Abstract:

A numerical calculation model of the ultimate bearing capacity of soft rock foundation based on the fast lagrangian analysis of continua (FLAC) is presented. The soft rock foundation is assumed as homogeneous, isotropic and continuous material which exhibits perfect linear elatoplasticity. According to the failure feature of rock, the Hoek-Brown nonlinear failure criterion and non-associated flow rule that can consider dilation angle of soft rock is used in analysis. To simulate easily, the Hoek-Brown nonlinear failure criterion is transformed to Mohr-Coulomb linear failure criterion by tangent method. The formula of instantaneous internal friction angle and instantaneous cohesion are derived from principle of equivalency; and then subprogram is compiled based on FISH language in FLAC. So the ultimate bearing capacity of circular footing on weight or weightless rock foundation is gained through adding vertical velocity vector. By comparing to theoretical values and in-situ values, the result is obtained of which the value from Hoek-Brown solution is more close to in-situ value than that from Bell solution; but all of them are too conservative. However, the numerical results are in better agreement with the in situ results. Especially there is only two percent deviation in the condition of considering gravity. It is shown that the numerical simulation by FLAC based on Hoek-Brown nonlinear failure criterion is appropriate to calculate ultimate bearing capacity of soft rock foundation.

Key words: Hoek-Brown nonlinear failure criterion, soft rock foundation, ultimate bearing capacity, FLAC, numerical simulation