TM 5-815-5/AFM 88-5, Chap 6/NAVFAC P-418
SEE FIG. 4-15. a, b, AND c FOR EXPLANATION OF TERMS NOT DEFINED IN THIS FIGURE.
D R A W D O W N . H - h e, PRODUCED BY PUMPING A FLOW OF QT FROM AN EQUIVALENT SLOT, IS COMPUTED
FROM EQ 1 (FIG. 4-6) FOR CIRCULAR SLOT AND EQ 1 (FIG. 4-8) FOR RECTANGULAR SLOT.
HEAD LOSS DUE TO CONVERGING FLOW AT WELL
U.S. Army Corps of Engineers
Figure 4-16. Flow and drawdown for partially penetrating circular and rectangular well arrays; circular source; artesian flow.
bottom of the excavation and more preferably 50 to
able is limited, the drainage trench or well screen
100 percent. Where the aquifer(s) to be dewatered is
should penetrate to the top of the underlying less per-
stratified, the drainage slots or well screens should
vious stratum. The hydraulic head loss through vari-
fully penetrate all the strata to be dewatered. If the
ous sizes and types of header or discharge pipe, and for
bottom of an excavation in a pervious formation is
certain well screens and (clean) filters, as determined
underlain at a shallow depth by an impervious forma-
from laboratory and field tests, are given in figures
tion and the amount of "wetted screen length" avail-
4-24 and 4-25.
4-17
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