Effect of penetration rate on bearing capacity of piles driven in dry sand

الملخص EN

The influence of constant rate of penetration on bearing capacity of piles driven in dry sand was thoroughly investigated and explored by conducting two series of tests.

The first set of tests aimed at qualifying the influence of sand’s initial density on its viscous behavior where a 6.1 cm diameter close-ended model pile was driven (40 cm) deep in uniformly graded, dry Sweileh sand, and tested at different penetration rates in the range (0.03 ~ 80 mm/s), The sand was initially prepared at one of the three test sand densities 1.55, 1.63, and 1.75 g/cm3 (35, 50, 70 %Dr, respectively).

The results indicated no significant change in the dry sand viscous properties, and the increase in the ultimate pile bearing capacity was in the range (3.5 ~ 15%), the maximum being at the least sand density.

The other set of tests was oriented to study dry sand viscous response at pile’s toe, shaft and the total pile at combinations of sand depths and pile embedments.

Dry sand densities were 1.55, 1.63, and 1.75 g/cm3 (35, 50, 70 % Dr, respectively), and pile embedments were 30,45, and 60-cm, i.e.

a total of 9 pile tests.

Two penetration rates were used, the first (0.03 mm/s) was specified for static pile load tests in accordance with the ASTM D1143-81, and the other was the maximum machine working rate (80 mm/s).

The results of those tests indicated that the bearing capacity of the pile’s shaft was not affected by penetration rate, and that pile’s toe was, to some extent, responsible for the increments in bearing capacity due to the built up soil inertia.

Pile’s toe bearing capacity was increased by about (4 to 18%)