TM 5-815-5/AFM 88-5, Chap 6/NAVFAC P-418
COMBINED ARTESIAN-GRAVITY FLOW
(Modified from "Foundation Engineering," G. A. Leonards, ed., 1962, McGraw-Hill Book Company.
Used with permission of McGraw- Hill Book Company.)
Figure 4-1. Flow and head for fully penetrating line slot; single-line source; artesian, gravity, and combined flows.
for slots and wells do not consider the effects of hy-
flow to trenches, French drains, and similar drainage
draulic head losses Hw in wells or wellpoints; proce-
systems. They may also be used where the drainage
dures for accounting for these effects are presented
system consists of closely spaced wells or wellpoints.
Assuming a well system equivalent to a slot usually
(3) Radius of influence R. Equations for flow to
simplifies the analysis; however, corrections must be
drainage systems from a circular seepage source are
made to consider that the drainage system consists of
based on the assumption that the system is centered
wells or wellpoints rather than the more efficient slot.
on an island of radius R. Generally, R is the radius of
These corrections are given with the well formulas dis-
influence that is defined as the radius of a circle be-
cussed in c below. When the well system cannot be
yond which pumping of a dewatering system has no
simulated with a slot, well equations must be used.
significant effect on the original groundwater level or
The figures in which equations for flow to slots and
piezometric surface. The value of R can be estimated
wells appear are indexed in table 4-1. The equations