Sewer Collapse Sinkhole Repair
The Job
This sewer collapse sinkhole repair project is located in central Virginia. When the operators of a tire and auto shop noticed a sinkhole developing next to their building. They weren’t sure what to do. After an employee crawled into the hole and discovered that he could stand up underneath their building, the owner reached out to the city. City crews determined that a 20″ VCP combined sewer & storm pipe had collapsed under the structure, roughly 25′ below grade.
The Challenge
An on-call contractor for the city installed a new manhole and rerouted the pipe around the building. However, addressing the sinkhole was out of their businesses’ scope. The project manager reached out to CJGeo, who visited the site and recommended DCP testing to better quantify the extent of the problem.
The Solution
DCP testing showed that outside of the large hole on the surface, there was little deep disturbance. Working with the city’s consulting engineer, CJGeo developed a grouting plan to install two different CJGrouts. 20SDB in the bulk voids near the surface. And 35NHV61 for soil grouting to address voids within the underlying ground near the failed sewer line.
While onsite for just 6 hours, a CJGeo crew completed the work with zero disruption to the businesses’ operations.
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Coal Pier Sinkhole Grouting
The Job
This pier sinkhole grouting project by CJGeo is located at the mouth of the Elizabeth River, off the Chesapeake Bay. With an annual throughput capacity of 48 million tons, Norfolk Southern’s Pier 6 at Lamberts Point in Norfolk, Virginia is one of the largest coal trans-loading facilities in the world. As an around-the-clock facility built around precision logistics, there’s little tolerance for disruption or downtime.
The Challenge
When two sinkholes opened up at the end of Pier 6 adjacent to the bulkhead, railroad personnel reached out to an onsite maintenance contractor. Steel plates were installed to provide temporary protection while a long-term solution could be implemented.
The Solution
CJGeo performed DCP testing at the site in order to quantify the depth of voids below the pavement adjacent to the sinkholes. The DCP testing showed that in addition to large voids visible from the sinkholes immediately below the pavement, there were large pockets of voids down to 15’ below the surface.
CJGeo crews then used CJGrout 35NHV61, a hydro insensitive, NSF-certified geotechnical polyurethane to fill all voids and restore stability to the area. The grouting work took five hours onsite to install 3400 pounds of material, with zero disruption to operations.
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PA Turnpike Undersealing
The Job
This PA Turnpike undersealing project is located on the Northeast Extension of the Pennsylvania Turnpike. The Northeast Extension runs from Philadelphia to Scranton. As part of a 24 lane mile mill & pave rehabilitation on the Pennsylvania Turnpike, slab stabilization was required. The Turnpike’s specification for stabilization is either liquid asphalt or polyurethane.
In this work area, the turnpike has two northbound and two southbound lanes. A cast in place barrier wall separates the lanes. The pavement is an approximately nine inch thick rigid concrete with up to eight inches of asphalt overlay. Joint spacing ranges from twenty feet to eighty feet.
The Challenge
In order to keep MOT in place continuously, work had to be done 24 hours per day. Multiple mobilizations were used to work around bridge repairs at three different overpasses in the undersealing work area.
The Solution
CJGeo proposed undersealing with CJGrout 40NHL, a 4.0 lb/cuft free rise polyurethane grout formulated specifically for undersealing thick pavements in transportation environments. 40NHL is hydro insensitive, so performs well in wet environments, as confirmed with NYSDOT GTP-9 testing.
Using a double gang drill and single grout truck, CJGeo crews undersealed up to 1.8 lane miles per shift. Drilling operations happened overnight. Grouting during the day is safest, and allows for easy visualization of the entire zone of influence. By working continuously, the general contractor was able to keep MOT in place continuously, avoiding the cost of setting and pulling MOT each day.
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Tub Crossing Repair
The Job
This tub crossing repair was done for a short line railroad in New Jersey. The sandy soils of South Jersey are great for growing produce and mining pure silica sand. While most of the produce is shipped by truck, a lot of the silica is shipped by rail. The rails inevitably cross the roads, and many of the crossings are at grade.
The Challenge
A short-line railroad was experiencing significant settlement and pumping of multiple precast modular crossings in the Vineland & Millville areas. Each crossing saw significant truck traffic, primarily from aggregate mining, and also significant heavy haul rail traffic from transporting sand.
Voids below the panels were holding water due to poor drainage. Each time a truck or train passed over the panels, they deflected downwards. This deflection pumps base material out from under the crossing, causing settlement.
The Solution
Working with a rail maintenance contractor, CJGeo performed polyurethane grouting on a total of four precast tub crossings in the area, using CJGrout 40NHL. Each crossing repair took a single day. Polyurethane grouting allowed for the immediate resumption of automobile traffic, and rail traffic. Th CJGeo crew installed supplemental bolting to address the deterioration of the panels resulting from the extensive movement of the panels.
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Industrial Short Line Tub Crossing Repair
The Job
This short line tub crossing repair project is located in Baltimore, Maryland. Sparrows Point, in Baltimore, Maryland is a brownfield site. It’s transforming from being steel manufacturing to industrial and logistics use. From it says as a heavy manufacturing facility, there is an extensive freight rail network throughout the site, with many grade crossings subject to significant heavy truck traffic & heavy haul rail traffic.
The Challenge
A precast tub-style grade crossing on a road feeding a metals recycling plant developed a 2.5″ belly. The local FRA inspector instructed the railroad to correct the settlement.
The Solution
CJGeo performed structural polyurethane grout injection to fill voids below the panels. And then lift them back into their correct alignment. The work took just a few hours, without disruption to the rail or auto traffic.
CJGrout 40NHL is a four pound per cubic foot geotechnical polyurethane grout. It’s specifically designed for high dynamic load environments like rail, port, and airfield traffic. CJGeo’s crews use 40NHL for modular grade crossing repairs to ensure the longest life repair possible.
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NC Tub Crossing Repair
THE JOB
This NC tub crossing repair project is located in Charlotte, North Carolina. The 8′ long panels of tub-style grade crossing settled. As a result, MOW placed a speed restriction on the crossing. This affected passenger schedules. The settlement affected three panels. The belly in the slabs was approximately 2 inches. The crossing deflected slightly with heavy truck traffic. The crossing deflected significantly with rail traffic.
THE CHALLENGE
The repair had to be completed in just a few hours, to avoid disruption to rail traffic. The repair had to allow for immediate resumption of rail traffic, and tolerate tamping of the adjacent truck during the repair. Additionally, the tub crossing repair had to be done in a manner that did not disturb the adjacent asphalt pavement.
THE SOLUTION
High-density geotechnical polyurethane grouting to stabilize and lift the affected modular grade crossing panels. Geotechnical polyurethane grouting is far superior to mudjacking, in that the process is faster, and can more easily ensure a complete filling of voids under the crossing panels. Lifting precision of fewer than 0.1 inches is standard.
A CJGeo modular grade crossing repair crew filled the voids and corrected settlement in a few hours. During the tub crossing repair, the rail system used a tamper on the approaches. This helps ensure the longevity of the grouting repair. The structural polymer grouting process used here is sometimes referred to as slab jacking.
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Industrial Driveway Crossing Repair
The Job
This industrial driveway crossing repair project is located in Frederick, Maryland. MARC’s Brunswick Line’s Frederick extension passes through multiple industrial sites & driveways. This particular crossing served as the driveway of a ready mix concrete operation, so saw extensive high dynamic loading in a wet environment.
The Challenge
The repair had to be performed without disrupting either rail or industrial traffic. There was a four-hour window between the last morning train and the first evening train for performing the repair to the eight modular tub crossing panels. The settlement was up to two inches, with extensive spalling.
The Solution
CJGeo’s crew installed supplemental bolts due to replace the OEM center panel anchors, and then grouted the crossing in the mid-day window, without disruption to any stakeholder. The structural polymer grouting work took less than a day onsite. The work was done between the morning and evening commuter trains, but multiple freight trains used the crossing during the repair.
CJGrout 48NHL was the grout of choice. CJGrout 48NHL is formulated specifically for high, dynamic loading environments, such as rail crossings, and airfields. It provides superior bearing capacity, excellent resiliency to dynamic loads, and is great for correcting differential settlement between panels. Because it is relatively low mobility, CJGrout 48NHL is unlikely to affect adjacent pavement.
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Light Rail Tub Crossing Repair
This light rail tub crossing repair project is located in Charlotte, North Carolina. It is part of Charlotte’s CATS system.
THE JOB
A suburban grade double-crossing was rebuilt to address poor drainage infrastructure in the area. This included installing two different culverts adjacent to the crossing panels, and then resetting all of the panels which had to be removed for the culvert installation. During routine track inspections, the panels showed signs of deflection up to one inch with rail traffic. The system’s track division was concerned that pumping of the crossing panels would lead to destabilization of the base, and settlement. At the lower elevation end of the crossing, there was extensive evidence of sub-base material being pumped out from under the crossing within two weeks of the crossing reconstruction. 368 track feet were affected.
THE CHALLENGE
Work had to be completed during non-revenue hours, between 0200 & 0430 over two nights. There was also a high probability of the voids below the panels being waterlogged.
THE SOLUTION
High-density polyurethane grouting to stabilize the grade crossing panels. Specially-formulated hydro-insensitive void filling (high-mobility) grout was proposed in order to ensure complete filling of voids below the panels, whether waterlogged or dry.
CJGeo successfully stabilized the crossing during the two-night work period.
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School Floor Leveling
The Job
This school floor leveling project is located in Princeton, West Virginia. The Princeton Middle School is a slab-on-grade masonry structure and serves approximately 550 students in grades 6 through 8.
The Challenge
The corridor floor in the arts wing settled up to 3.5 inches. A geotechnical investigation found voids up to 2.5 inches below the settled slab. Due to budgetary constraints, the repair needed to address the settlement & instability without requiring flooring replacement.
A hand auger confirmed that the fill material below the slab had consolidated to the point of providing sufficient capacity. So, there was no need for polyurethane compaction grouting, which would have been useful if the soils were still loose.
The Solution
CJGeo mobilized a two-person polyurethane grouting crew to the site. Over a few hours, they filled all the voids utilizing CJGrout geotechnical polyurethanes and corrected the settlement. After the floor was lifted back into position and the voids all filled, the custodian reinstalled the cove base at the correct height. CJGeo patched the injection holes with off-white stained grout to match the VCT flooring.
CJGeo used CJGrout 28FDL for this repair. 28FDL is a fast, dry environment lifting foam that works great for lifting bellies out of lightly loaded slabs. There were no water leaks below the slab, there was a significant belly, and the loads were less than one tenth of the grout’s capacity, so it was a great fit. To make sure there weren’t any remaining voids, the crew installed CJGrout 20SDB, which is higher mobility than 28FDL.
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Railroad Sinkhole Stabilization
The Job
This railroad sinkhole stabilization project is located in Martinsburg, West Virginia. During the installation of a 42″ jack & bore casing below a three-track Class 1 railroad, ballast started showing in the spoils. Soon afterward a sinkhole appeared between tracks 2 & 3, 15 feet above the casing. The jack & bore installation was stopped, and the contractor reached out CJGeo requesting an emergency mobilization.
The Challenge
CJGeo had to mobilize with very little notice, and work had to be performed adjacent to an operational track.
The Solution
CJGeo mobilized two polyurethane compaction grouting crews, who were on the road in less than an hour. Within four hours of the sinkhole formation, CJGeo was onsite with more than 250CY of material placement capacity.
CJGeo successfully grouted the sinkhole, using CJGrout 20SDB. Rail traffic continued on adjacent tracks, and the face of the bore was restored, allowing the jack & bore operation to safely restart. CJGeo performed this repair using a polyurethane grout with an elastic modulus similar to the existing soil in order to prevent creating a hard spot in the rail. CJGrout 20SDB was the best fit grout for railroad sinkhole stabilization project because:
- it cures to 95% strength within 15 minutes
- doesn’t impede auger boring
- is highly mobile, so will pass through ballast easily
- doesn’t have lifting capacity, so wouldn’t move the adjacent tracks
- is formulated for bulk placements without charring
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