Question

The total load of a chimney and its circular footing is 35 MN, as shown in the figure. Assume the average unit weight of soil below and above the water table is the same.

• Presume: B (diameter) = 8 m, H = 6 m, and D = 2 m.  

According to SPT results, the average N-value for sandy soil below the footing is 20.

1. Estimate the values of the friction angle and the average unit weight of soil based on N-value.
2. Determine the factor of safety of this footing against the bearing capacity failure using Hansen’s equations.
   HA11- 1 FRIFLFLIFFTRIFFT 111 B (diameter) HHILLAHHHHHHH HALLILLE! ID
   

Answer 1

Date 18/051 Given That Total Load CQ) = 35 MN MN=103KN Diametel (B) 800) Height of Goound water level foross GL (H) = 60 Depth of foundation (0) = 20m and also Given That, SPT N value -20 Generally for coarse Grained, boils (sandy soils) SPT N value lies blo 10 to 35. correspondling - 33-44 friction co unit weight (2) 17-20 kN/m3 Angle of frictions N 20-10 X-33 - 33 25-10 uu-33 20 x? 25 44 Із чо? foterion - ५० usit weight cel 20-10 Y-17 zle a 10 17 20-17 25-10 20 y? 20 25 ya 19 kubome my unit walat (0) > 1961/61,9 Sueledai

(5) Hansen's een ultimate Bea ealing capacity eNe se deiegebetog Ng Sadle aq bq+ LBt Ng Sącz 189 9969 whereas, escobeson - effective over bulden pressure 8=unit wt, Of = depth of foundation Sc, sa, so shape factors de, dq, dg a depth factes &, fou, is Lood enclination factors Ne, No, Ng falous beasing capacity factors Angle of friction (0) = 400 Bearing capacity for ale NC : 72.25 Nq - 6401 Ng=7904 shape faltas B Sc=lt na (B/L=1 circular felting) N8 L = 1.807 =lt Guolx 1 904 Sq altistan 40 = 1084 it tand 1-ood & 1-0.4*() -0,6

Ground factius ge al-Bº foundation is Haizontal (B) =0 14 = 1 ge similarly ge =qq=ge are Same for Horizontal fun Base falars (6) Jo I- (hizo (Hrizontal Ground) 147no be = 1 same , be a bq = 68 = 2 Depth factors (a) ão de = tool 믐 CD3B) dc = 1+0.4 ( 2 zlo dq=l+ 2 tang (1-8173933 2 tang (1-sing2 2 ron (40)(i-Sin 480)2 =1+0.214 x iş = 1.054 7 0.214 28 = 2 Inclination faciles de fa vertical loade icaiq - is=1

effective stress cool 8XD and also =19x2=38 en lange (Sandy soil) So, now Rewrite the haven's egn VaR oo Ng Sado q gebq + 1 st Naszag ig go bp 38x640141484x1-054X1XXX1 + 4x19x79.4*0-6X8X1XI XXL 4723.94 3620.64 =8344.54 Kulon 2 Net ultimat Beard Bearing Capacity [ang) =Q-80p 8344.54–1982-8306-5 kilon 2 Net Safe bearing capacity (ans) ans = Qnu fos 8306.5 * D-B Load ans = forea) cmculare 35x103KN « Des einse 696. 30 696.30 fos (872 8306.5 POS allo93 696.30 * fos - 11.93 Suenolow