HRSD’s Virginia Beach Boulevard Forcemain Replacement project installed more than a mile of new pipe to replace an aging 24″ forcemain.
As part of decommissioning the original forcemain, it needed to be filled completely with grout.
Due to extensive widening of the roadway the pipe was originally constructed alongside, extensive commercial and residential development, the number of access points needed to be as few as possible. This was driven by extensive structures over/adjacent to the old pipe, and a desire to reduce disruptions to adjacent stakeholders, and the risk of any utility strikes during access pit excavation.
CJGeo grouted more than 7,000LF of the 24″ pipe over a period of a four working days onsite. The pipe was completely filled, which was verified by uniform material venting from the far end of each run. Run lengths ranged from 450LF to more than 2000LF.
The DeRuyter Reservoir, in DeRuyter, New York, is a 557 reservoir originally developed as part of the Erie Canal system.
As part of a dam upgrade project, the three parallel 22″ diameter, 300LF outfall pipes needed to be abandoned, along with a stone box culvert downstream of the valve chamber the pipes terminated into.
Each of the three pipes had been previously blind 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, which were approximately 40′ below the water surface.
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 cellular concrete through each of the sacrificial grout pipes, until grout returned to the bulkhead vents, confirming fill. The work was completed over two days onsite–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.
As part of decommissioning an underground oil tank at an institutional facility 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 located in a small empty lot, which is slated for redevelopment in approximately three years.
To be officially considered decommissioned, the tank had to be completely filled. It is slated for removal as part of the redevelopment process of the area (it sits within a future basement excavation) so the fill material had to be excavatable.
CJGeo proposed 20lb/cuft cellular concrete for the abandonment grouting. This afforded plenty of factor of safety to reduce the likelihood of settlement induced by filling the tank, and maximized excavatability
CJGeo placed the 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.
Sanitary sewer right of ways straddling lot lines can be particularly troublesome if a problem occurs with a line and trenchless repairs aren’t possible. This was the case on an 8″ gravity line in Arlington, Virginia. Extensive structural damage to the line caused repeated backups and raised stability concerns for multiple retaining walls which had been constructed over the line.
The walls ranged from four to eight feet tall, and were a mix of concrete and natural stone.
Timber-shored, hand-excavated work was done on the high side of the wall to expose and replace the affected lines. Because of stability concerns with the walls, the geotechnical engineer specified material no heavier than 25lbs/cuft.
The only access was pumping material from the street, down a decorative flagstone pathway between two homes, and into the excavated pits.
CJGeo proposed 25lb/cuft wet cast density permeable cellular concrete for the backfill material. Because there is no aggregate, it can easily be pumped through small diameter lines at low pressure, which addressed the accessibility concerns.
Because the material is permeable (modified ASTM D-2434 2.0cm/sec), it is freely draining and reduces hydrostatic loads on adjacent structures.
CJGeo mobilized twice for the phased project, and backfilled each of the pits in a single lift.
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 be backgrouted, and the casing pipe’s annular space grout filled.
The proposed backgrout 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.
CJGeo proposed two different grout mixes to meet the project requirements. 85lb/cuft casing backgrout for displacement of the 10PPG (75lb/cuft) drilling mud, and 25lb/cuft annular space grout for within the casing.
CJGeo’s crew mobilized to the site, and successfully performed the backgrouting and annular space grouting in a single day.
As part of a water treatment plant rehabilitation project in Stamford, Connecticut, a 25,000sqft underground tank needed to be abandoned, and the concrete roof removed.
The geotechnical engineer required an average fill density less than 60lbs/cuft to avoid settlement.
The lightweight fill material had to to provide sufficient support for approximately 4′ of compacted fill material, and a delivery truck loading dock and future building.
CJGeo proposed 25lb/cuft permeable cellular concrete with an approximately 10ksf compressive strength to fill the structure.
CJGeo placed the 25lb/cuft cellular concrete in daily pours up to 980CY, in single lifts up to 36 inches thick. The roof demolition debris dropped onto the top of the cellular concrete and was then buried with fill material.
The total project volume was approximately 5520CY.
The geotechnical investigation for a double bridge replacement in Amelia County, Virginia found a layer of compressible soils below four proposed abutments.
Anticipated settlement exceeded allowable settlement, so the abutments were designed to be backfilled with expanded shale lightweight aggregate.
The two parallel bridges have an AAWDT of 14,000, and carry a rural divided highway (US-360) over Norfolk Southern Railway & Business 360 in Amelia Courthouse, Virginia.
Lightweight fill placement had to be unaffected by frequent rail traffic, have a limited footprint, and be economical.
CJGeo provided a value engineering proposal to utilize 30lb/cuft cellular concrete in place of the expanded shale lightweight aggregate. This significantly reduced the unit weight of the lightweight fill, given the 70lb/cuft density used in the design, further reducing the anticipated settlement.
CJGeo mobilized a 200CY/hour cellular grout plant to the site, and placed lifts ranging in size from 35 to 300CY. Wall erection crews were able to walk on the in place cellular concrete without leaving footprints as quickly as 4 hours after each placement.
The total project volume was approximately 7200CY.
A sewer trunkline expansion in Richmond, Virginia required five bored road crossings ranging from 60″ to 72″.
Tunnel lengths ranged from 200LF to nearly 600LF, and were mined through rock using slurry microtunneling.
The design engineer required cellular concrete for annular space grouting due to run length, and buoyancy control of the carrier during grouting.
Not many; the longest run on this project, 600LF is a relatively short distance to push cellular concrete.
CJGeo proposed 38lb/cuft non-permeable cellular concrete to meet the designer’s 200psi 28 day compressive strength requirement.
Over four different mobilizations, CJGeo successfully placed approximately 900CY of annular space grout.
Cellular concrete generation was performed using wet batch continuous generation. Wet batch generation was chosen due to the relatively small daily volume of material placement and very constrained sites.
A stone arch bridge constructed in the 1800s was experiencing significant scour at the bases of the arch. This caused differential settlement of the structure, and deterioration of the wing walls.
The bridge, which was adjacent to an historic mill structure, could not be removed and replaced with a modern structure, it had to be rehabilitated in a fashion which preserved its historic nature.
The bridge was constructed on shallow stone foundations.
As part of rehabilitating the structure, structural engineers designed two new mass footings in the stream bed to underpin the edges of the stone arch. Then, to strengthen the arch, designed a 12″ thick reinforced concrete arch overlay on top of the stone arch for the full length/width of the bridge.
In order to compensate for this additional weight, designers determined that a lightweight fill material was needed to reduce the chances of inducing settlement.
Designers also evaluated remedial deep foundations, but determined that lightweight fill was the fastest and most economical solution.
After the structure had been rehabilitated, CJGeo installed 325CY of 30lb/cuft cellular concrete to backfill the structure. Placed in lifts up to 4 feet thick, the work was completed over a period of three days.
By using 30lb/cuft non-permeable cellular concrete, the dead load on the underlying soil decreased by up to 935lbs/sqft relative to compacted soil backfill.
Because cellular concrete is self-consolidating and can easily be pumped hundreds of feet, single side access was not a problem, and no compaction equipment was necessary.
A crew of two workers completed the pour using continuous wet batch generation. Wet batch generation was chosen due to the relatively small daily volume of material placement.
During widening of Interstate 66 year the interchange with US-15, nine new culverts were installed by jack and bore, and one via direct jacking. The carrier pipes were a mix of spiral metal, precast concrete, and corrugated HDPE, and ranged in length from 150 to 350 feet.
The boring contractor, who was responsible for grouting, was concerned about carrier pipe buoyancy during grouting, and also run length. All work had to be done from one side of the interstate highway (three lanes in each direction, plus full width shoulders and a median strip), as there was no access on the far side.
CJGeo proposed 30lb/cuft cellular concrete for the annular space grouting. Cellular concrete is the preferred material for annular space grouting because it is highly flowable, and reduces the chances of damage to carrier pipes in long placements. Its low unit weight also reduces carrier pipe buoyancy. CJGeo placed 350CY of cellular concrete to successfully complete the jack and bore annular space grouting over three different mobilizations.