Abstract:
The present investigation has been conducted to study the load-displacement response
and horizontal load capacity of vertical unrestrained piles subjected to lateral load using
a finite difference method. Generally unifonn soil deposits are not found in nature and
the piles are embedded in layered soils. The effect of two-layer cohesive soil system in
the engineering behaviour of a laterally loaded pile is investigated analytically. Pile
deflection often governs the design of laterally loaded piles, as such the possibility of
reducing the pile head deflection using a stiff layer near the ground level has been
investigated
For piles subjected to a given horizontal load the deflection at pile head, is smaller for
piles embedded in stiff soils than piles embedded in soft soils. Therefore the allowable
capacity [the allowable horizontal load capacity according to BNBC (1993) is half of the
horizontal load which produces I inch deflection at pile head] of a pile is greater if the
. pile is embedded in stiff soil. However the maximum moment corresponding to allowable
load increases with the increase of soil modulus. The reason behind this is the increase in
allowable horizontal capacity in stiff soil. Higher horizontal load produces higher
,
maximum moment. To attain higher allowable capacity of a pile embedded in a better
soil the reinforcement of the pile should be increased according to the value of
maximum moment.
The horizontal capacity and corresponding moment of a pile embedded in soft soil and tip
resting on a stiff soil is similar to a pile embedded in a uniform soil having properties of
the top soft layer. When a pile is subjected to a given horizontal load, the presence of a thin stiff layer at
ground swface reduces the deflections and moments to a great extent. That is the
horizontal capacity of a vertical pile can be increased significantly by replacing the upper
soil with a thin stiff layer. The horizontal capacity depends on the modulus of subgrade
reaction and thickness of the top stiff layer.
When a pile is subjected to a given horizontal load the deflection of piles decreases with
the increase of thickness of the top stiff layer. However effect of thickness on the
values of maximum moment is negligible.
