrete project is located at the William McCray Playground in Manhattan. The existing playground had experienced significant subsidence, which damaged the already outdated equipment.
The entire playground was demolished, in order to install a new updated facility, including play equipment, basketball court and spray equipment.
The Challenge
Design documents called for three feet of 25lb/cuft lightweight fill material over roughly 4,000 square feet of the site. Two options were given to contractors; 25lb/cuft cellular concrete or foamed glass aggregate.
Logistics for any work in Manhattan are tricky. Challenges include truck traffic limitations, constraints on work time and noise, and the narrow, congested streets. There was no room on the site for any stockpiles.
The Solution
The customer determined using 25lb/cuft CJFill-Ultra Lightweight fill by CJGeo would be the lowest risk, most economical, and fastest method allowable by specification. Because the equipment for generating foamed concrete fill is mobile and compact, the tight site wasn’t a problem.
CJGeo brought in just four loads of cement in order to generate the approximately 550 cubic yards of foamed concrete material. Cold temperatures didn’t affect the operation; it froze the night between the two pours, and also the night afterwards. No tenting or protection is required.
The day following the second pour, the customer was able to start placing pavement base on top of the cellular concrete.
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Fairfax Polyurethane Grouting
The Job
This Fairfax polyurethane grouting project is located at a commercial building used for medical office space in Merrifield, Virginia. The facility is a clinical site for a large regional hospital operator. It houses a primary care and community outreach practice.
The Challenge
The building was built in the 1980s, and will eventually be torn down. However, over the past few years after build out, the floor along the exterior wall settled about 0.75 inches. As the floor settled, the interior finishes along the wall started to cause functional issues for the users. Most of the cabinet and desk drawers were racked and unable to completely close, and office chairs were always trying to roll towards the wall.
The tenant reached out to the owner/property manager, who brought in a forensic structural engineer to investigate the problem and recommend a repair. The structural engineer reached out to CJGeo for recommendations.
Due to the clinic schedule, all demo, grouting, and finish restoration had to be completed in no more than two days. The area of impact is about 1200 square feet.
The Solution
CJGeo recommended injection grouting with CJGrout 28FDL to the structural engineer due to the relatively narrow zone of settlement, and nominal loads due to the light duty use of the space.
A single CJGeo polyurethane grouting crew filled the voids below the floor, lifted back into place and turned it over to the general contractor in fewer than four hours onsite. The general contractor then replaced the VCT and LVP floor tiles that CJGeo drilled through to perform the grouting. The space returned to normal use the following day, without the chairs moving on their own.
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North Carolina Polyurethane Grouting
The Job
This North Carolina polyurethane grouting project is located at Elon University. It is part of the Innovation Quad project, being built by Whiting Turner.
The Challenge
The site concrete contractor poured a large set of steps near the entrance of the new building. The steps are approximately thirty feet wide, and have roughly eight feet in rise. The steps are constructed over fill material, including site soils and dense graded crushed aggregate.
During a precipitation event, the grading at the top of the steps directed a significant amount of water towards the top of the steps. The water had nowhere to go other than below the steps. This washed out a significant amount of material, and also caused consolidation of some backfill material.
The Solution
The project’s geotechnical consultant recommended the general contractor reach out to CJGeo to address the voids below the steps. They also recommended performing DCP testing as a minimally invasive way to check the bearing capacity of the underlying materials after the erosion event.
The most suitable polyurethane grout for this project was CJGrout 20SDB. CJGrout 20SDB is a high mobility grout designed specifically for undersealing and bulk void filling, with lifting ability designed out in order to manage risk of displacing the brand new structure.
CJGeo mobilized a single polyurethane grouting crew to the site. They started by performing DCP testing, which uncovered voids within the top three feet of fill material immediately below the steps. The crew used sacrificial tubing to ensure that these voids were completely full, along with the voids immediately below the steps.
Confirmation of fill was material returning to the surface.
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Yonkers Polyurethane Grouting
The Job
This Yonkers polyurethane grouting project is located in Yonkers, New York. The project is part of a renovation of a multi-tenant strip center into a single discount grocery tenant.
The Challenge
During construction, someone on the general contractor’s team thought that areas of the floor sounded hollow. Tapping on the floor, it sounded like a drum. The contractor reached out to CJGeo, and we recommended performing a few cores in the hollow sounding areas.
Coring revealed extensive voids in two areas of the building footprint. Both were along the side exterior walls. In one area of the floor, the voids were up to 4′ deep. The apparent cause for the voids was a longstanding problem with below slab plumbing when the space was a deli and dry cleaner.
The Solution
After the cores were used to confirm the size and extent of the voids, CJGeo recommended CJGrout 20SDB geotechnical polyurethane grout to fill the voids.
CJGrout 20SDB is ideal for filling large voids below floors because it is low exotherm. Many foams used for polyurethane grout are not well suited for filling very large voids.
A plumber installed new sanitary lines below the floor after CJGeo completed the void filling. The void filling only took a single day onsite. It’s important to fill voids first so that cutting new plumbing trenches doesn’t cause catastrophic, unexpected settlement.
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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, 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 using sonic drilling 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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Underground Storage Tank Fill
The Job
This underground storage tank fill project by CJGeo is located at a food manufacturing facility near Harrisonburg, Virginia. The tank is 30 thousand gallons, and designed to store diesel to feed backup power generation for the facility. As part of an equipment upgrade, the tank is no longer in use, and had to be filled.
The Challenge
The best way to address unused underground storage tanks that aren’t removable is to fill them. If left empty and out of mind, abandoned empty tanks can cause serious problems, such as sudden collapse, which can significantly affect operations. Unfilled, out of use tanks can also accumulate groundwater, leading to potential environmental liabilities.
The Solution
CJGeo proposed 30lb/cuft CJFill-Ultra Lightweight (CJFill-UL) to fill the tank. CJFill-Ultra Lightweight is easily hand and machine excavatable to ensure that when the tank is removed in a few years that it’s not difficult.
While easily hand excavatable, CJFill-Ultra Lightweight still provides more than adequate compressive strength. In this case, total loads were just a few hundred pounds per square foot, whereas the CJFill material provides more than 17ksf of unconfined compressive strength. The American Concrete Institute publishes a removability modulus calculation which helps to quantify the ease of removal of controlled low strength materials, read more about it and how it relates to cellular concrete here.
It took CJGeo less than an hour to completely fill this tank. Confirmation of complete fill was uniform material venting from the tank vent ports.
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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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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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