Assuming that pipe diameter (D) increases with the
pressure head at the pipe inlet ([H.sub.o]), according to a power-law model (D = C [H.sub.o.sup.p]), and that the head loss (J) decreases as the diameter increases, an equation of head loss for the uniform permanent flow was fitted, in the form of Eq.
The results show that when the radius of the cavern is constant, the
pressure head and seepage flow decrease as the distance between the tunnel and the cavern increases.
where [K.sub.x] (h), [K.sub.y] (h), and [K.sub.z] (h) represent hydraulic conductivity in the x, y and z axis, which are all functions of the pore water
pressure head h when unsaturated.
where Se is the degree of saturation; q is the volumetric water content ([cm.sup.3] [cm.sup.-3]); [theta]s is the saturated volumetric water content (cm3 [cm.sup.-3]); [theta]r is the residual volumetric water content (cm3 [cm.sup.-3]); a is an empirical parameter ([cm.sup.-1]) whose inverse is often referred to as the air entry value or bubbling pressure; h is the soil water
pressure head (cm); and n is a pore-size distribution parameter affecting the slope of the retention curve.
The primary direct laboratory methods used are the pressure extractor (Klute 1986), which estimates 9(h) from pairs of measured h and [theta] values, and the evaporative method, which calculates K and [theta] (h) from the
pressure head response of two tensiometers placed at different depths (Gardner and Miklich 1962).
whereas the maximum
pressure head ([h.sub.LM]) required at the upstream end of the lateral is
The difference in losses between plain lateral pipes and with sealed emitters were calculated for constant increasing
pressure head. Equal lengths locally extruded from four different pipe rolls were selected for diameters i.e.