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, 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 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 cellular 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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8′ CMP Joint Grouting
The Job
A spec warehouse was planned for a vacant piece of land which had 1700LF of 8′ CMP running through it. The pipe was 10 years old. Because the site was vacant, there was no maintenance. Nearly every joint showed signs of soil infiltration, and there were massive sinkholes along the entire alignment. Given the depth, size, and short work window, the contractor sought out a CMP joint grouting repair alternative to replacement.
The Challenge
To avoid replacing the entire run of pipe, the joints had to be sealed. There were 80 pipe joints and 12 pipe to structure joints to seal. The pipe crossed under a roadway, and then crossed the site at an angle. The downstream end of the pipe transitioned to new 96″ RCP.
The Solution
In preparation for the repair, CJGeo had to educate the town, contractor, owner & consulting engineers that polyurethane grouting is an effective CMP repair method.
CJGeo mobilized a polyurethane grouting crew to the the site. Over the course of a week onsite, the crew performed all of the CMP joint grouting.
CJGeo used CJGrout 20SDB geotechnical polyurethane. 20SDB is a high mobility geotechnical polyurethane, so seeks out and fills even the smallest of voids outside of pipes. Because it’s highly mobile, it doesn’t deflect or damage the CMP that needs repair.
The manholes also had significant defects. Made of non-parged sewer brick, they leaked extensively. To address the widespread infiltration through the structures, CJGeo sprayed the interior of each structure with CJGrout 60FDC. 60FDC is a hybrid polyurethane/polyurea spray coating. For durability, the 60FDC was coated with polyurea. The 20SDB, 60SDB & polyurea coating were all installed using the same equipment, significantly reducing costs.
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Veranda St Bridge Infill
The Job
This bridge infill work was part of Maine DOT’s Veranda Street Bridge Replacement Project, in Portland, Maine. Using rapid bridge replacement, the project took a three span bridge and converted it to a single span bridge.
The Challenge
To manage settlement due to up to 80′ of underlying WOH material, lightweight fill was needed to infill two spans, and backfill the new abutments. The absolute lowest unit weight possible requirement led to a hybrid cellular concrete/EPS fill design. The bulk of the infill is EPS blocks. However, due to the irregular surfaces, piers, etc., and the need for a lightweight load distribution slab, cellular concrete was integral to the design.
The Solution
Over two mobilizations for the bridge infill, through snow and freezing temperatures, CJGeo placed 3200CY of 25lb/cuft CJFill-Ultra Lightweight cellular concrete for abutment backfilling and existing pier infills. Then, CJGeo placed 778CY of 30lb/cuft CJFill-Ultra Lighweight as a topping slab over the EPS fill masses.
To ensure high quality material and minimize weather-related risks, CJGeo used onsite batching to generate the material. A mobile batch plant custom built for generating cellular concrete mixes water and dry bulk cement onsite. The cement paste and foam blend continuously to generate a completely homogenous material. With a slump of around 11.5 inches, both densities of CJFill-Ultra Lightweight cellular concrete were able to flow around all of the existing structures and provide a void-free fill.
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