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Author: CJGEO

By applying unique solutions to increase the safety and longevity of our environment.

Sewer Collapse Sinkhole Repair

The Job

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, but addressing the sinkhole was out of their businesses’s 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’s operations.

Coal Pier Sinkhole Grouting

The Job

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 transloading facilities in the world.  As a round-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 hydroinsensitive, 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.

CMP Joint Sealing

The Job

Due to an oversight during construction, acidic groundwater at a coal mine in West Virginia was causing deterioration of 7′, 9′ and 10′ CMP bypass pipes adjacent to a coal stockpile. The pipes had been installed to bypass streams below the surface elements of the mine, but high iron content and low acidity of water entering the pipes caused the mine to have to treat the water which was supposed to be bypassed.

The Challenge

The pH of the water affecting the metal pipes was as low as 2.1. While typical chemical grouts have excellent histories resisting chemical attack at low pHs, low pH can affect the initial reaction. The owner and geotechnical consultant were also concerned about leak stopping work on the pipe causing water to flow outside of the pipe downstream to other areas which were yet unaffected.

The Solution

CJGeo worked with multiple potential grout suppliers to identify a grout which would not be affected by the acidic environment. A 120cps high expansion prepolymer was chosen due to its ability to react properly in low pH environments, and also for its low viscosity to help ensure good coverage.

A CJGeo chemical grouting crew completed leak stopping on 31 joints and 25 point leaks throughout 600LF of pipe over a period of two weeks, in addition to grouting a 1200CF cutoff wall to stop water migration outside of the structure.

NNSY Helical Underpinning

The Job

As part of renovation of a storage/logistics building at the Norfolk Naval Shipyard, underpinning was required due to settlement of a column footing pile cap. In addition to settlement of the pile-supported pile cap under an exterior wall, two adjacent pile caps had settled on the outside of the loading dock.

The Challenge

Due to a limited overhead environment on the interior, but high torque requirement, piles had to be installed with a large machine from the exterior only. The bottom of footing elevation was nearly 6 feet below finish floor elevation, so extensive excavation was required on the interior, as well, further complicating the installation.

The Solution

CJGeo provided a turnkey design-build package for the piles. Due to the low count, 3.0FOS was used to avoid the load testing requirement associated with 2.0FOS.

CJGeo installed four underpinning piles and four new construction piles over two days. The 3.5″, grout-filled 10-12-14-14-14 helical piles were installed to an average depth of 57 feet, at 12,000ft-lbs. A small excavator was used inside for access excavation, while the install machine reached through the demolished wall.

PA Turnpike Undersealing

The Job

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.

The Challenge

In order to keep MOT in place continuously, work had to be done 24 hours per day. Due to work on three bridges within the repair area, undersealing also had to be phased.

CJGeo’s 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 hydroinsensitive, 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 was completed at night, and grouting during the day, to allow the general contractor to keep MOT in place continuously.

I-66 Annular Space Grouting

The Job:

During widening of Interstate 66 year the interchange with US-15, nine new culverts were installed by jack and bore, and one via direct jacking. The carrier pipes were a mix of spiral metal, precast concrete, and corrugated HDPE, and ranged in length from 150 to 350 feet.

The Challenge:

The boring contractor, who was responsible for grouting, was concerned about carrier pipe buoyancy during grouting, and also run length. All work had to be done from one side of the interstate highway (three lanes in each direction, plus full width shoulders and a median strip), as there was no access on the far side.

CJGeo’s Solution:

CJGeo proposed 30lb/cuft cellular concrete for the annular space grouting. Cellular concrete is the preferred material for annular space grouting because it is highly flowable, and reduces the chances of damage to carrier pipes in long placements. Its low unit weight also reduces carrier pipe buoyancy. CJGeo placed 350CY of cellular concrete to successfully complete the jack and bore annular space grouting over three different mobilizations.

Annular Space Grouting

The Job:

During construction of a commercial development, 200LF of 16″ CPVC waterline was installed via jack and bore, through a 36″ casing.

The Challenge:

Due to site limitations, only one end of the pipe was accessible for grouting. The length of the placement was approximately 200LF, so grout had to travel 200LF at low pressure, while ensuring a complete fill without damaging the delicate carrier pipe material.

CJGeo’s Solution:

CJGeo successfully complete the project in a few hours. Uniform material vented at the far end confirming complete fill.

Tub Crossing Repair

Crossing Use:

Heavy haul freight (silica mine), urban street by short line

The Job:

100 track feet of crossing panels settled. This caused the adjacent asphalt pavement to fail, and caused tripping hazards at the adjacent pedestrian sidewalk. The crossing ran diagonally across the roadway. The crossing had been replaced twice in the past. The last replacement used flowable fill as the base material. Due to the urban, primarily passenger automobile traffic, there was 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 approximately 8 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 that was flipped halfway through the repair. The repair also had to allow for immediate resumption of rail traffic. The crossing served a sand mine, so repair was designed around high service loads for heavy haul rail traffic.

Due to scheduling constraints of the railroad, the repair method had to tolerate the potential for rail traffic during the repair.

CJGeo’s Solution:

CJGeo modular grade crossing repair crew filled the voids and corrected settlement in less than a day using polyurethane grouting. 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. 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.

Industrial Short Line Tub Crossing Repair

The Job:

12 tub-style grade crossing panels developed a 2.5″ belly on a heavy haul industrial scrap short line. The railway’s FRA inspector directed the railway to address the settlement of the crossing panels to bring the crossing geometry back into compliance. Along with being non-compliant from a track geometry perspective, accumulation of water below the panels was causing deterioration of the adjacent asphalt pavement.

The Challenge::

The belly only affected one travel lane of the roadway, but repairs had to not affect the other lane, so that traffic could be maintained to the adjacent industrial properties. Due to rail traffic schedules, the repair had to allow for rail traffic during the repair.

CJGeo’s Solution:

CJGeo crews performed the crossing repair in a single day, using polyurethane grouting. During the repair, two trains utilized the crossing.

NC Tub Crossing Repair

The Job:

The 8′ long panels of tub style grade crossing settled. As a result, a speed restriction was placed on the crossing, which affected passenger schedules. Three panels were affected, and the belly in the slabs was approximately 2 inches. Slight deflection with heavy truck traffic was noted, and significant deflection with rail traffic was present.

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 which did not disturb the adjacent asphalt pavement.

CJGeo’s 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 less 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, tamping was done by the rail system to address settlement of the adjacent track.

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