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Type-2
Fig.5 Three dimensional Slope Model for the Numerical Calculation
Z
A
C 800 ..£400 . c 800 x,
r* *n^ "^ *n
/ V /
270
lower layer
Fig. 6 Dimension of the Slope Model
'
540
810
unit: m
-01 00 01 (m/s)
Fig. 7 Response Acceleration in y-Direction
(perpendicular to Excitation x-Direction)
model are connected with free field by viscous boundaries. Several cases with respect to stiffness and
strength properties are studied.
As an example of response analysis, the response acceleration in y direction at specific time with
homogeneous property model (shear velocity 340m/sec., Poisson's ratio 0.48, damping ratio 0.0) is
shown in Fig.7. Since the direction of excitation is in ^-direction, the response in y-direction
corresponds to the component perpendicular to the excitation, which means response due to 3-d effect.
The spectral ratios to the doubled input motion in ^-direction are shown in Fig.8. The response at point
A becomes large, while that of point B becomes small compared with 1-d response due to the slope
configuration. The response of Type-1 is larger than that of Type-2 generally.
Sliding Surface With Minimum Safety Factor
The sliding surface with minimum safety factor is searched by GA, for both models Type-1 and
Type-2. It is assumed that the models are divided into two layers, upper and lower layer as shown in
Fig.6. The properties of both layers are summarized in Table 1. The time history and Fourier spectrum
of the input motion, which is the record of Kera county earthquake at Taft, are shown in Fig.9. The
sliding surface is defined by crossing surface of the oval and the 3-d slopes. The parameters of the oval
are shown in Fig. 10. The coordinate of center (x, v, z), radius (a, b, c), angle around z axis, of the oval
are determined such that the safety factor becomes minimum by GA. The directions of sliding 9 l and
excitation #, for minimum safety factor are also searched in addition to the above parameters at the
same time. Population size and generation size for GA are is 150 and 40.
The obtained sliding surfaces with minimum safety factor of Type-1 are shown in Fig. 11 and 12.
Fig. 11 shows the critical surface when the search is performed under the limitation that the sliding