American Geophysical Union (AGU)
0002-8606
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The chemical potential of a stressed solid The distribution of the chemical potential in a non‐hydro statically stressed solid has been investigated. It is shown that in strained elastic bodies the potential must have the same value at all points in the solid; and a simple expression relating the chemical potential to the components of stress is derived. The effect of pure shear on the chemical equilibrium of elastic bodies appears to be small. For non‐elastic bodies which have not reached a stable configuration under stress there is an additional term in the chemical potential which is a continuous function of position in the body. The numerical value of this term cannot be computed without making additional assumptions concerning the mechanism of deformation or flow; but it appears to be small, at least for nearly elastic bodies. Elastic anisotropy is probably not an important factor in the development of an oriented fabric in rocks. Such recrystallization as may be caused by non‐hydrostatic (shear) stress is believed to result mostly from an initially uneven distribution of the stresses in the grains of the rock, or from the effect of shear on the rates of certain reactions.
Tập 32 Số 2 - Trang 251-258 - 1951
Moisture movement in porous materials under temperature gradients A theory of moisture movement in porous, materials under temperature gradients is developed which explains apparently discordant experimental information, including (a) the large value of the apparent vapor transfer, (b) effect of moisture content on net moisture transfer, and (c) the transfer of latent heat by distillation. The previous simple theory of water vapor diffusion in porous media under temperature gradients neglected the interaction of vapor, liquid and solid phases, and the difference between average temperature gradient in the air‐filled pores and in the soil as a whole. With these factors taken into account, an (admittedly approximate) analysis is developed which predicts orders of magnitude and general behavior in satisfactory agreement with the experimental facts. An important implication of the present approach is that experimental methods used to distinguish between liquid and vapor transfer have not done so, since what has been supposed to be vapor transfer has actually been series‐parallel flow through liquid ‘islands’ located in a vapor continuum. Equations describing moisture and heat transfer in porous materials under combined moisture and temperature gradients are developed. Four moisture‐dependent diffusivities arising in this connection are discussed briefly.
Tập 38 Số 2 - Trang 222-232 - 1957
Rainfall energy and its relationship to soil loss A relatively simple procedure is presented for computation of kinetic energy of a rainstorm from information on a recording‐raingage chart. An equation is developed describing rainfall energy as a function of rainfall intensity. The effects of rainfall energy and its interaction with other variables are evaluated in multiple regression analyses based on data representing four soil types. Application of this information to separate the effects of rainfall from those of physical and management characteristics in plot data is discussed briefly.
Tập 39 Số 2 - Trang 285-291 - 1958
On the hydraulic conductivity of unsaturated soils Unsaturated steady flow of mixtures of a liquid and a gas through sands and similar porous media at low Reynolds numbers obeys Darcy's law. The relative liquid permeability K is not constant, but a universal function of the degree of liquid saturation. An approximate theory gives its form, which is a cubic parabola. A similar expression is found for the gas permeability. Numerous experiments by Wyckoff ami Botset confirm the theory. This is in agreement with Gardner's hypothesis that K is a function of the concentration in water, and indirectly with Richards' hypothesis that it is a function of the capillary potential. The degree of liquid saturation seems to be a more useful unit of liquid percentage than any other.
Tập 35 Số 3 - Trang 463-467 - 1954
The relation of hydrographs of runoff to size and character of drainage‐basins In a previous paper entitled “stream‐flow from rainfall by unit method” (Eng. News‐Record, April 7, 1932), the writer defined a unit graph as the hydrograph of runoff from a given area, due to a one‐inch runoff‐depth applied in one day or in any other convenient unit of time. A procedure for deriving the unit graph from observed rainfall‐ and runoff‐records was presented. After the unit graph has been derived a runoff‐record for the given area, for any rain or series of rains, may be computed by a simple summation process. Figure 1, from the aforesaid paper, graphically illustrates the summation process and it will not be described further here.
Tập 13 Số 1 - Trang 332-339 - 1932
Quantitative analysis of watershed geomorphology Quantitative geomorphic methods developed within the past few years provide means of measuring size and form properties of drainage basins. Two general classes of descriptive numbers are (1) linear scale measurements, whereby geometrically analogous units of topography can be compared as to size; and (2) dimensionless numbers, usually angles or ratios of length measures, whereby the shapes of analogous units can be compared irrespective of scale. Linear scale measurements include length of stream channels of given order, drainage density, constant of channel maintenance, basin perimeter, and relief. Surface and crosssectional areas of basins are length products. If two drainage basins are geometrically similar, all corresponding length dimensions will be in a fixed ratio. Dimensionless properties include stream order numbers, stream length and bifurcation ratios, junction angles, maximum valley‐side slopes, mean slopes of watershed surfaces, channel gradients, relief ratios, and hypsometric curve properties and integrals. If geometrical similarity exists in two drainage basins, all corresponding dimensionless numbers will be identical, even though a vast size difference may exist. Dimensionless properties can be correlated with hydrologic and sediment‐yield data stated as mass or volume rates of flow per unit area, independent of total area of watershed.
Tập 38 Số 6 - Trang 913-920 - 1957
Non‐steady radial flow in an infinite leaky aquifer The non‐steady drawdown distribution near a well discharging from an infinite leaky aquifer is presented. Variation of drawdown with time and distance caused by a well of constant discharge in confined sand of uniform thickness and uniform permeability is obtained. The discharge is supplied by the reduction of storage through expansion of the water and the concomitant compression of the sand, and also by leakage through the confining bed. The leakage is assumed to be at a rate proportional to the drawdown at any point. Storage of water in the confining bed is neglected. Two forms of the solution are developed. One is suitable for computation for large values of time and the other suitable for small values of time. This solution is compared with earlier solutions for slightly different boundary conditions.
Tập 36 Số 1 - Trang 95-100 - 1955
On the determination of transmissibility and storage coefficients from pumping test data This paper presents a graphical procedure for determining the formation constants of an artesian aquifer from pumping test data. The procedure is based on the principle that the coefficient of transmissibility is determined by the ratio of the drawdown to its rate of change with respect to the logarithm of the time since pumping started, or s/(δ s/δ log10 t), use being made of the non‐equilibrium theory. The computation of formation constants may be performed in two ways, and their results should be checked against each other. A numerical example is given to illustrate the application of the procedure .
Tập 33 Số 3 - Trang 397-404 - 1952
A graphic procedure in the geochemical interpretation of water‐analyses This paper outlines certain fundamental principles in a graphic procedure which appears to be an effective tool in segregating analytical data for critical study with respect to sources of the dissolved constituents in waters, modifications in the character of a water as it passes through an area, and related geochemical problems. The procedure is based on a multiple‐trilinear diagram (Fig. 1) whose form has been evolved gradually and independently by the writer during the past several years through trial and modification of less comprehensive antecedent forms. Neither the diagram nor the procedure here described is a panacea for the easy solution of all geochemical problems. Many problems of interpretation can be answered only by intensive study of critical analytical data by other methods.
Tập 25 Số 6 - Trang 914-928 - 1944
The circulation over the Continental shelf south of Cape Hatteras South of Cape Hatteras, a southerly‐flowing coastal current, such as is common to the northward, is a transient affair. Such a current when present, is restricted to a very narrow portion of the continental shelf. The dynamic pressure gradient resulting from the combined effect of the runoff and the cross‐shelf thermal gradient together with the prevailing wind and the frictional drag of the Florida Current provides for a northeasterly drift over a broad part of the Carolina continental shelf.
Tập 36 Số 4 - Trang 601-611 - 1955