Bridge Approach Ground Improvement
The Job
With multiple S curves and merges, I-195 in Richmond, Virginia is one of the most accident prone sections of interstate in Central Virginia. Significant settlement of multiple approach and departure slabs at various bridges didn’t make things any better. Improving the ride quality by addressing up to 6 inches of settlement was identified as a critical part of a 2022 safety improvement plan.
The Challenge
Extensive settlement over the years had caused the pavement to become distressed. This was addressed over time with extensive patching of the pavement slabs. With no reasonable detour routes, shutting down traffic to facilitate repairs was not an option.
The Solution
While the original project designed required lifting all of the settled pavement, this would have been nearly impossible, given the extensive patching (including full depth filling of expansion joints with repair mortar).
CJGeo worked with the general contractor and VDOT to revise the repair plan to a combination of compaction grouting of the underlying soils, coupled with an asphalt overlay of the approach and departure slabs to restore the ride.
Polyurethane grouting was performed to a depth of up to 25′ below the pavement surface to consolidate poorly controlled backfill material, at two approaches (9 lanes total) and three departures (9 lanes total). Cutoff criteria was 0.05 inches of lift at each point/stage.
Milling and paving was then performed for a 30′ taper to provide a smooth transition and ride.
Dollar Store Floor Void Filling
The Job
A commercial contractor was performing a full gut renovation of a dollar store in a strip center. The building was approximately 30 years ago, and there were no signs of floor slab failure or settlement.
The Challenge
While cutting through the floor to install utilities, a 3″ void was discovered below the floor. Exploratory coring determined that voids ranged from 0.5 to 4″ throughout approximately 11,000 square feet of the space.
The Solution
CJGeo mobilized two geotechnical polyurethane grouting crews to the site and filled the voids over a period of two days. Approximately 7,000 pounds of CJGrout 20SDB were placed through approximately 500, 5/8″ holes, with cross-hole communication cutoff criteria. The work was performed without disruption to the renovation activities.
Fire Station Floor Lifting
The Job
The concrete slab on the grade floor inside of a fire station on the North Neck of Virginia settled up to two inches. As part of the investigation into the cause, an engineer discovered voids up to 8″ below the slab and multiple broken sanitary sewer pipes below the floor.
The affected areas included a dayroom, kitchen & meeting hall.
The Challenge
In order to minimize disruption to the fire station’s operations, the proposed repair had to be quick, clean, and minimize uncertainty associated with the plumbing repair slab cuts.
The Solution
CJGeo performed ground improvement grouting of the underlying soils to 5′ below-grade utilizing plural component polyurethane compaction grouting. Shallow voids were filled using plural component polyurethane, which was also used for settlement correction.
Because polyurethane grouts cure very quickly, the floor was repaired the day before the plumbing work was scheduled. This allowed the plumbers a stable work surface and eliminated the risk of stuck saws or sudden collapse of the floor during floor sawing for plumbing access.
Pre & post-grouting DCP testing was done to verify grout travel.
Florida Grade Crossing Repair
THE JOB
Settlement and deflection of precast grade crossing were causing highway pavements to deteriorate. The crossing is owned and maintained by the large business park it serves, is used by CSX, and crosses a major highway maintained by FDOT. Exploratory geotechnical investigations determined that the soil under the crossing had sufficient bearing capacity. However, a void had developed under the crossing, which allowed water to pool under the slabs. The slabs deflected under vehicle & rail traffic, which pumped the sandy backfill material out from under the slabs.
The adjacent asphalt had failed, which channeled water into the void below the panels, causing the problem to worsen.
THE CHALLENGE
This Florida grade crossing repair had to quickly and thoroughly address the voids and settlement of the panels. Additionally, the material used for void filling and lifting needed to be resilient under dynamic loading from the train and vehicular traffic, and capable of performing well in saturated environments.
THE SOLUTION
High-density polyurethane grouting to stabilize and lift the affected precast grade crossing panels. Polyurethane grouting is far superior to mudjacking because it allows for rail traffic during the repair and immediate resumption of road traffic. Because the adjacent asphalt had significantly deteriorated, the immediate return to service allowed full-size paving equipment to traverse the crossing immediately after the polyurethane grouting was done.
CJGeo modular grade crossing repair crew filled the voids and corrected settlement in fewer than four hours. Milling and paving of the adjacent roadway were done the following day. The roadway and rail opened up immediately afterward.
Railway Grade Crossing Repair
THE JOB
112 track feet of crossing panels settled. This caused the adjacent asphalt pavement to fail. The crossing ran diagonally across the highway. The road was graded so that the crossing was the primary flow path for surface water. The crossing had been replaced twice in the past. The last replacement used flowable fill as the base material. The crossing panels experienced approximately 1 inch of deflection with highway traffic. There were also 4-inch voids below the panels.
With highway traffic from heavily-loaded vehicles, the crossing deflected enough to squirt water three to four feet in the air. This water pumping action actively pumped the subbase material from under the crossing.
THE CHALLENGE
The repair had to allow immediate vehicular traffic to facilitate a single-lane closure that was flipped halfway through the repair. The repair also had to allow for immediate resumption of rail traffic. The crossing served as a sand mine, so the repair was designed around high service loads for heavy haul rail traffic.
THE SOLUTION
High-density polyurethane grouting to stabilize and lift the affected modular grade crossing panels.
Supplemental anchor bolting was also used to ensure the long-term integrity of the repair.
CJGeo modular grade crossing repair crew filled the voids and corrected settlement in less than a day. Asphalt patching was done concurrently with polyurethane injection. The entire repair was completed in less than one day. The roadway and rail opened up immediately after the repair.
Industrial Facility Floor Repair
THE JOB
The slab floor inside of a manufacturing facility in Hagerstown, Maryland settled. This caused equipment that was installed on the slab to become misaligned, requiring industrial facility floor repair.
A geotechnical investigation revealed voids below the slab due to the settlement of the underlying soil. The affected area was built over approximately 10 feet of fill during construction. Engineering analysis showed that the soil was likely poorly compacted, but had consolidated with time.
THE CHALLENGE
Due to the sensitive electronic equipment within the work area, the repair had to be very clean and dust-free. Though analysis determined that the underlying soils had most likely completed consolidating, the owner’s geotechnical consultant recommended limiting additional weight placed on the fill material.
The repair area was also more than 100 feet from the nearest exterior access. The floor had started to settle before the equipment was installed. It was very important that the slab not be lifted during the void filling process.
THE SOLUTION
Geotechnical polyurethane grouting to fill the voids below the slab floor. Polyurethane grouting is superior to mudjacking in situations like this because it is considerably cleaner, much faster, and allows for immediate reuse.
The material used in polyurethane grouting is much lower weight than mudjacking grout. This reduces the weight applied to the underlying soil. Lower weight materials reduce the chance of resettlement.
A single CJGeo polyurethane grouting crew completed the industrial facility floor repair in less than a day. Due to the extreme sensitivity of the equipment to lifting, a specially-formulated plural component polyurethane grout was selected for undersealing without lifting.
Precision equipment was used to monitor the floor during undersealing. A movement of 0.02 inches was used to determine the completeness of fill. This was confirmed by extensive extrusion of polyurethane through the adjacent saw cut control joints in the floor.
Urban Grade Crossing
THE JOB
32 track feet of crossing panels settled. This caused the adjacent asphalt pavement to fail and caused tripping hazards at the adjacent pedestrian sidewalk. The grading in the area was relatively good, however, the adjacent ballast was fouled, which caused water to accumulate under the crossing panels and wash out the sandy subbase material. The crossing had been replaced recently. Due to the urban, primarily passenger automobile traffic, there was a little deflection of the crossing panels from highway traffic. However, there were up to four inches of deflection from rail traffic loading.
The deflection from rail traffic loading caused the top edges of adjacent panels to be in compression with each other. This caused extensive spalling of the surface, which affected two of the panels. While not a functional problem for panel integrity, the spalled areas were within the sidewalk portion of the crossings and therefore posed tripping hazards.
THE CHALLENGE
The repair had to allow immediate vehicular traffic to facilitate a single-lane closure. The repair also had to allow for immediate resumption of rail traffic. The crossing served as a sand mine, so the repair was designed around high service loads for heavy haul rail traffic.
Due to the scheduling constraints of the railroad, the repair method had to tolerate the potential for rail traffic during the repair.
THE SOLUTION
High-density polyurethane grouting to stabilize and lift the affected modular grade crossing panels.
Supplemental anchor bolting was also used to ensure the long-term integrity of the repair.
Epoxy-augmented patching of the spalled areas to restore a smooth walkway for pedestrians.
CJGeo modular grade crossing repair crew filled the voids and corrected settlement in less than a day. Asphalt patching was done concurrently with polyurethane injection. The entire repair was completed in less than two hours. The roadway and rail opened up immediately after the repair. Traffic control was done to accommodate pedestrians and roadway traffic.
Two trains passed through the crossing over the panels being repaired during the repair. This did not affect the integrity of the repair.
Alley Settlement Correction
THE JOB
Dewatering associated with a basement excavation caused settlement of an adjacent alley’s pavement. The alley pavement consisted of 4″ concrete base, 2″ course of asphalt, and 3″ thick pavers. The alley served as the sole service and parking entrance to an adjacent residential tower, so could not be shut down. Due to the unpredictability of deliveries, the repair also had to allow for intermittent traffic during work.
The pavement had settled up to 3 inches, with nearly 3,000 square feet affected. In addition to being adjacent to two 50+ feet deep basements, one end of the work area was bound by the Navy Yard metro station.
THE CHALLENGE
While the customer was familiar with and inquired about cementitious pressure grouting, CJGeo proposed polyurethane grouting. Polyurethane grouting allows for immediate traffic after repairs, and also for intermittent traffic during repairs. With in-place unit weights of around 4 PCF, polyurethane grouts are significantly lighter than cementitious grouts, which reduces the propensity of future consolidation of underlying soils.
Polyurethane grouting is done using compact equipment, as well. Instead of large pumps, mixing equipment, and hard to maneuver hoses, polyurethane grouting is all down out of a box truck, with lightweight, small hoses that are easy to move out of the way if needed.
THE SOLUTION
A CJGeo polyurethane grouting crew spent two days raising the alley. Sawing was done prior to lifting in order to facilitate differential movement between the settled slabs & the adjacent paved areas. Multiple trash pickups and material deliveries were made to the adjacent property during the grouting work, without disruption to either party.
Grain Bin Floor Repair
THE JOB
The floor of a 105′ diameter grain bin settled. The floor had a bin sweep installed, that was mounted on the top of the unloading tunnel, which ran down the center of the structure. Where the slab floor butted up to the tunnel walls, the floor had settled 2″ on one half, and 3.5″ on the other half. This caused issues with operating the bin sweep because it was designed for a smooth, level floor.
The owner’s alternative was to remove the entire floor and pour a new floor. This would have been incredibly expensive and taken a very long time. The only access into the bin was two 2′ wide by 4′ tall doors, located 5′ above exterior finish grade, and 2′ above the bin floor elevation.
THE CHALLENGE
Due to the nature of the commodity business, mobilization and completion of the grain bin floor repair had to be fast. Additionally, the repair had to return the floor to its original profile, along with the turned-down ventilation trenches in the floor. The extensive turned-down ventilation troughs made this floor very susceptible to cracking. The floor was 6″ thick but then went to 24″ thick at the ventilation troughs. Slabs with non-uniform thickness require extreme care and attention to avoid differential lifting.
The design loads for the floor are approximately 3500psf, so the material used for lifting the floor had to be relatively high strength.
THE SOLUTION
CJGeo proposed polyurethane grouting for filling the voids below the floor and lifting them back into place. The minimum bearing capacity of the proposed materials was 5500PSF, ensuring adequate bearing capacity even under full load.
CJGeo mobilized two polyurethane grouting crews to the site. The work was completed over a period of two days, during which more than 7,000 pounds of polyurethane grout were installed using three reactors running simultaneously. Multiple reactors (pumps) helped to ensure thorough lifting of the slab and the ventilation troughs. The crews that completed this job have collectively performed millions of pounds of polyurethane grouting, ensuring the successful completion of this grain bin floor repair job.
Blower Slab Stabilization
THE JOB
During a routine inspection, extensive voids were discovered under the slab supporting a ventilation blower at a wastewater treatment plant. Staff was concerned that the lack of support under the slab would cause it to settle. As visible in the pictures, this would easily cause extensive damage to this critical equipment.
THE CHALLENGE
The repair had to address the voids under the entire area of the slab, including the areas where the slab surface was unaccessible.
THE SOLUTION
CJGeo proposed polyurethane grouting for filling the voids below the blower slab. The minimum bearing capacity of the proposed materials was 3700PSF, ensuring adequate bearing capacity and long-term stability.
A CJGeo polyurethane grouting crew filled the voids below the blower base and adjacent sidewalk in less than two hours. Operations were not affected; the equipment stayed in service during the entire repair.
