Laserfiche WebLink
By ATL Date 10/11/2020 Client Aggregate Industries Sheet 2 of 7 <br /> Updated Rockfall Evaluation—Lyons Quarry.Technical Review <br /> Chkd.By NA Date 10/21/2020 Description Update Job# 10246984-002 <br /> 2.OINPUTS: <br /> The program requires several inputs which are each described below. For more detailed explanation <br /> of the program refer to the CRSP Manual in Appendix A of this memo. <br /> • Surface Roughness:is a function of the size of the rock and the irregularity of the slope <br /> surface. Surface roughness is an estimation of how much the slope angle may vary within the <br /> radius of the rock. <br /> • Tangential Coefficient:of frictional resistance determines how much the component of the <br /> rock's velocity parallel to the slope is slowed during impact. Vegetation and, to a lesser extent, <br /> slope material influence the tangential coefficient. <br /> • Normal Coefficient:of restitution is a measure of the change in the velocity normal to the slope <br /> after impact, compared to the normal velocity before the impact. The normal coefficient is <br /> determined by the rigidity of the slope surface. <br /> • Rock Densitv:varies according to rock type. <br /> • Rock Shape:can be selected from "spherical", "cylindrical", or"dischoidal". Spherical is <br /> typically used for analysis and is the most conservative, as this shape provides the most mass <br /> concentration for a given radius. However other shapes are provided for when the <br /> discontinuities in the rock mass tend to create blocks of varying shapes. <br /> • Rock Size: is given by diameter when "spherical" is selected, length and diameter when <br /> "cylindrical" is selected, and thickness and diameter when "dischoidal" is selected. <br /> The slope configuration is based on the most recent survey of the existing ground conducted by <br /> Aggregate Industries in September, 2020. The proposed reclamation plan includes excavating the <br /> sandstone above the dacite highwalls back at a 2H:1V (horizontal:vertical) slope ratio. The 2H:1V <br /> Fountain Formation sandstone slope exceeds stability requirements laid out in the Kleinfelder report <br /> (Kleinfelder, 2008), and should not contribute significantly to rockfall; however, for conservatism the <br /> sandstone was still simulated as a rockfall source. The dacite/sandstone contact is shown as a yellow <br /> line on Figure 1. The slope topography is simplified into cells and each cell is assigned a set of <br /> coefficients based on the material properties of the slope. All catchment berms evaluated are assumed <br /> to have 1 H:1 V side slopes. No site-specific data was collected for this evaluation; such as measured <br /> surface roughness, amount of vegetation (tangential coefficient), elastic properties of the dacite or <br /> sandstone (normal coefficient) or rock density. Therefore judgment was used in selecting conservative <br /> values for the coefficients based on the guidance in the CRSP manual (Appendix A) and Kleinfelder <br /> (2008). For simplicity, the slope cells were divided into five slope types based on material and slope <br /> angle and assigned the set of coefficients shown in Table 1. <br /> Due to the sandstone and dacite having different unit weights and rock shapes, each rock type was <br /> simulated separately with the source of rocks being isolated to the individual rock type only. The inputs <br /> used for each rock type are shown in Table 2. It should be noted that based on the discontinuity data <br /> and historic performance, rock sizes above 6 feet in any dimension are unlikely or rare, although they <br /> were evaluated to provide a factor of safety. For each simulation 1,000 rocks were rolled and the <br /> percent of rocks stopping before the analysis point was evaluated. <br />