HomeMy WebLinkAbout1.07 Subsoil study) ) ~tech HEPWORTH -PAWLAK GEOTECHNICAL SUBSOIL STUDY 11'::-11\\, ')"l L·f':ll' h k l 10;, 'lu h!;i, ;,1. it". :, C ]~ll~"lIn r ': R, n .. 1 1 ')-1 ( ,krn\-'.-!!),! Srri l l.~5 . C"L
' I ~IJ" fll(\,)] Ph· ,n(': ')/0-'>4 S, I');+' Ere Yi l)·9'1 ,)·:;'454 \",n ,liJ: hpg.;\, (i · hpg,~,)!,,"\·h.(\ fill FOR FOUNDATION DESIGN PROPOSED MONO PINE TOWER 5445 COUNTY ROAD
154 GARFIELD COUNTY, COLORADO JOB NO. 110 407A DECEMBER 16, 2010 PREPARED FOR: CHARLES STECKL Y ARCHITECTURE, INC. ATTN: CHARLES STECKLY, AlA 5935 SOUTH ZANG STREET, SUITE 280 LITTLETON,
COLORADO 80127
) TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY ..... .... ..... ....................... ........ ........................ ... -1 -PROPOSED CONSTRUCTION ................ .. ...........................
.................................... -1 -SITE CONDITIONS ................. ................. .... .. ........... ................................................ -2 -FIELD EXPLORATION
...... ........ ...................... .. .... ........................ .......................... -2-SUBSURFACE CONDITIONS .................. ........................................................
........ -2 -DESIGN RECOMMENDATIONS .. ............... .. ............................................. ........... .. -3 -FOUNDATIONS ................... .. .. ..........................
....................................... .. .......... -3 -SURFACE DRAINAGE .... ........................... .. ............. ........... ...... ............ .............. -4 -LIMITATIONS
................... .... .. ........ ......................................................................... -4 -FIGURE 1 -LOCATION OF EXPLORATORY BORING FIGURE 2 -LOG OF EXPLORA TORY
BORING FIGURE 3 -LEGEND AND NOTES ) FIGURE 4 -GRADATION TEST RESULTS
) PURPOSE AND SCOPE OF STUDY Tins report presents the results of a subsoil study for a proposed monopine tower to be located at 5445 County Road 154, Garfield COW1ty, Colorado. The project
site is shown on Figure I. The purpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with our proposal for geotechnical
engineering services to Charles Steckly Architecture dated November 30, 2010. A field exploration program consisting of an exploratory boring was conducted to obtain information on the
subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to detelmine their classification and other engineering characteristics.
The results of the field exploration and laboratOlY testing were analyzed to develop recommendations for fOW1dation types, depths and allowable pressures for the proposed monopine tower
fOW1dation. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on
the proposed constlUction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The proposed monopine commnnications tower will be about 45 feet tall and located as shown
on Figure 1. Grading for the structure will be relatively minor and consist of cut depth needed for the tower foundation. The surrounding grade will essentially stay unchanged. We assume
foundation loadings will include lateral and overturning loads in addition to the tower weight. Iffoundation loadings, tower location or grading plans change significantly from those
described above, we should be notified to re-evaluate the recommendations contained in this report. Job No. 110 407A ~tech
) ) -2-SITE CONDITIONS The monopine tower site is located in an asphalt paved parking area/driveway at the north end ofthe middle storage building as shown on Figure I. The existing
storage building is a single story metal stlUcture with s lab-on-grade floor. The ground surface slope is down the west with about one foot of elevation difference across the mono pine
tower site. FIELD EXPLORATION The field exploration for the project was conducted on December 9, 2010. One exploratory boring was drilled at the location shown on Figure 1 to evaluate
the subsurface conditions. The boring was advanced with 4 inch diameter continuous flight augers powered by a !tuck-mounted CME-4SB drill rig. The boring was logged by a representative
of Hepworth-Pawlak Geotechnical, Inc. Samples ofthe subsoils were taken with a I Ys inch LD. spoon sampler. The sampler was driven into the subsoils at various depths with blows from
a 140 pound hammer falling 30 inches. Tills test is similar to the standard penetration test described by ASTM Method D-IS86. The penetration resistance values are an indication of the
relative density or ------,consistency ofthe subsoils:-Bepths-at will-ch-the s-amples were-taken-and tlie penetraribn resistance values are shown on the Log of Exploratory Boring, Figure
2. The samples were returned to our laboratOlY for review by the project engineer and testing. SUBSURFACE CONDITIONS A graphic log ofthe subsurface conditions encountered at the site
is shown on Figure 2. The subsoils encountered, below the pavement materials, consist of relatively dense silty sandy gravel, cobbles and boulders to the drilled depth of IS V, feet.
Drilling in the dense granular soils with auger equipment was difficult due to the cobbles and boulders and drilling refusal was encountered in the deposit. Job No. 110 Q07A c;&I)tech
) ) -3 -Laboratory testing performed on samples obtained from the boring consisted of naturaL moisture content and gradation analyses. ResuLts of gradation analyses perfonned on small
diameter drive samples (minus I Y, inch fraction) of the coarse granular subsoils are shown on Figure 4. No fi'ee water was encountered in the boring at the time of drilling and the
subsoiLs were slightly moist to moist. The boring was backfilled with cuttings and patched DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the
expLoratory boring and the nature ofthe proposed construction, we reconunend the monopine tower be founded with a spread footing bearing on the naturaL granular soils. If a different
foundation type is proposed for the mopopine tower, we should be contacted for additional recommendations. -----'I'he design and constructicm-criteria presentea below should be oBserved
for a spread-footing foundation system. I) The footing should be placed on the undisturbed naturaL granular so ils and designed for an allowable bearing pressure of 5,000 psi Based on
experience, we expect settlement of footings designed and conshucted as discussed in this section will be about Y, inch or less. 2) The footing should have a minimum width of 4 feet.
3) The footing should be provided with adequate soil cover above the bearing elevation for fi'ost protection. Placemeni of foundations at least 36 inches beLow extelior grade is typically
used in this area. 4) LateraL loading on the footing can be resisted by a sliding coefficient of 0.50, a passive earth pressure of 400 pcf equivaLent fluid unit weight, and a Job No.
110 407A ~tech
) -4 -backfill weight of 135 pcffor compacted granular material. The values are for ultimate loading conditions and a safety factor should be used for allowable loading conditions. 5)
Any existing fill and loose or disturbed so ils should be removed and the footing bearing level extended down to the relatively dense natural granular soils. The exposed so ils in footing
area should then be moistened and compacted. 6) A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions.
SURFACE DRAINAGE The following drainage criteria should be followed and maintained at all times after the monopine tower has been completed: 1) Inundation of the foundation excavation
should be avoided during constmction. 2) The backfill should be adjusted to near optimum moisture and compacted to at least 95% of the maximum standard Proctor density. 3) The ground
surface should be sloped to drain away from the foundation at __________ ,a minimum slope of6-inches in-the-first 10 feet-in-unpaved areas and-a-minimum slope of3 inches in the first
10 feet in paved areas. LIMITATIONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area at this time. We
make no warranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained fi'om the exploratory boring drilled at the
location indicated on Figure I, the proposed type of construction and our experience in the area. Our fmdings include interpolation and extrapolation of the subsurface conditions identified
at the exploratory boring and variations in the subsurface conditions may not become Job No. 110 407 A ~tech
) -5 -evident until excavation is performed, If conditions encountered during construction appear different Ii-om those described in this repOli, we should be notified so that reeva
luation ofthe recommendations may be made, This repOlt has been prepared for the exclusive use by our client for design purposes, We are not responsible for teclUlical interpretations
by others of our information, As the project evolves, we should provide continued consultation and field serv ices during construction to review and monitor the implementation of our
recommendations, and to verify that the recommendations have been appropriately interpreted, Significant design changes may require additional analysis or modifications to the recommendations
presented herein, We recommend on-site observation of excavations and foundation bearing strata and testing of structural fi ll by a representative of the geotechnical engll1eer. Respectfully
Submitted, Steven 1. Pawlak, P,E Reviewed by: fj~~ Daniel E, Hardin, P, E, SLP/ksw Joh No. 110 407A ~d)'tech
) ) 110407A APPROXIMATE SCALE 1" = 50' " ./! \ CT1\ (» , ~ \ ,I I I I I I I ! I I \ I \ \ ---EXISTING STORAGE BUILDING \.. ---H lAZY F SELF STORAGE 5445 COUN1Y ROAD 154 S6'6'~ > ----.
-----:-'-_-=P":RO==POSED MONO PINE roWER LOCATION -... \ • BO'RNJ.G 1 " ...... -... \ " J..-=c=~ /J \ \ \ EXISTING STORAGE BUILDING EXISTING STORAGE BUILDING 1 1---1---,1----" . ~ 05'£tech
LOCATION OF EXPLORATORY BORING Figure 1 He worth-Pawlak Geotechnical
) 5885 5880 Q) Q) LL, 5875 c 0 ~ > $1 w ) 5870 5865 110407A BORING 1 ELEV. ~ 5883' 20112 19/6,25/5 ) WC-2.2 +4-43 -200~16 77/12 .~ . .". NOTE: Explanalion of symbols is shown on Figure
3. ~tech LOG OF EXPLORATORY BORING He worth-Pawlak Geotechnical 5885 5880 Q) L'"L 5875 c 0 1 ill 5870 5865 Figure 2
) LEGEND: ~ ASPHALT PAVEMENT; about 3 inches thick. ~ ROAD BASE; silty sandy gravel, medium dense, moist, brown. About 6 inches thick. ~ GRAVEL (GM); w[th cobbles and boulders, sandy,
silly, dense, slightly moist to moist. light brown, subrounded ~ rocks. _ Drive sample; standard penetration test (Spn, 1 3/8 inch 1.0. split spoon sample, ASTM·1586. Drive sample blow
count; indicates that 20 blows of a 140 pound hammer falling 30 inches were 20/12 required to drive the SPT sampler 12 inches. T Practical drilling refusal. NOTES: 1. The exploratOlY
boring was drilled on December 9, 2010 with a 4·inch diameter continuous flight power auger. 2. Location of the exploratory boring was measured approximately by pacing from features
shown on the site plan provided. 3. The exploratory boring elevation was obtained by interpolation between contours on the site plan provided. 4. The exploratory boring location and
elevation should be considered accurate only to the degree implied by the method used. 5. The lines between materials shown on the exploratory boring log represent the approximate boundaries
between material types and transitions may be gradual. 6. No free water was encountered in the boring at the time of drilling. Fluctuation in water level may occur with time. 7. Laboratory
Testing Results: -WC = Water Content (%) +4 = Percent retained on the No.4 sieve ·200 = Percent passing No. 200 sieve ~ch Hepworth-Pawlak GeotechnIcal 110407A LEGEND AND NOTES Figure
3
) ) 0 w z ~ w I>: IZ W 0 0:: w 0.. I HYDRDMETER ANALYSIS I SIEVE ANALYSIS I /R 7 HR TIME READINGS I U.S. STANDARD SERIES I ClEAR SQUARE OPENINGS I o ~5 ~IN. 1 5MIN. 60MIN19MIN.4 MIN.
1 MIN. #200 # 100 #50 #30 #16 #8 #4 3/8" 3/4" 11/Z' 3" 6"6" 8" 100 10 20 30 40 50 60 70 80 90 100 .001 .002 .005 .009 .019 .037 90 80 70 60 50 40 30 20 10 o .074 .150 .300 .800 1.18
2.36 4.75 9.5 19.0 37.5 76.2 152 203 12.5 127 DIAMETER OF PARTICLES IN MILLIMETERS QAYTOSILT "" """'" I C08!ll..ES GRAVEL 43 % SAND 41 % SILT ANDCLAY 16 % LIQUID LIMIT % PLASTICITY INDEX
% SAMPLE OF: Silly Sand and Gravel FROM: Boring 1 at 5 and 10 Feet Combined 'Z" in Ul « (L l-Z W 0 I>: W (L 110407A ~ GRADATION TEST RESULTS Figure 4 Hepworth-Pawlok Gcotechnlctll