Abstract:
The behaviour of horizontal strip anchors buried in clay
is examined in this paper. A brief critique of the various
approaches suggested for the design of these anchors is
presented, with emphasis placed on estimation of the
ultimate load that these anchors can withstand when
loaded rapidly in uplift under undrained conditions.
Possible mechanisms of failure are reviewed, including
shear and tensile failure within the soil and the development
of suction within the pore fluid, and the results of
finite element predictions are compared with experimental
data for ultimate loads. The analyses reveal that the
behaviour of strip anchors in uplift is a function of the
following non-dimensional parameters: H/B, yH/c and
uc/c, where H is the depth of embedment of the anchor,
B is the width of the strip anchor, y is the unit weight of
the soil, c is its undrained shear strength, and u; is the
magnitude of the maximum tensile stress that can be
sustained by the pore water in the soil. It is demonstrated
that the ultimate uplift capacity is dependent on the
availability of water at the surface of the soil and within
the soil beneath the strip anchor. The analyses also show
that shallow anchors in relatively strong soil tend to fail
by the development of tensile failure in the soil above the
anchor. The ultimate capacity of these shallow anchors is
a function of the undrained shear strength of the soil, its
self-weight and the tensile capacity of the pore fluid. By
contrast, the failure mechanism for deeply buried anchors
where the initial vertical total stress at the plate
exceeds 7c involves only localised shear failure around
the anchor, and as a result the ultimate capacity effectively
becomes a function only of the undrained shear
strength of the soil.
