well Efficient well construction depends on a comprehensive understanding of the factors that influence the hydraulics of groundwater flow to wells Considerable field and experimental study has been devoted to the subject Many investigators have proposed solutions for the flow of groundwater to wells These solutions, for the most part, have been confirmed to be sufficiently accurate to allow engineers to properly design and managegroundwater resources In some cases, however, design parameters not fully understood were oversimplified or grossly approximated-resulting in inefficient wells culated for the six screens based on differences in water levels inside and outside the screen Testing procedures involved varying the discharge rates and measuring water levels in the aquifer, filter zone, and well Entrance velocities and sand content were measured for each of the tests A complete description is given elsewhere] dh/dr = a$R2/gkd (2) in which R= Reynolds number = ud/v; v = velocity; k = intrinsic permeability; d = characteristic grain diameter (assumed = 50 percent passing size); v = kinematic viscosity of water (1233 X 10-5 sq ft/s); = constants (aI = 1 for laminar %$ uz = l/R,); and g = gravitational constant (322 fpsz [98 m/s’]) Much of the information presented in this article is based on results obtained from five years of testing and analysis using this model Emphasis is placed on those aspects of well design that pertain to wasteful losses of energy and the methods used to control or minimize such losses The characteristic length in the standard definition of Reynolds number has been replaced by a characteristic grain diameter, assumed equal to the 50 percent passinggrain size This substitution was made because the microscopic passageways occupied by water in porous media are difficult to measure

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Modern Techniques in Well Design

A wide variety of well drilling techniques and well completion methods is used in the installation of dewatering and artificial recharge wells for the purpose of construction dewatering. The selection of the optimal well type is always a trade-off between the overall costs of well completion and development, the optimal well hydraulics of the well itself, the hydraulic impact of the well on its surroundings, and the required operational life span of the well. The present study provides an analytical framework that can be used by dewatering and drilling companies to quantify the contribution to head loss of typical dewatering and artificial-recharge well configurations. The analysis shows that the placement of partially penetrating wells in high-permeability layers could promote the use of quick and cheap installation of naturally developed wells using jetting or straight-flush rotary drilling. In high-permeability layers, such wells can be favorable over wells completed with filter pack, which require extensive well development to remove the fines from the filter cake layer. The amount of total head loss during discharge/recharge at a volumetric rate of 20 m3/h per meter of filter length, into or from a gravely aquifer layer, is reduced by factors of 3–4 while using naturally developed well types instead of well types completed with a filter pack that contains a filter cake layer due to borehole smearing.

M. R. Lewis

Papers

Discussion on “Boulton On Artesian Wells”

Discussion of Drawdown Test to Determine Effective Radius of Artesian Well by C. E. Jacob