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HomeMy WebLinkAboutSubsoils Report for Foundation DesignlGrt*ffiffii#'i*"5020 County Road 154 Glenwood Springs, CO 81601 phone: (970)945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com An Bnp{oy*r Olfnq{ Cqmpcfty wwwkumarusa'com Office Locations: Denver (HQ), Parker, Colorado Spdngs, Fort Collins, Glenwood Springs, and Summit County, Cnlorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE LOT 910 TRONBRTDGE 382 RIVER BEND WAY GARFIELD couNTY, coLoRADO PROJECT NO.21-7-643 SEPTEMBER 8,2021 PREPARED FOR: BRADLEY AND ROZ BIRKELO 22212 CHIPPEWA LANE GOLDEN, COLORADO 80401 bbirkelo@gmail.com rbirkelo-@gmail.com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY.. PROPOSED CONSTRUCTION SITE CONDITIONS FIELD EXPLORATION SUBSURFACE CONDITIONS ... FOLINDATION BEARING CONDITIONS ... DESIGN RECOMMENDATIONS .................... FOUNDATIONS FOUNDATION AND RETAINING WALLS FLOOR SLABS UNDERDRAIN SYSTEM ............. SURFACE DRAINAGE................. LIMITATIONS... FIGURE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURES 4 AND 5 _ SWELL-CONSOLIDATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS a -3 - -3- -4- 1 1 4 4 5 7 7 8 .-8- Kumar & Associates, lnc.Project No.21-7-643 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 91, Ironbri dge, 382 River Bend Way, Garfield County, Colorado. The project site is shown on Figure 1. The purpose of the study was to develop recornmendations for the foundation design. The study was conducted in accordance with our agreement for geotechnical engineering services to Roz Birkelo dated August 2,202I. Hepworth-Pawlak Geotechnical (now Kumar & Associates) previously conducted geotechnical engineering studies for the subdivision development and presented the findings in reports dated October 29,1997 and February 12, 1998. Job No. 197 327 . A field exploration program consisting of exploratory borings was conducted to obtain information on the subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their classification, compressibility or expansion potential and other engineering characteristics. The results of the field exploration and laboratorv testine were analvzedto develo:o recommendations for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The proposed construction on the lot was prelimrnary at the time of our study. In general, the residence will be a one and two-story structure with a walkout lower level and located in the area of the exploratory borings shown on Figure 1. Ground floors could be structural above crawlspace or slab-on-grade. Grading for the structure is assumed to be relatively minor with cut depths between about 4 to 8 feet. We assume relatively light foundation loadings, typical of the proposed type of construction. If building location, grading or loading information is significantly different than described, we should be notified to re-evaluate the recommendations presented in this report. Kumar & Associates, lnc. @ Project No.21-7.643 ", SITE CONDITIONS The lot was vacant at the time of our study. The site topography consists of two relatively flat L^-----.^,-1-:^1-^,-^1- ^^ ^1^^--r - L- O.C^-+ A:.Cf-,-^,---:-- ^1 ^-,^L:^,^ ---:L1^ ^,^-^l^,-^L^7- :,-L^,---^--:,-.ft vY rlu u rravsvr QLvrJ DrvvP urlvr Y vrrluB slope. The upper, southwestemarea encompasses most of the building envelope and is vegetated mainly with sparse grass and weeds. The lower area is vegetated with lush grass and is generally known to have shallow groundwater during irrigation season. The Roaring Fork River is around 150 feet east of the lot and around 15 to 25 feet lower than the lot. Scattered cobbles are exposed at the surface of the upper level of the lot. A minor drainage swaie crosses through roughly the middle of the lot. SUBSIDENCE POTENTIAL Bedrock of the Pennsylvantan age Eagle Valley Evaporite underlies the Ironbridge development. These rocks are a sequence of gypsiferous shale, fine-grained sandstone and siltstone with some massive beds of gypsum and limestone. There is a possibility that massive gypsum deposits associated with the Eagle Valley Evaporite underlie portions of the lot. Dissolution of the gypsum under certain conditions can cause sinkholes to develop and can produce areas of localized subsidence. During previous studies for the subdivision development, several sinkholes were observed scattered throughout the Ironbridge area. These sinkholes appear similar to others associated with the Eagle Valley Evaporite in areas of the Roaring Fork River valley. The closest mapped sinkhole is located below the intersection of River Bank Lane and River Bend Way about % mlle to the north which was remediated b;r sub-excavation down to bedrock and placement of structural fill. Sinkholes were not observed in the immediate area of the subject lot. No evidence of cavities was encountered in the subsurface materials; however, the exploratory borings were relatively shallow. for foundation design onlv. Based on our oresent knowledse of the subsurface conditions at the site, it cannot be said for certain that sinkholes will not develop. The risk of future ground subsidence on Lot 91 throughout the service life of the proposed residence, in our opinion, is low; however, the owner should be made aware of the potential for sinkhole Kumar & Assoctates, lnc..B ProJect No. 21.I.tt43 -3- development. If further investigation of possible cavities in the bedrock below the site is desired, we should be contacted. FIELD EXPLORATION The field exploration for the project was conducted on August 23,2021. Three exploratory borings were drilled at the locations shown on Figure 1 to evaluate the subsurface conditions. The borings were advanced with 4-inch diameter continuous flight augers powered by a truck- mounted CME-458 drill rig. The borings were logged by a representative of Kumar & Associates. Samples of the subsoils were taken with I% inch and 2-inch I.D. spoon samplers. The samplers were driven into the subsurface materials at various depths with blows from a 140-pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-1586. The penetration resistance values are an indication of the relative density or consistencv of the subsoils and hardness of the bedrock. Depths at which the samples were taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The subsoils, below about 1 to 2 feet of topsoil and fill soils, consist of 3 to 5 feet of silty sand and sandy clayey silt overlying dense, silty sandy gravel and cobbles with probable boulders. Below a depth of about 8 feet in Boring 1, medium hard weathered siltstone/claystone was encountered that transitioned to hard bedrock with depth. Drilline in the coarse granular soils with auger equipment was difficult due to the cobbles and boulders and drilling refusal was encountered in the deposit atBorrng2. Laboratory testing performed on samples obtained from the borings included nafural moisture content and densitv and finer than sand size gradation analyses. Results of swell-consolidation Kumar & Associates, lnc. @ Project No. 21.7.643 -4- testing performed on drive samples of the silt soils, shown on Figures 4 ar:d 5, indicate moderate to relatively high compressibility under conditions of loading wetting. The laboratory testing is summarized in Table 1. Free water was encountered at depths of about 5 and lllz feet in Borings I and 3 at the time of drilling and when checked 15 days later. The upper soils were typically slightly moist to moist with depth. FOUNDATION BEARING CONDTTIONS The soils encountered across the building area are variable in type, depth and engineering properties. The sand and silt soils have variable compressibility and low bearing capacity and are generalty unsuitable for support of building loads. The underlying silty sandy gravel and cobble soils have low compressibility and moderate bearing capacity and are suitable for support of shallow spread footin-es with low settlement potential. Wlrere sand and silt soils are encountered, sub-excavation and replacement with structural fill appears feasible to reestablish design bearing level. The groundwater level will probably be encountered and impact foundation excavations made atthe lower level of the site requiring temporary dewatering. Due to the potential high groundwater level, crawlspace should be avoided at the lower level of the site. Micro-piles that extend into hard competent bedrock could also be used at the lower level of the site and may be apractical choice to support the foundation if the footing excavation cannot be dewatered for placement of structural fill for support of shallow spread footings. DESIGN RECOMMENDATIONS FOIjNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural coarse granular soils or compacted structural fill after removal of the compressible sand and silt soils. Kumar & Associates, lnc, o Project No. 21-7-643 5 The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed natural granular soils or on compacted Based on experience, we expect settlement of footings designed and constructed as discussed in this section will be about 1 inch or less. 2) The footings should have a minimum width of 16 inches for continuous walls and 2 feet for isolated pads. 3) Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundations at least 36 inches below exterior grade is typically used in this atea. 4) Continuons foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 12 feet. Foundation walls acting as retaining structures should also be designed to resist lateral earth pressures as discussed in the "Foundation and Retaining Walls" section of this report. 5) The topsoil., sand and silt soils and loose or disturbed soils should be removed and the footing bearing level extended down to the relatively dense natural granular soils. The exposed soils in footing area should then be moistened and compacted. If water seepage is encountered, the footing areas should be dewatered before concrete placement. Structural fill should consist of a relatively well graded sand and gravel such as road base compacted to at least 98o/, of standard Proctor density and extended laterally beyond the footing edges a distance equal to at least the depth of fillbelow the footing. 6) A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FOTINDATION AND RETAINING WALLS Foundation walls and retaining structures which are laterally supported and can be expected to undergo only a slight amount.of deflection should be designed for a lateral earth pressure numar & Assoctates, tnc, u Fropcr No. z'r./.643 -6- computed on the basis of an equivalent fluid unit weight of at least 55 pcf for backfill consisting of the on-site soils. Cantilevered retaining structures which are separate from the building and can be expected to deflect sufficiently to mobilize the full active earth pressure condition should L^ J^-i---^J f^-- ^ l^r^,.^1 -^--L1^ "-,"-^^- ^.1 ^-- L1- ^ 1-^^i^ ^f ^-^ ^---:--^1^--L Cl--: I --.-:a ---^:-1-f{ro uvur6..v of at least 45 pcf for backfill consisting of the on-site soils. Backfill should not contain organics, debris or rock larger than about 6 inches. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain should be provided to orevent hvdrostatic oressure builduo behind walls. Backfill should be placed in uniform lifts and compacted to at least 90o/o of the maximum standard Proctor density atnear optimum moisture content. Backfill placed in pavement and walkway areas should be compacted to at least 95Yo of the maximum standard Proctor density. Care should be taken not to overcompact the backfill or use large equipment near the wall, since this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall backfrll should be expected, even if the material is placed correctly, and could result in distress to facilities constructed on the backfill. The lateral resistance of foundation or retaining wall footings will be a combination of the slidin-u resistance of the footins on the foundation materials and oassive earth oressure asainst the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated based on a coefficient of friction of 0.45. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 350 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strensth. Suitable factors of safetv should be included in the design to limit the strain which will occur at the ultimate strength, parlicularly in the case of passive resistance. Fill placed against the sides of the footings to resist Iateral loads should be compacted to at least 95o/o of the maximum standard Proctor density at a moisture content near optimum. Kumar & Associates, lnc. @ Project No.21.7.643 -7 - FLOOR SLABS Th::;;i;:;l ::: ;;i: vv'uv', ,--i;i;l;b ;;i-gradc construction. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A minimum 4-inch layer of free- draining gravel should be placed beneath basement level slabs to facilitate drainage. This material should consist of minus Z-tnch aggregate with at least 50% retained on the No. 4 sieve and less than2%o passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95Y, of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site gravel soils or a suitable imported material devoid of vegetation, topsoil and oversized rock. We recommend vapor retarders conform to at least the minimum requirements of ASTME|741 Class C material. Certain floor types are more sensitive to water vapor transmission than others. For floor slabs bearing on angular gravel or where flooring system sensitive to water vapor transmission arc utilized, we recommend a vapor barrier be utilized conforming to the minimum requirements of ASTM 81745 Class A material. The vapor retarder should be installed in accordance with the manufacturers' recommendations and ASTM 81643. UNDERDRAIN SYSTEM Although free water was encountered in the exploratory borings below expected excavation depth, it has been our experience in the areathat the groundwater level could rise close to ground surface on the lower level of the site and local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. We recommend below-grade construction, such as retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. Kumar & Assnciates .lnc o Proiacl No 2'1.7-643 -8- The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free-draining granular material. The drain should be placed at each level of g.vca'rzafinn and af leasf .l fnof helnrv lnrvesf nrliae.e.nf finish srnde and slnned at a minim1nrn 1o/n fo a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than 2%o passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least l1/z feet deep. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: 1) Inundation of the foundation excavations and underslab areas should be avoided during construction. 2) Extedor backfill should be adjusted to near optimum moisture and compacted to at least 95Yo of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 12 inches in the first 10 feet in uqpaved areas and a minimum slope of 3 inches in the first 10 feet in paved areas. Free-draining wall backfill should be covered with filter fabric and capped with about 2 feet of the on-site finer grained soils to reduce surface water infiltration. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from foundation walls. 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 Kumar & Associates, lnc.Project No. 21.7-643 -9- from the exploratory borings drilled at the locations indicated on Figwe 1, the proposed type of construction and our experience in the area. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developing in the future. If the client is concerned about MOBC, then a professional in this special field of practice should be consulted. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory borings and variations in the subsurface --,...1,i.-,;-..^;1 ;.;i 1-;;;;;;; ;;;.1-.^i ;^;i.;1 -^-*"*',^-,^ ^, y-ift.,^.-J. If ;;;^i;t;;:; ;;^;;;i;i-ed during construction appear different from those described in this report, we should be notified so that re-evaluation of the {ecommendations may be made. This report has been prepared for the exclusive use by our client for design purposes. We are not responsiOte ror tgcnnlcar rnrerprelauons Dy orners or our rnrorrnauon. AS rnc proJcsl Evolves, wc should provide continued consultation and field services during construction to review and monitor the implementation of our recolnmendations, and to verifu that the recommendations have been appropriately inte,rpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommend on-site observation of excavations and foundation bearing shata and testing of structural fill by a representative of the geotechnical engineer. Respectfu lly Submitted, Kueegar" &L AssoeEefee, {:ne. Steven L. Pawlak, P.E. Reviewed by: tr\ - Daniel E. Hardin, P.E. t slP/rjf t i.rg*'-"rt,'-e{ i, !- 3 a : ei:|:i!., ridc :, :.oot}lur .at*,*q .. 1 LOT 91NG --,i* F.(, S3S6 .t BORING 5 :s 2 .. :' { $% Q/,' -(i5 \\%:;$cr;$ irf, $6Fsc - rf eri dg'rtlr LOT 92 0 APPROXIMATE SCALE_FEET #,r$s'f{F* aff 5 iG$ sFT* ?r* roeJr*flrsr \""t e ! 21 -7 -643 Kumar & Associates LOCATION OF TXPLORATORY BORINGS Fig.1 BORING 1 EL. 5938' BORING 2 EL. 5943' BORING 3 EL. 5945' 5945 _ 5940 11/12 WC=3.4 DD=92 1o/ 12 WC=6.4 DD=9 6 -2OO=77 11/12 WC=3.8 DD=9 6 s0/5.5 40/6, 57 /6 5945 5940 - 5935 5930 5925 s920 n ASSUMED BASEMENT LEVEL 4e/12 7 /12\l/a-11 c DD= 1 09 -2AO=75 4/6, 1 1 /6 WC=27.O DD=97 -2QQ=45 38/ 12 r-J 1Aa-/ 6, FtrlLItL Iz.o F LdJ Ld - 5935 5920 W tiiw I 7 h q = ---- Ft!LIl! Izo F trJJ TJ q - 5930 - 5925 I ! E I 21 -7 -643 Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 2 LEGEND n IA TOPSOIL; ORGANIC SANDY SILT AND CLAY, DARK BROWN FILL; SAND AND SILT WITH GRAVEL AND COBBLES, LOOSE, SLIGHTLY MOIST, MIXED BROWN. SAND AND SILT (SM-ML); SLIGHTLY CLAYEY, SOME ORGANICS, LOOSE/MEDIUM STIFF, SLIGHTLY MOIST TO VERY MOIST AT BORING 1, LIGHT BROWN TO BROWN. GRAVEL (OI"I); SLICHTLY SILTY TO SILTY, SANDY, COBBLES, SCATTERED BOULDERS, DENSE, SLIGHTLY MOIST TO WET WITH DEPTH, GRAY_BROWN. ROUNDED ROCK. yvcAinLnLU JrLrJrvr\L, rnAvtvnLU At\u t K\rl\Ll\, MLuluM nAKLr, vYE I, r.rKA1, SILTSTONE/CLAYSTONE BEDROCK; VERY HARD, MOIST, DARK GRAY. EAGLE VALLEY EVAPORITE DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE DRrVE SAMPLE, 1 3/8-tNCH t.D. SPLTT SPoON STANDARD PENETRATTON TEST. DRIVE SAMPLE BLOW COUNT. INDICATES THAT 7 BLOWS OF A 14o-POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE THE SAMPLER 12 INCHES. DEPTH TO WATER LEVEL AND NUMBER OF DAYS AFTER DRILLING MEASUREMENT WAS MADE. PPAr^TlnAr AllCrp PtrrilsA,l . DEPTH AT WHICH BORING CAVED WHEN CHECKED ON SEPTEMBER 7,2021, f-:a V':d li:i:Y IVI I 7/12 0J5 -.-> A 'i NOTES 1 . THE EXPLORATORY BORINGS WERE DRILLED ON AUGUST 23, 2021 WITH A 4-INCH DIAMETER CONTINUOUS_FLIGHT POWER AUGER. 2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE OBTAINED BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN PROVIDED. 4. THE EXPLORATORY BORING LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5 IHL LINLs BLIWLLN MAILf{IALS SI-IOWN ON IHE EXPLORATORY tsORING LOGS REPRTSENI' IHE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER LEVELS SHOWN ON THE LOGS WERE MEASURTD AT THE TIME AND UNDER CONDITIONS INDICATED. FLUCTUATIONS IN THE WATER LEVEL MAY OCCUR WITH TIME. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D2216); DD = DRY DENSITY (PCT) (NSTV D2216); onn- DrD^rf,lrl^r DAcct\t^ f,tn onn ctr\/r /lcrr/ nr, /n\ I E i 21 *7 -643 Kumar & Associates LEGTND AND NOTTS Fig.3 SAMPLE OF: Very Sondy Silt wiih Orgonics FROM:Boring2@2.5' WC = 5.4 %, DD = 92 pcf U 2 2 -10 -12 )q JJg (/, I zotr ofoaz.o() -4 6 :i ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1 PRESS RE - KSF1.0 F d e3 21 -7 -643 Kumar & Associates SWTLL_CONSOLIDATION TIST RTSULTS Fig. 4 SAMPLE OF: Very Sondy Silt FROM:BoringS@5' WC = 3.8 %, DD = 96 pcf :; i:ii::-l--..,:. -1..- .-,- .r....: ll ii 1l ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 0 2 5 )q JJ =ua I z.otr o =o UIzo() -5 -6 -7 1.0 APPLIED PRESSURE - KSF 10 100 Th666 t$t r68un6 opply only to th6 sompl.s t6Eted. Th6 iosting r6pod Bholl not b3 r8producod, 6xcopt in full, wlthout th6 writlsn opprovol of Xumor ond A€Eociot€E, lnc. Sw€ll ConBolidotion tssting podormsd ln occorddnco sith ASM D-4546. !i I 45 P € 3 E 21 -7 -643 Kumar & Associates SWTLL-CONSOLIDATION TIST RISULTS Fig. 5 l(ttt ltm&Ms *hrc,s { toteclnieal and Mstsrifi{$ fi[ )insers n d Environffisni*l $cientisl$ SAMPLE TABLE 1 SUII/ II'IARY OF LABORA-TORY TEST RESULT } GMDATIOl ATTERBERG LIMITS ! AND t%l Pr'No. 21-7-643 SOII TYPE Sandy Claye. Silt Very Silty Sa nd Very Sandy I ilt with Sandy Silt with Orgamcs Very Sandy I ilt DEPTl 2% 5 NAT IRAL DIY DEI\ S]TY 1il9 97 c) 96 96 I QUID LIMIT PLASTIC INDEX aJ 2 1 BORING 2y, 5 2 3.8 6.4 3.4 27.0 8ll MI NATURAL MOISTURE CONTENT %l GRAVEL 77 45 75 PERCENT PASSING NO. 200 stEvE (psfl UNCONFINED COMPRESSIVE STRENGTH