Georgia Annular Space Grouting
The Job
This Georgia annular space grouting project is located in Athens, Georgia. The project involves three tunnels connecting four shafts. Tunnel lengths range from 116LF of 700LF, with diameters between 58.5″ ID to 9×9 arch segments.
The Challenge
In order to keep the carrier pipe from floating during grouting, the maximum allowable grout density was 70lb/cuft, and the minimum compressive strength was 200psi. Material had to be highly mobile, to facilitate placement through the 700LF of tunnel.
The Solution
CJGeo proposed 38lb/cuft cellular grout to the tunneling contractor. Over a period of three days, CJGeo batched and placed 1320CY of CJFill-Standard. Batching was performed utilizing an onsite dry mix plant, which was fed directly by bulk cement trailers. The minimizes the required laydown area on a very tight site.
Because of the very low grout density, the carrier pipe buoyancy control was simply water filling.
To address the transition from a round tunnel to an arch tunnel, CJGeo worked with tunneling contractor to design a sacrificial pipe venting system.
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30k CY Lightweight Embankment
The Job
As part of the redevelopment of the Sparrows Point industrial area of Baltimore, three bridges were to be replaced. The owner specified lightweight embankment techniques due to extensive compressible soils. Sparrows Point is undergoing a transition from a brownfield site to a buzzing logistics hub. Multiple new distribution centers, berths and manufacturing facilities have driven an explosion in vehicle volume.
The Challenge
The original embankments are industrial byproducts over underlying compressible soils. As part of the reconstruction, the embankments needed to be widened and raised up to six feet to increase clearance below the bridges for both highway and rail traffic.
Due to the underlying compressible soils, there were concerns that the approximately 30,000 cubic yards of fill material needed would cause settlement.
Most material was immediately behind the new abutments, and helped to optimize the deep foundations by reducing axial & lateral loads.
The compressive strength for the material was 80psi, with a target density of 25lb/cuft.
The Solution
CJGeo proposed 25lb/cuft cellular concrete as a lightweight fill material buildable with locally-sourced materials to reduce transportation related risks and exposure to trucking shortages. Cellular concrete was several hundred thousand dollars less expensive than either Lightweight Expanded Shale Aggregate or Foamed Glass Aggregate. It also doesn’t require onsite stockpiling, and freed up the general contractor’s labor force to perform work other than placing aggregate.
CJGeo poured the lightweight embankment structures using 25lb/cuft CJFill-Ultra Lightweight cellular concrete over four mobilizations. Because CJFill-UL is so lightweight, all forming was silt fence. Silt fence facilitates complex curves, and is very economical. Side slopes were poured at 2′ vertical steps on 4′ horizontal insets.
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Low Level Outfall Abandonment
The Job
This low level outfall abandonment grouting project is located in New Jersey. The Round Valley Reservoir, in Clinton Township, New Jersey is a 2300 acre man-made drinking water reservoir. It serves extensive portions of New Jersey. It was constructed by damming up two openings in a naturally-curved mountain.
As part of a dam upgrade project, a 1400LF, 36″ inner diameter LLO pipe needed to be grouted to place it out of service.
The Challenge
The pipe had been previously blind flanged, 180′ below the lake surface. There was a single, 12″ riser pedestal. There were numerous significant challenges to face, including:
- 2GPM residual leak from the blind flange buried in 15′ of lake floor debris
- inability to push sacrificial pipes more than 500′ up the pipe
- remote site with limited ready mix service
The Solution
CJGeo worked with the general contractor, diving subcontractor, sacrificial grout pipe installation subcontractor, geotechnical and civil EORs, and the owner, to develop a single stage grouting plan to place approximately 350CY of 68lb/cuft CJFill-Under Water cellular grout from the downstream end.
Venting was achieved by installing a 4″ removable vent pipe from the pedestal riser. The vent pipe ran 180VF to the lake surface, terminating on a barge. There was only one opportunity to do the job correctly. Therefore, CJGeo had two fully staffed grout plants onsite, and had all cement and mix water staged in onsite storage. This was all prior to the start of grouting to avoid any material logistics disruptions affecting the work.
CJGeo placed the 68lb/cuft grout over a period of a few hours, leaving an intentional air pocket at the high end to capture infiltrating lake water long enough for the grout to set prior to seeing lake head.
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Sloped Pit Lightweight Backfill
The Job
This sloped pit lightweight backfill project is located in Western Virginia, at James Madison University. This work is part of the conversion the basketball arena at JMU in Harrisonburg, Virginia into a practice and competition facility for other sports.
The Challenge
An area of sloped stadium seating needed to be removed, and the mezzanine level floor extended over the sloped soil, which stayed in place, and onto a new wall at the toe of the slope. To reduce the likelihood of inducing settlement by adding up to 10 feet of backfill over the existing soils, the architect originally designed the backfill material as Expanded Polystyrene (EPS blocks). However, given the uneven soil slope, this would have been very challenging to install.
The general contractor reached out to CJGeo to see if there was a more practical load reducing fill.
The Solution
Working with the general contractor, architect and geotechnical EOR, CJGeo designed a backfill system that could be installed in fewer than six hours onsite, still provided a significant reduction in load, and cost significantly less than the foam blocks. The optimal product to meet the project criteria was 25lb/cuft CJFill-Ultra Lightweight low density flowable fill. CJFill-Ultra Lightweight has all the constructibility advantages of flowable fill, along with the following additional benefits:
- is made at up to 200CY/hour onsite
- provides up to 150CY of final material per load of raw material to the site
- applies minimal lateral pressure on adjacent walls during installation
- significantly reduces dead loads to underlying soils & structures
CJGeo generated the material onsite using dry batch generation, and placed the material in two lifts in order the limit the lateral loads on the new CMU wall during placement to 0.9psi.
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Rail Bridge Pier Stabilization
The Job
This rail bridge pier stabilization project is located adjacent to the Congaree National Park. This project was a capital repair to a bridge pier for a Class I railroad. The rail line serves the Port of Charleston, SC.
The Challenge
The Congaree River south east of Columbia, South Carolina frequently sees high flow events, inundating the surrounding low country. At the transition from timber trestle to a bridge, the first bridge pier was originally constructed of stone. The pier bears on a timber mat with timber pile supports. Over time, the river channel migrated and began to expose the timber substructure and scour below the pier.
The nearest road was more than four miles away through impassible swamp. So, all work had to be performed from the river. All material had to be pumped across the bridge, a distance of approximately 600 feet. Due to the compressive nature of the underlying materials, any backfill material needed to be as light as possible. But, due to the high likelihood of flooding, couldn’t contribute significant potential uplift.
The Solution
To address the scour, minimize additional load to the underlying soils, and ensure long term stability of the structure, a third party consultant designed a two tier sheet pile jacket for the structure. They specified the backfill material as 65lb/cuft cellular concrete for the lower segment. And, approximately 45lb/cuft cellular concrete for the upper segment.
CJGeo designed mixes which would meet these requirements:
- be pumpable 600LF,
- tolerate the high vibration environment from the more than 12 trains per day, and
- facilitate a short installation timeframe.
After the general contractor installed the first level of sheet piling and dewatered the area, CJGeo placed approximately 150CY of 65lb/cuft CJFill-Under Water material. Next came installation of the second, smaller diameter sheeting ring. CJGeo then filled the annular space between it and the necked down pier with 45lb/cuft CJFill-Standard material.
CJGeo generated and placed all of the CJFill low density controlled low strength material over a period of four days onsite.
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Lightweight Stem Wall Backfill
The Job
This lightweight stem wall backfill work is part of the construction of a new academic building at a school in Lynchburg, Virginia.
The Challenge
There was up to an 8′ difference in elevation between the existing ground and the desired finish floor elevation. Various options for filling the CMU stem walls included soil, aggregates and EPS foam blocks. EPS foam blocks were chosen to reduce loads on the footings. Otherwise, which would have required deep foundations in the case of soil or aggregate backfilling.
Due to the extensive sub-slab plumbing, the design called for EPS blocks cut to fit the curved walls & uneven ground profile, and then backfilled with 18″ of stone dust, to allow for the plumbers to dig and install the plumbing.
The Solution
The goal was to speed construction and reduce costs. CJGeo worked with the general contractor, structural engineer and geotechnical engineer to design a self-consolidating backfill system as a geofoam alternative. The final design for the lightweight stem wall backfill was 25lb/cuft CJFill-Ultra Lightweight load reducing backfill.
Using the dry batch generation process, a single CJGeo crew made up to two hundred cubic yards per hour of CJFill-UL. Pouring in two foot lifts, the work took about four days onsite. Instead of having to install an 18″ thick sand layer, the plumbers hand dug through the CJFill-UL to install the plumbing. Plumbing trenches were backfilled with stone dust.
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Precast Lagging Wall Lateral Load Reduction
The Job
This load reduction backfill work as associated with the replacement of Scaife Hall, at Carnegie Mellon University, in Pittsburgh, Pennsylvania.
The Challenge
The H-pile and precast lagging wall is at the top of a steep slope. There is a Class I railroad line at the base. Because of site constraints, an HDPE stormwater detention structure is within the fill area. Along with extensive stormwater pipes and manholes.
In order to optimize the drilled shafts for the H-piles by reducing the lateral loads, the designer sought a lightweight, permeable backfill material that would not apply lateral loads once in place.
The Solution
CJGeo proposed 20lb/cuft CJFill-High Permeability cellular concrete. CJFill-HP would minimize lateral loading on the wall during construction, buoyancy of of the stormwater system components, and ensure a free draining material.
Because the material is permeable (modified ASTM D-2434 2.0cm/sec), it is freely draining and reduces hydrostatic loads on adjacent structures.
620 cubic yards of lightweight backfill were placed over two mobilizations to complete this load reduction backfill project.
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HRSD 24″ Forcemain Abandonment
The Job
HRSD‘s Virginia Beach Boulevard Forcemain Replacement project installed more than a mile of new pipe to replace an aging 24″ force main. The owner specified forcemain abandonment using grout.
The Challenge
The original alignment was outside the pavement limits. Over time due to extensive widening, most of the pipe was now under the roadway. The areas not under the roadway crossed under significant commercial & residential development.
To avoid the risk of utility strikes digging access pits, and disruption to traffic and citizens, the number of access points needed to be limited.
The Forcemain Abandonment Solution
CJGeo grouted more than 7,000LF of the 24″ pipe over a period of four working days onsite, using CJFill-Ultra Lightweight. The CJFill-UL completely filled each run of pipe. This was verified by uniform material venting from the far end of each run. Run lengths for the forcemain abandonment ranged from 450LF to more than 2000LF.
The CJFill-UL for this project was generated onsite using the wet batch process. Wet batching uses slurry delivered to the site by ready mix trucks. This method was best here because of very limited access at each of the placement points. The relatively short runs also lean towards wet batching.
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DeRuyter Reservoir Outfall Abandonment
The Job
This outfall abandonment project is located in Upstate New York. The DeRuyter Reservoir, in DeRuyter, New York, is a 557 reservoir that’s originally part of the Erie Canal system.
As part of a dam upgrade project, the three parallel 22″ diameter, 300LF outfall pipes were to be abandoned. Along with a stone box culvert downstream of the valve chamber the pipes terminated into.
The Challenge
Each of the three pipes had been previously blindly flanged by divers. Therefore, the only access was from the downstream end within the valve chamber. In order to vent the air displaced by the abandonment grout, vent or placement points needed to be installed just behind the upstream blind flanges. The blind flanges are approximately 40′ below the water surface.
The Solution
CJGeo worked with the general contractor to design an internal venting system utilizing sacrificial placement pipes installed from the valve chamber. After each of the sacrificial grout pipes was installed, the downstream terminations were bulkheaded, with vent stubs.
CJGeo mobilized a cellular grouting crew, who placed 30lb/cuft CJFill-Ultra Lightweight cellular concrete through each of the sacrificial grout pipes, until grout returned to the bulkhead vents, confirming fill. The work took two days. The first day for the abandonment pipes and first lift in the box culvert, and the second day for a top-off pour on the box culvert.
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250000 Gallon Oil Tank Abandonment
The Job
This oil tank abandonment project is located in the nation’s capitol, Washington, DC. As part of decommissioning an underground oil tank at Howard University in Washington, DC, it needed to be filled with excavatable material that was lighter than the roughly 55lb/cuft heating oil it was designed to hold.
The tank is under a small empty lot. The lot is up for redevelopment in approximately three years.
The Challenge
For a complete decomissioning, the tank had to be completely full of grout. Since it sits within a planned basement excavation, the fill material has to be easily excavatable.
The Solution
CJGeo proposed 20lb/cuft cellular concrete for the oil tank abandonment grouting. This afforded plenty of factors of safety to reduce the likelihood of settlement induced by filling the tank and maximized excavatability. The removability modulus of 20lb/cuft (a quantifiable method for determining excavatability of various types of flowable fill) is much less than one. This means it is easily hand excavatable.
CJGeo placed the CJFill-Ultra Lightweight fill material over a period of two days onsite. Because cellular grout is highly mobile, no entry was required during the placement of the fill material, which designed a significant amount of risk out of the process.
The 1200CY placement was performed over two days onsite.
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