Electric Bore Annular Space Grouting
The Job
This electric bore annular space grouting project is located in Norfolk, Virginia. As part of significant work at the Port of Virginia’s Norfolk International Terminal, an electrical contractor installed seven jack & bore crossings of various roadways and railroad lines within the port.
The Challenge
There are seven bores, ranging from 85 feet to 362 feet. Each bore is 36″ steel casing, with eight, eight inch conduits. Most conduits are for electrical lines, some are reserve, and some are for communication and data.
The designer’s specification call for annular grouting of all the conduits, with a minimum 1000psi grout. There was no thermal conductivity requirement.
The Solution
CJGeo proposed a 60lb/cuft CJFill-Standard cellular grout in order to meet the 1000psi requirement. Buoyancy control was achieved through water filling of the conduits, along with a conduit & casing spacer design which presumed some buoyancy.
The customer filled each of the conduits with water prior to grouting. Due to the relatively low volume of grout per bore (ranging between 16 & 57 cubic yards), CJGeo used a local ready mix supplier for paste, and the wet batch generation method. CJGeo successfully performed the electric bore annular space grouting work over two days.
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Railroad Bore Annular Space Grouting
The Job
This railroad bore annular space grouting project is located in Winchester, Virginia. As part of a new development, three parallel stormwater pipes were bored under a CSX right of way.
The Challenge
The railroad requirements include annular space grouting. The three casings (80 feet long each), are 48″ by 0.725 wall thickness steel. The carrier pipes are 30″ N-12 pipe, with a 35.50″ outside diameter.
This annulus requires about 16 cubic yards of grout per bore. One of the challenges of double wall HDPE drainage pipe is that it is exceptionally light. This can make uplift management during grouting particularly challenging.
The Solution
In order to manage buoyancy during the annular grouting, the boring contractor installed longitudinal blocking on each of the carrier pipes during installation. To reduce the uplift by six times compared to flowable fill, CJGeo proposed a 30lb/cuft cellular grout for the annular grouting.
Between the blocking and the very low density CJFill-Ultra Lightweight cellular grout, single lift grouting was possible without damaging the new carrier pipes. Single lift grouting eliminates the risk of trapped air pockets or partial fills associated with multi-lift grouting.
Due to the relatively low volume, and to reduce heat of hydration, wet batch generation using slurry from a local ready mix plant was used.
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New Jersey permeation grouting
The Job
This New Jersey permeation grouting project is located in Elizabeth, New Jersey. It is at a large wastewater treatment plant owned by the JMEUC.
The Challenge
During installation of a new building on site, a large excavation was required. Primarily comprised of H piles and wood lagging, it crossed a 24 foot wide influent conduit. The influent conduit is a double barrel box structure, cast in place on 12 inch thick bed of open graded stone.
During test pitting to the bottom of footing elevation, the test pit appeared to be tidally influenced. The site is immediately adjacent to a creek that feeds into the Elizabeth River. At high tide, and due to the permeability of the stone layer, inflow into the test pit was not controllable, and was higher than the footing elevation.
Specific challenges here included:
- potentially high velocity water flows due to tidal influence
- 12 foot minimum spacing of grout holes due to structure wall locations
- potential fouling of bedding stone with fines
The Solution
The general contractor reached out to CJGeo about grouting the stone bed. The structure is 24 feet wide, but only has a single, eight inch wall down the middle.
CJGeo proposed that a coring contractor drill a two inch core down through the center and side walls from the surface. This gave us three access points to place grout from at each location.
Due to the large grout hole spacing, CJGeo selected acrylic grout. Acrylics are excellent for this type of application because they are exceptionally low viscosity (pump & flow pretty much like water).
A single CJGeo chemical grouting crew performed the acrylic grouting over two days onsite. Afterwards, infiltration into the excavation was down to a submersible garden hose pump. The use of acrylic grout ensured that:
- coverage was uniform despite the large distance between placement points
- any fines fouling the bedding stone were uniformly bound together, immobilized & made impermeable
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Outfall Leak Grouting
The Job
This outfall leak grouting project is located near Emporia, Virginia. The work is located at two different stormwater ponds at an industrial scale solar facility. The facility is owned by Dominion Energy.
The Challenge
This facility has a mix of both dry and wet ponds. At two wet ponds, leaks developed along the outfall pipes, which prevented them from holding water long term. During a precipitation event, water would build up, but then afterwards, slowly drain out by piping alongside the outfall pipes. In order to turn over the facility to the owner, the contractor needed to address the leaks to ensure the ponds functioned as designed.
The Solution
Due to the small diameter of the pipes, they weren’t accessible from the inside. CJGeo proposed grouting along the pipe alignments using single component expanding chemical grout. The pipes are reinforced concrete.
To facilitate this, CJGeo drove sacrificial injection tubes along both sides of each of the two pipes. No grout returned to the inside of the pipes, which confirms that the root cause of the problem was poor control of the backfill, as opposed to problems with the pipe joints. When bedding isn’t properly installed, and backfill properly compacted, water can flow outside of stormwater pipes, which is what was happening here.
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SOE Leak Grouting
The Job
This SOE leak grouting project is located in Alexandria, Virginia. It is part of the RiverRenew project, which is a large CSO tunnel and drop shaft project. This location is immediately adjacent to the Woodrow Wilson Bridge, and the Potomac River.
The Challenge
At a drop shaft location, the contract installed two parallel slurry walls between an existing combined sewer box culvert and a drop shaft to the new tunnel. During excavation of the pit, two high volume leaks, each around 125GPM opened up below the existing conduit.
The customer installed road plates to stabilize the area, and pumped flowable fill behind the road plates. This provided short term stability to the area, but did not address the high velocity flow of water through an unanticipated open graded sand seam that was causing the leaks.
The Solution
CJGeo mobilized a grouting crew capable of performing both high volume geotechnical polyurethane grouting and acrylic permeation grouting at the same time for this SOE leak grouting work. The first step was to install CJGrout 35NHV61 to fill voids which had washed out immediately behind the road plates.
After grouting the bulk voids and slowing the velocity of the leaks, CJGeo installed acrylic grout up to 20 feet behind the slurry wall face. The only way to reliably stop water flow through sands is to bind them together with a very low viscosity grout. The acrylic grout installed on this project has a viscosity less than 10 centipoise. This allows it to uniformly permeate the sands, react into a cooked egg white consistency, and make the treated sands impermeable.
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HDPE Annular Grouting
The Job
This HDPE annular grouting project is located in Portsmouth, Virginia. The project owner is the Hampton Roads Sanitation District, which provides sanitary transmission and treatment for coastal Virginia.
The Challenge
CJGeo was originally part of this project to perform abandonment grouting of around 1000 linear feet of 24″ gravity sewer. During construction, a 1600 linear feet of 36″ gravity sewer in the project area was inspected. The inspection revealed multiple defects needing repair. The design and construction team identified slip lining as the most appropriate repair.
Slip lining generally requires annular grouting between the new carrier pipe and the original pipe. In this case, fused 24″ solid wall HDPE was the slip lining material of choice. This left an approximately 6″ annulus to be fill in order to ensure long term stability of the new pipe and the surrounding ground.
The Solution
CJGeo proposed using 30lb/cuft CJFill-Ultra Lightweight cellular concrete for the annular grout. Cellular grout is the ideal material for HDPE annular grouting because the placement pressures are incredibly low. This is because cellular grout is primarily air, because of its high preformed foam content. Preformed foam on this project came from Aerix Industries.
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48 Inch RCP Joint Repair
The Job
This 48 inch RCP joint repair project is located in Raleigh, North Carolina. The pipe is located at a commercial facility. The slope covering the pipe experienced a slope failure. Upon inspection, six joints were showing signs of soil infiltration and water exfiltration.
The Challenge
The primary challenge for the general contractor on this project was minimizing cost and time. It would have been expensive and disruptive to excavate the pipe. Cover depths were up to 15 feet, and there was a road that would be impacted by excavation, as well.
The exfiltration from the leaking joints was washing away bedding material and adjacent backfill. This caused significant amounts of erosion, and destabilized the slope soils by completely saturating them.
Piping outside of reinforced concrete pipe is an ideal candidate for polyurethane grouting.
The Solution
CJGeo worked with the general contractor and owner’s civil engineering to design a grouting program to repair the pipe. The general concept for this 48 inch RCP joint repair project was to backgrout the pipe with rigid geotechnical polyurethane grout. CJGrout 35NHV61 was the grout of choice; it can be injected directly into flowing water, provides nearly 10ksf in compressive strength, and migrates into both large and small voids with ease.
A CJGeo polyurethane grouting crew took a single day to perform the repair. The average circumferential void around the pipe was nearly nine inches. Cutoff criteria were:
- grout hole to joint communication
- cross hole communication
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North Carolina Abandonment Grouting
The Job
This North Carolina pipe abandonment project is located in Raleigh, North Carolina. It is part of the Upper Walnut Creek sewer replacement. After installation of a new gravity sewer, more than three miles of 42″ sewer was requiring abandonment grouting. The specification calls for completely filling the pipe with controlled low strength material (flowable fill).
The Challenge
The primary challenge for the general contractor on this project was minimizing cost and time. The owner’s specification calls for an NCDOT-approved flowable fill material. Most flowable fills can only be placed for up to a few hundred feet before requiring another access point. The contractor wanted to minimize the number of placement points to ensure the fastest placement possible.
The Solution
CJGeo designed a grouting program using one of our NCDOT-approved mixes. Using dry batch generation, CJGeo can make up to 200 cubic yards per hour of material, which is enough to fill 562 feet of 42″ pipe per hour.
CJGeo mobilized a dry batch cellular grout plant to the site, and made a total of 5,539 CY of cellular concrete to complete this North Carolina abandonment grouting project over a few weeks. Some of the pipe was completely full of water. Even though cellular grout is significantly lighter than water, it can still displace water out of pipes.
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Virginia Pipe Abandonment
The Job
This Virginia pipe abandonment project is located in Norfolk, Virginia. It is part of the HRSD’s capital improvement program. After installation of a new gravity sewer, 875 linear feet of 24 inch sewer required grout filling for abandonment.
The Challenge
The primary challenge for the general contractor on this project was avoiding installing placement points every 150 feet to use traditional flowable fill. The owner’s specification if using traditional flowable fill requires placement points every 150 feet. The owner allows other controlled low strength materials to be pumped further, as long as uniform material vents at the far end of each placement.
The Solution
CJGeo proposed using 30lb/cuft CJFill-Ultra Lightweight cellular concrete. CJFill-Ultra Lightweight is pumpable thousands of feet per placement. This eliminates the need for most intermediate access points.
CJGeo mobilized a wet batch cellular grout plant to the site, and made 101 CY of cellular concrete grout to complete this Virginia pipe abandonment project in a few hours. The pipe was completely full of water. Even though cellular grout is significantly lighter than water, it can still displace water out of pipes.
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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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