摘要(英) |
ABSTRACT A
constitutive model for sand named “SHSE” and FLAC3D software were used
to study the anchorage behavior of inclined underreamed anchors in
dense sand. The anchor has a diameter D of 0.076mm,
length-to-diameter ratio L/D of 4.5, and overburden head of 8D, all
anchors were placed in sand with Dr=70%. It was found that the total
load, end resistance, and shaft friction were increased
with increasing embedded depth. Total load and end resistance were
increased with decreasing inclined angle, too. The maximum shaft
friction occurs when the inclination angle “a ” equals to 20o, an
inclination angle of 2 / 45 f - O may be the optimum angle for a
friction type anchor. Total load, end resistance, and shaft
friction do not reach peak values at the same anchor displacement.
Evident peak value and residual value can be seen when anchors were
pulled. An anchor displacement equals to 15%D is need for the shaft
friction reaches peak value. Shaft friction reaches residual state at
an anchor displacement of about 50%D. No peak value of end resistance
can be found when free length of an anchor is greater than 5D and named
a depth anchor herein. According to the definition of yielding
end-resistance, the yielding end-resistance of deep anchor develops
at an anchor displacement of about 35%D. The end resistance
coefficient Nq was decreased with increasing embedded depth
and inclination angle of an anchor. The coefficient of lateral earth
pressure Kf is less than coefficient of passive earth pressure Kp,
but is greater than coefficient of earth pressure at rest K0. A
concave upward behavior can be seen from load transfer
curve. Friction stress concentration on the upper fixed end results
from an anchor of Z/D<10, hence do not place the free length of
anchor in 10D. From the process of yielding soil surround the fixed
end can be found, soil surround bottom of an anchor reaches
yield first due to stress relaxation, the range of yielding soil
above fixed length is larger than the range of yielding soil below
fixed length, the yielding range upon fixed end will reaches
structural wall if an anchor is placed in shorter free length. The
yielding range will develop to ground surface when overburden depth
of an anchor is less than 8D, so do not placed those anchors in this
area. |