||Because of its inferior geological conditions and environmental factors, geological hazards like landslides are of great concern in Taiwan. The stability of soil slopes which mainly involve arc-shape failure surfaces are used to be analyzed by the limit equilibrium method (LEM), presuming shear-dominant failure surface and rigid failed mass. The objective of this thesis is to investigate the same problem by use of a deformation analysis (FLAC), in which the deformability and tensile strength of soil mass can be considered.|
The deformation analysis program used is the FLAC code, in which finite-difference scheme is employed for both the spatial and time domains. The corresponding factor of safety (FS) and failure surface are determined by the strength-reduction concept plus the displacement history of a control point and the maximum shear strain contour, respectively. Two slope models were examined in this thesis, including a completely dry soil slope and another having varying groundwater table. For all computation cases, Mohr-Coulomb law was adopted for soil mass and the slope height was kept constant, but with changing slope inclination, soil modulus (E), soil tensile strength (T0), and groundwater table. The most popular LEM slope stability code — STABL5 (using Bishop slice method) was also used for a comparison reason.
The analysis results are summarized as follows: 1) at the same slope inclination and groundwater table, FLAC yields a FS value and failure surface comparable to STABL5 for a soil mass with high modulus and infinite tensile strength; 2) as the slope inclination and/or groundwater table increase, the value of FS computed decreases; 3) when the slope inclination is greater than 60°, and E is smaller than 1MPa with limited value of T0, the value of FS computed by FLAC is lower by at least 5% than that by STABL5 (here, indicating the limitation of STABL5's application; 4) as the groundwater table increases, the difference in FS between FLAC and STABL5 becomes larger.
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