Lightweight Temporary Dam Foundation
The Job
As part of flood proofing project a nuclear power plant, a temporary dam was designed for installation as needed between two large structures.
The Challenge
The cooling water pipes for a reactor passed under where the dam would need to be constructed in the case of a predicted flood. If placed, the dam would add up more load to the underlying cooling pipes than they were designed for.
The Solution
To reduce the load on the underlying pipes in case the dam needed to be placed, the designer elected to excavate 3′ of fill from above the pipes and replace it with 25lb/cuft CJFill-UL . To address buoyancy, given the minimal cover (2″ of asphalt), geogrid was cast into adjacent high density flowable fill, and then cast into the CJFill-UL.
CJGeo placed the material in two lifts.
Industrial Basement Abandonment
The Job
As part of an adaptive reuse project of an abandoned industrial site, the former onsite power plant’s stacks were being rehabilitated. Multiple tunnels and basement rooms needed to be completely filled.
The Challenge
Due to safety concerns, nobody could enter the basement. No as-builts were available. Camera inspection through holes cored in the ceiling showed significant numbers of passageways and obstructions. The fill material had to be exceptionally mobile, able to be placed in deep lifts, and as light as possible.
Fill density was a concern because the basement was up to 15′ deep. The structural and geotechnical consultants were concerned about inducing settlement if flowable fill (typically around 150lb/cuft) was used.
The Solution
CJGeo proposed 25lb/cuft cellular concrete for the fill material. Using onsite colloidal batching, CJGeo can place material up to 20′ deep in a single lift, without consolidation. Because the material is so lightweight, the entire 15′ deep basement could be filled for the same dead load as just two feet of flowable fill.
CJGeo mobilized a 150CY/hour dry batch plant to the site after staging 300 tons of cement onsite using our in-house cement pig & trucking operation. Without being affected by trucking or cement supply chain disruptions, CJGeo started placing immediately. Over four days onsite, CJGeo place 2700CY of material.
Power Station Pipe Abandonment
The Job
Dominion’s Bremo Bluff Power Station was taken off line in 2019. As part of complete decommissioning, demolition was performed in 2022.
The Challenge
Four, 48″ cooling water pipes needed to be filled with grout to ensure longterm stability of the surrounding area. In addition to the pipes, a junction box they all connected to needed to be filled.
The Solution
CJGeo generated and placed approximately 300CY of 50psi cellular concrete to fill the junction box and pipes. The material was generated onsite over the course of a few hours using dry batch generation.
25MGD Sinkhole Leak Grouting
The Job
An underground minerals mine started to lose up to 8VF per day of mine due to water infiltration. Investigation of an adjacent stream uncovered multiple sinkholes which had opened up where the stream crossed a fault. Two sinkholes were adjacent to bridge abutments of a public road, which served as the sole access for multiple homes and farms.
The Challenge
Mine personnel started to self-perform chemical grout in some of the sinkholes. Due to the slow rate of grout installation relative to the water flow, the self-performed grouting was unsuccessful.
Due to endangered fish habitats within the stream, cementitious grouts weren’t allowed, and any chemical grouts needed to be certified for potable water use.
The Solution
CJGeo mobilized two polyurethane grouting crews in the third week of the Covid-19 pandemic to the site. To facilitate safe access to the site, all grouting was performed from aerial platforms reaching out over the work area.
During the grouting process, multiple additional sinkholes opened up; CJGeo would seal one sinkhole, and an adjacent soil filled feature would blow out. Super sacs of aggregate were dropped in the sinkhole throats to fill the bulk of voids, and then polyurethane grouting was performed below the super sacs.
Using nearly 50,000 pounds of CJGrout 35NHV61, CJGeo was able to slow the leaks to the point where no additional sinkholes formed, and the mine’s pumps were able to dewater the facility.
NY Thruway HDD Annular Space Grouting
The Job
As part of distribution improvements, National Grid’s contractor bored 830LF through rock using HDD. The bore was 30″, with a 16″ HDPE casing, carrying three, 4″ HDPE conduits.
As part of the installation, the NY Thruway Authority required the casing to be back-grouted, and the casing pipe’s annular space grout filled.
The Challenge
The proposed back-grout had to be pumpable 830LF at very low pressure, dense enough to displace the 10PPG drilling mud and provide sufficient strength to meet Thruway requirements. The proposed annular space grout had to be pumpable 830LF at very low pressure, light enough to not apply excessive pressure on the conduit pipes, and also provide sufficient strength to meet Thruway requirements.
The Solution
CJGeo proposed two different grout mixes to meet the project requirements. 85lb/cuft casing background for the displacement of the 10PPG (75lb/cuft) drilling mud, and 25lb/cuft annular space grout within the casing.
CJGeo’s crew mobilized to the site, and successfully performed the back-grouting and annular space grouting in a single day.
Coal Pier Sinkhole Grouting
The Job
With an annual throughput capacity of 48 million tons, Norfolk Southern’s Pier 6 at Lamberts Point in Norfolk, Virginia is one of the largest coal trans-loading facilities in the world. As an around-the-clock facility built around precision logistics, there’s little tolerance for disruption or downtime.
The Challenge
When two sinkholes opened up at the end of Pier 6 adjacent to the bulkhead, railroad personnel reached out to an onsite maintenance contractor. Steel plates were installed to provide temporary protection while a long-term solution could be implemented.
The Solution
CJGeo performed DCP testing at the site in order to quantify the depth of voids below the pavement adjacent to the sinkholes. The DCP testing showed that in addition to large voids visible from the sinkholes immediately below the pavement, there were large pockets of voids down to 15’ below the surface.
CJGeo crews then used CJGrout 35NHV61, a hydro insensitive, NSF-certified geotechnical polyurethane to fill all voids and restore stability to the area. The grouting work took five hours onsite to install 3400 pounds of material, with zero disruption to operations.
Acid Drainage Grouting
The Job
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.
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. 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.
Tub Crossing Repair
The Job
The sandy soils of South Jersey are great for growing produce and mining pure silica sand. While most of the produce is shipped by truck, a lot of the silica is shipped by rail. The rails inevitably cross the roads, and many of the crossings are at grade.
The Challenge
A short-line railroad was experiencing significant settlement and pumping of multiple precast modular crossings in the Vineland & Millville areas. Each crossing saw significant truck traffic, primarily from aggregate mining, and also significant heavy haul rail traffic from transporting sand.
The Solution
Working with a rail maintenance contractor, CJGeo performed polyurethane grouting on a total of four precast tub crossings in the area. Each was done in a single day, with the immediate resumption of automobile traffic, and rail traffic. Supplemental bolting was performed to address the deterioration of the panels that had resulted from the extensive movement of the panels.
Industrial Driveway Crossing Repair
The Job
MARC’s Brunswick Line’s Frederick extension passes through multiple industrial sites & driveways. This particular crossing served as the driveway of a ready mix concrete operation, so saw extensive high dynamic loading in a wet environment.
The Challenge
The repair had to be performed without disrupting either rail or industrial traffic. There was a four-hour window between the last morning train and the first evening train for performing the repair to the eight modular tub crossing panels. The settlement was up to two inches, with extensive spalling.
The Solution
CJGeo’s crew installed supplemental bolts due to replace the OEM center panel anchors, and then grouted the crossing in the mid-day window, without disruption to any stakeholder.
Mine Shaft Abandonment
THE JOB
The inverted pyramid concrete cap on a Civil War-era coal mine shaft collapsed catastrophically. The mine shaft was located in the middle of a suburban golf course in Richmond, Virginia. The collapse was due to the deterioration of timbers lining the shaft through soft sandy soils. The soft sandy soils extended approximately 25VF down to rock. As the timbers deteriorated with time, they lost the ability to support the cap.
THE CHALLENGE
The tunnel shaft was completely full of water, which was approximately 60 degrees. The area around the cap was very unstable and did not facilitate top-down access over the mine shaft.
THE SOLUTION
The repair was designed around drilling well casing at an angle to intercept the mine shaft at various elevations between the bottom of the cap and socketed down into the underlying rock. 3.5PCF hydro insensitive polyurethane grout was chosen for its ability to provide the necessary structural support to the cap.
CJGeo performed pre-mobilization testing at our facility in collaboration with the design engineer to ensure that the grout would perform as desired. CJGeo placed polyurethane grout through approximately 15 different injection points, grouting from the top down. The end result was a plug extending at least 5′ into the shaft through rock, ensuring that the shaft through soft soils was completely stabilized.
