Problem No. 2 – Design of a Braced Cofferdam in Cohesive Soil Follow Example No.1 on page 114, with the following modifi
Posted: Mon May 02, 2022 10:48 am
Problem No. 2 – Design of a Braced Cofferdam in Cohesive
Soil
Follow Example No.1 on page 114, with the following
modifications:
The water table is at 15 feet; the surcharge behind the wall is
250 psf.
(No. 1) DESIGN OF BRACED COFFE FFERDAM IN COHESIVE SOIL STABILITY NUMBER METHOD - MEDIUM SOFT CLAY) SURCHARGE 300 PS Soin PROPERTIES-MED. Soft CLAY r = 115 PCE (SATURATED) F = 53 PC (SUBMERGED) C = 1000 PSI, * = 0 TIER Nat 의 11.4 | 81 13'-0 4 STABILITY > 1) CONSIDER N. Fres WATER TABLE NUMBER No. XH+ SURCH. 115 (36) + 300 1OOO = 4.67 с 10% TIER No.2 1 + 38-0 BH = 20.91 1 Do - iſo ( 7 No? + 10 N.) [7(4.67)² + 10 (4.67) 596 1000 150 + - 8-012-0 SPRESSURE DIAGRAM WITH NO WATER TARLE Pressure DIAGRAM LWITH WATER TABLE TIER 1946 = 1330 PS4 No.3 1990 a=0.3 (1-Mee But Not >0.15 H-5.7' 1750 71737=== a=0.23 > 0.15; .. LET LE 0.15 Р. 1330 psf B= 4 (-o) But Not30.55 PRESSURE DIAGRAMS B = 0.85 > 0.55; .. LET B=0.55 TH= 0.15 (38) = 5.7' BH = 0.55(38) - 20.9' 2) CONSIDER THE SATURATED AND SUBMERGED Densities With A WATER TABLE No- 115 (10) + 53(28) + 300 2.93 por 1966 [162.93) +1012.93)] = 596 PSt. Note, X = 0.15 AND B = 0.55. ADD HYDROSTATIC Pressure (SEE DIAGRAM) 1000 1000
SHEET PILE WALL ASSUME MAXIMUM MOMENT OCCURS AT TIER No. 3 Anois APPROX. EQUAL TO THE NEGATIVE MOMENT AT ANY INTERIOR SUPPORT OF A CONTINUOUS BEAM HAVING A UNIFORMLY DISTRIBUTED LOAD OF 2000 Pef (LOAD AT TIER NO.BIS 1846 PS$ PER FT Wioru). MMAX = to we2 = to (2000) (12) ²/1.000 = 28.8 kip.FT./FT. WIDTH REQ'D. SECTION MODULUS, S : MMAX 28.8(12) 13.8 IN.FT. WIDTH VREGULAR CARSON STEEL 28.8 (12) S = = 10.8 IN.?/FIWIDTH U.S.S. Ex-TEN 50 STEEL ALL 25 KS OR 32 KST USE PZ-22 IN REGULAR CARBON STEEL OR PDA-27 IN Ex-TEN 50 STEEL ALTERNATE SECTION STRUTS To COMPUTE THE AXIAL LOAD IN EACH STRUT ASSUME A PLACTIC HINGE AT EACH STRUT POINT CA CONSERVATIVE ASSUMPTION) AND Sum MOMENT ABOUT Tier No. 2 TO SOLVE FOR TIER Noi, Sum MOMENTS ABOUT TIER No.3 To SOLVE FOR TIER No.2 AND SUM MOMENT ABOUT THE BOTTOM OF THE EXCAVATION TO SOLVE FOR TIER No. 3. THE SOLUTIONS ARE: Axial Londla Tier Nal = 4.12 Kips/Ft. WIDTH 2= 13.0 3= 27.4 TOTAL AXIAL LOAD PER FOOT WIDTH - 44.52 kips CHECK TOTAL LATERAL PRESSURE LOAD: 1000 P (kips) - [{C11.5)+20.9 +į (5.7)](596)+{ (26.6%(1750) P: 40,9 Kips/FT. WIDTH O.K.(Less Than Tier Londs) 11 11 1
DETERMINE SAFETY FACTOR AGAINST HEAVE AT THE BOTTOM OF THE EXCAVATION CUSE BJERRUM RELATIONSHIP-NEGATIVE FOOTING) ASSUME A VERY LONG EXCAVATION AND WIDTH=50F7....-6-0,76 No 26.0 (SEE Fig. 6) 100006) S.F. Ye Htq 10 (115)+28 (53) + 300 > 1.5 CNC 2.05 BASE IS STABLE WITHOUT DRIVING SHEETING BEYOND BOTTOM OF EXCAVATION,
Soil
Follow Example No.1 on page 114, with the following
modifications:
The water table is at 15 feet; the surcharge behind the wall is
250 psf.
- Problem No 2 Design Of A Braced Cofferdam In Cohesive Soil Follow Example No 1 On Page 114 With The Following Modifi 1 (118.31 KiB) Viewed 28 times
SHEET PILE WALL ASSUME MAXIMUM MOMENT OCCURS AT TIER No. 3 Anois APPROX. EQUAL TO THE NEGATIVE MOMENT AT ANY INTERIOR SUPPORT OF A CONTINUOUS BEAM HAVING A UNIFORMLY DISTRIBUTED LOAD OF 2000 Pef (LOAD AT TIER NO.BIS 1846 PS$ PER FT Wioru). MMAX = to we2 = to (2000) (12) ²/1.000 = 28.8 kip.FT./FT. WIDTH REQ'D. SECTION MODULUS, S : MMAX 28.8(12) 13.8 IN.FT. WIDTH VREGULAR CARSON STEEL 28.8 (12) S = = 10.8 IN.?/FIWIDTH U.S.S. Ex-TEN 50 STEEL ALL 25 KS OR 32 KST USE PZ-22 IN REGULAR CARBON STEEL OR PDA-27 IN Ex-TEN 50 STEEL ALTERNATE SECTION STRUTS To COMPUTE THE AXIAL LOAD IN EACH STRUT ASSUME A PLACTIC HINGE AT EACH STRUT POINT CA CONSERVATIVE ASSUMPTION) AND Sum MOMENT ABOUT Tier No. 2 TO SOLVE FOR TIER Noi, Sum MOMENTS ABOUT TIER No.3 To SOLVE FOR TIER No.2 AND SUM MOMENT ABOUT THE BOTTOM OF THE EXCAVATION TO SOLVE FOR TIER No. 3. THE SOLUTIONS ARE: Axial Londla Tier Nal = 4.12 Kips/Ft. WIDTH 2= 13.0 3= 27.4 TOTAL AXIAL LOAD PER FOOT WIDTH - 44.52 kips CHECK TOTAL LATERAL PRESSURE LOAD: 1000 P (kips) - [{C11.5)+20.9 +į (5.7)](596)+{ (26.6%(1750) P: 40,9 Kips/FT. WIDTH O.K.(Less Than Tier Londs) 11 11 1
DETERMINE SAFETY FACTOR AGAINST HEAVE AT THE BOTTOM OF THE EXCAVATION CUSE BJERRUM RELATIONSHIP-NEGATIVE FOOTING) ASSUME A VERY LONG EXCAVATION AND WIDTH=50F7....-6-0,76 No 26.0 (SEE Fig. 6) 100006) S.F. Ye Htq 10 (115)+28 (53) + 300 > 1.5 CNC 2.05 BASE IS STABLE WITHOUT DRIVING SHEETING BEYOND BOTTOM OF EXCAVATION,