Abstract:
ABSTRACT
The screw pile is a famous solution used in various engineering
applications, which have relatively low capacity foundations offering
stability against compression, overturning moment, uplift tension, and
horizontal loads.
This study presents a series of model experiments conducted on
single screw pile embedded in soft clay soil over laying a sandy soil under
compressive loads. The effects of different parameters, such as screw pile
length (L), number of helix plate, helix diameter (Dh), inter helix spacing
(s) and screw pile settlement, are studied. Three different pile length (300,
350 and 400) mm, single and double helix and pile without helix, (1.5D,
3D and 4D) helix diameter, (30 and 50) mm spacing between helix plate
are used in this study (where D is the diameter of the pile shaft). Also,
buckling in screw pile is checked and a comparison between the measured
and predicted compressive forces on the screw piles is investigated.
The results of the experiment showed that the screw piles settlement
for piles embedded in soft clay soil overlaying a sandy soil layer decrease
(59-182)% with increasing depth of embedment in the sandy layer L/D
from 35 to 40, helix diameter and number of helix those provide anchorage
against settlement. Deeper screw piles with higher L/D ratios showed
compressive capacity (24-55) times greater than the shallower piles (screw
pile embedded in soft clay). In addition, screw piles showed resistance to
the applied compressive forces (9-16) times more than ordinary piles.
II
The compressive force increases with increasing diameters and
number of helix plates. Furthermore, from this study, it is found that the
screw piles with double helix principally failed by cylindrical surface
occurred in the region between two helix plates. Another failure mode is
individual bearing that occurred at double helix screw pile with spacing
ratio (s/Dh) greater than 2 and at the base of screw piles, which has single
helix plate. Comparing the predicted theoretical results with the actual
measured load test results, it was found that the failure criterion (20% helix
diameter) used to determine the ultimate compressive capacity was best
suited for a valid comparison than other failure criteria (5%, 10% and
15%).
