Savannah Tunnel Abandonment
The Job
The JW Marriott Plant Riverside is 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 tunnels were cast in place during original construction, and integrated into the pile supported foundation.
The Challenge
As part of the conversion from thermal power generation to luxury hotel, the tunnels needed to be filled. 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. 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.
Nashville Basement Backfill
The Job
Nashville Yards is a block-wide new build project in downtown Nashville, Tennessee. With multiple underground levels of parking, the basement 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.
Veranda St Bridge Infill
The Job
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 had to be used 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 was performed using 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, through snow and freezing temperatures, CJGeo placed 3200CY of 25lb/cuft CJFill cellular concrete for abutment backfilling and existing pier infills. A 778CY 30lb/cuft topping slab was then poured over the EPS fill masses.
Niles Avenue Annular Space Grouting
The Job
Atlanta Watershed Management’s Niles Avenue Sewer Improvements project involved approximately 2500LF of microtunneling to install a new 18″ sewer main.
The Challenge
A 72″ microtunnel was chosen, which required approximately 1200CY of annular space grouting. Operations were challenged by the pandemic hitting in the middle of the project.
The Solution
CJGeo proposed 30lb/cuft CJFill-UL cellular grout for the annular space grout. This allowed the contractor to avoid mechanical buoyancy control during grouting operations during single lift grouting.
Over two mobilizations, CJGeo generated the cellular grout onsite and placed it via shafts which were up to 40 feet deep.
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.
66″ Water Main Abandonment
The Job
The Purple Line is a light rail line project in suburban Maryland designed to increase connectivity within Maryland’s suburbs of Washington, DC. The project involves extensive utility relocation to facilitate installation of large embankments and the extensive infrastructure required for a double track rail corridor dropped into the middle of an already exceptionally congested/dense corridor.
The Challenge
As part of the project, a large MSE wall needed to be installed over approximately 3000LF of 66″ PCCP water main. In order to avoid any future maintenance problems under the rail alignment, a new line was installed adjacent to the embankment, and the old line needed to be abandoned.
Due to construction sequencing, the embankment was already in place well before the water line relocation was performed.
The Solution
CJGeo worked with the utility relocation contractor to design a grout mix and grouting program that provided sufficient bearing capacity to eliminate concerns about future stability. The ultimate design for the mix was a 100psi cellular grout. Given that the embankment was already in place, the entire 3000LF stretch had to be grouted from just two access points.
CJGeo used a 200CY/hour dry mix batch plant onsite to generate and pump the cellular concrete up to 1500LF to place the material. 2800CY of material were placed over a period of four days onsite with no disruptions to adjacent construction activities.
Garden State Parkway grouting
The Job
As part of ongoing large diameter culvert rehabilitations and replacements, four new bored stormwater crossings and the original culvert they replaced needed to be grouted. The tunnels ranged from 120″ down to 74″, for a total of 312CY, and the abandonment required 405CY.
The Challenge
Grout needed to meet the minimum strength requirements of the owner, and ideally needed to be light enough to facilitate single lift annular space grouting.
The Solution
CJGeo’s preconstruction team worked with the general contractor to design a grouting program which facilitated single lift abandonment of the original culvert, and single lift grouting of the four various annular space runs. CJGeo utilized onsite dry batching to generate 30lb/cuft CJFill cellular concrete.
Lightweight Plaza Fill
The Job
Lightweight plaza fill for a private age restricted high rise new build in Tysons Corner, Virginia.
The Challenge
To manage dead loads over the four story parking deck, while achieving a landscape design requiring up to five feet of fill, the designer specified 20lb/cuft cellular concrete for the plaza fill material. The material had to be permeable, and placed up to 600′ from the closest access point for a plant.
The Solution
CJGeo mobilized a 200CY/hour dry batch plant and crew, who generated up to 500CY/day for placement via hoses and a boom pump to successfully fill the plaza areas. Total project volume was approximately 2200CY.
Hollow Abutment Filling
The Job
As part of a bridge rehabilitation for MassDOT, two hollow abutments needed to be filled in order to turn the structural approach/departure slabs into slab on grade.
The Challenge
It was up to 30′ from the bottom of slab to the underlying soil which had originally been installed to backfill the abutments. In order to reduce the loads applied to the bridge from the backfill, the lightest possible material capable of providing sufficient support to the pavement was required.
Due to integrated beams for the structural slabs, there were 12 different individual pockets which were up to 2′ tall, which had to be vented independently during the final lift, 4 of which had to be under live traffic because the road couldn’t be completely closed.
The Solution
CJGeo worked with the general contractor to formulate a plan to vent the individual pockets from outside of the open lanes, to ensure a complete fill without requiring a complete road closure. Over the course of two mobilizations, CJGeo placed 2,840CY of 25lb/cuft cellular concrete to fill the abutments.
8″ Pipe Abandonment
The Job
As part of continuing waterline replacements, a utility contractor in Fort Washington, Maryland, needed to abandon 10,600LF of 8″ water main. The utility and DOT both require grouting of all utilities 6″ and larger taken out of service.
The Challenge
In order to minimize the number of placement points, the grout needed to be exceptionally mobile.
The Solution
CJGeo proposed a 30lb/cuft cellular grout, and worked with the client to design a grouting plan that would allow grouting all 10,600LF of pipe from just three access points. CJGeo performed the grouting over a period of two days, with no additional excavation required from the customer other than their original tie ins/disconnects.
