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The Richards equation represents the movement of water in unsaturated soils, and is attributed to Lorenzo A. Richards who published the equation in 1931. [1] It is a quasilinear partial differential equation; its analytical solution is often limited to specific initial and boundary conditions. [2]
e * is the saturation water vapor pressure T is the absolute air temperature in kelvins T st is the steam-point (i.e. boiling point at 1 atm.) temperature (373.15 K) e * st is e * at the steam-point pressure (1 atm = 1013.25 hPa) Similarly, the correlation for the saturation water vapor pressure over ice is:
the rate of rise of the water level in the hole is recorded; the K-value is calculated from the data as: [8] = where: K is the horizontal saturated hydraulic conductivity (m/day) H is the depth of the water level in the hole relative to the water table in the soil (cm): H t = H at time t; H o = H at time t = 0
The water-cement ratio of the fresh concrete mix is one of the main, if not the most important, factors determining the quality and properties of hardened concrete, as it directly affects the concrete porosity, and a good concrete is always a concrete as compact and as dense as possible.
The maximum rate at that water can enter soil in a given condition is the infiltration capacity. If the arrival of the water at the soil surface is less than the infiltration capacity, it is sometimes analyzed using hydrology transport models , mathematical models that consider infiltration, runoff, and channel flow to predict river flow rates ...
It causes an obstruction to the flow of water in the pores and hence reduces the permeability of soils. According to Casagrande , it may be taken as the void ratio occupied by absorbed water and the permeability may be roughly assumed to be proportional to the square of the net voids ratio of (e - 0.1) [ 4 ]
In 2007, on the recommendations of the International Water Management Institute, the Indian government allocated ₹ 1,800 crore (equivalent to ₹ 54 billion or US$630 million in 2023) to fund dug-well recharge projects (a dug-well is a wide, shallow well, often lined with concrete) in 100 districts within seven states where water stored in ...
The ultimate strength of concrete is influenced by the water-cementitious ratio (w/cm), the design constituents, and the mixing, placement and curing methods employed. All things being equal, concrete with a lower water-cement (cementitious) ratio makes a stronger concrete than that with a higher ratio. [2]