Keeping Mines Productive
URETEK was asked to review a project involving void filling and stabilization of a thick concrete pad that supported a large electrical motor and a critical production pumping unit located in Minnesota.
Settling of Electrical Motor and Pumping Equipment
The concrete pad, which is 6’ x 24’ in dimension and 4’ thick had settled due to sub-surface voids. The void areas, which varied from 6″ to 2 feet in size were caused by soil erosion from an adjacent drainage way. The result was a settlement of concrete pads at one end and the lifting of the pad at the opposite end – leading to increased stress on connection joints with related equipment. The customer installed an “L” shaped bracket to the settled area to slow down the rate and distance of the erosion. While effective, concrete settlement continued and the productivity of the mine was to be severely impacted if not repaired properly.
A key consideration for the customer was minimizing production downtime. Barring safety concerns, facility managers requested electrical motor and pumping equipment to continue running during the repair. Based upon their understanding of URETEK ICR’s capabilities and successes, URETEK ICR was given the ‘green light’ to proceed to fill the existing voids and raise the 125,000 lb pad concrete pad.
First phase of the repair plan was to fill any voids that may be present and get the pad on a ‘sure footing.’ This was to be done by direct injection of our proprietary, expanding structural resin materials. Because of the presence of water and saturated soils, it was critically important to use a structural resin material that didn’t interact and/or absorb the water. The material needed to work at full strength in the presence of water so as to not compromise the repair in any way.
URETEK ICR recommended a different method for the lifting of the pad, leading to a reduction of stress on equipment couplings and to get the pad back to level as close as possible.
URETEK ICR asked the customer to reinforce the area between the pad and the water drainage area so as to maximize the containment of the structural resin for the greatest strength.
The customer weighed these recommendations and with their engineers determined to go forward with URETEK ICR.
URETEK ICR crews rolled onto the site. The customer had previously reinforced the area between the settled pad and drainage area as we had requested. All were ready to get to work.
First, URETEK crews drilled a series of holes through the settled pad to have direct access to the existing voids. Into these holes was injected a high density structural resin, or structural polymer that expanded to completely fill the voids and to provide renewed structural support/contact between the heavy pad and the sub-surface soils. The previously installed reinforced area between the pad and the drainage area provided just the needed containment for the material to reach its strength specification. The material was at 90% strength in 15 minutes, and full strength within 30 mins.
Next, URETEK crews drilled another series of small injection holes and inserted mid-length tubing into the drilled holes surrounding the pad. This action provided diagonal access to sub-surface soils, beneath the just-filled void areas. Into the inserted tubing and into the wet soils was injected the proper structural resin material.
The material, as it expanded, provided the necessary lift of the heavy pad as well as compaction and stabilization of the unstable soil area.
Taking this two-step approach provided the greatest results in taking care of the soils weakness and getting the heavy pad lifted back to where it needed to be.
Remember that key to the customer was to not disrupt production and to repair the area quickly and effectively. The customer had considered removing and replacing the entire pad as an option before they found URETEK. To do so would have meant a 2-3.5 week repair time and the removal of the equipment. With URETEK ICR the project was initiated and completed in 13 hours without the removal of any equipment. This represents an 89% time savings and a 100% elimination of production interruption.
URETEK ICR counts this as a successful project because our customer deems this a successful project. Both agree that these factors contribute to the success of the project:
- The project was completed within the tightest timeline available only 13 hours instead of weeks.
- The speed and efficiency of the URETEK ICR crew and the unique, proprietary material characteristics allowed the repair to be successful even though the soils were very wet to saturated with water.
- There was no need to remove any equipment from the concrete pad for the repair to happen.
- The stress on the joints where the various equipment connected was significantly reduced.
The Bottom Line
The estimated cost of downtime, for this one area, is $5000/hour; with production running 24/7. By using URETEK ICR, the customer eliminated an approximate downtime cost, as compared to tear out and replacement, of $1,600,000 (the cost of 14 days of downtime). A substantial advantage to the customer’s budget.
The URETEK ICR processes, products, experience, and crew skill allowed the customer to exceed their original repair specification without disrupting mine production operations. The customer was able to solve the void, the soil stabilization, and equipment stress issues all at once and in a very fast timeframe.
The mine was able to put this structural and equipment maintenance issue behind them for a substantially lower cost than other methods due to no need for production interruption or disruption to the work areas.