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Larry Perino Page 11 August 17, 2000 <br /> Appendix A. Terry Tunnel near portal bulkhead design calculations (Continued) <br /> K= 3.5 - 2.5d = 3.5 - 2.5[ 233700 J = 3.5 - 0.41 = 3.09 <br /> 213900(12 J <br /> K cannot exceed 2.5 Therefore K=2.5 <br /> Ag <br /> p W = bP d = ("'40 s =0.002629 Trial, #10 bars on 6-in centers, two-way <br /> V�=K�1.9 f� +2500pW Md)bWd <br /> 213900(80 5 <br /> V�= 2.5 1.9 3000 +2500(0.002629) 233900Z J 12(80.5) <br /> V� = 2.5[104.1 +40.33]966 = 2.5[144.43]966 = 348,800 lb <br /> Allowable Vc <(6 f�)bWd <(6 3000 )12(80.5) =317,5001b (ACI 318-95, Sec 11.8.7) <br /> Therefore FS = °o —_ 317500 <br /> vu 213900 <br /> = 1.48 <br /> Terry Tunnel bulkhead depth below surface(Z) required to prevent hydrofrac of rock around tunnel <br /> by 469-ft hydraulic head (203 psi pressure head): (Einarson & Abel, 1990) <br /> Bp= 36,,,;,,—or.,, =2a.vb =2Z( -Lr) =2Z(144)= 2.292Z psi =203 psi <br /> Z= 2.292 = 89 ft <br /> Therefore, the bulkhead must be centered at least 160 ft inside the portal to develop 89 ft of <br /> overburden. Therefore, the fluid pressure developed behind the recommended bulkhead <br /> location, from 305 ft to 312 ft inside the portal for average distance from the portal of 308 ft, <br /> and an average depth of 200 ft will not result in formation hydrofracturing. <br /> Earthquake bulkhead design; Load factors (ACI 318-95, Sec 9.2.2, 9.2.3, 9.2.5): Factor for fluid <br /> load under earthquake acceleration(F) = 1.05; Load factor for earthquake accelerated mass <br /> (E) = 1.40. Maximum credible earthquake acceleration(a) is 0.0872Sec <br /> . <br /> U= 1.05F + 1.40E <br /> Loads on bulkhead resulting from maximum credible earthquake acceleration of the fluid (F) and <br /> bulkhead (E) masses bearing on a 7-ft thick bulkhead. <br /> _ Sjywhl+Lhlyc — [3500(62.4)13(12.7)E7(13)12.7(151)] — 136,058,000+175,0001 lb-sec E,. S — 32.2 — 32.2 = 1, 125,0�� ft <br />