褶皺逆衝帶加積楔的幾何形貌受楔形體強度與底滑面強度之比值所控制，過去研究顯示，加積楔的幾何形貌具有明顯地側向變化。本研究嘗試利用非線性破壞準則之加積楔模型結合野外調查與室內實驗，以束限加積楔強度，並利用台灣中部褶皺逆衝帶內幾條重要斷層將加積楔進行分段，藉此量測各逆衝斷塊之厚度與臨界角，逆算各斷塊之底滑面孔隙水壓比(λb)。本研究根據大量現地調查以及室內實驗，以獲得地質強度指標(GSI)及完整岩石單壓強度(σci)，再分段代入加積楔模型，並考量材料強度於側向之變化，楔形體內部之流體壓力(λ)則假設為0.43 (靜水壓條件)，底滑面摩擦係數由旋剪試驗獲得為0.34(實驗條件正向應力範圍0.5-2.5 MPa，速度範圍10-1-10-2 m/s)。研究結果顯示，地質強度指標由西向東遞減，而地層之單壓強度則由西向東遞增，利用修正之加積楔模型計算加積楔強度則是呈現由西向東變大之趨勢(0.70、0.60、0.94)，而b由西向東分別為0.80、0.77與0.55，此一結果與台灣中部鑽井資料顯示深度約4 km處之孔隙水壓比約在0.6~0.8之間大致相符，顯示本研究逆算λb之方法有其合理性。 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 incorporated nonlinear Hoek-Brown failure criterion into the critical taper model to evaluate the variation of the critical taper angle of thrust belt with changes of wedge thickness and wedge strength. Extensively field works (measure the geological strength index GSI) and laboratory tests (measure the uniaxial compressive strength) are conducted to obtain the parameters of the adopted failure criterion. The derived detachment pore-fluid pressure ratios from accretionary wedge geometric morphology are decreased from the west to the east of the study area. The calibrated pore-fluid pressure ratios are close to the measured ones from deep broeholes near the study area. The study results show that the increased critical taper angle from the west to east is dominated by the wedge strength heterogeneity, which contributed from the decreased wedge strength and proe pressure ratio on the detachment, as well as the increased wedge thickness from the west to the east of the study area.
