PERMFILE116033 - Laserfiche WebLink

Home Browse Search

Impacts of Mechanical Equipment at Benson Brothers Quarry on Neazby Rock In Colorado, where daily 40-degree temperature changes are not uncommon, differential expansion of stone, especially in rock with southern exposure, creates strains that aze much greater than the dynamic strains caused by ground motions with PPV intensities less than 0.048 in/s. It should also be noted that over long periods of time, forces caused by swelling ice when water in vertical and near vertical rock joints and fractures freezes, causes rock wedging failures. Physical evidence of the site clearly indicates that rock-spalling caused by freeze-thaw-cycles and other normal weathering processes have been at work over time. Several years ago, the author did a similaz vibration-effects study involving the effects of vibrations caused by mechanical excavation equipment operating near steep rock bluffs adjacent to residential homes in Castle Rock, CO. In that case (Revey, 2002) mechanical rock trenching and back-hoe mounted hoe-rams would eventually operate within 200 feet of the near vertical rock bluffs. Predicted maximum ground motion intensifies, based on actual site vibration measurements were expected to approach 0.2 in/s, which is 4 times greater than the 0.048 in/s motion intensities expected in this case. All excavation work was subsequently done without incident. 4.0 CONCLUSIONS Based on these findings and comparisons, it is reasonable to conclude that motions caused by vibrations of operating quarry machinery at the proposed Red Shale Quarry will have no impact whatsoever on the stability of rock slopes because they are virtually immeasurable and any stresses that would occur are orders of magnitude less than the sffesses caused by natural environmental stresses and forces and freeze-thaw cycles. Similarly, equipment-induced vibrations caused in underground coal mine openings that may exist at greater distances below neighboring homes will also be immeasurable and will have no impact on current ground stability. In light of the fact that rock falls have occurred in the Rollins sandstone bluff in the past, it is very likely that the forces of nature will continue to causes erosion and rock falls within this formation. When they might occur and to what degree is impossible to predict, but depending on the in situ condition of the rock bluff, it can be concluded that when they do occur, they will be caused by natural environmental forces and time they might occur will not be accelerated by immeasurably low levels of ground vibration. 5.0 REFERENCES Revey, G.F, (2005), Assessment of Blast-Induced Ground Motion at Homes Involved in: James P. Melton III et al vs. Harrod Concrete & Stone Co. Revey, G. F., (2002), Review and analysis of Ground Vibration Induced by a Trencher and Hoe- ram at the Castlewood Canyon Residential Development Project. REVEY Associates, Inc. Page 7 of 7 February 2006