Engineering Geology Field Manual Volume I Chap11

8/13/2019 Engineering Geology Field Manual Volume I Chap11

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Figure 11-1.Log of test pit or auger hole.


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Figure 11-2.Clean coarse-grained soils.


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Figure 11-3.Fine-grained soils.


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Figure 11-4.Soil classifications based on laboratory test data.


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Figure 11-5.Auger hole with samples taken.


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Figure 11-6.Reporting laboratory classification inaddition to visual classification.


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Figure 11-7.Undisturbed soils.


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Figure 11-8.Coarse-grained soils with fines.


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Figure 11-10.Reporting in-place density tests andpercent compaction.


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Figure 11-11.Soil with measured percentages of cobbles and boulders.


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Formats for Test Pits and Auger Hole Logs

General Instructions

The follow ing subsect ion provides genera l inst ructions forlog form a t a nd descriptions. Refer to cha pter 3 fordescriptive criteria , cla ssifica tion, a nd gr oup na mes a ndsymbols. Ca pita l ize th e group na me. If cobbles a nd boulders a represent , include th em in th e typica l na me.

Describe pla st ici ty of fines a s:

a pproxima t ely 30 percent (%) fines w it h h igh plasticitya pproxima t ely 60% fines w ith low t o medium

plasticitya pproxima t ely 10% nonpla st ic fines

G ive results of ha nd t es ts w hen performed.

U se rea ct ion w ith h ydr ochloric a cid (H Cl).

Do not give unnecessa ry informa tion such a s no odor,no gra vel, a nd no fines.

H ow ever, th e nega t ive result of a h a nd t est is positive in-formation and should be reported as no dilatancy,nonpla st ic, no dry st rengt h, or no rea ct ion w ith H Cl.

For report ing m a ximum pa rt icle size, use t he follow ing:Fine sa ndMedium san d

Coarse sa nd5-millimeter (mm ) increment s fr om 5 mm t o 75 mm25-mm increment s fr om 75 mm t o 300 mm100-mm increm ent s over 300 mm


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For example, maximum particle size 35 mm orma ximum pa rt icle size 400 mm a re th e corr ect form a ta nd size increment .

Ta ble 11-1 is a checklist for log descript ors . Form a t fordescriptions, results, and other information are in thefollow ing subsections .

Ta ble 11-1.C hecklist for t he descript ion of soilsin test pit a nd a uger hole logs

1. G roup sym bol. - C a pit a lized a nd show n in th e left-ha nd column.2. D ept h. - D ept hs of interva l cla ssified, shown in eit hermeters or feet a nd t enth s of unit s in second column fr omt he left .3. Id ent ifica t ion of sa mple. - Type a nd size of sa mple a ndorigin of sam ple, show n in t hird column from t he left .

4. Cla ssifica t ion a nd description column. -a . Fi rs t pa ra gra ph. -

(1) D ept h of int erva l cla ssified(2) G roup na me ca pita lized(3) P ercent of fines san d a nd gr a vel by w eight

(include tr a ce a mount s but not a dded topercent a ge w hich must equa l 100 percent)

(4) D escription of pa rt icles(a ) P a rt icle size ra nge: describe a s either

gra vel - fine or coa rse, or sa nd fine,medium, or coa rse

(b) H a rdn ess of pa rt icles (coa rse sa nd a ndlarger)(c) P a rt icle a ngular i ty (a ngular ,

suba ngula r, sub-rounded, or rounded)(d) P a rt icle sha pe (fla t , elonga t ed, or fla t

a nd elonga ted)(e) Ma ximum pa rt icle size or dimen sion


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(5) D escript ion of fines(a ) P la st icity (nonpla st ic, low , medium, or

high)(b) D ila t a ncy (none, slow , or r a pid)(c) D ry st rengt h (none, low , medium, high ,

or very high)(d) Toughn ess (low , medium , or h igh )

(6) Moistu re cond it ion (dr y, m oist , or w et )(7) C olor (moist color)(8) Odor (ment ion only if org a nic or unu sua l)(9) Rea ct ion w ith H C l (none, w ea k, or st rong)

b. TOTAL S AMP LE (B Y VOLU ME ): second pa ra -gr a ph, if a pplica ble - i.e., more th a n 50 per-cent plus 75-mm ma t erial(1) P ercent of cobbles a nd percent of boulders(2) S a me inform a t ion a s item 4.a (4)

c. IN-P LACE CONDITION: th ird para gra ph(second pa ra gra ph if less tha n 50 percent

oversize)(1) C onsist ency; fine-gr a ined soils only (very

soft, soft , firm , ha rd, or very ha rd)(2) S t ru ct ure (st ra t ified, lensed, slickensided,

blocky, fissured, homogeneous)(3) C ementa t ion (w ea k, modera t e, st rong)(4) Moist ur e (if a n in -pla ce condit ion

pa ra gra ph is included, moistur e is notdescribed in t he f irst par a gra ph)

(5) C olor (if a n in-pla ce cond ition pa ra gr a ph isincluded, color is not described in t he firstparagraph)

(6) Resu lt of in -pla ce densit y a nd /or moist ur etes ts

d. G E OLOG IC INTE RP RE TATION: (fourt h par a -gr a ph) geologic descript ion includin g genet icna me, s t ra t igra phic na me if know n, and a nyloca l na me.


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5. Rema rks block. - P rovide a ddit iona l descript ion orrema rks such a s root holes, ot her debris found, caving,degree of difficult y t o a uger or exca va t e, rea son forrefusa l or rea ched predetermined depth, a nd w a terlevel informa t ion or hole completion.

F igur e 11-12 is a field form for loggin g soils.

Reporting by Method of Classification

Preparation of Logs Based on Visual Classifica-tion. List fines, san d, a nd gr a vel in descending order ofpercent (mu st a dd up to 100 percent ). For visua l cla ssi-fication, estimate percentages to the closest 5 percent.Precede the estimated percentages with approx., notabout. If a component is present but is less than5 percent of th e t ot a l, use tr a ce. Tra ce is not in cluded

in t he 100 percent .

Preparation of Logs Based on Laboratory Classifi-cation. When logs are prepared using laboratorycla ssifica t ions (ba sed on la bora t ory t ests), t he informa t ionmust be presented on the log as shown in figure 11-4.The difference between a laboratory and a visualcla ssifica t ion is d epicted in figur e 11-6.

The visual classification should not be changed, norshould t he estima t ed percent a ges, pla st icity description,or t he results of the ha nd t ests (dry st rength , dilat a ncy,and toughness) be changed to reflect laboratory testsresults. The visua l cla ssifica t ion is ba sed on th e t ot a lma teria l observed; wherea s, th e labora tory cla ssifica t ionis based on a represent a t ive sam ple of the ma teria l .


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FIELD FORMSOIL LOGGING HOLE NO. ____

DATE _______ PROJECT ___________________ FEATURE ___________________ AREA _________________ DRILLER _________ LOGGED BY __________________

SAMPLE INTERVAL AND TYPE:Type MoistureSample SampleInterval _________ Sample Weight (Lbs) ______ Interval___________________

Typical Name __________________________________________________________ Group Symbol _________________________________________________________

SIZE DISTRIBUTION, CHARACTERISTICS:(5-mm increments from 5 to 75 mm, 255-mm increments from 75 to 300 mm, 100mmincrements over 300 mm)

Boulders (>300 mm) __% (vol.) Max. size (mm) __ Hardness __ Angularity _____

Cobbles (75-300 mm) __% (vol.) Max. size (mm) ___ Hardness ___ Angularity ____

Gravel __% Coarse (20-75 mm) __ Fine (5-20 mm) ___ Hardness ___ Angularity __

Sand ___% Coarse ___ Medium ___ Fine ___ Hardness ___ Angularity _____

Fines _____%

Plasticity: Nonplastic _____ Low _____ Medium _____ High _____ Dilatancy: No _____ Slow _____ Rapid _____ Dry Strength: No ____ Low ____ Medium ____ High ____ Very High ____ Toughness: Low _____ Medium _____ High _____

Maximum Size: Fine Sand ____ Medium Sand ____ Coarse Sand ____ ____mm

Moisture: Dry _____ Moist _____ Wet _____

Color _______________ Odor __________ Organic Debris and Type ___________

Reaction with HCl: None _____ Weak _____ Strong _____

EXCAVATING/AUGERING/DRILLING CONDITIONS:

Hardness: Very Soft _____ Soft _____ Hard _____ Very Hard _____

Penetration Action: Smooth ___ Mod. Smooth ___ Mod. Rough ___ Rough ____

Penetration Rate: Very Fast ____ Fast _____ Slow _____ Very Slow _____

PAGE ___ OF ___

Figure 11-12.Field form - soil logging.


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The specimens for t esting a re t o be sa mples t ha t repre-sent t he entire int erva l being described (see U S B R 7000a nd 7010 [1]). The ma t eria l collect ed mus t be split orqua rt ered to obta in th e specimen t ha t is t o be tested inthe la bora tory.

C oefficient s of uniform ity a nd curva t ure (C u a n d C c ) a reto be calculated and reported on the logs for coarse-gra ined ma t eria ls cont a ining 12 percent or less fines.

Laboratory gradation percentages and Atterberg l imitsa re to be report ed to t he nea rest w hole num ber.

Procedures for Reporting Laboratory Data in Addi-tion to Visual Classification and Description. Insome inst a nces, gra da t ion a na lyses a nd Att erberg l imitt ests a re perform ed on s oil sa mples in conjunct ion w ithprepa ra t ion of logs of test pit s or a uger holes. These da t a

should be shown on the logs and clearly identified asla bora tory test da ta .

Specimens for test ing are to be from samples thatrepresent t he entire int erva l being described. If th is isnot possible, t he loca t ion of t he sa mple should be given a spa rt of the w ord description. The sa mple t a ken should besplit or quartered to get the specimen size required fort est ing (figur e 11-5, int erva l 0.0 t o 9.8 feet (ft ).

Laboratory tes t data are to be presented in a separatepar a gra ph. If the test results indica te a different classi-fica t ion, a nd t herefore different group sym bol a nd /orgroup name than the visual classif icat ion, give thelaboratory classif icat ion symbol and name in thispa ra gr a ph (figur e 11-6).


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For pipeline invest iga t ions, t he percent of t he ma ximumdry density or the percent relative density should be inpa ren t heses on t he logs (figur e 11-10).

D ensities a re report ed to th e nea rest 0.1 pound per cubicfoot (lb/ft 3) or 1 kilogra m per cub ic met er (kg/m 3).Moistur e cont ent is report ed to t he nea rest 0.1 percent .Percent of laboratory maximum dry density or relat ivedensity is report ed to t he near est w hole num ber.

Geologic Interpretations

G eologic int erpret a t ions sh ould be ma de by or un der t hesupervision of a geologist . G ive geologic int erpret a t ion ina sepa ra te pa ra gra ph (figure 11-7). In t erpret a t ion shoulda lso be included in th e na rr a t ive sect ion of the ma t erialsport ion of th e design da ta submitta ls .

Description Formats on Test Pit and Auger HoleLogs for Soils with Cobbles and Boulders

If t he soil ha s less th a n 50 percent cobbles a nd boulders(by volume), give the group name of the minus 75-mmport ion a nd include cobbles a nd /or boulder s in t he gr oupna me (figure 11-11). U se tw o pa ra gra phs t o describe soil.Refer to chapter 3 for a more complete discussion ofclassifica tion a nd cla ssifica tion group na mes a nd symbols.

Describe th e minus 75-mm fra ction in th e first pa ra -gra ph. These component percent a ges a re estima t ed byweight .

Describe th e tota l sa mple in a second pa ra gra ph. Thesepercenta ges a re est ima t ed by volume. E ven if th epercentage of cobbles and boulders is determined bymea surement , use a pprox. in the w ord description.


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If t he soil ha s more th a n 50 percent cobbles a nd boulders(by volume), list cobbles and boulders first in the name(figur e 11-13). D o not g ive a g roup sym bol or group na me.

Descr ibe the tota l sa mple in the f irs t pa ra gra ph.P ercenta ges a re est ima ted by volume.

Describe th e minus 75-mm fra ction in a secondpa ra gra ph. P ercenta ges a re es t ima ted by w eight .

Angula r pa rt icles lar ger th a n 75 mm a re described a s cob-bles a nd boulders, not a s rock fra gment s. A descriptionof th eir sh a pe should be provided in t he w ord d escript ion.

Description of Materials Other than Natural Soils

Ma teria ls wh ich a re not na tur a l soils a re not described orcla ssified in t he sa me ma nner as na tur a l soils . The

section tit led Use of Soil Classification as SecondaryIdent ifica t ion Meth ods for Ma teria ls oth er th a n Na tur a lS oils, cha pter 3, out lines t he criteria t o be follow ed a ndprovides exa mple descriptions for t est pit a nd a uger holelogs. Refer t o a ppropria t e sect ions in cha pter 3 forexa mple form a t a nd descript ions. Figu res 11-14 t hr ough11-17 show a va riety of logs of test pits a nd a uger holesreflect ing miscella neous cond itions.

Format of Word Descriptions forDrill Hole Logs

The descriptions of surficial deposits and soil-likema t eria ls in geologic logs of explora t ion h oles should usesimila r descriptive criteria a nd form a t est a blished for t estpits and auger holes except as noted in the followingparagraphs .


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Figure 11-13.Soil with more than 50 percentcobbles and boulders.


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Figure 11-14.Borderline soils.


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Figure 11-15.Test pit with samples taken.


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Figure 11-16.Disturbed samples.


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Figure 11-17.Two descriptions from the same horizon.(Top) Undisturbed soil containing estimated percent

of boulders. (Bottom) Disturbed soil containingtrace of cobbles.


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Exceptions to Test Pit and Auger HoleFormat and Descriptions for Drill Hole Logs

U nlike test pit logs w here geologic int erpret a t ions m a y beprovided at the bottom of the log form, geologic inter-pret a t ions a re requ ired on dr ill hole logs. The geologicclassification (e.g., Quaternary Alluvium, QuaternaryG lacia l Outwa sh, Qua terna ry La ndslide, Ter t ia ry B a sinFill Deposits) should be provided a s ma in hea dings on th egeologica l dr ill hole log.

G roup nam es a re ca pita l ized in a l l test pi t a nd a uger holelogs. Where ca pit a liza t ion of t he group na me w ouldconflict w ith ma in hea dings on dr ill hole logs, ca pit a lizeonly t he f irst let t er of each w ord of the group na me a ndt he group sym bol. If th e first lett er of ea ch w ord is notca pit a lized, t he group na me is considered inform a l usa geonly a nd n ot a classif ica t ion.

C la ssifica t ion a nd w ord description form a t for drill holelogs is simila r to t hose used for test pit logs. Also,materials recovered from drill holes are generallycons idered t o repr esent in-pla ce cond it ions . Thesecriteria do not a pply w hen sa mples a re not recovered orw hen poor recovery precludes cla ss ifica t ion (figure 11-18).

Samples Recovered from Wash Borings or asCuttings

When drill holes ar e ad va nced w ith a rock bit , w a t er jet,or other nonsam pling methods, a group symbol a nd n a meor cla ssifica t ion of t he recovered ma t eria ls should n ot beassigned, nor should in-place descriptions, such asconsist ency, be used. H ow ever, descriptive crit eria , suchas part icle size, dry strength, and reaction with HCl,should be provided using the same terminology andform a t u sed for a uger holes.


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Figure 11-18.Drill hole advanced by tri-cone rock bit.


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D escriptions sh ould be preceded by R ecovered cutt ingsa s . . . or Recovered w a sh sa mples a s. . . (figure 11-18,int erva l 0.0-11.7 ft.

Poor or Partial Recovery

Where poor or pa rt ia l recovery precludes a ccura t e cla ssi-fica t ion, a prima ry cla ssifica t ion should not be a ssigned,but a s m uch d escriptive inform a t ion a s possible should beprovided. Recovered ma t eria ls, t ogether wit h drill ingcond itions, cut t ings, a nd d rilling fluid color or losses, ma ybe used to interpret reasons for losses and types ofma t eria ls lost . H ow ever, a n a ppropria t e subhea ding (i .e.,P oor Recovery ) sh ould be used (figur e 11-19, 2.1 to3.9 ft .

Materials Other Than Soils and Special Cases

As discussed in cha pter 3, U se of S oil Cla ssifica t ion a sSecondary Identif icat ion Methods for Materials OtherThan Natural Soils, exceptions to the test pit and holecla ssifica t ion a nd forma t a re a lso a pplica ble t o hole logs.These special cases include processed or manmadematerials, shells, partially li thified or poorly cementedma t eria ls a nd decomposed bedrock, an d sha llow surficia ldeposits or soils. Ot her specia l ca t egories of soil-likematerials should be classified by USBR 5000 orU S B R 5005[1]. These a re soil-like slid e-fa ilur e zones orplanes; shear or fault zones; bedrock units which arerecovered as soil-like material or consist of soil-likema t eria l; a nd la nd slides a nd t a lus (figures 11-20, 11-21,a nd 11-22).

Format and classification for these exceptions aredescribed below.


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Figure 11-19.Log showing poor recovery.


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3 4 3 Figure 11-20.Log of landslide material (a).


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Figure 11-21.Log of landslide material (b).


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3 4 5 Figure 11-22.Log of bedrock.


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Processed or Manmade Materials. S ur ficia l deposit ssuch a s t a ilings, crush ed rock, shells, or sla g a re a ssigneda genetic name such as f i l ter, bedding, drain material ,shells, tailings, or road base, and a classification groupna me a nd symbol a re a ss igned in quota t ion m a rks , forexa mple: Filter ma t erial, poorly gra ded sa nd (S P -S M).S oil descriptors a re th en used to describe the ma t eria ls.

Where drill holes penet ra t e emba nkment ma t erials, ma inhea dings on t he dr ill hole logs sh ould be a cla ssifica t ionof the type of embankment, such as Zone 3Miscella neous Em ba nkm ent . The ma t eria ls recovered ineach interval are classif ied, and group names andsym bols a re provided a s subhea ding s. S ee 1.0- t o 3.9-fta nd 3.9- t o 15.4-ft int erva ls sh own in figur e 11-19.

Partially Lithified or Poorly Cemented Materialsand Decomposed Rock. Descriptions of partially

lit hified or poorly cement ed ma t eria ls such a s siltst one,cla yst one, sa ndst one, a nd sh a le or decomposed rock w hichare broken down during drill ing or field classificationt esting sh ould be cla ssified by a n a ppropria t e rock unitna me or by geologic form a t ion n a me, if know n, of t he in-pla ce ma t eria ls. The ma t eria ls a re t hen described usingdescriptors for rock (cha pt er 4). A soil cla ssifica t ion forthe broken down materials should be reported inquota t ion m a rks on t he dri ll logs a nd a l l f igures, t a bles,dra w ings, or na rr a t ive descriptions. The disa ggrega t ingmecha nism (e.g., drilling or t est ing) should be s pecified(figu re 11-22, int erv a l 17.3 to 67.9 ft ).

Shallow Surficial Deposits. S urficia l deposits s uch a sdr ill pa d or dozer t rench fill for dr ill set ups, sha llow slopewash, or topsoil materials which will not be used in, orinfluence, design or construction may be classified bygenet ic cla ssifica t ion (e.g., fill, slopew a sh , or t opsoil).C omplet e cla ssifica t ion d escriptions a re not required ondr ill hole logs; h ow ever, a cla ssifica t ion na me a nd /or


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sym bol ma y be a ssigned an d is often desira ble. Althougha complete description is not required on each log, anadequate descript ion of these materials should beprovided in a genera l legend or explan a tion dr a w ing a ndin t he na rra t ive of t he report , if not complet ely d escribedin d rill hole logs.

Slide Failure Zones or Planes, Shear or FaultZones, and Interbeds Recovered as Soil-likeMaterials. These features should be described usinggeologic names as well as behavior and soilclassifications.

Landslides and Talus. Surficial deposits such aslandslides and talus should be assigned their geneticgeologic na me in t he ma in h ea dings of th e drill hole log.La nd slide debris composed prim a rily of soils is cla ssifieda s la ndslides in th e ma in hea ding. Soil-l ike ma teria ls

should be classified and group names and symbolsprovided in th e hea dings. The ma teria ls a re t hendescribed usin g t he descriptive crit eria for d rill hole logs.Where ma teria ls a re predomina nt ly rock fra gments sucha s t a lus a nd block slides, t he ma t eria ls should be loggedsimila r t o t he m eth od us ed in figure 11-22.

Equipment Necessary forPreparing the Field Log

The follow ing is a list of equipment for field t esting a nddescribing ma teria ls .

Required equ ipment :

Sm a l l supply of wa ter (squir t bot t le)forperform ing field test s P ocket kn ife or sma l l spa tu la Ma teria ls for t a king or preserving sam plessa cks,

ja rs, la bels, clot h, w a x, hea t er, et c.


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Ha mmerfor ha rdness descr iptors Ta pe mea sure a nd/or r ule (engineer 's sca le a nd

met ric sca le) P et r ie d ish for wa shing specimens S ma ll bot t le of dilut e hydr ochloric a cid [one par t

H Cl (10 N) t o t hree pa rt s distil led wa t er. Whenpreparing the di lute HCl solution, s lowly addacid into the water fol lowing necessary safetypreca utions. H a ndle w ith ca ution a nd storesa fely. If solution comes in cont a ct w ith skin,r inse th oroughly with w a ter.]

R a gs for clea n in g ha n d s Log forms

Optiona l a ppa ra tus:

Sma ll t est tube a nd stopper or ja r wi th lid P la s t ic bags for ca lib ra t ion sa mples

H a nd lens Color iden t ifica t ion cha r t s P a int brush a nd/or scrub brush a nd w a ter for

clea ning sa mples Ma rking pens P rot ra ct or Dri llers ' repor ts for dr i ll holes Compar ison sa mples (in ja rs): f ine gra vel3/4

inchto No. 4 sieve; medium sandNo. 4 to No. 10sieve; a nd coa rse s a nd No. 10 to No. 40 sieve

Sma ll No. 4 a nd 200 s ieves


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Example Descriptions and Format

The examples which follow illustrate the preferredformat, descript ion, and organization, and some of themore significa nt except ions t o t ypica l sta nda rds.

Laboratory Classifications in Addition toVisual Classifications

In some instances, laboratory classif icat ions may bedeterm ined in a ddit ion t o t he field visua l cla ssifica t ion.This may be done to confirm the visual classification,part icularly when start ing work in a new location orbeca use th e cla ssifica t ion m a y be crit ica l.

The la bora tory da ta used must be report ed in a separ a tepar a gra ph a t th e end of th e work descript ion, a s show n in

t he exa mples in figure 11-23. If th e la bora t ory cla s-sifica t ion is different fr om t he visua l cla ssifica t ion, a s int he upper exa mple, give t he group sym bol in the left-ha nd column a nd t he group name in the pa ra gra ph on t hela bora tory da t a .

DO NOT C H ANG E TH E VIS U AL C LASS IF IC ATION ORD E S CR IP TION. The visua l cla ssifica t ion is ba sed on aw idely observed a rea in th e exca va tion, w herea s t he labo-ra tory classif ica t ion is ba sed on a sa mple of th e ma t eria l .

If t he visua l classif ica t ion w a s t he best judgment of a nexperienced classifier, both are correct in what theyrepresent.


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Figure 11-23.Geologic interpretation in test pit(sheet 1).


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Word Descriptions for Various SoilClassifications

Figures 11-6 to 11-17 illustrate some typical worddescript ions ba sed on t he soil cla ssifica t ions.

Logs a re genera lly t yped a nd single spa ced. Theexa mples in th is ma nua l a re presented double spa ced forlegibility.

Samples Taken

In a ddit ion t o t he brief description of t he sa mples t a kenund er t he cla ssifica t ion g roup symbol column, a morecomplete description of any samples taken from eachdepth int erva l is included in t he word descript ions. Thedescription should include the size of the sample, theloca tion represent ed by t he sa mple, a nd h ow th e sa mple

w a s obta ined (e.g. , qua rt ering a nd split t ing).

E xa mples of how t o report t he sa mple inform a t ion for apit or t rench a re sh ow n in figur es 11-24 t hr ough 11-33.

S ome exa mples use t he a bbrevia t ed method of indica t ingt he group na me wit h th e group sym bol. This abbr evia t edmethod is described in appendix X5 in USBR 5000,Determining Unified Soil Classification (LaboratoryMet hod) [1] a nd cha pter 3.

Reporting Laboratory Data

Classifications Based on Laboratory Data

If t he soil cla ssifica t ion r eport ed on t he logs is ba sed onlaborat ory da ta a nd not a visua l classif ica t ion, this shouldbe clea rly a nd distinctly r eflect ed on t he log.


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Figure 11-25.Geologic interpretation in test pitusing a geologic profile (1).


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Figure 11-28.Geologic interpretation in test pitusing a geologic profile (2).


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Figure 11-32.Geologic interpretation in test pit (sheet 8).


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Figure 11-33.Geologic interpretation in test pit using a geologic profile (3).


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The labora t ory d a t a should be report ed on t he log form a ssh ow n in t he exa mples in figur e 11-4.

The location of the sample and any laboratory testsperform ed need t o be clea rly described.

The coefficient s of uniform ity a nd cur va t ur e (C u , C c ) a reto be calculated and reported for coarse-grained soilscont a ining 12 percent fines or less.

G ra da tion percenta ges a nd Att erberg limits a re to be re-port ed to t he nea rest w hole num ber.

The fact that the classif icat ion is a laboratory classi-fica t ion n eeds t o be indica t ed in t he cla ssifica t ion g roupsym bol column .

The w ords a bout or a pproxima t ely a re not used in th e

w ord descript ion.

Soils with More Than 50 Percent Cobbles andBoulders

If the soil contains more than 50 percent (by volume)cobbles a nd /or bould ers :

1. The first pa ra gra ph describes t he t ot a l sa mpleand includes the information on the cobbles andboulders. The inform a t ion in the pa ra gra ph is t hesame as described previously for cobbles andboulders.

2. The w ords COB B LE S or COB B LE S ANDBOULDERS are l is ted f irst in the classif icat iongroup na me:


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COBBLES WITH POORLY GRADED GRAVELCOB B LE S AND B OULD E RS WITH SIL TY GRAVEL

3. A cla ssifica t ion sy mbol is not given . Wher e areport or form requires a cla ssifica t ion s ym bol, usethe words cobbles or cobbles and bouldersinstead.

An example of a word description for a soil with morethan 50 percent cobbles and boulders is shown infigur e 11-13.

Special Cases for USCS Classification

Some mater ia ls that require a c lass i f icat ion anddescript ion a ccording t o U SC S should not ha ve a hea dingth a t is a classif ica t ion group na me. When th ese

ma t eria ls w ill be used in, or h a ve influence on, design a ndconstruction, they should be described according to thecri teria for logs of tests pi ts and auger holes, and theclassification symbol and group name should be inqu ot a t ion ma rks. The hea ding should be a s follow s:

TOPSOILDRILL P ADG RAVE L ROAD SU RFACI NGMINE TAIL ING SUNCOMPACTED FILLFILL

For exa mple:

C la ssifica t ion sym bol D escription

TOP S OI L 0.0 t o 1.6-ft TOP S OI Lw ouldbe classified as ORGANICS OI L (OL /OH ). About 90%


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fines with low plasticity, slow dilatancy, low dry strength,a nd low t oughn ess; a bout 10%fine t o medium sa nd; soft, w et,da rk brown , orga nic odor; root spresent throughout s t ra ta ;w ea k rea ct ion w ith H Cl.

Reporting In-Place Density Tests

In-place density tests are sometimes performed in testpits in borrow areas so that in-place densities can becompa red w ith t he expect ed compa ct ed densities for t heemba nkment . The required volume of ma t eria l neededfrom t he borr ow a rea ca n a lso be ca lcula t ed. The in-pla cedensity is a lso used to eva lua t e the expa nsion or colla psepot entia l for certa in soils.

The density should be reported in the paragraph onin-pla ce condit ion. E xa mples of the form a t a re show n infigur e 11-10. The upper exa mple is used w hen only t hedensity is determined. The low er exa mple is used w hena laboratory compaction test is also performed tocalculate the percent compaction (or D value if rapidmet hod is us ed) (U S B R 7240, [1]). For cohesionless s oils,similar information is reported for the maximum indexdensity, the minimum index density, and the percentrela t ive density .

I f th e in-pla ce density t est h ole spa ns t w o (or m ore) depthinterva ls of classif ica t ion, th e da ta a nd comment s for t hetest should be placed in the interval description corre-sponding t o t he top of th e test h ole. At t he end of th e in-formation reported, the comment (in all capital letters)mu st be a dded: NOTE : TE S T E XTE ND E D IN TOU ND E RLYING INTE RVAL. An in-pla ce density testshould not span different ma teria ls or la yers.


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Because the laboratory compaction test is general lyperformed on the material removed from the test hole,note that the data are for a mixture of in tervals bya dding, NOTE : C OMP ACTION TE S T P E RFORME DON MATERIAL MIXED FROM TWO DIFFERENTINTERVALS.

The d ensit y un it s a re lb/ft 3 or kilonew t ons per cubic meter(kN/m 3).

Samples Taken

In a ddit ion t o t he brief description of t he sa mples t a kenund er the Cla ssifica t ion G roup S ym bol column, a morecomplete description of any samples taken from eachdept h int erva l is included in t he word description. Thedescription should include the size of the sample, theloca t ion represent ed by th e sa mple, a nd for ea ch sa mple,

how the sample was obtained (e.g. , quartering andsplitting).

An exa mple of how t o report t he sa mple informa t ion fora n a uger hole is show n in figure 11-17. An exa mple ofhow to report the sample information for a test pi t ortrench is shown in the section on word descriptions ofundisturbed sa mples.

The a pproxima t e weight of sa mples should be sta t ed.

Measured Percentages of Cobbles and Boulders

If t he percent a ges of t he plus 3-inch pa rt icles a re mea -sured, not est ima t ed, t he percent a ges a re report ed t o

t he nea rest 1 percent . In t he w ord description for th eplus 3-inch pa rt icles, do not use t he t erm a bout beforet he percenta ges.


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The procedure for measuring the percent by volume ofcobbles and boulders is given in the test procedure,U S B R 7000, P erform ing D istur bed Soil Sa mpling in TestP its [1]. This met hod is ra rely used; percent a ges a reusua lly est ima ted. I t is not recomm ended th a t th epercent a ges be mea sured for a uger holes, since the ma ssof ma t erial r ecovered is genera lly insufficient to obta in arelia ble gr a da t ion of plus 3-inch pa rt icles.

Figu res 11-23 t hr ough 11-33 show a va riety of logs of t estpits using both t he US CS a nd t he geologic int erpret a t ionof the pa rent ma ter ia l . Note tha t US CS indica tes tha tbedrock has been altered or weathered to a soil-likema teria l . For engineering considera t ions, use th e U SC Sbut present t he rock condit ions a s w ell.

BIBLIOGRAPHY

[1] B urea u of Reclama t ion , U .S . Depa r tmen t of t heInterior E a r t h M a nu a l , P a rt 2, th ird edition, 1990.

[2] U .S . Depa r tmen t of Agr icu ltu re, Agr icu l tu re H and book N o. 436 , Appendix I (Soil Taxonomy),December 1975.

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Engineering Geology Field Manual Volume I Chap11

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