The Job
This Virginia annular grouting project supports Henrico County’s ongoing water infrastructure upgrades. The microtunnel is located in Glen Allen and crosses beneath Interstate 295, running parallel to a railroad track and a rural road.
The Challenge
The project features a 450-foot microtunnel made of 48-inch casing pipe with an 18-inch ductile iron carrier pipe inside. The customer wanted to manage the risk of carrier pipe buoyancy over this long distance. They required a low-density grout that utilized very low placement pressures. The contractor reached out to CJGeo to see if we could grout the entire annulus in a single pass using CJFill cellular grout.
The Solution
CJGeo’s in-house engineering team analyzed the tunnel to determine the necessary strength requirements. We then calculated the ideal density using locally available cement. Next, we developed a buoyancy control plan to allow for single-lift grouting.
Single-lift grouting offers several advantages:
Enhanced Safety: It removes the need for personnel to enter the pipes.
Structural Integrity: It eliminates the need to drill grout placement ports into brand-new pipes.
Efficiency: It minimizes the risk of trapping air pockets or fouling slick lines.
After the EOR accepted the program, CJGeo mobilized and installed roughly 168 cubic yards of 38lb/cuft CJFill-Standard cellular grout. We confirmed a successful fill when uniform grout vented from the 12 o’clock port at the far end. During placement, we maintained a high speed of 100 cubic yards per hour while keeping peak pumping pressure below 5 psi.
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