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.
Speak With An Expert
Facing a similar challenge to this MTBM recovery 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.
Acid Drainage Grouting
The Job
This acid drainage grouting project is located in West Virginia. A 72″ CMP stream diversion pipe under a coal stockpile at a coal mine in West Virginia was experiencing acidic water infiltration. This was causing bypassed stream water to become acidic, so regulators required all of the stream flow to be pumped to treatment ponds and treated. This was expensive, and the flow volume was greater than the design capacity of the treatment system.
The Challenge
Access was quite challenging. The pipe was either 700LF or 1300LF from the nearest access points to the farthest grouting location. Additionally, the infiltrating water was pH 2.
Due to location, all personnel had to be MSHA 40 hour trained, and the company registered as a mine contractor with the state.
The Solution
CJGeo recommended a hydrophobic prepolymer chemical grout with an extensive performance history in high acidity environments. CJGeo crews sealed a combination of 20 joint leaks and point infiltration sources using the prepolymer chemical grout.
To address acidic water migrating through the stone dust backfill outside of the pipe, CJGeo crews then grouted an in-situ cutoff wall in the trench just downstream of the lowest leak using permeation grouting. Permeation grouting is optimal for creating small footprint cutoff walls because it typically doesn’t require large equipment. The mine operator installed two dewatering wells immediately upstream of the cutoff wall to intercept and pump out the acidic drainage, to keep it isolated from the stream water.
Speak With An Expert
Facing a similar challenge to this acid drainage 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.
