USE OF THE HARVARD MINIATURE APPARATUS FOR OBTAINING MOISTURE-UNIT WEIGHT RELATIONSHIPS OF SOILS September 7 984 Engineering and Research Center U. S. Department of the Interior NO. GR-84-14 Bureau of Reclamation Division of Research and Laboratory Services Geotechnical Branch Bureau bt ~iclarnation 4. TITLE AND SUBTITLE 5. REPORT DATE Use of the Harvard Miniature Apparatus for Obtaining Moisture-Unit Weight Relationships of Soils 7. AUTHOR(S) 8. PERFORMING ORGANIZATION REPORT NO. Robert Scavuzzo GR-84- 14 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. WORK UNIT NO. Bureau of Reclamation Engineering and Research Center 11. CONTRACT OR GRANT NO. Denver, Colorado 80225 13. TYPE OF REPORT AND PERIOD COVERED 12. SPONSORING AGENCY NAME AND ADDRESS Same 14. SPONSORING AGENCY CODE DlBR 15. SUPPLEMENTARY NOTES Microfiche and/or hard copy available at the Engineering and Research Center, Denver, Colorado. Editor: JMT(c) 16. ABSTRACT A study was performed to investigate the use of the Harvard miniature apparatus as a potentially viable means for obtaining moisture-unit weight relationships of soils. A literature search was performed along with a series of pilot tests on representative soil samples to compare the results obtained from the Harvard miniature apparatus with those from the USBR Proctor compaction test procedure. The use of the Harvard miniature apparatus is recommended for obtaining moisture-unit weight relationships under certain conditions for two reasons: (I) it saves time and (2) less material is required to perform the test. 17. KEY WORDS AND DOCUMENT ANALYSIS a. DESCRIPTORS-- *Harvard miniature apparatus/ "Proctor compaction test/moisture-unit weight relat~onship/c onstruction control/ soil compaction/ dry density/ optimum moisture content/ Proctor curves/ compaction/ compaction tests/ "compaction equipment/ field tests/ laboratory tests I I c. cosar~F icld/Group 08M COWRR: 0813 SX IM: USE OF THE HARVARD MINIATURE APPARATUS FOR OBTAINING MOISTURE-UNIT WEIGHT RELATIONSHIPS OF SOILS by Robert Scavuzzo Geotechnical Branch Division of Research and Laboratory Services Engineering and Research Center Denver, Colorado September 1984 UNITED STATES DEPARTMENT OF THE INTERIOR .k BUREAU OF RECLAMATION As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our nationally owned public lands and natural resources. This includes fostering the wisest use of our land and water resources, protecting our fish and wildlife, preserv- ing the environmental and cultural values of our national parks and historical places, and providing for the enjoyment of life through out- door recreation. The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also has a major respon- sibility for American Indian reservation communities and for people who live in Island Territories under U.S. Administration. The information contained in this report regarding commercial prod- ucts or firms may not be used for advertising or promotional purposes and is not to be construed as an endorsement of any. product or firm by the Bureau of Reclamation. ii CONTENTS Page Introduction. ......... .. .... ...... ............. . .... "" .., ... .... ....... ..., .................... ...,. . ..... 1 " "" '" '" " " " '" Compaction test methods 1 """""'" ..., .., .: , """"'" "" "" '" " "'" Comparison of Harvard miniature with Proctor compaction 2 , """"""'" """"""""""""" Conclusions """""'" , ... """"""" 3 Bibliography 7 """"""" Appendix - Procedure for Performing Laboratory Compaction of Soils - Harvard Miniature 9 FIGURES Figure Field and laboratory results compared for various methods of obtaining moisture-density 3 curves """"""""""""""'" """""""""""""""" '" """""""""""""'" """ 2 Harvard miniature vs. USBR E-11 compaction test results (3 sheets) 4 iii INTRODUCTION Optimum moisture content and maximum dry unit weight are two important criteria for evaluating the state of compactness for most cohesive soil masses whether they are deposited naturally or placed by man. The "Proctor Compaction Test (Moisture-Density Relations of Soils)," USBR(Bu- reau of Reclamation) Designation E-11 [1]*, is performed inallUSBRsoil laboratories, both at the E&RCenter (Engineering and Research Center) and inthe field. Two disadvantages of the currently used test method are (1)the amount of material required to complete the test - approximately 25 to 50 Ibm (11.4 to 22.7 kg), depending on the type of material being evaluated; and (2)the length of time required to perform the test. This report is intended to introduce a new test procedure, "USBR 5510, PerformingLaboratory Compaction of Soils - Harvard Miniature" and present the results of a search of the literature comparing the results obtained from standard Proctor compaction with those obtained from the Harvard miniature apparatus. COMPACTION TEST METHODS The compaction test was originally developed as a basis for controlling compaction in the field. Itwas intended as a tool to obtain a maximum unit weight that would aid inconstruction control; Le., improved settlement characteristics and strength. However, some engineers have erroneously come to accept "maximum unit weight" and "optimum moisture content" as fixed values irre- spective of the soil type or compactive effort. The traditional standard Proctor compaction test requires that the soil specimen be compacted in 3 layers, with 25 blows per layer, in a mold having a volume of 1/30 ft3 (944 cm3). The compactive effort is achieved by dropping a 5.5-lbm (2.5 kg) rammer from a height of 12 in(30.5 cm). The standard USBRprocedure also requires that the soil specimen be compacted in3 layers, with 25 blows per layer.However,the standard USBRtest usesa moldhavinga volumeof 1/20 ft3(1416 cm3),and the compactive effort is achieved by using a 5.5-lbm (2.5 kg)rammer dropped from a height of 18 in (45.7 cm). Both techniques impart the same compactive effort, 12,375 ft-lbf/ft3 (5.925 x 105 N.m/m3), to the soil specimen. A moisture-unit weight plot is obtained when a series of soil specimens are * Numbers in brackets refer to entries inthe bibliography. compacted at predetermined moisture contents using either the USSR procedure or the standard Proctor compaction test. The corresponding dry unit weight at each moisture content is deter- mined, and a moisture-unit weight plot is obtained. Recently, the Harvard miniature compaction apparatus, introduced by Wilson in 1950 [2], has been used by researchers for preparing triaxial specimens [2, 3] and by others to obtain moisture- unit weight relationships of soils [2, 4]. The use of this device results in a quick moisture-unit weight determination and requires only 4 to 6 Ibm (1.8 to 2.7 kg) of material. The current USBR test procedure for compacting soil specimens using the Harvard miniature compaction apparatus is presented in the appendix. This procedure was adapted from the method suggested by Wilson in 1970 [4] and from the experience of USBR personnel. In 1962, the Highway Research Board studied a number of factors that could influence compaction test results [5]. The report concentrated on three principal types of compaction efforts currently used: impact type, kneading type, and the vibratory type. In addition to the different types of compaction efforts, the Highway Research Board report also cited other variations that influence the moisture-unit weight relationships of soils: . Size of mold . Amount of compactive effort . Maximum size aggregate permitted . Method of supporting the mold . Method of preparing the soil for testing COMPARISON OF HARVARD MINIATURE WITH PROCTOR COMPACTION In 1950, Wilson [2] compared field compaction characteristics that had been studied extensively by the Waterways Experiment Station [6] with the results obtained using the Harvard miniature compaction apparatus. Figure 1 shows the results obtained from compacting a clayey sand and a silty clay. Fig'Jre 1 shows that it is possible to obtain moisture-unit weight curves that closely duplicate field compaction curves by selecting suitable spring force, number of layers, and tamps per layer. The test results obtained by Wilson also indicate that no standard procedure can successfully duplicate field compaction curves for all soil types. Similar compaction tests were performed at the E&R Center geotechnical laboratories. The USSR compaction procedure (Designation E-11) and Harvard miniature compaction tests were per- 2 Figure 1.- Fieldand laboratory results compared for various methods ofobtaining moisture-unit weight curves. formed on a number of soil types. Harvard miniature compaction tests were performed by applying 25 tamps with a 20-lbf (89-N) spring force to each ofthe 5 liftsinthe Harvard miniature mold (seeappendix Afor a detailed description of the testing procedure). Results of the com- paction tests are shown on figure 2. The Harvard miniature compaction test resulted in optimum moisture contents that were 1.1 to 1.8 percent greater than those obtained from the USBRcompaction method. Maximum dry unit weights from the Harvard miniature compaction ranged from 0.4 to 3.3 Ibf/ft3(6.4 to 52.8 kg/m3) lower than maximum dry unit weights obtained from the USBRcompaction method. CONCLUSIONS Use of the Harvard miniature compaction apparatus produces moisture-unit weight curves in less time than the Proctor compaction test and requires only a fraction of the material. Com- parative results indicate that the Harvard miniature method can be used to match standard compaction values when the spring force, the number of layers, and the number of tamps per layer are adjusted according to the soil type. Because time and materials could be saved by using the Harvard miniature apparatus instead of the standard Proctor device, similar investi- gations should be conducted on a variety of soil types to develop a data base, from which laboratory and field personnel can draw, to ensure quality moisture-unit weight determinations. 3 CLASS IFICA TIONSY~L 5C. GRADATION SUMMARY . GRAVEL ~ SAND ~ FINES ATTERBERG LIMITS ;)., . LIQUID LIMIT 120 '!JO CTOHMEOPRLEETTEICALSATUCRUARTVIOEN.AT '80 PSHLRAISNTKIACGITEYLIIMNIOTEX 10 . '\ "\ PENRUCMEENRTAALGSE IQNFDICVAOTIEDS ,.'35' SPECI FIC GRAVITY ;1..'73 ,..c- 1--- MINUS NO. 4 "\ !5 PLUS NO. 4 1.130 BULK ".~... /10 / I0 /[ [f' L:Jr'(?~ '< "\ 1.7~ ~~u AABPPSAORREPNTTION J D / "'~ \:; ~ v .. .. I IEkb' ~~ COMPACT ION ~.c 1.70 ... ~~~:~ ~~~;~~~ ~I b/ft3 .j::>. ..0.1 \. 'v~ I" f.b5 -~ (,.,as ~kg/c.)r . \. OPTIMUM ~ISTURE CONT ~- c PENETRATIONRESISTANC ~ Ibf/tn2 :I:Is: 100 cl.:vj.Sjj~Re.-1 1.60 ::s ( (p kg/c) '" L>- ~"" >L- - 0 0 H~RvAIRIt> i--I/lflI ~1/)~~ ." 1.65 NOTES: UN IT #1, cl~ i"-. ~ /.5e '\. _ik.f'V~,cl M.~,,~~-+Vt'~ " Cfo 10 IS 20 25 30 I.4-5 ~ ~ blows (i) ;1.0' ~.f' - .for ~4t-l 5 Ii.f+s . MoIsture content of dry weIght ::. IJj.S Ib/f:t3 - ><rw~){ COMPACTION PENETRATION RESISTANCE CURVES Lc) 0 PT ~ 11,." ~D Figure2. - Harvardminiature VS.USBRE-11 compaction test results (sheet 1of 3).