水利水電專業(yè)外文翻譯(參考版)
2025-06-30 10:43本頁(yè)面
【正文】 and for divergent radial flow, G=2π/ln (re/), where and re are the borehole and external cylindrical surface radiuses, respectively.Jointed rock mass permeability change with depthAlternatively, the rock mass equivalent permeability, km, can be expressed in the same form as the modified cubic law, or in terms of hydraulic aperture, to account for spacing of the joints, S:Changes in jointed rock mass permeability due to 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 cm/s near the surface to cm/s at depths of 600– 1000 m.The rock mass permeability estimates were obtained assuming f=, = and =10, 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
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