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D

(After H.P.G. Darcy, 1856) Concerns the laminar flow of water through porous media and states that the velocity of flow (v) in a saturated soil is equal to the product of the coefficient of permeability (k) and the hydraulic gradient (i).

v = ki

The proportion of consolidation that has occurred after a given elapsed time; may refer to the dissipation of excess pore pressure at a point, or to the average dissipation throughout a consolidating layer.

The proportion of the void space occupied by liquid.



where
V_w = volume of liquid
V_v = volume of voids

The mass per unit volume of a substance.
Units: Mg/m³ , kg/m³ , g/ml.

(Also relative density D_r) A measure of the relationship between the current void ratio and the maximum and minimum void ratios; will indicate the state of compaction in sands.



In the loosest state, I_D = 0; in the densest state, I_D = 1

The average density of the mineral or rock of which the soil particles are composed.

r_s = G_s r_w

The density of water varies with temperature and pressure, the standard value being 1.00Mg/m³ at 4º Celsius; this value is sufficently accurate in all soil mechanics problems.

The ratio between the depth of a slip circle below the top of a slope and the height of the slope; often used to specify the depth of a harder stratum below the slope which may control the depth of the critical circle.

For a triaxial sample,
q = s_a - s_r
q´ = s´_a - s´_r

Literally meaning 'double birth', describes the processes of change that turn loose sediments into solid rock; these are a combination of consolidation (the squeezing out of water) due to the increasing pressure of overlying deposits and the formation of mineral cement between grains.

The displacement due to settlement of one point in a foundation with respect to another point.

The ratio of the change in length to the original length.

Distance measured in the direction of flow in a seepage system.

The length of path followed by water flow in seepage problems. For vertical flow in horizontal layers, the maximum flow path followed to the outflow boundary i.e. d=H/2 for open layers or d=H for half-closed layers.

Loading which is so slow that water is able to seep (drain) from the soil as the total stresses increase; consequently, there will be no change in pore pressure and volume change will follow change in loading.

The magnitude of the lowering of a water surface or water table, e.g. in or adjacent to a pumping or observation well.

The mass of soil grains (ignoring water) contained in a unit volume of soil. Units: Mg/m³.

The weight of soil grains in a unit volume of soil. Units kN/m³.