水利水電流體力學(xué)外文翻譯外文文獻(xiàn)英文文獻(xiàn)混凝土重力壩基礎(chǔ)流體力學(xué)行為分析-預(yù)覽頁(yè)
【正文】 overburden and confining stresses were calculated using eqs. [1]– [3].The results of a theoretical relationship of rock mass permeability, k, for depths up to 1000 m, using eq. [5] are presented in reduction of hydraulic apertures with increasing overburden stresses results in a rock mass permeability that decreases with an increase in depth from 310? cm/s near the surface to 810? cm/s at depths of 600– 1000 m. The rock mass permeability estimates were obtained assuming f=, mcV = hoa and nik =10 ?mcv , which are representative of the values obtained in laboratory tests carried out in granitic formations(Alvarez et )similar to those of the Brazilian test location described in this section. Overburden stresses were estimated using a unit weight of kN/ this case it was assumed that horizontal and vertical stresses are about the same (coefficient of earth pressure at rest Ko=), which are also considered to be representative of the igneous formations at the Brazil test location, but other values of in situ stresses could be estimated, ., for Ko, vertical joints would have larger permeabilities. Field permeability measurements obtained in Packer tests at a deep openpit mining project in granitic rock in Brazil are also plotted in for parison with the theoretical relationship. Values of joint spacing observed from borehole cores are in the range of a few meters, and thus a constant spacing of 5m was assumed in the putations. Values of aho in the range of 300–1000μm were used to determine the theoretical relationships of km=f (z), where z is the depth, and pare with field measurements. Measured permeability values in the two boreholes are relatively high at depths between 100 and 200m, probably denoting the presence of a sheared zone or a zone of more jointed rock. The measured rock permeabilities decrease steadily with an increase in depth, however, and their values correspond well with the theoretical trend of rock mass permeability estimated with the model. Typical hydraulic apertures of 400–500μm and joint stiffness following a hyperbolic relationship with NIK =10V mc and mcV = hoa seem to agree well with observed field behavior for these crystalline rock masses. jointed rock mass permeability relationship with depth. Although real Hydromechanical behavior of jointed rock masses is site specific and depends on geologic factors, which need to be taken into account, the proposed approach provides a framework to estimate rock mass permeability during design stages where information is not yet available.
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