Due to an oversight during construction, acidic groundwater at a coal mine in West Virginia was causing deterioration of 7′, 9′ and 10′ CMP bypass pipes adjacent to a coal stockpile. The pipes had been installed to bypass streams below the surface elements of the mine, but high iron content and low acidity of water entering the pipes caused the mine to have to treat the water which was supposed to be bypassed.
The pH of the water affecting the metal pipes was as low as 2.1. While typical chemical grouts have excellent histories resisting chemical attack at low pHs, low pH can affect the initial reaction. The owner and geotechnical consultant were also concerned about leak stopping work on the pipe causing water to flow outside of the pipe downstream to other areas which were yet unaffected.
CJGeo worked with multiple potential grout suppliers to identify a grout which would not be affected by the acidic environment. A 120cps high expansion prepolymer was chosen due to its ability to react properly in low pH environments, and also for its low viscosity to help ensure good coverage.
A CJGeo chemical grouting crew completed leak stopping on 31 joints and 25 point leaks throughout 600LF of pipe over a period of two weeks, in addition to grouting a 1200CF cutoff wall to stop water migration outside of the structure.
Water began to seep through the floor of the shop, break room and bathrooms inside a manufacturing facility. Investigation determined that a water line had broken, and weekend soils below the floor, causing the settlement. Voids were also present.
The client’s primary concern was addressing the stability of the area without affecting normal usage.
CJGeo proposed chemical grouting to stabilize the weakened soils, along with polyurethane grouting to fill voids. Previous repairs to address floor settlement had been completed, so a hydroinsensitive undersealing polyurethane grout was used to ensure stability without lifting the slab.
Two underground stormwater sand filters at an apartment community wouldn’t hold water. The structures, which were assembled from 10′ diameter metal pipes needed to pass a water loss test before the property could come off bond. Previous repairs attempted included installation of internal joint rings and seals, which did not stop enough flow to pass the water loss tests.
The proposed repair had to accommodate multiple layers of previous repairs. The joints included four different materials–aluminized metal, galvanized metal, neoprene, and polyethylene. The structures were bedded in washed #57 stone, and were connected to the stormwater drainage system, so subject to live flow.
Sprayed high density polyurethane/polyurea hybrid to seal the joints internally. In addition, chemical grouting for joints which had been repaired previously using internal bands and polyethylene seals. The chemical grouting repair was designed to minimize loss of chemical grout into the surrounding stone beds. The previously-installed internal seals and bands were left in place and encapsulated in the joint sealant.
CJGeo large diameter pipe repair crew installed chemical grout to seal the leaking joints. Immediately after the sealing was performed, the structures were tested by the municipality. Neither structure leaked any water after CJGeo sealed the joints.
An area of floor inside of a produce processing facility experienced water intrusion through joints in the floor. Considerable amounts of process water were dumped on the floor each day, and unsealed joints in the floor allowed water to collect under the floor slab. With dynamic loading from material handling equipment, water was displaced through the joint onto the floor. The facility’s health & safety staff was concerned that the water could introduce contaminants to the food processing area.
The proposed repair had to perform well in saturated conditions, allow for near immediate resumption of material handler equipment, and ensure a longterm fix. Since no settlement had occurred, the grout material had to be able to seal the very small voids, displace water, and not exert any lifting forces on the floor.
The material & process also had to be performed at cold temperatures–the facility is maintained at 34 degrees year-round.
CJGeo proposed chemical grouting using a hydrophilic prepolymer grout. Chemical grouting is ideal for saturated environments and helps to ensure complete stabilization and sealing of floors.
A single CJGeo chemical grouting crew mobilized to the site and performed the work in a few hours. The work started after second shift, and was completed in time for the grout to set and tolerate material handling equipment at the start of first shift.
The following day, the facility reported no water extrusion under material handler traffic.
A large sinkhole opened up in the parking lot of a manufacturing facility. The sinkhole was adjacent to a cast-in-place stormwater drop inlet structure. The structure was 14VF deep, and was fed and discharged by 54″ HDPE pipes, requiring HDPE pipe joint sealing.
Facility maintenance personnel had been monitoring the sinkhole and noted that it was growing rapidly. Inspection of the pipe revealed that there were joint failures at the first joint out from the manhole, and deterioration of the parging. The parging between the HDPE and concrete pipe had failed to the point of significant amounts of soil washing out during rain events.
The repair had to be done without disrupting traffic in the parking lot. It also had to provide a long term solution to the failed pipe joints.
Along with gently filling the voids around the HDPE pipe without deflecting or damaging it, the repair material had to have enough expansive force to thoroughly seal the small cracks and leaks in the parging between the HDPE pipe and concrete structure walls.
Chemical grouting was chosen for injection through the joints of the HDPE pipe. Prepolymer chemical grouting uses single component polyurethane grouts with exceptionally long gel times. This virtually eliminates localized expansive pressure, which could further damage the HDPE pipe, which was already out of round.
Plural component structural foam was used for void filling the large sinkhole that extended from the bottom of the structure to the surface.
Prepolymer chemical grout was injected through the joints in the HDPE pipe. This successfully sealed the bell and spigot joints without causing further deflection of the pipes.
The large sinkhole void was grouting using plural component polyurethane grouting. A low exotherm structural foam was chosen due to the very large size of the void. Structural foams are important in situations where there are very large voids in areas subject to traffic loading.
Dam outfall pipe seep grouting, Fairfax, Virginia
A 36″ RCP outfall pipe for a dam terminated at an end wall. As part of a dam rehabilitation, small seeping leaks at the end wall/pipe joint needed to be stopped. The leaks had to be stopped so the wall could be resurfaced.
The engineer specified chemical grouting.
Access to the area was quite difficult. It was more than 150 feet from the closest vehicle access, which was only accessible by 4×4 vehicle down a steep slope.
While unknown during the planning of the chemical grouting repair, what was thought to be 36″ RCP was actually larger diameter RCP that had been lined with steel casing pipe. An interior poured-in-place concrete liner had been installed afterwards.
Super low viscosity prepolymer chemical grout was selected. This was for two reasons: 1) the ability to easily pump more than 150LF from the lay-down area. and 2) the ability to seek out and stop leaks through very tight cracks in the structures.
Prepolymer chemical grouts are water-reactive, so can be injected into active water flows. The grout expands when it comes into contact with the water, which seals of the leak.
The initial grouting plan was to install the chemical grout through the pipe wall starting beyond the first joint in. However, because the pipe had been cased, placement had to be done through the end-wall structure only. Multiple injection holes were drilled through the end wall structure, and the chemical grout was pumped through the end-wall structure.
Extensive catalyzation was used to first seal the leaks at the end wall and then chase the water flow pathways up along the outside of the pipe. The job was messy due to the forced proximity of the injection points and the leaks. But all the leaks were successfully stopped.