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 105,000 gallons of acrylic grout, at rates of nearly 15 gallons per minute.
The grouting facilitated the hyperbaric intervention. Following the intervention, the contractor resumed mining.
Speak With An Expert
Facing a similar challenge to this TBM intervention permeation grouting 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.
Flooded Shaft Grouting
The Job
This flooded shaft grouting project by CJGeo is located outside of Washington, DC at a data center site. As the 60″ microtunneling machine was entering the retrieval shaft, a piece broke off of the secant pile wall, and tore the seal. This resulted in water infiltration of around 600 gallons per minute into the shaft. The machine was recovered, but the shaft filled with nearly 15 feet of water in a matter of hours.
The casing crown has roughly 20 feet of cover, and is about 15 feet below the ground water level. The ground in the area is a mix of clays and sands. The tunnel is primarily in the underlying fractured rock. For the last 30 feet of tunnel before the secant pile receiving shaft, the tunnel is in a mix of weathered rock and sandy clay.
The Challenge
Having used CJGeo in the past to address high volume leaks into shafts, the tunneling contractor reached out to CJGeo for this flood shaft grouting problem. The primary constraints were:
- time – the project was already behind schedule
- water management – any groundwater was considered contaminated
Typically, grouting a leak such as this would be as simple as throwing bigger pumps into the shaft, dewatering it, then grouting the leak from inside the shaft. However, because of the costs associated with treating potentially very high volumes of water at this site, this wasn’t an option.
The Solution
CJGeo proposed, and then successfully performed, a two stage grouting program. Primary grouting was done using CJGrout 35NHV61 geotechnical polyurethane on a Saturday. The CJGrout 35NHV61 was installed immediately behind the secant pile wall through three holes drilled from the surface to intercept the over cut. Grout injection through these holes resulted in grout return to the retrieval shaft. Off gassing also showed up at the launch shaft. This indicates that the rapid inflow of water during the flooding event had washed out some of the mud in the over cut.
After completion of the plural component primary seal injection, CJGeo dye tested the primary grouting program. This was done through Tube-A-Manchette grout pipes installed using sonic drilling along the tunnel alignment, further out from the shaft. No dyed water returned to either shaft.
The following day (Sunday), CJGeo performed permeation grouting using colloidal silica through the TAM grouting tubes. This secondary grouting program served two purposes:
- seal any rock fractures that weren’t penetrable by the higher viscosity plural component polyurethane grout
- replace any overcut mud washed out during the initial flooding event
Speak With An Expert
Facing a similar challenge to this flooded shaft grouting 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.
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.
Speak With An Expert
Facing a similar challenge to this SOE closure Manchette grouting 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.
