摘要(英) |
Both
numerical analyses and field tests were accomplished to
elucidate the anchorage behavior of frictional anchor groups in
silty sand. A series of triaxial tests was performed on
specimens taken from test site, based on the frame of
constitutive model for the cohesionless soil named SHASOVOD (A
continuous strain hardening- softening and volumetric dilatancy
model), to obtained the parameters needed for the model. This
study along with FLAC3D software to analyze behaviors of single
anchors and anchor groups in silty sand. In addition, to verify
the suitability of the numerical program, filed tests on a
single shaft anchors and an anchor group arranged in 2*2 matrix
form were conducted in silty sand. After the calibration, a
succession of parameteric analyses was carried out to study the
anchorage behaviors of single shaft anchors and anchor groups in
silty sand.
It was found from triaxial tests on silty sand, the shear
strength increases as relative density and confining pressure
increases. The failure plane occurs when the deviator stress
reaches peak point. Hence, the shear strength decreases to
residual state and tends to constant as axial strain increases.
The volume decreases in the beginning, then dillates, and
finally comes to the steady state. This stress-strain phenomenon
meets the SHASOVOD model.
It can be seen from field test results, the ultimate load of
542kN was estimated meanwhile the anchor head displacement
reached 13cm for a single anchor with diameter of 15cm, free
length of 10m, and fixed length of 15m; while the ultimate load
of 522kN was measured with respect to the average of anchor head
displacement of 12.5cm for a 2*2 anchor group with spacing of
60cm, efficiency of an anchor group was computed to be 95%. The
load-displacement relations and ultimate loads calculated from
numerical analyses were closed to those measured by field tests
not only for the single anchor but also for the anchor group.
When a 2*2 anchor group with spacing of 2D (D: anchor diameter),
efficiency of the anchor group was calculated to be only 75%~
80%. There is no interference when spacing was 6D, and the
efficiency of an anchor group could more than 95%. The yielding
zone of the anchor groups increase as overburden depth increase.
The efficiency of anchor groups can be eliminated as the anchor
spacing are increase horizontally. It can be found from the
numerical results, the efficiency of 3*3 anchor group is greater
than that of 2*2 anchor group. |