12. A Limit State is a defined condition beyond which a structural component, ceases to satisfy the provisions for which it is designed. Resistance is a quantifiable value that defines the point beyond which the particular limit state under investigation for a particular component will be exceeded.
29. Soil Shear Strength ’ = c’ + n ’ tan f ’ ’ a ’ a ’ r ’ r ’ ’ n ’ ’ n ’ f ’ ’ c’ Strength envelope
30. Undrained Strength of Cohesive Soils, s u Unconfined Compression s u = q u /2 Vane Shear Test s u q u =0 Typical Values s u = 250 - 4000 psf
31. Drained Strength of Cohesive Soils, c’ and ’ f Triaxial Compression CU Test Typical Values c’ = 100 - 500 psf ’ f = 20 o - 35 o
32. Drained Strength of Cohesionless Soils, ’ f Standard Penetration Test (SPT) Typical Values ’ f = 25 o - 45 o Friction angle is correlated to SPT results. ’ f ’ q’ c=0
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34. Guided Walk Through For N 1 60 = 10, select ’ f = 30 o (modified after Bowles, 1977) N 1 60 f <4 25-30 4 27-32 10 30-35 30 35-40 50 38-43
36. Consolidation Properties Log 10 v ’ Void Ratio (e) p ’ = Preconsolidation Stress C s C r C c 0.1 1 10 100 0.5 1 e o
37. One log cycle e=C =0.06 0.1 1 10 100 1000 10000 Elapsed Time (min) Void ratio (e) 2.65 2.6 2.55 2.5 2.45 2.4 2.35 2.3 2.25 Stress Range, 40 – 80 kPa t p
38. Typical Consolidation Properties Property Typical Value C c 0.1 to 1.0 C r 10 % of C c C s Approximately C r C 4% to 6% of C c C v 0.01 to 1.0 ft 2 /day
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41. Intact Rock Strength Point Load Test Unconfined Compression, q u Typical Values q u = 1500 - 50000 psi
42. Rock Quality Length, L 0.8 ft 0.7 ft 0.8 ft 0.6 ft 0.2 ft 0.7 ft Sound Not sound, highly weathered Not sound, centerline pieces < 4 inches, highly weathered Sound Not sound Sound Core Run Total = 4 ft CR = 95% RQD = 53%
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44. Rock Mass Strength C 1 ’ Shear stress, Effective Normal Stress, ’ tm 3 1 ’ i = (cot ’ i – cos ’ i )mq u /8 ’ i = tan -1 (4 h cos 2 [30+0.33sin -1 (h -3/2 )]-1) -1/2 h = 1 + 16(m ’ n +sq u )/(3m 2 q u )
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47. Rock Mass Deformation E = 2 RMR - 100 90 70 50 30 10 In situ modulus of deformation, E M (GPa) 10 30 50 70 90 12 10 8 6 4 2 (psi x 10 6 ) Rock mass rating RMR
49. Jerry A. DiMaggio P. E. Principal Bridge Engineer TEL: (202) 366-1569 FAX: (202) 366-3077 The best Geotechnical web site in town! www.fhwa.dot.gov/bridge WOW! FREE STUFF FROM THE FEDERAL GOVERNMENT!