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.
As part of a 24 lane mile mill & pave rehabilitation on the Pennsylvania Turnpike, slab stabilization was required. The Turnpike’s specification for stabilization is either liquid asphalt or polyurethane.
In order to keep MOT in place continuously, work had to be done 24 hours per day. Due to work on three bridges within the repair area, undersealing also had to be phased.
CJGeo proposed undersealing with CJGrout 40NHL, a 4.0 lb/cuft free rise polyurethane grout formulated specifically for undersealing thick pavements in transportation environments. 40NHL is hydroinsensitive, so performs well in wet environments, as confirmed with NYSDOT GTP-9 testing.
Using a double gang drill and single grout truck, CJGeo crews undersealed up to 1.8 lane miles per shift. Drilling was completed at night, and grouting during the day, to allow the general contractor to keep MOT in place continuously.
During widening of Interstate 66 year the interchange with US-15, nine new culverts were installed by jack and bore, and one via direct jacking. The carrier pipes were a mix of spiral metal, precast concrete, and corrugated HDPE, and ranged in length from 150 to 350 feet.
The boring contractor, who was responsible for grouting, was concerned about carrier pipe buoyancy during grouting, and also run length. All work had to be done from one side of the interstate highway (three lanes in each direction, plus full width shoulders and a median strip), as there was no access on the far side.
CJGeo proposed 30lb/cuft cellular concrete for the annular space grouting. Cellular concrete is the preferred material for annular space grouting because it is highly flowable, and reduces the chances of damage to carrier pipes in long placements. Its low unit weight also reduces carrier pipe buoyancy. CJGeo placed 350CY of cellular concrete to successfully complete the jack and bore annular space grouting over three different mobilizations.
During construction of a commercial development, 200LF of 16″ CPVC waterline was installed via jack and bore, through a 36″ casing.
Due to site limitations, only one end of the pipe was accessible for grouting. The length of the placement was approximately 200LF, so grout had to travel 200LF at low pressure, while ensuring a complete fill without damaging the delicate carrier pipe material.
CJGeo successfully complete the project in a few hours. Uniform material vented at the far end confirming complete fill.
Heavy haul freight (silica mine), urban street by short line
100 track feet of crossing panels settled. This caused the adjacent asphalt pavement to fail, and caused tripping hazards at the adjacent pedestrian sidewalk. The crossing ran diagonally across the roadway. The crossing had been replaced twice in the past. The last replacement used flowable fill as the base material. Due to the urban, primarily passenger automobile traffic, there was little deflection of the crossing panels from highway traffic. However, there were up to four inches of deflection from rail traffic loading.
The deflection from rail traffic loading caused the top edges of adjacent panels to be in compression with each other. This caused extensive spalling of the surface, which affected approximately 8 panels. While not a functional problem for panel integrity, the spalled areas were within the sidewalk portion of the crossings, and therefore posed tripping hazards.
The repair had to allow immediate vehicular traffic to facilitate a single lane closure that was flipped halfway through the repair. The repair also had to allow for immediate resumption of rail traffic. The crossing served a sand mine, so repair was designed around high service loads for heavy haul rail traffic.
Due to scheduling constraints of the railroad, the repair method had to tolerate the potential for rail traffic during the repair.
CJGeo modular grade crossing repair crew filled the voids and corrected settlement in less than a day using polyurethane grouting. Asphalt patching was done concurrently with polyurethane injection. The entire repair was completed in less than one day. The roadway and rail opened up immediately after the repair. Traffic control was done to accommodate pedestrians and roadway traffic.
Two trains passed through the crossing over the panels being repaired during the repair. This did not affect the integrity of the repair.
12 tub-style grade crossing panels developed a 2.5″ belly on a heavy haul industrial scrap short line. The railway’s FRA inspector directed the railway to address the settlement of the crossing panels to bring the crossing geometry back into compliance. Along with being non-compliant from a track geometry perspective, accumulation of water below the panels was causing deterioration of the adjacent asphalt pavement.
The belly only affected one travel lane of the roadway, but repairs had to not affect the other lane, so that traffic could be maintained to the adjacent industrial properties. Due to rail traffic schedules, the repair had to allow for rail traffic during the repair.
CJGeo crews performed the crossing repair in a single day, using polyurethane grouting. During the repair, two trains utilized the crossing.
The 8′ long panels of tub style grade crossing settled. As a result, a speed restriction was placed on the crossing, which affected passenger schedules. Three panels were affected, and the belly in the slabs was approximately 2 inches. Slight deflection with heavy truck traffic was noted, and significant deflection with rail traffic was present.
The repair had to be completed in just a few hours, to avoid disruption to rail traffic. The repair had to allow for immediate resumption of rail traffic, and tolerate tamping of the adjacent truck during the repair. Additionally, the tub crossing repair had to be done in a manner which did not disturb the adjacent asphalt pavement.
High density geotechnical polyurethane grouting to stabilize and lift the affected modular grade crossing panels. Geotechnical polyurethane grouting is far superior to mudjacking, in that the process is faster, and can more easily ensure a complete filling of voids under the crossing panels. Lifting precision of less than 0.1 inches is standard.
A CJGeo modular grade crossing repair crew filled the voids and corrected settlement in a few hours. During the tub crossing repair, tamping was done by the rail system to address settlement of the adjacent track.
Settlement and deflection were affecting an eight panel modular grade crossing in an industrial driveway. The crossing was used by both commuter rail and freight. Settlement of modular grade crossing was causing spalling of the panel edges due to more than 2 inches of deflection from rail traffic.
The repair had to quickly and thoroughly address the voids and settlement of the panels to avoid disruption to commuter revenue traffic. A daily window of four hours between last morning and first afternoon commuter traffic was available for the repair.
Due to scheduling constraints within the busy Washington, DC metro area freight market, the repair area had to be openable to freight traffic on 15 minute notice any time during the repair.
High density polyurethane polyurethane grouting to stabilize and lift the affected precast grade crossing panels. Polyurethane grouting is an effective repair for both void filling to address deflection, and also lifting panels to correct settlement.
The crossing was repaired and returned to service without disruption to commuter or freight rail service.
A suburban grade double crossing was rebuilt to address poor drainage infrastructure in the area. This included installing two different culverts adjacent to the crossing panels, and then resetting all of the panels which had to be removed for the culvert installation. During routine track inspections, the panels showed signs of deflection up to one inch with rail traffic. The system’s track division was concerned that pumping of the crossing panels would lead to destabilization of the base, and settlement. At the lower elevation end of the crossing, there was extensive evidence of sub base material being pumped out from under the crossing within two weeks of the crossing reconstruction. 368 track feet were affected.
Work had to be completed during non-revenue hours, between 0200 & 0430 over two nights. There was also a high probability of the voids below the panels being waterlogged.
High density polyurethane grouting to stabilize the grade crossing panels. Specially-formulated hydro-insensitive void filling (high-mobility) grout was proposed in order to ensure complete filling of voids below the panels, whether waterlogged or dry.
CJGeo successfully stabilized the crossing during the two night work period.
The slab floor of a hallway in a middle school settled up to 3.5 inches. A geotechnical study identified voids up to 2.5 inches below the slab throughout the corridor.
The proposed repair needed to address the settlement by lifting the floor. Due to budgetary constraints, the repair could not disturb the VCT flooring.
CJGeo proposed polyurethane grouting for this slab foundation repair project. Polyurethane grouting uses low unit weight grout, which decreases the chances of future settlement. Polyurethane grouting is performed through 5/8″ holes drilled through the slab. This reduces impacts to flooring, and facilitates fast, efficient repairs.
CJGeo successfully performed this concrete floor repair project in less than a day. By using polyurethane grouting, there was no disturbance to the VCT flooring, and the corridor was able to be used normally immediately afterwards.