研究期間：10108~10207;Critical-taper wedge theory explains the first-order geometry of fold and thrust belts as a function of the internal strength of the wedge of deforming material and the strength of the basal detachment. This study incorporates the nonlinear Hoek and Brown failure criterion into the critical taper model to evaluate the variation of the taper angle of thrust belt with changes of wedge thickness. From collected wedge profile found wedge geometry about three types of morphology were fixed angle, convex upward and concave upward. The effects of the lateral pore pressure changes at the wedge and the detachment, and formation strength (GSI) change at the wedge, as well as effect of non-linear wedge strength contribute to the results. Non-linear Hoek-Brown failure criterion will be incorporated into the proposed model where the linear Mohr-Coulomb failure envelop seems oversimplified. Extensively field works (measure the geological strength index; GSI), laboratory tests (measure the uniaxial compressive strength) and numerical simulations (seepage analysis) will be conducted to build the non-linear model which the influence of earthquake and pore pressure is considered. Consequently, the strength of rock mass could be inferred from the wedge geometry. If the internal strength of the wedge could be obtained from field data, it is anticipated that the long term frictional coefficient of the detachment and overpressure distributed in the crust could be constrained. A low to high velocity rotary shear apparatus is utilized to measure the “drained” frictional coefficient. Together with the pore pressure measured in CPC oil well, this ideal could be validated.