Fort Lauderdale Permeation Grouting
The Job
This Fort Lauderdale permeation grouting project is located next to Port Everglades. Port Everglades is a crucial piece of Florida’s infrastructure, with annual economic impact exceeding $30 billion dollars per year. The tunnel, which is being mined with a 72″ MTBM, crosses under Eisenhower Boulevard from the George T Lohmeyer Wastewater Treatment Plant towards the Broward County Convention Center.
The tunnel is more than 20′ below grade, below the water table, in limestone with pockets of silty sand.
The Challenge
On this project, the microtunneling contractor had two tunnel crossings. On the first, they elected to not pre-grout their break in & break outs through the SOE. This resulted in a significant water and soil inflow event during the first break in. This crossing, under the entrance to the cruise port and between two other pieces of critical infrastructure, would not tolerate any surface disturbances associated with a flooding event.
The contractor reached out to CJGeo about stabilizing the launch & retrieval shafts to ensure stability during the launch & retrieval processes, by performing permeation grouting.
The Solution
CJGeo proposed permeation grouting of the limestone with an acrylic grout to ensure stability of the launch & retrieval shafts. Permeation grouting with acrylic grout ensures uniform permeation, and displacement of groundwater. It also ensures that the soils are sufficiently bound together to not fail while cutting the launch & retrieval holes in the sheet pile.
CJGeo installed the sacrificial tubing for this installation from the shaft. Occasionally, sonic drilling is useful for pre-grouting, but in this case, it was more economical and less disruptive to go through the shaft walls.
CJGeo performed the permeation grouting work in a single shift at each shaft.
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TBM Intervention Permeation Grouting
The Job
This TBM intervention permeation grouting project is located in Virginia. It is part of a highway tunnel installation project to increase capacity on a bridge tunnel.
The Challenge
During mining, the TBM, which is more than 40′ in diameter, began to pull pieces of sheet pile & wire rope through the face. To prevent further damage to the machine, tunneling was stopped. The machine encountered the debris approximately 250 feet short of the exit structure, underneath a constructed island.
The island is built out of relatively loose beach sand that’s commonly available in the area. The crown of the machine is approximately 25′ below grade, with the invert of the machine being about 70 feet below grade. Mean high tide is also about 25′ below grade.
In order to facilitate a hyperbaric intervention, the contractor needed a solid plug in front of and around the machine face. The criteria for the plug included:
- easily excavatable, to prevent issues for the TBM upon resumption of mining, and also to ensure that divers doing the hyperbaric intervention wouldn’t have issues removing grouted material in the case of grout entry into the machine face.
- low viscosity, to ensure uniform permeation into the soils in front of the machine, though they were relatively course (only 1% fines)
- readily available, in order to meet the incredibly short schedule requirement
The Solution
CJGeo proposed permeation grouting to create the plug using acrylic grout. Acrylic grout is:
- readily available through the mining supply chain
- very low viscosity, so well suited for permeating sands
- forms a stiff gel that’s stable, but still easily hand-excavatable
To perform permeation grouting up to 75 feet below grade, CJGeo proposed sonic drilling to install Tube-a-Manchette (TAM) pipes.
Due to the compressed timeframe, CJGeo subcontracted a sonic driller to install 86 different TAM wells, ranging from 25 to 75 feet deep. Once the first 10 TAM tubes were in place, CJGeo started placing acrylic grout through up to 10 simultaneous TAM pipes, using straddle packers and a PLC-controlled grouting system.
CJGeo was onsite within 10 days of the first call. Then, over 23 calendar days, CJGeo successfully installed more than 85,000 gallons of acrylic grout, at rates of nearly 15 gallons per minute.
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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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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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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. CJGeo used sonic drilling to install the TAM tubing.
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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Pregrouting for Hand Mining
The Job
This large CSO project in Alexandria, Virginia required pregrouting for hand mining. The hand mining was to install a new pipe below an existing influent tunnel, which is on piles. The hand mined tunnel was to connect two a secant pile shaft to a slurry wall pit, which are roughly 25′ apart.
The Challenge
The challenges on this project included:
- no drilling allowed without pre-probing
- 3′ thick secant pile walls
- unknown exact pile support layout of influent tunnel
- fully saturated soils
- potential debris in backfill under existing influent tunnel
The Solution
CJGeo proposed performing the permeation grouting using acrylate. Acrylate is exceptionally low viscosity, so well suited to the organic, fine-grained soils. Previous permeation grouting on the project was done with acrylamide. However, acrylamide is neurotoxic and carcinogenic, so the owner was happy to learn about acrylate, which has very similar properties, but is not neurotoxic or carcinogenic.
To avoid drilling, CJGeo developed a pushed/driven probe grouting installation. This approach uses 1/2″ diameter steel tubing driven to depth, and then grouted through during extraction.
The 3′ thick secant pile walls didn’t pose too much of an issue, clearance holes were drilled with hand-held percussion drills.
Drilling wasn’t allowed. The owner and design team were concerned about potentially hitting and damaging the pile foundation. Because there was the potential for debris, there would be no way to distinguish debris from a pile until it was potentially too late. By using groutable probe rods, CJGeo avoided all of this risk.
The fully saturated soils had relatively low permeability, and the site was constrained on two sides by the existing SOE structures. Performing permeation grouting when below the water table you’re limits the placement rate by the ability to displace the existing groundwater. Because of the water-tight walls on two sides of this pregrouting for hand mining application, take was slower than originally anticipated.
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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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