Project: Century Asphalt Rock Crusher
Location: Houston, TX
Asset: Rock crusher foundation: 50 ft × 14 ft × 5 ft concrete pad with columns, on a former landfill site
CHALLENGE
Century Asphalt built a new asphalt plant in Houston on a site that had previously been a landfill. The rock crusher sat on a 50 ft × 14 ft × 5 ft concrete pad with columns, and the combined foundation and equipment weighed roughly 750,000 pounds. Once the crusher went into operation, continual intense vibration exposed the weak subgrade beneath the pad. The structure settled 14 inches in one area and twisted out of level across the rest of the foundation. Repair access was complicated by low overhead clearance, and the crusher's operating specifications required the foundation to be leveled back to within 1/8 inch throughout.
SOLUTION
Superior Grouting was contracted to stabilize and re-level the foundation in place. Testing first established the depth of load-bearing soils. Two-inch ID high-pressure seamless pipe was set to a 32 ft depth on an approximate 5 ft grid, and a low-mobility, 0-to-1-inch slump, cement-based grout was injected at high pressure to densify the weak subgrade soils. The process was repeated in 2 ft lifts up to the top of the grout zone, with the foundation monitored for lift continuously throughout. The small-diameter injection pipes allowed the work to proceed under the low overhead clearance. The roughly 750,000-pound structure was stabilized and raised back to within the required tolerance.
RESULTS
The settled, twisted foundation was raised and re-leveled to within the required 1/8-inch tolerance.
The weak subgrade was densified in place.
After completion, the plant returned to operation and Century Asphalt monitored the foundation continuously for over a year. No movement has been detected to date.
