Role of Fluid Pressure in Mechanics of Overthrust Faulting: Reply

摘要: Promise of resolving the paradox overthrust faulting arises from a consideration influence pressure interstitial fluids upon effective stresses in rocks. If, porous rock filled with fluid at p, normal and shear components total stress across any given plane are S T, then ![Formula][1] ![Formula][2] corresponding solid alone. According to Mohr-Coulomb law, slippage along internal should occur when that reaches critical value ![Formula][3] where σ is slippage, τ strength material zero, ϕ angle friction. However, once fracture started eliminated, further results ![Formula][4] This can be simplified by expressing p terms means equation ![Formula][5] which, introduced into (4), gives ![Formula][6] From equations (4) (6) it follows that, without changing coefficient friction tan , shearing made arbitrarily small simply increasing p. In horizontal block weight per unit area zz jointly supported residual σzz; as increased, σzz correspondingly diminished until, approaches limit zz, or λ 1, 0. For case gravitational sliding, on subaerial slope θ ![Formula][7] T stress, inclined plane. (2) ![Formula][8] Then, equating right-hand (7) (8), we obtain ![Formula][9] which indicates down will slide approach 0 . Hence, sufficiently high pressures, very much longer fault blocks could pushed over nearly surface, under their own gentler slopes than otherwise would possible. That requisite pressures actually do exist attested frequency great 0.9 being observed deep oil wells various parts world. [1]: /embed/graphic-1.gif [2]: /embed/graphic-2.gif [3]: /embed/graphic-3.gif [4]: /embed/graphic-4.gif [5]: /embed/graphic-5.gif [6]: /embed/graphic-6.gif [7]: /embed/graphic-7.gif [8]: /embed/graphic-8.gif [9]: /embed/graphic-9.gif