Designation: D5334 − 14
Standard Test Method for
Determination of Thermal Conductivity of Soil and Soft Rock by Thermal Needle Probe Procedure 1 This standard is issued under the fixed designation D5334; the number immediately following the designation indicates the year of original origin al adoption or, in the case of revis revision, ion, the year of last revision. revision. A number in paren parenthese thesess indicates the year of last reappr reapproval. oval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Sco Scope* pe* 1.1 This test method presents a proce procedure dure for determining determining the ther thermal mal con conduc ductivi tivity ty (λ ) of soil soil an and d so soft ft rock rock us usin ing g a transient heat method. This test method is applicable for both intact inta ct and reco reconst nstitu ituted ted soi soill spe specime cimens ns and sof softt roc rock k spe specicimens. men s. Thi Thiss test meth method od is sui suitab table le onl only y for homogene homogeneous ous materials. 1.2 This test method method is app applica licable ble to dry or uns unsatu aturate rated d mater mat erial ialss ov over er tem tempe pera ratu ture ress ra rang ngin ing g fr from om <0 to >1 >100 00°C °C,, depe de pend ndin ing g on th thee su suita itabi bilit lity y of th thee th ther erma mall ne need edle le pr prob obee construction to temperature extremes. However, care must be taken to preve prevent nt significant error from: (1) redistrib redistribution ution of water due to thermal gradients resulting from heating of the needle probe probe;; (2) redistr redistribu ibutio tion n of wate waterr due to hyd hydrau raulic lic gradients (gravity drainage for high degrees of saturation or surface evaporation); (3) phase change of water in specimens with wit h te temp mper erat atur ures es <0 <0°C °C or >1 >100 00°C. °C. Th Thes esee er erro rors rs can be minimized by adding less total heat to the specimen through either minimizing power applied to the needle probe and/or minimizing the heating duration of the measurement.
of this standard to consider significant digits used in analytical methodss for engine method engineering ering design. 1.5 This standar standard d doe doess not purport purport to add addre ress ss all of the safe sa fety ty co conc ncern erns, s, if an anyy, as asso socia ciated ted wit with h its us use. e. It is th thee responsibility of the user of this standard to establish appro priate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. Referenc Referenced ed Documents 2.1 ASTM Standards: 2 D653 Termino erminology logy Relating to Soil, Rock, and Contain Contained ed Fluids D2216 Test D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass D3740 Practic Practicee for Minimu Minimum m Requir Requirements ements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction D4439 Terminology D4439 Terminology for Geosynthetics D4753 Guide D4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and Construction Materials Testing D6026 Practice D6026 Practice for Using Significant Significant Digits in Geotechnical Data
1.3 Units— The The values stated in SI units are to be regarded as the standard. No other units of measurements are included in this standa standard. rd. 1.4 All observed observed and calculated values values shall conform conform to the guidelines for signifi guidelines significant cant digits and rounding established established in Practice D6026 Practice D6026.. 1.4.1 The procedure procedure used to specify how data are collected/ collected/ recorde reco rded d or calc calculat ulated ed in thi thiss stan standar dard d are reg regard arded ed as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures dur es use used d do not con consid sider er mate materia riall var variati iation, on, pur purpos posee for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and it is common practice to increase incr ease or red reduce uce sig signifi nifican cantt dig digits its of rep report orted ed data to be commensurate with these considerations. It is beyond the scope
3. Terminology 3.1 Definitions— For For definitions of common technical terms, refer to Terminology standards D653 and and D4439 D4439.. 3.2 Definitions of Terms Specific to This Standard: 3.2.1 heat input, n— power power consumption of heater wire in watts per unit length that is assumed to be the equivalent of heat output per unit length of wire. 3.2.2 thermal epoxy, n— any any heat conductive resin material having a value of λ > > 4 W/(m·K). 3.2.3 thermal any heat conductive lubricating lubricating thermal gre grease, ase, n— any material having a value of λ > > 4 W/(m·K).
1
This test method is under the jurisdiction jurisdiction of ASTM Committee D18 Committee D18 on on Soil and Rock and is the direct responsibility of Subcommittee D18.12 D18.12 on on Rock Mechanics. Current edition approved June 1, 2014. Published July 2014. Originally approved in 1992. Last previous edition approved in 2008 as D5334 – 08. DOI: 10.1520/ D5334-0814.
2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at
[email protected]. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D5334 − 14 4. Summ Summary ary of Test Test Method 4.1 Therm Thermal al conductivity conductivity is determined by a variation of the line source test method using a needle probe having a large length to diameter ratio to simulate conditions for an infinitely long, lon g, infi infinite nitely ly thi thin n hea heatin ting g sou source. rce. The pro probe be con consis sists ts of a heating element and a temperature measuring element and is inserted into the specimen. A known current and voltage are appl ap plied ied to th thee pr prob obee an and d th thee tem tempe pera ratu ture re ri rise se wi with th tim timee is recorded over a period of time. The temperature decay with time after the cessation of heating can also be included in the analysis to minimize effects of temperature drift during measurement. Thermal conductivity is obtained from an analysis of the temperature time series data during the heating cycle and cooling cycle if applicable. 5. Sign Significan ificance ce and Use 5.1 The the therma rmall con conduc ductivi tivity ty of bot both h inta intact ct and rec recons onstitituted soil specimens as well as soft rock specimens is used to analyze and design systems used, for example, in underground transmis tran smissio sion n lin lines, es, oil and gas pip pipelin elines, es, rad radioac ioactiv tivee was waste te disposal, dispo sal, geoth geothermal ermal applications, applications, and solar therma thermall storag storagee facilities. NOTE 1—The 1—The qu qual alit ity y of th thee re resu sult lt pr prod oduc uced ed by th this is st stan anda dard rd is dependent depend ent on the com compet petenc encee of the per person sonnel nel per perfor formin ming g it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 Practice D3740 are are generally considered capable of competent and objective testing. Users of this standard are cautioned that compliance with Practice D3740 Practice D3740 does not in itself ensure reliable results. Reliable resultss depend on many factors; Practice result Practice D3740 provid provides es a mea means ns of evaluating some of those factors.
6. Appar Apparatus atus 6.1 Thermal Needle Probe— A device that creates a linear heat source and incorporates a thermocouple or thermistor to measure the variation of temperature at a point along the line. The construction of a suitable device is described in Ann in Annex ex A1 A1.. 6.2 Constant Current Source— A device to produce a constant curre current. nt. 6.3 Tempera Temperatur turee Reado Readout ut Unit or Recor Recorder— der— A device to record the temperature from the thermo thermocoupl couplee or thermistor with a readability of 0.01 K or better. 6.4 Voltage-Ohm-Meter Voltage-Ohm-Meter (VOM)— A device to read voltage and current to the nearest 0.01 V and 0.01 A. 6.5 Timer— A clock, stopwatch, digital timer, or integrated electronic timer capable of measuring to the nearest 0.1 s or better for the duration of the measurement. 6.6 Drilling Device— A drill capable of making a straight vertical hole having a diameter as close as possible to that of the needle and to a depth equivalent equivalent to the length of the needle needle.. 6.7 Balance— A ba balan lance ce th that at mee meets ts th thee re requ quir irem emen ents ts of Guide D4753 and has a readability of 0.01 g for specimens having a mass of up to 200 g and a readability of 0.1 g for specimens with a mass over 200 g. However, the balance used may be controlled by the number of significant digits needed. 7. Specimen Preparatio Preparation n 7.1 Intact Soil Specimens:
7.1.1 Thin-Walled Tube or Drive Specimens— Cut Cut a 200 6 30-mm long section of a sampling tube containing an intact soil specimen. The tube section shall have a minimum diameter of 50 mm. 7.1.2 7.1 .2 Det Determ ermine ine and record the mass of the specimen specimen in a sampling tube or brass ring to the nearest 0.01 gram. 7.1.3 7.1 .3 Mea Measur suree and record record the length and diam diamete eterr of the specimen to 0.1 mm. Take a minimum of three length measurements 120° apart and at least three diameter measurements at the qua quarter rter points points of the hei height ght.. Dete Determi rmine ne the ave averag ragee length and diameter of the specimen. 7.1.4 Inser Insertt the therm thermal al needle probe down the axis of the specimen by either pushing the probe into a predrilled hole (dense specimen) to a depth equal to the length of the probe or pushing the probe into the specimen (loose specimen). Make sure the thermal probe shaft is fully embedded embedded in the specimen and not left partially exposed. See Note 2. 2. NOTE 2—To provide better thermal contact between the specimen and the probe, the probe may be coated with a thin layer of thermal grease. If a hole is predrilled for the needle probe, the diameter of the hole should be equivalent to the diameter of the needle probe to make sure there is a tight fit. A device, such as a drill press, may be used to insert the probe to make sure the probe is inserted vertically and that no void spaces are formed between the specimen and the probe.
7.2 Reconstituted Soil Specimens: 7.2.1 Compac Compactt the specimen to the desired dry density density and gravimetric gravi metric water content in a thinthin-walled walled metal or plastic tube using an appropriate compaction technique. For further guidancee on the ef anc effec fectt of the var variou iouss com compac pactio tion n tech techniq niques ues on 3 thermal conductivity, refer to Mitchell et al. ( al. (1 1). The tube shall have a minimum diameter of 50 mm and a length of 200 6 30 mm. 7.2.2 Follow the procedure procedure given 7.1.2 given 7.1.2,, 7.1.3 7.1.3,, and and 7.1.4 7.1.4.. 7.3 Soft Rock Specimens: 7.3.1 Determ Determine ine and record record the mass of the specimen to the neares nea restt 0.0 0.01 1 g and follow follow the procedur proceduree giv given en in 7.1.4 to determ det ermine ine the spe specim cimen en dia diamete meterr and len length gth.. The spe specime cimen n dime di mens nsio ions ns sh shall all be no les lesss th than an th thos osee of th thee cal calib ibra ratio tion n standard (8.3 8.3)). 7.3.2 Inser Insertt the therma thermall needle probe into the specimen by predrilling a hole to a depth equivalent to the length of the probe. Make sure the thermal probe shaft is fully embedded in the specimen and not left partially exposed. See Note See Note 2. 2. 8. Cali Calibrati bration on 8.1 The thermal needle probe apparatus apparatus shall be calibr calibrated ated before its use. Perform calibration by comparing the experimental determination of the thermal conductivity of a standard material to its known value. A calibration factor, C , is calculated as follows: C 5
λ material λ measured
(1 )
where: λ material
3
= the known known therm thermal al conductiv conductivity ity of of the the calibratio calibration n material, and
The boldface numbers given in parentheses refer to the list of references at the end of this standard.
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D5334 − 14 λ measured
= the thermal thermal conductiv conductivity ity of tha thatt mate materia riall measured with the thermal needle probe apparatus.
8.1.1 All subsequent subsequent measurements measurements with the therm thermal al needle probe apparatus shall be multiplied by C before before being reported. Although calibration is mandatory, it is especially important with large diameter needle probes (that is, d > > 2.54 mm) where depart dep arture uress fro from m the ass assump umption tion of an infi infinite nitely ly thin pro probe be cause potentially significant significant dif differen ferences ces in estimati estimation on of the thermal conductivity conductivity due to nonnon-neglig negligible ible heat storag storagee and transmission in the needle probe itself. 8.1.2 The calibra calibration tion factor factor,, C , has been shown to be a function of thermal conductivity when using a large diameter needle probe (see Hanson et al., 2004) (2). For users of large diameter probes, probes, it may be necess necessary ary to determ determine ine C at at several thermal conductivities in the range of measurement and construct a calibration function which is then applied to subsequent data collected with the thermal needle probe. 8.2 Condu Conduct ct the test specified in Section 9 using a calibration standard as specified in 8.3 8.3.. 8.3 Calibration O ne or mo more re ma mate teri rial alss wi with th Calibration Stand Standard ard— — One known know n va valu lues es of th ther erma mall co cond nduc uctiv tivity ity in th thee ra rang ngee of th thee material mate rialss bei being ng meas measure ured, d, whi which ch is typ typical ically ly 0.2 < λ < 5 W/m·K. W/m· K. Sui Suitab table le mat materia erials ls incl include ude dry Otta Ottawa wa san sand, d, Pyr Pyrex ex 7740, fused silica, Pryoc Pryoceram eram 9606 (3), glycerine (glycerol) with a known thermal conductivity of 0.286 W/(m·K at 25°C (3), or water stabilized with 5 g agar per litre (to prevent free conv co nvect ectio ion) n) wi with th a kn know own n th ther erma mall co cond nduc uctiv tivity ity of 0. 0.60 607 7 W/m·K at 25°C ( 25°C (3 (See Annex A2 for details on preparation 3). (See Annex of calibration standards.) The calibration standard shall be in the shape of a cylinder. cylinder. The diamet diameter er of the cylinder shall be at least 40 mm or 10 times the diameter of the thermal needle probe, whichever is larger, and the length shall be at least 20 % longer than the needle probe. On solid specimens, a hole is drilled along the axis of the cylinder to a depth equivalent to the length of the probe. The diameter of the hole shall be equal to the diameter of the probe so that the probe fits tightly into the hole. hol e. For drilled drilled spe specime cimens ns the probe shall be coa coated ted with thermal grease to minimize contact resistance. 8.4 The meas measure ured d the therma rmall con conduc ductivi tivity ty of the cal calibr ibratio ation n specimen specime n mus mustt agr agree ee with within in one sta standa ndard rd dev deviati iation on of the published value of thermal conductivity, or with the value of thermal conductivity determined by an independent method. 8.5 8. 5 Fo Forr pu purp rpos oses es of co comp mpar arin ing g a me meas asur ured ed va valu luee wi with th specified limits, the measured value shall be rounded to the nearest decimal given in the specification limits in accordance with the provisions of Practice D6026 Practice D6026..
FIG. 1 Therma Thermall Probe Experimental Experimental Setup Setup
9.3 Conne Connect ct the temperature temperature measuring measuring element leads to the readout unit. 9.4 Apply a known constant current, current, for exampl example, e, equivalentt to 1. len 1.0 0 A, to th thee he heat ater er wi wire re su such ch th that at th thee te temp mper erat atur uree change is less than 10 K in 1000 s. 9.5 Record time and temperature temperature readings readings for at least 20–3 20–30 0 steps thr steps throug oughou houtt the hea heatin ting g per period iod.. The tota totall hea heating ting time should be appropriate to the thermal needle probe size. For a small diameter needle (that is, d < < 2.54 mm), a 30 to 60 second heating heatin g durat duration ion is suf suffficient to accurat accurately ely measur measuree thermal conductivity. With a larger diameter needle, a longer heating duration may be necessary. However, this method is only valid if the thermal pulse does not encounter the boundaries of the spec sp ecim imen en,, so car caree mu must st be tak taken en no nott to ch choo oose se to too o lo long ng a heating duration. Also note that potential errors from redistribution of water in unsaturated specimens increase with heating time as discussed in 1.2 1.2.. 9.6 Tur Turn n off the constant current current source. 9.7 If cooling cooling data are to be included in the analysis, analysis, record the tim timee and temperatu temperature re rea readin dings gs for at leas leastt 20– 20–30 30 ste steps ps throug thr oughou houtt a coo cooling ling period period equ equiva ivalen lentt in dur duratio ation n to the heating heatin g cycle. 9.8 Use a suitabl suitablee inverse method (graph (graphical ical or statisti statistical) cal) to det determ ermine ine the therma rmall con conduc ductivi tivity ty.. (Se (Seee Sec Sectio tion n 10 10,, Data Analysis.) 9.9 De 9.9 Deter termin minee an and d re reco cord rd th thee in initi itial al gr grav avime imetr tric ic wa water ter content in accordance with Test Method D2216 and calculate the dry density of a representative sample of the specimen. 10. Calc Calculat ulations ions and Data Analysi Analysiss 10.1 Theory: 10.1.1 10.1. 1 If a constant amount amount of heat is applied to a zero mass heater over a period of time, the temperature response is: ∆ T 5 2
Q
4 πλ
S D 2
Ei
2 r
4 Dt
0 , t # t 1
(2 )
9.1 Al 9.1 Allo low w th thee sp speci ecime men n to co come me to eq equi uilib libri rium um at th thee selected testing temperature. temperature. This equaliz equalization ation is especia especially lly impor imp orta tant nt if on only ly th thee he heati ating ng da data ta ar aree to be an analy alyze zed d as temperature drift will cause a significant error in the thermal conduc con ductiv tivity ity mea measur suremen ement. t. Err Errors ors fro from m sma small ll temp tempera eratur turee drifts are minimized if both heating and cooling data are used in the analysis.
where: = t ∆T = = Q = r = D = λ Ei = = t 1
9.2 Co 9.2 Conn nnec ectt th thee he heate aterr wi wire re of th thee th ther ermal mal pr prob obee to th thee constant current source. (See Fig. 1. 1.)
10.1.2 The cha 10.1.2 change nge in temp tempera eratur turee aft after er the heat inp input ut is turned off is given by:
9. Pro Procedu cedure re
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time from the begin beginning ning of heatin heating g (s), changee in temperatur chang temperaturee from time time zero (K), (K), heatt input hea input per unit unit lengt length h of heater heater (W/m (W/m), ), distance distan ce from the heated needle (m), thermall dif therma diffusiv fusivity ity (m2 /s), thermall condu therma conductivity ctivity (W/(m· (W/(m·K)), K)), exponential expon ential integr integral, al, and heatin hea ting g time time..
D5334 − 14 ∆ T 5 2
Q
4 πλ
F S D S 2
2 Ei
2 r
4 Dt
1 Ei
2
2 r
4 D ~ t 2 t 1
!DG
t . t 1
(3 )
10.1.3 10. 1.3 The beh behavi avior or of fini finite te dia diamete meterr and finite leng length th probes can be approximated using these same equations, but D and λ will not rep repres resent ent the actu actual al dif diffus fusivi ivity ty and the therma rmall conductivity, so calibration factors must be obtained for these probes as outlined in Section 8 8.. 10.1 10 .1.4 .4 Th Thee mo most st di dire rect ct an and d pr preci ecise se me meth thod od to cal calcu culat latee thermal conductivity is to use Eq use Eq 2 and 3 directly 3 directly with the time series data collected as described in Section 9. Unfortunately, Eq 2 and 3 cannot cannot be sol solved ved for λ and D explicitly explicitly,, so a non-linear least-squares inversion technique must be used. A simplified analysis, which gives adequate results, approximates the exponential integral in Eq in Eq 2 and 3 by the most significant term of its series expansion: ∆ T >
∆ T >
Q ln~ t ! 4 π λ Q
4 πλ
S
ln
0 , t # t 1 t
t 2 t 1
D
t . t 1
(4 ) (5 )
10.2 Simplified Method: 10.2.1 10.2. 1 For thermal needle needle probes with diameter diameter of 2.54 mm or less, exclude from the analysis the first 10 to 30 seconds of data from both the heating and, if used, cooling data. For larger diameter thermal needle probes it will be necessary to plot the data on a semi-log plot as described in 10.2.2 10.2.2 and and identify the duration of the non-linear portion of initial data that shall be exclud exc luded. ed. The These se dat dataa are mos mostt str strong ongly ly af affec fected ted by ter terms ms ignored ignor ed in in Eq Eq 4 and 5, 5 , and will result in decreased accuracy if they are included in the subsequent analysis. The total time duration of the data included in the analysis, and duration of initial values excluded from the analysis, shall be fixed for any thermal needle probe configuration and used during calibration and all subse subsequent quent thermal conductivity conductivity measur measurements ements with that th at pr prob obee ty type pe to av avoi oid d bi bias asin ing g re resu sults lts du duee to su subj bject ectiv ivee selection of the time range for analysis. 10.2.2 10.2. 2 Using the remaining remaining data, determine the slope, S h of a str straig aight ht lin linee rep repres resent enting ing temp temperat erature ure ver versus sus ln t for the
heating heatin g pha phase, se, and and,, if use used, d, the slope, S c of a str straig aight ht line representin repre senting g temper temperature ature versu versuss ln[t /(t –t 1)] fo forr th thee co cool olin ing g phase (see Fig. Fig. 2). As shown in Fig. 2, 2, the ea early rly and lat latee portio por tions ns of the test (re (repre presen sentin ting g tran transien sientt con condit dition ionss and boundary effects, respectively) shall not be used for the curve fitting. These slopes can be determined using linear regression with wit h any stan standar dard d spr spread eadshe sheet et or dat dataa ana analys lysis is sof softwa tware, re, or manually, by plotting the data and fitting a straight line to the data by eye. If manual methods are used to determine the slope, it may be convenient to use semi-log graph paper with log 10 time. If the slope of temperature versus log10t is used in the analysis, the slopes of the plots are termed S h10for the heating phase, and S c10 for the cooling phase. 10.2.3 The dat 10.2.3 dataa incl include uded d in the analysis analysis sha shall ll be eve evenly nly spaced with the logarithm of time ( X -axis). -axis). If data are collected in even time increments and subsequently plotted on a log time scale, then the distribution becomes uneven biasing the analysis too heavily toward the long-term of the testing period. Fig. 2 shows a data set that has been properly filtered to provide an even data distribution along the log time axis. 10.2.4 Compute thermal conductivity using Eq using Eq 6, where S is is the average of S S h and S c and S 10 is the average of S S h10 and S c10 if both heating and cooling data are used for the analysis or just S h (or S h10) if only heating data are used. Typically, S h and S c differ because of specimen temperature drift during the measurement. Averaging the two values minimizes the effects of the drift, which can cause large errors in determination of λ . Note that C is is the calibration coefficient determined in Section 8. λ 5
CQ
4 π S
5
where: = Q I 2
Q
2.3CQ 4 π S 10
R L
5
EI L
= hea heatt inp input ut (W/ (W/m), m),
NOTE 1—2a shows data from the heating portion of the cycle and 2b shows data from the cooling portion of the cycle. NOTE 2—The slopes (S h and S c) are shown in bold. NOTE 3—The data are approximately evenly spaced on the X -axis -axis to avoid bias as discussed in 10.2.2 in 10.2.2.. FIG. 2 (a & b) Ty Typical pical Experiment Experimental al Test Test Results Results Copyright by ASTM Int'l (all rights reserved); reserved); Wed Aug 6 06:31:43 EDT 2014 4 Downloaded/printed by Fugro Peninsular pursuant to License Agreement. No further reproductions authorized.
(6 )
D5334 − 14 C λ
S S 10 t I R L E
= calibration calibration const constant ant from Sectio Section n 8, = therma thermall conductivity conductivity [W/(m· [W/(m·K)], K)], = slope used to compute compute therm thermal al conducti conductivity vity if ln( ln( t ) is used in analysis, = slope used used to compute compute thermal thermal conducti conductivity vity if log log10(t ) is used in analysis, = time time (s (s), ), = curre current nt flowin flowing g throu through gh heater wire (A), = tota totall resis resistan tance ce of of heater heater wir wiree (Ω), = len length gth of hea heated ted nee needle dle (m) (m),, and and = measur measured ed voltag voltagee (V).
10.3 Der 10.3 Deriva ivatio tions ns for formin ming g the bas basis is of of E q 2 a n d 3 are presented by Carslaw and Jaeger (4), and adapted to soils by VanRooyen and Winterkorn ( (5 5); VanHerzen and Maxwell ( (6 6); and Winterkorn (7). 11. Report: Test Test Data Sheet(s)/Form(s) 11.1 The met method hodolo ology gy use used d to spe specif cify y how data are recorded on the tes corded testt dat dataa she sheet(s et(s)/f )/form orm(s) (s),, as giv given en bel below ow,, is covered in 1.4.1 in 1.4.1 and and Practice D6026 Practice D6026.. 11.2 Record as a minimu 11.2 minimum m the follow following ing general informainformation (data): 11.2.1 11 .2.1 Projec Projectt infor information mation,, such as proje project ct name, number, number, source of test specimens, including other pertinent data that helps identify the specimen. 11.2.2 11 .2.2 Name or initials of the perso person(s) n(s) who prepared prepared and tested the samples, including the date(s) performed. 11.2.3 11 .2.3 Type of material tested: soil or soft rock, and if soil, indicate if the specimen was intact or reconstituted. 11.2.4 11 .2.4 Physi Physical cal description description of sample including including soil or rock type. typ e. If roc rock, k, des describ cribee loca locatio tion n and ori orient entatio ation n of app appare arent nt weakness planes, bedding planes, and any large inclusions or inhomogeneities.
11.3.5 Metho 11.3.5 Method d of needle insertion: insertion: pushed or pre-d pre-drilled rilled 11.3.6 11 .3.6 Calibr Calibration ation factor, factor, if any 11.3.7 11 .3.7 Tim Time, e, nearest 0.1 s, and temperature, temperature, nearest 0.01 K, readings for heating, cooling, or both as necessary 11.3.8 11 .3.8 Time Time ver versus sus temp tempera eratur turee plo plott see Fig. Fig. 3, i s a n example of an idealized curve of the data 11.3.9 11 .3.9 Therm Thermal al conductivity conductivity to the neares nearestt 0.01 W/(m·K) W/(m·K) 12. Pre Precisi cision on and Bias 12.1 An An inte interlab rlaborat oratory ory stud study y invo involvin lving g line line-sou -source rce methods, including needle probes used for rock and soils, was undertaken by ASTM Committee C16 (8). The materials of known kno wn ther thermal mal con conduc ductivi tivity ty tha thatt wer weree eva evaluat luated ed incl include uded d Ottawa sand and paraffin wax (having a thermal conductivity similar to certain soil and soft rock types). The results indicated a mea measur sureme ement nt pr precis ecision ion of bet betwee ween n 610 an and d 615 %, respectively, with a tendency to a positive bias (higher value) over the known values for the materials studied. With careful calibra cali bratio tion n of ther thermal mal nee needle dle pro probes bes in mat materia erials ls of kno known wn thermal conductivity as outlined in Section 8 Section 8,, this precision can be improved upon, and the positive bias should be removed. 12.1.1 12. 1.1 Subcomm Subcommitte itteee D18 D18.12 .12 wel welcom comes es pr propo oposal salss tha thatt would wou ld allo allow w for a mor moree com compre prehen hensiv sivee pre precisi cision on and bia biass statement covering the full range of soil and rock materials. 13. Keyw Keywords ords 13.1 heat flow; needle probe; temperature; temperature; thermal conductivity; thermal probe; thermal properties
11.3 Record as a minimum the following 11.3 following test specimen data: 11. 1.3.1 3.1 Initi Initial al gr gravi avimet metric ric wa water ter co conte ntent nt to the nea neares restt 0.01 % 11.3.2 11 .3.2 Dry density to the nearest 0.1 g/cm3 11.3.3 11 .3.3 The mass of the specimen to the nearest 0.01 0.01 g 11.3.4 11 .3.4 The average diameter diameter and length of the specime specimen n to the nearest 0.01 mm
FIG. 3 Typical Record Record of Data (Idealized Curve)
ANNEXES (Mandatory Information) A1. COMPONENT COMPONENTS S AND ASSEMBLY ASSEMBLY OF THERMAL NEEDLE
A1.1 The thermal needle consists consists of a stainle stainless ss steel hypodermic tubing containing containing a heater element and a thermo thermocoupl couplee as shown in Fig. A1.1. A1.1. To construct a thermal needle, hypoderm de rmic ic tu tubi bing ng is cu cutt to 115 mm in le leng ngth th.. Th Thee en end d to be inser in serted ted in into to th thee ba bake kelit litee he head ad of a th ther ermo moco coup uple le ja jack ck is roug ro ughe hene ned d fo forr a len lengt gth h of 15 mm mm.. A co copp pper er-c -con onst stan antan tan thermocoupl thermo couplee wire junction previously previously coated with an insula insulatting varnish is threaded into the hypodermic needle with the
junction 50 mm from the end of the needle (see (see Note Note A1.1). A1.1). At the same time time,, a man mangan ganin in hea heater ter element element is ins insert erted ed wit with h approximately 75-mm long pigtails extending from the top of the needle as shown in Fig. in Fig. A1.2. A1.2. The uncut end of the needle is the then n ins insert erted ed int into o an eva evacua cuatin ting g flas flask k thr throug ough h a rub rubber ber stopper and the other end is placed in a reservoir of thermal epoxy primer as shown in Fig. A1.2. A1.2. A vacuum pump connected nec ted to the evacuatin evacuating g flas flask k is use used d to dra draw w the thermal thermal
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D5334 − 14
FIG. A1.1 Ty Typical pical Probe Components Components
FIG. A1.2 Drawin Drawing g Thermal Epoxy Into Hypodermic Hypodermic Tubing Tubing
epoxy epo xy up throug through h the needle. needle. The The needle needle is removed removed from from the
reserv res ervoir oir and flask, flask, and and a blo blob b of putty is placed placed at the end end of
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D5334 − 14 the needle to hold the thermal epoxy in place for hardening. After the thermal epoxy hardens, the thermocouple wires are soldered to the pins of a polarized thermocouple jack and the roughened end of the needle is placed in the bakelite head of the jack. The heater leads are brought out through two holes in the back of the bakelite head (see Fig. A1.1). A1.1).
NOTE A1.1—For soft rock specimens it may not be possible to drill a hole to accommodate a 115-mm long thermal needle. In this case a shorter needle may be used. The length of the needle shall not be less than 25.4 mm to avoid boundary effects.
A2. PREP PREPARA ARATION TION OF CALIBRA CALIBRATION TION ST STANDARDS ANDARDS
A2.1 Glycerol:
A2.2 Water :
A2.1.1 Glycerol (Glycerin) has a published thermal conductivity of 0.286 W/(m·K) at 25°C ( (3 3), and therefore falls within the low end of thermal conductivities expected in soil and rock. The thermal conductivity of glycerol is affected by the amount of water present in the glycerol, so only anhydrous (99% or greater gre ater)) gly glycer cerol ol sha shall ll be use used d for calibratio calibration. n. It sho should uld be noted that glycerol will readily take up water in both liquid and vapor phase, so care must be taken to prevent the sorption of water vapor into glycerol stored in improperly sealed containers. Note that glycerol is a fluid, and can be subject to mixing by free conv convection. ection. Free convection arises from densit density y gradients in fluids caused by thermal gradients in the fluid. If the thermal needle probe is heated too much, free convection could occur.. Accord occur Accordingly ingly,, glycer glycerol ol is only appro appropriate priate for therma thermall needle probes that will heat less than 2°C over the course of the thermal conductivity measurement. 99+% anhydrous glycerol can be ob obtai taine ned d fr from om nu nume mero rous us so sour urce ces, s, in incl clud udin ing g lo local cal drugstores.
A2.2.1 Water (de A2.2.1 (deion ionize ized d or tap tap)) has a pub publish lished ed ther thermal mal conductivity of 0.607 W/(m·K) at 25°C ( (3 3), and therefore falls within the range of thermal conductivities expected in soil and rock. However, with most thermal needle probes, the heating of the needle will result in free convection in the water that will cause very large errors in the thermal conductivity measurement me nt.. To pr prev even entt th this is er erro rorr, th thee wa water ter sp spec ecime imen n mu must st be physically stabilized. The preferred method for stabilizing the water is with a 5 g agar/1 L water mixture. The agar should be adde ad ded d to ho hott wa wate terr an and d st stir irre red d we well ll un unti till th thee mi mixt xtur uree is homogenous. The mixture should then be brought to a boil, and then re-homogenized in the container that will be used to hold the specimen during calibration. After cooling back to room temperature, the mixture should be a solid with the consistency of jelly.
REFERENCES (1) Mitchell, J. K., Kao, T. C., and Abdel-Hadi, O. N., “Backfill Materials for Underground Power Cables,” Department of Civil Engineering, University Unive rsity of Califo California rnia at Berkel Berkeley ey,, EPRI EL-506, June 1977. (2) Hans Hanson, on, J., Neu Neuhau hauser ser,, S., and Yesi esiller ller,, N. “De “Devel velopm opment ent and Calibration of Large-Scale Thermal Conductivity Probe,” Geotechnical Testing Journal, ASTM, Vol 27, No. 4, 2004, pp. 393–403. (3) CRC Handbook of Chemi Chemistry stry and Physi Physics cs, 74th Edition, David R. Lide, editor, CRC Press, Ann Arbor, MI, 1994 (4) Carslaw Carslaw,, H. S., and Jaeger, J. C., Conduction of Heat in Solids, Oxford Press, 2nd ed., 1946. (5) Van Rooyen, M., and Winterkorn, H. F., “Theoretical and Practical Concepts Conce pts of the Thermal Conductivity Conductivity of Soils and Simil Similar ar Granular Systems,” Highway Research Board, Bulletin 168—Fundamental and
Practical Practi cal Conce Concepts pts of Soil Freezing, 1957, pp. 143–205. (6) Von Herzen, R., and Maxwell, A. E., “The Measurement of Thermal Conductivity Condu ctivity of DeepDeep-Sea Sea Sedim Sediments ents by a Needle Needle-Prob -Probee Metho Method,” d,” Journal of Geophysical Research, Vol 64, No. 10, October 1959, pp. 1557–1563. (7) Winterkorn, H. K., “Suggested Method of Test Test for Thermal Resistivity of Soil by the Thermal Probe,” Special Procedures for Testing Soil and Rock for Engineering Purposes, ASTM STP 479 , ASTM, 1970, pp. 264–270. (8) Hust, J. G., and Smith, D. R., “Interlaboratory Comparison of Two Types Ty pes of Line-S Line-Source ource Thermal Condu Conductivity ctivity Apparatus Apparatus Measu Measuring ring Five Insulating Materials,” NISTIR, 89-3908, 1989.
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D5334 − 14 SUMMARY OF CHANGES In accordance with Committee D18 policy, this section identifies the location of changes to this standard since the last edition (2008) that may impact the use of this standard. (Approved June 1, 2014) Sections 1 and 3 3,, Note 1 including 1 including D18.91 review (1) Edits to Sections 1 updates. (2) Added Guide D4753 to Section 2. Sections 4,, 5 5,, and 6 6,, including the addition of 6.7. 6.7 . (3) Edits to Sections 4 Section 7,, including the dimensional measurements (4) Edits to Section 7 of the specimen.
9,, and 10. (5) Edits to Sections 8, 9 (6) Removed the data sheet, old Fig. 2. 11.. (7) Significantly updated Section 11 12.. (8) Edits to Section 12 13.. (9) Added “needle probe” to Section 13 (10) Edits to the Annex and renumbered the references.
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