Standard Practice for (Analytical Procedure) for Determining Transmissivity and Storage Coefficient of Nonleaky Confined Aquifers by the Theis Nonequilibrium Method
Designation standards: ASTM D4106-20 Publication date standards: 1.6.2020 SKU: NS-995303 The number of pages: 5 Approximate weight : 15 g (0.03 lbs) Country: American technical standard Category:Technical standards ASTM
Keywords: aquifer tests, aquifers, control wells, groundwater, hydraulic conductivity, observation wells, storage coefficient, transmissivity,, ICS Number Code 93.160 (Hydraulic construction)
Additional information
Significance and Use
5.1Assumptions:
5.1.1 Well discharges at a constant rate,
5.1.2 Well is of infinitesimal diameter
and fully penetrates the aquifer.
5.1.3 The nonleaky aquifer is
homogeneous, isotropic, and aerially extensive. A nonleaky aquifer
receives insignificant contribution of water from confining
beds.
5.1.4 Discharge from the well is derived
exclusively from storage in the aquifer.
5.1.5 The geometry of the assumed aquifer
and well conditions are shown in Fig. 1.
5.2.3Application of Theis Method to Unconfined
Aquifers:
5.2.3.1 Although the assumptions are
applicable to artesian or confined conditions, the Theis solution
may be applied to unconfined aquifers if drawdown is small compared
with the saturated thickness of the aquifer or if the drawdown is
corrected for reduction in thickness of the aquifer, and the
effects of delayed gravity yield are small.
5.2.3.2Reduction in Aquifer Thickness—In an
unconfined aquifer dewatering occurs when the water levels decline
in the vicinity of a pumping well. Corrections in drawdown need to
be made when the drawdown is a significant fraction of the aquifer
thickness as shown by Jacob 5.2.3.3Gravity Yield Effects—In unconfined
aquifers, delayed gravity yield effects may invalidate measurements
of drawdown during the early part of the test for application to
the Theis method. Effects of delayed gravity yield are negligible
in partially penetrating observation wells at and beyond a
distance, After the time, t, as given in Eq 9 from Neuman (6).
Note 1:The quality of the result produced by this standard is
dependent on the competence of the personnel performing it, and the
suitability of the equipment and facilities used. Agencies that
meet the criteria of Practice D3740 are generally considered capable of
competent and objective testing/sampling/inspection/etc. Users of
this standard are cautioned that compliance with Practice
D3740 does not in itself
ensure reliable results. Reliable results depend on many factors;
Practice D3740 provides a
means of evaluating some of those factors.
1. Scope
1.1 This practice covers an analytical
procedure for determining the transmissivity and storage
coefficient of a nonleaky confined aquifer. It is used to analyze
data on water-level response collected during radial flow to or
from a well of constant discharge or injection.
1.2 This analytical procedure, along with
others, is used in conjunction with the field procedure given in
Test Method D4050.
1.3Limitations—The limitations of this
practice for determination of hydraulic properties of aquifers are
primarily related to the correspondence between the field situation
and the simplifying assumptions of this practice (see 5.1).
1.4 All observed and calculated values
shall conform to the guidelines for significant digits and rounding
established in Practice D6026.
1.4.1 The procedures used to specify how
data are collected/recorded or calculated, in this standard are
regarded as the industry standard. In addition, they are
representative of the significant digits that generally should be
retained. The procedures used do not consider material variation,
purpose for obtaining the data, special purpose studies, or any
considerations for the user’s objectives; and it is common practice
to increase or reduce significant digits of reported data to be
commensurate with these considerations. It is beyond the scope of
this standard to consider significant digits used in analytical
methods for engineering design.
1.5This practice offers a set of instructions for
performing one or more specific operations. This document cannot
replace education or experience and should be used in conjunction
with professional judgment. Not all aspects of the practice may be
applicable in all circumstances. This ASTM standard is not intended
to represent or replace the standard of care by which the adequacy
of a given professional service must be judged, nor should this
document be applied without the consideration of a project’s many
unique aspects. The word “Standard” in the title of this document
means only that the document has been approved through the ASTM
consensus process.
1.6This standard does not purport to
address all of the safety concerns, if any, associated with its
use. It is the responsibility of the user of this standard to
establish appropriate safety, health, and environmental practices
and determine the applicability of regulatory limitations prior to
use.
1.7This international standard was
developed in accordance with internationally recognized principles
on standardization established in the Decision on Principles for
the Development of International Standards, Guides and
Recommendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
Standard Practice for Minimum
Requirements for Agencies Engaged in Testing and/or Inspection of
Soil and Rock as Used in Engineering Design and Construction
Standard Guide for Selection of Aquifer
Test Method in Determining Hydraulic Properties by Well
Techniques
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