Question

12.19 A 20 m long bored concrete pile having a diameter of 350 mm is load tested, and the data are given below: Load (kN) 0 250 500 750 1000 1250 1000 750 500 2500 Settlement 0 2.0 5.0 8.2 15.0 39.6 39.5 38.2 37.5 36.1 35.5 (mm) Also given: Econcrete = 25 X 10' MN/m² a. Estimate the allowable pile load using Davisson's (1973) method, with FS = 2.5. b. At the maximum load of 1250 kN, what are the total and net settlements?

Answer 1

By ubing Dawfmon's method, ultimate Load Can be determined from the load settlement plota Accolding to this method ultimate Load occurs at a settlement of Su, Su = 0.012 Du + 0.1 () + Qua IT APER where; Dp = reference pile dia = 300mm k - Pile Length = 20m = 20000 mm D = Diameter of file (mm) = 350 mm Ap = (3502) = 96211.275 mm Ep = Young's modules of clasticity ( KN/mo) = 25 * 103 my ant e = 25 KN/mm/ Qu id in KN. Su = 0.012 Dn + 0.1 D + Quh " Dr A,Ep Su = 0.012 (300) + 0.1(350) + Qu (20000) 96211.275 (25) - 3.6 +0.11667 +0.00832 Qu Su = 3.71667 + 0.00832 Cod.

The Line Su-3.71667 +0.00832 Que is drawn in the Load settlement graph , The intersection of thick line with the load settlement Curve givees the ultimate Load. Therefore; at Que = OKN, Su = 3.71667 mm Q = 250 K , Su - 5.781 10) Que = 500 KN, Su = 7.877mm a = 750 KN, Su - 1957 mm Qu = 1000KN, Su = 12.037 mm C = 1250 kN, SA = 14, 87 m ) Theere fore from graph shown below, the Line Su - 3. 71667 +0.00832 Qu intere seets the load rettlement Curve at 2 = 860 KN. Allowable file doad = Go - 360 = 344 KN. from the graph, total settlement serb. St = 39.6 mm. Net Settlement - St-Se = 39.6– (39.6-35.5) Snet = 35.5 mm.7 FOS

> 250 Load (kn) 500 750 860 1000 1250 00083284 3.71667 + . (mm) dag Settlement 9 linoedd Uno