Laserfiche WebLink
Evaluation of Proposed Bias• a[ [he ACA Riprap Quarry Haar Quena Vis • ,_` <br />result of the ,train that exceeds the rock's tensile strength. 't'he 2li-charge-radii cracking limit is <br />confirmed in two independent studies [IJS Bureau of Mines (RI ?901, 1983) and Butkovitch & <br />I-Iearst t,l97ti)J. IYthe diameter of explosive charges for the blasting occurring near the Rc:C llam <br />were limited to 4 inches, the maximum radial crack length would be ~2 inches, which is much <br />less than the closest 150-foot distance from the RCC Dam and the nearest potential blast <br />location. I-Ience, there is no possibility that blasting will rupture, crack or otherw2sc disturb the <br />rock supporting the Trout Creek Dam. <br />Vdithin and beyond the cracking zone, stress ~+•aves spread through the rock mass and along the <br />ground surface. Some waves pass through the "hndy" o]' the rock mass. Primary compression <br />waves and shear avaves are examples of body waves. Other waves, -like Rayleigh waves, travel <br />along the ground surface. In an ideal isotropic and homogenous rock mass, wave energy would <br />travel evenly in all directions. Howrevar, tttost rock maesae are far front ideal, so wave energ}r is <br />ret7ected, refracted attd attenuated by various geological and topographical conditions. "fhc <br />elastic properties of rock greatly influence vibration magnitude and attenuation rate. When <br />seismic waves pass through the ground, ground particles oscillate within three-dimensional <br />space. Soon alter blasting has stopped, vibration energy dissipates and the grotutd particles <br />become still. <br />Abbreviations: <br />5H =Shear wove. horisontel <br />SV =Shear wave, vertical <br />R =Rayleigh wave <br />P =Compressional wavo <br />~t1a' cs~ <br />SV <br /> <br />oetona4ng <br />`i^~ <br />R <br />C mrpc w ovhor <br />Inpularca <br />n,SNrEBnCP <br />Figure 2.1 -Typical'l'ibration Waves <br />REVEY Associates. Inc. Fate Y fury ~uot <br />