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Author: Kirk Roberts

By applying unique solutions to increase the safety and longevity of our environment.

14′ CMP Repair

The Job

During a real estate transaction, civil engineers walked a 1400LF run of 14′ diameter multiplate tunnel running underneath a strip center in Asheville, NC.

A previous inspection had indicated impending section loss of the pipe due to corrosion, and had recommended grouting of incidental voids, but no work had been performed at that time.

The pipe, which had up to 20′ of cover, bypasses a large stream, and runs under 200LF of building footprint, the main entrance roadway, two out-parcels, and ties into an NCDOT box culvert to discharge.

The Challenge

Significant debris were present in the pipe, and access was exceptionally difficult. Because dewatering was not practical, all work proposed had to be performed under flow.

The Solution

CJGeo proposed polyurethane backgrouting using plural component CJGrout material, specifically CJGrout 35NHV61.

CJGrout 35NHV61 is a hydroinsensitive, moderate mobility grout designed for backgrouting in wet environments, and is certified for potable water contact.

Despite a bear wandering into the pipe during repairs, CJGeo crews successfully backgrouted the pipe to address piping and erosion outside of the structure over a period of two weeks. More than 40,000 pounds of CJGrout 35NHV61 were needed to underseal the headwall structure and pipe.

Upham Brook Annular Space Grouting

The Job

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.

The Challenge

Not many; the longest run on this project, 600LF is a relatively short distance to push cellular concrete.

The Solution

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.

Stone Arch Lightweight Backfill

The Job

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.

The Challenge

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.

The 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.

Corporate HQ Stabilization

The Job

Starting immediately after construction was completed, the slab on grade floor within the cafeteria, loading dock and kitchen at a corporate headquarters building in Pittsburgh, Pennsylvania settled. Over the course of 12 years, the owner had four different grouting companies attempt to address the problem. Lime slurry injection below the slab was disruptive, and settlement always resumed shortly thereafter.

Compaction grouting was performed in one area, but was so disruptive that despite the fact that it was the only method where settlement didn’t resume, the owner kicked the contractor off the site after nearly four months of not having access to their executive dining room.

The Challenge

Settlement progressed over time to be as much as four inches, affecting nearly 20,000 square feet of floor. A general contractor retained by the owner reached out to CJGeo about performing low impact grouting to address the settlement.

Because settlement affected the entire kitchen, food prep, serving and majority of the dining areas, repairs had to be facilitate continuous use of the facility. Additionally, due to 24 hour staffing of the facility, noise had to be limited, and there was zero tolerance of dust.

Video inspection of the extensive gravity sanitary and floor drains below the floor revealed six defects, including a 2″ offset in a sanitary drain line for a 6 stall restroom.

The Solution

CJGeo performed 17 DCP tests to determine the depth of uncontrolled fill, which was the presumed cause of settlement. DCP testing showed pockets of WOH fill down to 35′ below finish floor, and voids ranging from 2″ to 18″ immediately below the floor.

Over the course of 7 nights onsite, CJGeo crews installed 12,000 pounds of CJGrout 20SDB into voids immediately below the floor, and 53,000 pounds of CJGrout 35NHV61 for polyurethane compaction grouting. Compaction grouting was performed up to 35′ deep, but to an average depth of 15′ over the entire area.

All work was completed off hours. As soon as the kitchen shut down for the evening, CJGeo crews swung into action, grouting through the night until wrapping up in time for the food prep crews to get ready for breakfast at 0500.

To facilitate grouting under four walk-in freezers and refrigerators, over the course of a 24 hour shift, all cold contents were moved to reefer trailers, CJGeo grouted to 30′ under the freezers and refrigerators, which were then immediately turned back on, and then refilled.

Through careful coordination with multiple operational divisions for the owner, general contractor, flooring restoration contractors, plumbers, and remediation contractors, CJGeo successfully completed the project under budget and on time.

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