同济培训FLAC--FLAC2.ppt

FLAC/FLAC3D Short Course Itasca Software Training Course Tongji University Shanghai, China October 27-31, 2008 Training ScheduleOctober 28, 2008 (morning) External sources quiet boundaries Soil Characteristics Equivalent-Linear Method Characteristics of the Equivalent-Linear Method Characteristics of the Fully Nonlinear Method Using elastic/plastic models Elastic/plastic Models Rayleigh damping Rayleigh damping – cont. Rayleigh damping – cont. Hysteretic Damping in FLAC and FLAC3D Further Hysteretic Damping points … Liquefaction - principles Liquefaction principles (2) Analysis Methods to Assess Liquefaction Analysis Methods to Assess Liquefaction UBCTOT: Post-liquefaction The scheme has been applied to several cases of dam shaking. The following plot of excess pore pressures is reproduced from Roth, Inel, Davis Brodt (1993). Finn/Byrne Model For simple shear loading (dry conditions): Drained properties for wharf soils Modulus reduction curve Damping ratio curve Horizontal acceleration time history Baseline correction Mesh creation Zone size Establish stress/strain state of wharf sitebefore earthquake * * * * * Yielding is a prerequisite for sand production, sand is produced if hydrodynamic forces are large enough to dislodge the grains * * * * * * * * * * * * * * * * * * * * * * * * Soils 2 and 3 can liquefy - SPT blow count = 10 assume applies to Soils 1, 2 and 3 assume applies to Soils 1, 2 and 3 Liquefaction Behavior Use the Byrne formula: Embankment material contains Finn model (Byrne formula). For (N1)60 = 10 : C1 = 0.49044 C2 = 0.81559 (based on volume-change modification to Mohr-Coulomb model) For the liquefaction simulations: back acceleration (g’s) time (sec) Target motion at ground surface Check frequency content of input acceleration(for selecting element size) power (N-m/sec) frequency (Hz) Power spectrum (from FFT.FIS) Filter acceleration at 10 Hz cutoff frequency (using FILTER.FIS) power (N-m/se