Four Corner - Texas Water Development Board

OCT. -08' 98ITHUl 16:14 TC&B HOU LA~D DEV SV TEL:i13 26~ 32'0 p 015
Report No. 1).401-3956
STANDARD PENETRATION TEST (SPT)
A 2-in . .OO. 1-3/8-in.·IO split spoon sampler IS dliven 1.5 It Into undisturbed soil with a 14.0 ·pound hammer free falling 30 in.
After the sampler is. aeilled 6 in. Into undisturbed soli, the number of blows ntqUired to driVQ the sampler the last 12 in.
is the Standard Penetration Resistance or "N" value, which is rQcorded as blows per foot ss described below.
Blows Per Foot
Dvscription
25 .................................................... 25 blows drive sampler 12 inc.'lu, alter initial e inches of saatlng.
50{7" ............_................................ so blows dlive sampler 7 Inch•. alter inl!iel 6 Inch seating.
Aef,'3' ....._ ..............................:-.... 50 blows dlive Mmpler 3 inches, during Initial 6 incne~; of sealing intetVal.
NOTE: To !IVoid damage to 581!1pHng tools, dlivlng i_, limited to 50 blows during or alter H41Jng interval.
Descriptive
Term
DENSITY OF GRANULAR SOILS
•Rellllive
Censily, ,.. ••Blows Per Foot {SFT) Term
STRENGTii OF COHESIVE SOILS
Undrained
Sheer SO'ength,
k&f
Blows Per Foot (SFT)
(approximele)
Very Loosa ........................... --- < 1 S ........................ 0 to 4 Very Soft ........................... __ < 0.25 .......................... 0 to 2
LcOGe ..................................... 1 5 to 35 ..................... 5 to 1 o Soft ................................ 0.25 to 0.50 ......................... 2 to 4
Mlidium Oe'lw .................. 35 to 65 .................. -11 to 30
Firm ............................... 0.50 to 1.00 ......................... 4 to B
Oerl5e .................................... !5 to 85 .................... 31 to SO Slltf ................................. 1.00 to 2.00 ....................... B to 1 6
Very Dense ............-............... > 85 .................. ...... > 50 Very Stitt ...................... 2.00 ro 4.00 ..................... 16to 32
•E,t~meted from sampler driving record. Hard .......................................... :> 4.00 ......-............... :> 32
... Requires correction for depth, groundweter level, and grain size.
SHEAR STRENGTH TEST METHOD
U - Unconfined
P = Pocket Pemrtrometer
T .. Torvet~e
Q = Unconsolidated • Undrained Tri!IXial
V = Miniature Vane
F -
Field Vane
HAND PENETROMETER CORREcnON
Our experience hes shown thB! the hand penetrometer genefl!lly overestimales the irl-$itu undrained shear itrength of
overconsolldB!ed Pleistocene Gult Coest clays. Thew strengths are partiwly controlled by the presence of m~ter0$copic soil
defQcls such as &llekansidell, which generolly do not influence smaller ~~~ tests Uke the hand penetrometer. Based on our
experience, we have adjusted these field estimates of the undrained shear mengt11 of natural, overconsortdeled
Pleistocene Gult Coast SQils by multiplying the measured penetrometer readings by a factor of O.B. These adjusted strength
estimates are recorded In the •Shew Strength" column on the boring logs. Except ~ described in the text, we have
not adjusted BStimB!es of the undreined shear strength for proj~ located oU!side of the Pleistocene Gu~ Coast _formations.
Information on each boring log is 11 compilation of subsurface conditions and soil or rock classiflca!ions obtained
from the field as well as from labornlory testing of samples. Stl'81a have been interpreted by commonly •ccepted
prOC9dures. The strelum lines on the logs may be trans~ional and approximate in na!Ure. Water level messurements
refer only to these observed at ll'le time and places indicated. and can vary with time, geologic condition, or construction
activity.
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TERMS AND SYMBOLS USED ON BORING LOGS
SOIL CLASSIFICATION