1、Designation: D5786 95 (Reapproved 2012)Standard Practice for(Field Procedure) for Constant Drawdown Tests in FlowingWells for Determining Hydraulic Properties of AquiferSystems1This standard is issued under the fixed designation D5786; the number immediately following the designation indicates the y
2、ear oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the methods for controlling draw
3、-down and measuring discharge rates and head to analyze thehydraulic properties of an aquifer or aquifers.1.2 This practice is used in conjunction with analyticalprocedures such as those of Jacob and Lohman (1)/(2),2andHantush (3)/(4).1.3 The appropriate field and analytical procedures fordeterminin
4、g hydraulic properties of aquifer systems are se-lected as described in Guide D4043.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and
5、 determine the applica-bility of regulatory limitations prior to use.1.5 This practice offers a set of instructions for performingone or more specific operations. This document cannot replaceeducation or experience and should be used in conjunctionwith professional judgment. Not all aspects of this
6、practice maybe applicable in all circumstances. This ASTM standard is notintended to represent or replace the standard of care by whichthe adequacy of a given professional service must be judged,nor should this document be applied without consideration ofa projects many unique aspects. The word “Sta
7、ndard” in thetitle of this document means only that the document has beenapproved through the ASTM consensus process.2. Referenced Documents2.1 ASTM Standards:3D653 Terminology Relating to Soil, Rock, and ContainedFluidsD4043 Guide for Selection of Aquifer Test Method inDetermining Hydraulic Propert
8、ies by Well TechniquesD4750 Test Method for Determining Subsurface LiquidLevels in a Borehole or Monitoring Well (ObservationWell) (Withdrawn 2010)43. Terminology3.1 DefinitionsFor definitions of terms used in thispractice, see Terminology D653.4. Summary of Practice4.1 This practice describes the f
9、ield procedures for conduct-ing an aquifer test on a well that is flowing, that is, the head inthe well remains above the top of the well casing. This methodinvolves inducing a constant drawdown and measuring thevarying discharge rate from the control well.5. Significance and Use5.1 Constant drawdow
10、n test procedures are used with ap-propriate analytical procedures to determine transmissivity,hydraulic conductivity, and storage coefficient of aquifers.6. Apparatus6.1 Various types of equipment can be used to measure theflow rate of the well. The equipment shall be sized so that itdoes not const
11、rict the flow rate from the well.6.2 An apparatus shall be placed on the control welldischarge line such that the well can be shut in to prevent flowprior to conducting this field procedure and so that theapparatus will not constrict flow from the well when it isallowed to flow.6.3 Head measurements
12、 can be made using one of thefollowing apparatuses:6.3.1 StandpipeA pipe or piece of well casing may beinstalled to extend above the elevation of the discharge. This1This practice is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.21
13、on Groundwater andVadose Zone Investigations.Current edition approved May 1, 2012. Published December 2012. Originallyapproved in 1995. Last previous edition approved in 2006 as D5786 95 (2006).DOI: 10.1520/D5786-95R12.2The boldface numbers in parentheses refer to a list of references at the end oft
14、his standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4The last approved version of this historical st
15、andard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1standpipe will also extend above the elevation of the head inthe control well. This standpipe will allow for direct measure-ment of the water level fo
16、llowing methods described in TestMethod D4750.6.3.2 Pressure MeasurementA pressure gauge (mechani-cal gage, manometer, or pressure transducer) may be installedbelow the shut-in mechanism in the control well. Determinethe head elevation by adding the pressure reading (expressed inthe height of the wa
17、ter) to the elevation of the sensor of thepressure gage.6.4 Control WellThis practice requires that water flowfrom a single well. This well, known as the control well, shallbe drilled and completed such that it transmits water from theaquifer (usually the entire thickness of the aquifer) as effi-cie
18、ntly as possible to reduce head loss between the aquifer andthe well. Well development should be as complete as possibleto eliminate additional production of sediments (aquifer par-ticles or drill cuttings) and consequent changes in well effi-ciency during the test.7. Procedure7.1 Pretest Procedures
19、:7.1.1 Select Aquifer Test MethodDevelop a conceptualmodel of the site hydrogeology and select the appropriateaquifer test method according to Guide D4043. Observe therequirements of the selected test method with regard tospecifications for the control well and observation wells.7.1.2 Field Reconnai
20、ssanceMake a field reconnaissanceof the site before conducting the test to collect as much detailas possible on the depth, continuity, extent, and preliminaryestimates of the hydrologic properties of the aquifers andconfining beds. Note the location of existing wells and water-holding or conveying s
21、tructures that might interfere with thetest. Turn off nearby wells well before the test, and disableautomatic pump controls throughout the anticipated test period.Alternately, it may be necessary to pump some nearby wells orallow them to flow throughout the test. If so, the discharge shallbe at a co
22、nstant rate, and shall not be started or stopped duringthe test and prior to the test for a duration at least equal to thatof the test. The control well should be equipped with a pipelineor conveyance structure adequate to transmit water away fromthe test site, such that the structure does not imped
23、e the flow ofwater from the control well.7.1.3 Construction of Control WellScreen the control wellthroughout the full extent of the aquifer to be tested.7.1.4 Test of Control WellTest the control well by allowingthe well to flow and then stopping the flow. Based on therecovery response, make a preli
24、minary estimate of the hydrau-lic properties of the aquifer and estimate the initial flow ratefrom the control well expected during the aquifer test.7.1.5 Testing Observation WellsTest observation wells orpiezometers prior to the aquifer test to ensure that they arehydraulically connected to the aqu
25、ifer. Accomplish this byadding or withdrawing a known volume of water (slug) andmeasure the water-level response in the well. The resultantresponse should be rapid enough to ensure that the water levelin the observation well or piezometer will reflect the waterlevel in the aquifer during the test. A
26、lternatively, if observationwells are flowing, measure their response in a manner similarto that described for the control well. Redevelop wells orpiezometers with unusually sluggish response.7.1.6 Measure the pressure head in the shut-in control welland observation wells (if any) to determine the t
27、rend of waterlevels before the commencement of the test. This period shouldbe at least equal to the length of the flowing portion of the test.7.2 Test Procedure:7.2.1 Based on pretesting results and the conceptual modelof the site (see Guide D4043), select the duration of the test.7.2.2 Shut in the
28、Control WellCompletely stop flow fromthe control well prior to conducting the test for a period at leastas long as the anticipated duration of the flowing portion of thetest.7.2.3 Discharge from Control WellAllow the control wellto flow at a variable rate. The flow rate will vary naturally tomaintai
29、n a constant drawdown at the control well.7.2.4 Measure Discharge RateMeasure and record thedischarge rate frequently during the early phase of discharge;increase the interval between measurements in a logarithmicmanner as pumping continues.NOTE 1Table 1 presents a suggested frequency of discharge m
30、easure-ments.7.2.5 Measure Water LevelMeasure and record the waterlevels in nearby wells at a frequency similar as presented inTable 1.7.3 Post-Testing Procedures:7.3.1 Tabulate water levels, including pre-flowing (shut-in),flowing, and post-flowing levels. For each well or piezometerrecord the date
31、, clock time, time since flowing started orstopped, and the measurement point.7.3.2 Tabulate the rate of discharge of the control well, thedate, clock time, time since flowing started or stopped, and themethod of measurement.7.3.3 Prepare a written description of each well, describingthe measuring p
32、oint, giving its elevation and the method ofobtaining the elevation, and the distance of the measuring pointabove the mean land surface.7.3.4 Plot the Rate of Discharge Versus TimePrepare aplot of the rate of discharge versus the time since dischargebegan.8. Report8.1 Prepare a report containing fie
33、ld data including a de-scription of the field site, plots of water level and dischargewith time, and preliminary analysis of data:TABLE 1 Example of Measurement FrequencyFrequency Elapsed Time1 measurement every:30 s 3 min1min 3to15min5 min 15 to 60 min10 min 60 to 120 min20 min 2 to 3 h1h 3to15h5 h
34、 15 to 60 hD5786 95 (2012)28.1.1 An introduction stating the purpose of the test, datesand times water-level measurements commenced, dates andtimes the control well was shut in, dates and times the controlwell began to flow, and the stabilized head in the control wellprior to the test.8.1.2 The as-b
35、uilt description and diagrams of all controlwells, observation wells, and piezometers.8.1.3 A map of the site showing all well locations, thedistances between wells, and locations of all geologic bound-aries or surface-water bodies which might affect the test.8.1.3.1 The locations of wells and bound
36、aries that affect theaquifer tests need to be known with sufficient accuracy toprovide a valid analysis. For most analyses, this means thelocations must provide data points within the plotting accuracyon the semilog or log-log graph paper used in the analysis.Radial distances from the control well t
37、o the observation wellsusually need to be known with 60.5 %. For prolonged large-scale testing, it may be sufficient to locate wells from maps oraerial photographs. However, for small-scale tests, well loca-tions should be surveyed using land surveying methods. Whentest wells are deep relative to th
38、eir spacing it may be necessaryto conduct well-deviation surveys to determine the true hori-zontal distance between well screens in the aquifer.8.1.4 Include tabulated field data collected during the test.9. Keywords9.1 aquifers; aquifer tests; control wells; groundwater; hy-draulic conductivity; ob
39、servation wells; storage coefficient;transmissivityREFERENCES(1) Jacob, C. E., and Lohman, S. W., “Nonsteady Flow to a Well ofConstant Drawdown in an Extensive Aquifer,” American GeophysicalUnion Transactions, Vol 33, No. 4, 1952, pp. 552569.(2) Lohman, S. W., “Ground-Water Hydraulics,” Professional
40、 Paper 708,U.S. Geological Survey, 1972.(3) Hantush, M. S., “Nonsteady Flow to Flowing Wells in LeakyAquifer,” Journal of Geophysical Research, Vol 64, No. 8, 1959, pp.10431052.(4) This document is presently under development in D18.21.04 and maybe obtained by contacting the Committee D-18 Staff Man
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