The Job
This Virginia annular grouting project is part of Henrico County’s continuing enhancement of its water infrastructure. This particular tunnel is located in the Glen Allen area, and crosses Interstate 295, parallel to a railroad track and rural road.
The Challenge
This microtunnel is 450 feet of 48 inch casing pipe, with 18″ inch ductile iron carrier pipe. To manage risk of carrier pipe buoyancy and relatively long placement distance, the customer wanted a low density grout with very low placement pressures. They reached out to CJGeo to assess the viability of grouting the annulus in a single pass.
The Solution
CJGeo’s in house engineering team analyzed the tunnel to determine a strength requirement, and associated density to achieve the strength requirement given locally-available cement. Next, we performed buoyancy calculations to configure a buoyancy control plan which would facilitate single lift grouting. Single lift grouting is advantageous because it:
- designs out the safety risks of having personnel inside of pipes
- eliminates the need for swiss cheesing brand new pipes with grout placement ports
- minimizes the risk of trapping air pockets or fouling slick lines
After acceptance of the grouting program by the EOR, CJGeo mobilized to the site and installed roughly 168 cubic yards of 38lb/cuft CJFill-Standard cellular grout. Confirmation of fill on this Virginia annular grout project was uniform grout venting from the 12 o’clock port at the far end from placement. Peak pumping pressure was less than 5psi, while placing at approximately 100 cubic yards per hour.
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