2006-02-21_REVISION - M1983141 - Laserfiche WebLink

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Memo to Tom Schreiner 9 February 21, 2006 Bulkhead Cost Estimate Permit No. M-1983-141 Design for Hydraulic Pressure Gradient, Secondary Bulkhead Ungrouted Bulkhead Low Pressure Grouted Bulkhead L _ 66 psi =13.2 feet Spsi / ft 66 psi L= =1.6feet 41 pst / ft Clearly, with an almost ten fold decrease in required bulkhead length, and the difficulty in concrete pouring for bulkheads greater than 10 feet in length, low pressure grouting is a necessity for the proposed main bulkhead. Design for Concrete Shearon Mount Royale Adit No. 1 Perimeter The required bulkhead length for the concrete shear component of design, assuming minimum bulkhead concrete compressive strength is specified at 3000 psi, is calculated as follows: L_ pxhxP _ 66x8x8 =1.2feet 2x~h+P~x f', 2x~8+8~x110 where: L =bulkhead length (feet) p =pressure head (psi) h = adit height (feet) f = adit width (feet) f', =concrete shear strength (psi) Therefore, the 1.6 foot minimum bulkhead length required for pressure gradient exceeds the bulkhead length requires for concrete shear, and pressure gradient controls the design at this stage of the analysis. Design for Plain Concrete Deep Beam Bending Stress The Applicant has proposed that plain concrete (unreinforced) bulkheads be constructed. American Concrete Institute codes can be used to determine the required length for a plain concrete bulkhead to resist deep-beam bending stress. For the analysis, the dead or fluid load acting on the bulkhead is multiplied by 1.4 (ACI 318-89, Section 9.2.1) and the plain concrete bending strength reduction factor of 0.65 is applied (ACI 318-77, Section 9.3.2). ACI directs that the design tensile bending strength be: f, =5 f'~ (ACI318-77, Section 15.11.1) f = 5 3000 = 273 psi, assuming that minimum 3000 psi compressive strength is specified w =1.4 x p x 144in Z l ft z =1.4 x 66 x 144 =13306 pounds per foot