Neuse River Annular Grouting
The Job
This annular grouting project is located in North Carolina. The City of Raleigh’s Neuse River East Parallel Interceptor project involves the installation of miles of large diameter gravity sewer. Two road crossings required 120″ tunnels for installation of the 96″ HOBAS pipe.
The Challenge
While neither tunnel was very long, due to the 10′ diameter tunnels, grouting needed to be performed in two lifts. This allowed buoyancy control of the HOBAS carrier pipes to be maintained with partial water filling, and eliminated the need to perform hold down blocking during the carrier pipe installation.
The Solution
CJGeo proposed an NCDOT approved 40lb/cuft CJFill-Standard cellular grout mix due to passage through an NCDOT right of way, and then grouted the two tunnels each in two lifts. Fill was confirmed with uniform grout vented out the 12 o’clock vent position at the far end of each tunnel.
By using cellular grout instead of a traditional high unit weight grout, CJGeo designed three lifts out of the placement. This is because carrier pipe buoyancy is a function of the displaced mass. When the grout is less than 1/3 the density of traditional grout, deeper lifts are possible without floating the new carrier.
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Dairy Branch Annular Space Grouting
The Job
CJGeo’s Dairy Branch annular space grouting project is located in North Carolina. Charlotte Water’s Dairy Branch Tributary Sewer project is an approximately $30mm capacity improvement project to address increasing population density.
The Challenge
As part of the project, the tunneling contractor mined a 430LF tunnel ranging from 58″ bore to a four foot arch. The carrier pipe was 36″ ductile iron, and required annular space grouting using a mix which wouldn’t float the carrier pipe, and would be able to entirely fill the tunnel at low pressure.
The Solution
CJGeo proposed an NCDOT approved cellular grout mix due to passage through an NCDOT right of way. This annular space mix design is weighs around 30lb/cuft, so falls withing CJGeo’s CJFill-Ultra Lightweight range. The tunnel was completely dry, so displacing water was not a concern. It took less than two hours to place all 275 cubic yards of grout into the annulus.
Peak pumping pressure was less than five psi. Complete water filling of the carrier pipe provided more than a two time factor of safety for buoyancy control. CJFill-Ultra Lightweight cellular grout is sometimes called foamed concrete fill.
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New York Annular Space Grouting
The Job
This New York annular space grouting work is part of the Bay Park Conveyance Project. The Bay Park Conveyance Project is using a combination of microtunneling and slip-lining. This is to redirect effluent discharge from Western Bay to an existing ocean outfall several miles away.
The Challenge
Approximately 7 miles of the discharge pipe is being sliplined into an existing 72″ riveted iron pipe. The pipe runs underneath the Sunset Highway. Access pits are between 700LF & 3000LF apart, requiring annular space grouting placements ranging from 200CY to 850CY.
Due to maintenance of traffic concerns, all grouting is night work. There is nowhere to stage materials onsite.
The Solution
Working with the design and construction teams, CJGeo designed a 30lb/cuft, 150psi at 28 day compressive strength CJFill-Ultra Lightweight cellular grout for the annular space grouting. By using dry batch mixing onsite, CJGeo is able to achieve the compressive strength required, and place the distances required in the very short nightly placement windows.
Pipe jacking is the installation method for the carrier pipe, so there are no casing spacers. Because there are no casing spacers, water filling is the buoyancy control method. With water fill and a grout density significantly lower than water, the carrier uplift factor of safety is approximately 2.5 times.
To address material logistics, each night’s cement consumption is staged locally during the day. The cement is then brought to each placement location during the pours.
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SW Florida Annular Space Grouting
The Job
This Florida annular space grouting project by CJGeo is located in For Myers, Florida. The work is part of the City of Fort Myers’s South AWWTF Reclaimed Water Transmission Main. The goal of the project is to facilitate the beneficial reuse of treated wastewater, primarily for uses such as irrigation which historically utilized drinking water.
The Challenge
The majority of this pipeline uses open cut installation. However at two road crossings with extensive existing buried utilities, trenchless installation is most appropriate. The first crossing is 170 linear feet. The second crossing is 607 linear feet. Each tunnel is 52 inches in diameter steel. The reclaimed water line is 32 inch diameter ductile iron pipe.
The Solution
The tunneling contractor for this project was under contract to provide turn key installation, including annular grouting. The tunneling contractor reached out to CJGeo, knowing that CJGeo’s CJFill cellular grout could:
- fill each annulus in a single lift
- not over-pressurize or damage the brand new carrier pipe
- not float the brand new carrier pipe
CJGeo took two days onsite to grout both tunnels (one day per tunnel). The final design for the grout on this Florida annular space grouting project was 38lb/cuft CJFill-Standard, with a 250psi unconfined compressive strength at 28 days. While the Florida DOT’s minimum strength for cellular grout is only 80psi at 28 days, the designer wanted a higher strength grout than the minimum acceptable by the DOT.
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Rising Mains 48″ Abandonments
The Job
This Pittsburgh pipe abandonment project is located within the city of Pittsburgh, Pennsylvania. It is part of the Rising Mains No 3 & 4 replacement project. Plans call for filling with grout roughly 1575LF of 48″ water main.
The Challenge
The abandonment was specified for traditional controlled low strength material (flowable fill). However the contractor had doubts about being able to successfully perform the pipe abandonments with flowable fill. These concerns were based on access limitations, ready mix delivery limitations and the roughly 20′ of elevation change over the length of the pipe.
The Solution
The contractor reached out to CJGeo about using low density controlled low strength material (LD-CLSM). CJGeo evaluated the pipeline as-builts and recommended a CJGeo 25lb/cuft CJFill-Ultra Lightweight cellular concrete mix design. 25lb/cuft CJFill-Ultra Lightweight’s average 80psi compressive strength at 28 days (ASTM C495) is ideal for abandoning the pipes. The low density maximizes yield (finished volume per ton of cement), and provides adequate bearing capacity in most situations.
Using onsite dry batching, CJGeo generated and placed 730CY of grout to successfully fill the pipe, which was access near the middle to create two segments. The work took two days onsite to complete. Onsite batching directly from bulk cement was advantageous on this project for the following reasons:
- economical – it costs significantly less than ready mix flowable fill
- speed – CJGeo made more than 100CY of CJFill-UL per hour
- safety – peak placement pressures were less than ten psi
- logistics – it only took five loads of cement, whereas flowable fill would have taken 92 loads
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Facing a similar challenge to this Pittsburgh pipe abandonment project that CJGeo completed with CJFill-Ultra Lightweight cellular grout? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.
Power Station Pipe Abandonment
The Job
This power station pipe abandonment project is between Richmond & Lynchburg, Virginia, along the James River. Dominion’s Bremo Bluff Power Station was taken off line in 2019. As part of complete decommissioning, demolition and site restoration took place in 2022.
The Challenge
Power stations typically have extensive pipes for cooling water circulation. At Bremo Bluff, the buried cooling pipe network consists for four, four foot diameter pipes, connecting to a junction box. Total linear footage of the forty-eight inch pipes is about six hundred linear feet.
Due to the remote location, the demolition contractor knew that it would be difficult to get timely deliveries of the nearly 40 loads of flowable fill needed to fill the pipes.
The Solution
The demolition contractor reached out to CJGeo for consultation on the best type of flowable fill for the pipe abandonment work. CJGeo recommended 25lb/cuft CJFill-Ultra Lightweight. 25lb/cuft CJFill-Ultra Lightweight has a 28 day compressive strength (ASTM C495) greater than 50 psi. This met the owner’s requirements.
25lb/cuft CJFill-Ultra Lightweight is nearly 80% air content. Therefore, each twenty-five ton load of cement delivered to the site turns into nearly 150 cubic yards of finished product. Due to this on-site expansion, instead of needing nearly 40 loads of ready mix flowable fill, the work only needed two loads of cement.
CJGeo generated and placed approximately 300CY of CJFill-Ultra Lightweight cellular concrete to fill the junction box and pipes. CJGeo made all of the material over a few hours onsite, using dry batch generation.
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Facing a similar challenge to this power station pipe abandonment project? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.
Tennessee Annular Space Grouting
The Job
This Tennessee annular space grouting project is located in Brentwood. Brentwood is part of the Nashville metro area, which is rapidly expanding. As part of large water main installation, a 970′ tunnel, ranging from 60 to 78 inch diameter was mined through a small mountain. To ensure long term service improvements, a 42″ DIP water line occupies the tunnel.
The Challenge
The tunnel support is wood lagging, which is not permanent. Therefore, the annular space requires grouting to ensure long term stability of the new water line and adjacent ground.
Because the Nashville market is so hot, it’s really hard to get any concrete deliveries, let alone specialty mixes. The tunneling contractor knew that they would be hard pressed to self-perform the grouting using flowable fill. This was if they could even get material. So, they reached out to CJGeo about performing the annular space grouting with cellular grout made onsite with one of CJGeo’s custom mobile cellular batch plants.
The Solution
CJGeo proposed and installed 25lb/cuft CJFill-Ultra Lightweight cellular grout for the annular space grouting. By generating material onsite directly from bulk cement, using a dry batch plant, the 425CY annular space grouting took fewer than five hours.
Buoyancy control on this project was very easy. Because CJFill-Ultra Lightweight cellular grout is so much lighter than water, filling the carrier with water was sufficient to ballast the pipe against uplift during grouting. No casing spacers or top blocking needed. The American Concrete Institute classifies CJFill-Ultra Lightweight as low density controlled low strength material.
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Georgia Annular Space Grouting
The Job
This Georgia annular space grouting project is located in Athens, Georgia. The project involves three tunnels connecting four shafts. Tunnel lengths range from 116LF of 700LF, with diameters between 58.5″ ID to 9×9 arch segments.
The Challenge
In order to keep the carrier pipe from floating during grouting, the maximum allowable grout density was 70lb/cuft, and the minimum compressive strength was 200psi. Material had to be highly mobile, to facilitate placement through the 700LF of tunnel.
The Solution
CJGeo proposed 38lb/cuft cellular grout to the tunneling contractor. Over a period of three days, CJGeo batched and placed 1320CY of CJFill-Standard. Batching was performed utilizing an onsite dry mix plant, which was fed directly by bulk cement trailers. The minimizes the required laydown area on a very tight site.
Because of the very low grout density, the carrier pipe buoyancy control was simply water filling.
To address the transition from a round tunnel to an arch tunnel, CJGeo worked with tunneling contractor to design a sacrificial pipe venting system.
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Launch Shaft Permeation Grouting
The Job
This launch shaft permeation grouting project is located in Fort Myers, Florida. As part of a utility installation project, a 60″ MTBM was being launched from a shaft sunk in the middle of a nest of buried utilities, adjacent to an arterial roadway. Utilities included water, sewer, ITS, traffic signals, and others. The MTBM launch elevation was approximately 18′ below ground water.
The Challenge
The shaft installation contractor and adjacent open cut utility installations had experienced flowing sands, which had proven problematic. The tunneling contractor knew that without increasing the stability of the soils adjacent to 60″ hole they needed to cut in the sheet pile shaft walls, there would likely be significant loss of ground into the shaft, potentially damaging the adjacent utilities and roadway.
Soils excavated from the shaft were primarily fine sands, silty sands, and silt. Previous attempts at grouting the same soils with a prepolymer chemical grout had proven unsuccessful.
The Solution
CJGeo determined that acrylic grout would be the most appropriate. Acrylate can bind the soils together very well. This makes flowing silty sands stand vertically during cutting of the launch hold in the sheet pile wall.
Because acrylic grouts have single digit viscosities, they are able to permeate very find grained soils with ease, ensuring uniform stabilization.
CJGeo performed the launch shaft permeation grouting via holes cut in the sheet piling, and treated an approximately 8CY mass of soil. In addition to grouting the soils immediately adjacent to the launch hole, CJGeo performed leak stop grouting on numerous nuisance leaks throughout the joints of the sheet pile shaft.
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MTBM Recovery Grouting
The Job
This MTBM recovery grouting project is located in Florida. When a 42″ MTBM stopped advancing under the shoulder of I-75 in Miami, Florida, the tunneling contractor had to sink a shaft adjacent to the roadway, and then hand mine in to recover the machine.
The Challenge
The MTBM was stalled approximately four feet from where the recover shaft was sunk. The face of the machine was under the shoulder. The tail of the machine was under the outside lane of the interstate. The machine was approximately 15′ below ground water level. There was also extensive ground water infiltration into the sheet pile rescue shaft. Further complicating things, an intelligent transportation system duct bank runs right over where the machine came to a halt.
In order to ensure that the ground would be stable to facilitate hand mining in from the shaft while avoiding settlement of the interstate, the tunneling contractor reached out to CJGeo about increasing the stability of the soils.
The desire was to increase the stability of the soils. However, the treated soils had to be hand excavatable by divers working in a casing slightly larger than the MTBM. Soils in the desired treatment zone included lime rock, course sands and silty sands.
The Solution
CJGeo determined that acrylic grout would be the most appropriate to bind the soils together. This method would also significantly reduce their permeability, but still facilitate hand excavation in an underwater confined space.
The failure mechanism of the MTBM was unknown. So, CJGeo grouted the zone between the MTBM face and the rescue shaft. We then grouted a collar around the entire MTBM machine in case the machine needed to be completely uncovered.
CJGeo successfully performed the permeation grouting, then divers excavated back to the machine, freeing it. The grouted face held once the receiving ring was installed and the sheet pile wall cut. The treatment zone soil was easily excavatable for the divers.
In addition to grouting the soils, CJGeo’s crew also performed grouting of numerous nuisance ground water leaks through various joints in the sheet pile shaft.
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