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Page 2 of 6 <br /> Response to Comments from March 6, 2024, DRMS Memorandum April 26, 2024 <br /> 3) Upper Wall Calculations. Input variables are presented in Table 1 and Figure 1; results are presented <br /> in Table 2 and Table 3. <br /> a) KA, Coefficient of Active Earth Pressure calculated using equation 13.69 in Das (2010). <br /> KA = Cost(fl + (p) <br /> r 2 <br /> COs2(/3) * COs2((5—/3) * I 1 + sin(o+ S) cos (,p— a s ] <br /> i) jcos((5 /l) (—/l— ) <br /> ii) The configuration of the above equation varies depending on how the wall backface angle is <br /> defined (e.g., +/-). <br /> iii) KA_Uppefwa„=0.05 (it should be noted that when P>b there is a reversal of the computed <br /> direction of the vertical component of the lateral earth pressure; that is, it acts upward instead <br /> of downward. This can be seen in Figure 1 which has been developed specifically for this <br /> design. <br /> b) Pa, Active Pressure calculated using equation 13.68 in Das (2010): <br /> I) Pa= 1 1 KayH2 <br /> ii) Pa= 53.1lb/ft (This value does not include surcharge) <br /> c) Surcharge force: <br /> i) PS = gKaH <br /> ii) PS 63.8 Ib/ft (assumed to act horizontally to be conservative) <br /> d) Overturning Moment Calculation: The total Horizontal Overturning Force consists of the horizontal <br /> component of Pa, Ph plus the surcharge, Ps. Ph (yellow highlight) acts at 1/3 of the height, and PS <br /> (green highlight) acts at'h of the height. The Overturing Moment is calculated using the following <br /> equation (Mack, et. al., 2006, Figure 37. 38, and 39): <br /> Mo = 2 KaYrH2 cos(8—/3) \3/ + gKaH\2/ <br /> i) <br /> e) The Resisting Overturing Forces consist of the mass of the boulder wall plus the vertical <br /> component of the Active Pressure, which in this case is negative, reducing the resisting force. <br /> The wall is divided into three zones to calculate the moments, as shown in Figure 1. The <br /> Resisting Moment is defined as: <br /> 1 <br /> i M'r = Wi di +2 Kay,H2 COs((5—/3)(d4) <br /> f) The Factor of Safety for Overturning, FSOT , shown in Table 4, is defined as: <br /> o:Iproject1201001201IW05 documentslworking fileslwnrlwall design120119b poudre ponds wall design memo 2024-04-26.docx <br />