Dumfries Pipe Abandonment
The Job
This utility relocation included abandonment grouting as part of a VDOT roadway reconstruction and realignment of US Route 1 in Dumfries, Virginia. This Dumfries pipe abandonment job is located in a rapidly growing town in Northern Virginia. US Route 1 is a major local traffic corridor, as well as a bailout route for I-95 congestion.
The Challenge
1,575LF of pipe, a combination of 54″ & 60″ needed to be completely filled with grout. Due to sequencing, the pipe was underneath new roadway at the time of abandonment. So, the fewer the number of access points, the better.
The Solution
CJGeo placed 995CY of 25lb/cuft CJFill-Ultra Lightweight cellular grout to completely fill the pipe run. The material was placed in a single day, from a single access point near the center of the pipe run.
To facilitate such a large placement in a single day on this Dumfries pipe abandonment job, CJGeo used dry batch generation. Dry batch generation mixed water with bulk cement onsite, using a mobile batch plant. CJGeo’s mobile batch plants are designed specifically to generate foamed concrete. They generate preformed foam at the same time as making the cement slurry. The preformed foam and cement slurry pass through an in line mixer, at up to 200CY/hour.
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Lightweight Pipe Backfill
The Job
This lightweight pipe backfill is part of the City of Alexandria’s RiverRenew project, its largest in history. The project includes installation of new interceptors, and a large CSO/conveyance tunnel.
The Challenge
A pile-supported, concrete-encased interceptor needed to be backfilled. Due to the pile support capacity, the maximum allowable density of the load reducing backfill was 90lb/cuft.
The Solution
To bring the average backfill density to 90lb/cuft, CJGeo proposed filling between the SOE & concrete encasement with 30lb/cuft CJFill-High Permeability (HP). CJFill-HP has very high permeability, so reduces buoyancy when saturated when compared to other lightweight fill materials. CJGeo successfully filled between the concrete encasement and SOE with 145CY of CJFill-HP. The placements was done in a single, 6′ deep lift in less than an hour.
To facilitate the fast placement speed, CJGeo used a mobile batch plant to generate the CJFill-High Permeability cellular grout onsite. Onsite generation blends dry, bulk cement onsite with water, using custom batch plants which also make generate the preformed foam on site. The cement slurry is around 110lb/cuft, and the preformed foam is around 2.5lb/cuft. CJGeo’s batch plants utilize colloidal mixing, which ensures the highest quality cement paste, and therefore the highest quality finished product possible.
The use of very low density material then allowed the client to backfill on top of the structure with normal unit weight material while maintaining the average 90lb/cuft density through the full depth of the fill column. Aerix Industries supplied the preformed foam.
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Nashville Basement Abandonment
The Job
This Nashville basement abandonment project is located along Church Street, in downtown Nashville, Tennessee. A privately owned building was constructed inside of the basement of a previous building, but with a smaller footprint. Structural slabs spanning between 4′ and 20′ from the original basement walls to the new basement walls served as a parking lot and public sidewalk.
The Challenge
As the structural slabs over the unused basement deteriorated, there were concerns about stability. Uses included a public sidewalk and parking/driveway area. The wall isolating the occupied space of the new building and the unoccupied area of basement was constructed of hollow clay block, metal studs & drywall. The maximum lateral load of any backfill material could only be 50PSF.
The Solution
CJGeo successfully completed this Nashville basement abandonment with 775CY of 25lb/cuft CJFill-Ultra Lightweight cellular concrete. CJGeoGeo used 2′ lifts to meet the maximum 50PSF liquid head limit on the containing wall.
To address the unreliability of ready mix availability, CJGeo used the dry batch generation process to make the CJFill-UL onsite. Dry batch generation blends dry bulk cement and water onsite using a custom batch plant, which also generates the preformed foam. The cement slurry and preformed foam pass through a static mixer to ensure a homogenous mixture.
Because the roof slab was close to 18″ thick, and had multiple cast in place beams, CJGeo worked with the customer to design a sacrificial vent pipe system. This minimized the number of holes to core through the slab, while ensuring continuous bearing of the vault roof on the cellular concrete fill material.
Prior to placement of the CJFill-UL, a shotcrete contractor coated the hollow clay block wall to make it grout tight.
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Valve Vault Infiltration Grouting
The Job
This valve vault infiltration grouting project is part of the Purple Line project in Maryland. A large diameter water line was relocated, with the tie-in done inside a 10′ diameter vault that was about 20′ deep. The vault structure, which is precast, and set inside a line plate shaft, was leaking at multiple joints and at a poured in place pipe penetration closure.
The Challenge
The vault structure wasn’t concentric in the shaft. This left little room to pour the closure around the pipe penetrations. One of the penetrations leaked, causing the structure to completely fill with water. Per specifications, it needed to be dry.
Most of the shaft was backfilled with 57 stone. Highly permeable backfill material can make water control grouting particularly difficult. When grouting to seal relatively tight leaks in a structure, the less permeable the adjacent soils the better. All grouts want to take the path of least resistance, and with highly permeable backfills, that often means traveling out into, and permeating, the backfill material instead of into tight cracks and water passageways.
The Solution
CJGeo proposed grouting the infiltration points with CJGrout-35NHV61. 35NHV61 is a hydroinsensitive, plural component geotechnical polyurethane injection grout, certified for potable water contact. 35NHV61 is a moderately mobile grout, selected to minimize mobility into the 57 stone backfill and reduce material loss during grouting.
CJGeo mobilized a three person crew to the site, and performed the valve vault infiltration grouting over a few hours.
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Steam Tunnel Lightweight Backfill
The Job
This steam tunnel lightweight backfill project is located at Western Carolina University, in Cullowhee, North Carolina. As part of the expansion and renovation of the steam plant, a section of existing steam tunnel needed to be uncovered to install a new wall. The wall needed to be backfilled, and due to the condition of the tunnel, the lighter the backfill the better.
The Challenge
The site was exceptionally tight, and the location was more than 30 minutes from the closest ready mix plant. The backfill depth was nearly 15 feet, but the project was only about 1200CY. So, doing 2′ lifts would have been slow and expensive.
To effectively eliminate axial loads from the tunnel, the structural engineer designed a cardboard void form system to temporarily support precast planks on top of the tunnel, which was approximately 5′ wide and 5′ tall. The planks extended about 18 inches beyond the sides of the tunnel. The void forms were wrapped in plastic. This ensured they wouldn’t be fouled by the CJFill-Ultra Lightweight cellular concrete during the pour. After the CJFill-UL was in place, the ends of the beams were encapsulated in, and bearing on, the cellular concrete, while spanning over the tunnel, and transferring the load of the backfill above the tunnel away from it.
The Solution
CJGeo proposed a CJFill-UL as a value improvement over the organic foaming agent cellular concrete that was specified. The architect and structural engineer approved the proposed change.
CJGeo mobilized a four person crew and a 200CY/hour mobile batch plant, and completed the steam tunnel lightweight backfill work in three pours over two days. The CJFill-UL was generated using a synthetic foaming agent. It can be placed up to 20 thick at a time, and is generated onsite directly from bulk cement, so isn’t dependent on ready mix plant locations.
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Illinois Spillway Grouting
The Job
A spillway serving as a dam for a lake owned & maintained by a property owner association outside of Carbondale, Illinois stopped having water flowing over the spillway, requiring spillway grouting. The property owners determined that the lake was draining through voids under the spillway slab. This made them concerned about destabilization of the spillway, which was the sole access for six homes.
The Challenge
The flow velocity was rather high, and immediately on the other side of the spillway was a 30′ cliff. The water was designed to spill over as a waterfall. Given the extraordinary difficulty of retrieving any material washed over the waterfall, the grout had to have an exceptionally fast set. It also needed to provide adequate bearing capacity for the roadway slabs.
The Solution
CJGeo proposed grouting below the spillway with CJGrout 40NHL. CJGrout 40NHL is usually used for differential settlement correction. CJGrout 40NHL performs well for differential settlement correction because it reacts very quickly. It’s used for medium duty lifting, such as highway pavement, so it would provide more than enough bearing capacity.
The owners were very excited that it would be significantly less expensive to grout the existing spillway than to have someone local install a portadam and replace the entire structure. CJGeo mobilized a single polyurethane grouting crew to the site. They stopped the leaks and kicked all the water flow over the spillway in a single day.
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I-64 Soundwall Backfill
The Job
VDOT’s I-64 widening project is a multi-phase widening of Interstate 64 between Richmond & Newport News. This soundwall backfill work occurred as part of Segment 2, near the Queen’s Creek bridge.
The Challenge
Approximately 150LF of a combination sound & retaining wall needed to retain more than 10′ of backfill. In order to keep the drilled foundation size consistent along the alignment, the backfill material needed to be significantly lighter than the soil backfill used in other segments, where there was minimal retained depth.
The material needed to be freely-draining and less than 40lb/cuft. To ensure proper drainage, the lightweight fill material couldn’t impact the function of the combination drain waterproofing system applied to the wall.
The Solution
CJGeo proposed backfilling the affected wall segments with 30lb/cuft CJFill-UL. Used extensively by VDOT for backfilling the retained zones of MSE walls, CJFill-UL provides significantly better bearing capacity than soils or aggregates, and once cured does not apply lateral loads to the structures it is placed against.
During installation, lateral pressure from the cellular concrete is simply the hydraulic head. Hydraulic head is calculated by multiplying the pour thickness, in this case 5′, by the wet cast density, here 30lb/cuft, so 150PSF. Because CJFill-Ultra Lightweight cellular concrete does not contain any aggregate, there is no internal friction to contribute towards lowering pressures.
CJGeo placed approximately 200CY of CJFill-UL for the soundwall backfill the wall in two pours, each approximately 5′ thick. The contractor was able to place the pavement base on top of the material the following day.
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Chicago polyurethane grouting
The Job
This Chicago polyurethane grouting project is located at BNSF’s Willow Springs Intermodal yard, a critical facility in United States’ freight rail network. The facility is colocated with a large UPS trucking operation. BNSF has very tight time lines for transferring containers from inbound trains to UPS. There are dozens of crossings within the facility, which is primarily concrete pavement.
The Challenge
80 StarTrack modular grade crossing panels across 10 different crossings in the facility experienced settlement. The settlement was affecting the safe operation of yard trucks, causing delays in container transfer times.
Because of the 24/7/365 operation, and very tight performance times, there was no tolerance for downtime.
The Solution
CJGeo proposed grouting the affected panels with CJGrout-48NHL. 48NHL is best for differential settlement correction in high load applications, such as heavy haul rail. It cures within a few minutes, which allows immediate resumption of rail traffic and truck traffic.
CJGeo mobilized a polyurethane injection grouting crew with extensive modular grade crossing repair experience and grouted the 10 crossings over a period of five days onsite. This Chicago polyurethane grouting project did not affect rail traffic, yard truck operations, or performance metrics.
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Savannah Tunnel Abandonment
The Job
This Savannah tunnel abandonment job is part of the JW Marriott Plant Riverside conversion. It’s an adaptive reuse hotel project of a decommissioned power plant in Savannah, Georgia. As a thermal generation facility, there are extensive water tunnels below the structure. The cast in place tunnels are part of the piled foundation.
The Challenge
As part of the conversion from thermal power generation to luxury hotel, the tunnels posed a maintenance concern. Due to concerns about inducing settlement with traditional flowable fill, the designer specified EPS Geofoam blocks. These would have effectively eliminated loads, but were deemed impossible to install.
The Solution
Someone onsite had heard of foamed concrete, so reached out to CJGeo. CJGeo evaluated the layout of the tunnels, isolation methods from the river, and designed a mix which would ensure both complete filling of the structures without adding any additional load.
CJGeo placed approximately 930CY of 20lb/cuft CJFill-UL cellular concrete over a period of three days to complete the Savannah tunnel abandonment. Because CJFill-UL is highly mobile, demo debris from the access holes for building bulkheads was left in the tunnels, and encapsulated with the CJFill-UL.
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Nashville Basement Backfill
The Job
Nashville Yards is a block-wide new build project in downtown Nashville, Tennessee. With multiple underground levels of parking, this Nashville basement backfill excavation is more than 30′ below grade in spots. The excavation walls are a combination of blasted rock and soil nail walls.
The Challenge
The designer wanted to reduce lateral loading on the basement walls as much as possible. Due to the irregular face of the blasted rock & soil nail walls, lightweight aggregate would have been very difficult to install and compact, and would have applied lateral loads for the life of the structure. Flowable fill would have been easy to install, but applied too much lateral loading during installation if done in practical pour volumes.
The structural engineer determined that 25lb/cuft cellular concrete would be the best backfill material. The project volume was approximately 1500CY, and the maximum fill depth was 30′.
The Solution
CJGeo mobilized a mobile batch plant which uses colloidal mixing to the site. Due to the extremely high quality mixing, the crew placed CJFill-Ultra Lightweight up to 10′ deep per pour. This included three pours 10′ deep and 250CY each to complete this Nashville basement backfill project on time.
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