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HomeMy WebLinkAboutSubsoils Report for Foundation DesignH-PVI(UMAR 5020 County Road 154 Glenwood Springs, C0 81601 Phone: (970) 945-7988 Fax: (970) 945-8454 Email: hpkglenwcod@kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado SUBSOIT- STUÐY FOR FOUNDATION ÐÐSIGN PR.TPÛSÐÐ RESIDENCE AND SHOP EUTLÐING l-oT'1, BLOCK 1, CANYON CREEK pR.ûpERTnES COUÌ\TY ROAÐ 263 G.A.R.FIELÐ COUNTY, COLOR,AÐO PROJECT NO. X8-7-202 MAY 4,2019 PR.EPAR.ED FOR.: ER.TAN KI,EII{ 1543 BEECH STREET RIF[,E, COI-ORADO 91650 ccrower@netzero.net Geotechnical Engineering I Engineering Geology Materials Testing I Environmental TABT,E OF CONTITNTS PURPOSE AND SCOPE OF STUDY. PROPOSED CONSTRUCTION SITE CONDITIONS ... FIEI-D EXPLORATION SUBSURFACE CONDITIONS . FOUNDATION BEARING CONDITIONS DESIGN RECOMMENDATIONS .................... FOUNDATIONS FOUNDATION AND RETAINING V/ALLS 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 through 6 - SV/ELL-CONSOLIDATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS 1 a .........- 3 ,,,.,'''.- 3 ,.....'..- 4 .........- 5 .'''.,.".- 6 -7 a -2- -2- -7 - H-P!KUMAR Project No. 18-7-202 PUR,PÛSE AT{Ð SCOPE ÛF'' ST'UÐV This report presents the results of a subsoil str,rdy for a proposed residence and shop building to be located on Lot 1, Block 1, Canyon Creek Properties, County Road 263, east of New Castle, Garfield County, Colorado. The project site is shown on Figure 1. The purpose of the study was to develop recommendations for the foundation design, The study was conducted in accordance with our agreement for geotechnical engineering services to Brian Klein dated March 15, 2018. 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 swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recomnendations for foundation types, depths and allowable pressures for the proposed builcling foundations. This repofi summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction ancl the subsurface conditions encountered. PROPC}SED CONSTR.UCTION The proposed residence will be a two story wood frame structure and the shop building will be a single story steel frame structuLe, located on the property as shown on Figure l. Both buildings with have slab-on-grade ground floors at an elevation near to slightly above the existing ground surface. Grading for the structures is assumed to be relatively minor with cut depths between about 3 to 5 feet. We assume relatively light foundation loadings, typical of the proposed type of construction. If building loadings, location or grading plans change significantly from those described above, we should be notified to re-evaluate the recommendations contained in this report. H.PryKUMAR -2- STTE CONÐXT'IONS The site was a vacant lot at the time of field exploration and the ground surface appears mostly natural. The lot was previously an irrigated field. The ground surface is strongly sloping to the south at a grades estimated at from about 4 to 57o. The elevation difference across individual building areas is estimated at about 2 to 4 feet. The site is vegetated by grass and weeds. F'TELÐ EXPT,ÛR.ATIÛIE The field exploration for the ploject was conducted on AprtI2,2018. Three exploratory borings were drilied at the locations shown on Figure 1 to evaluate the subsurface conditions. Boning 1 was drillecl at the shop building site and borings 2 and 3 were dlilled at the residence site. The borings were advanced with 4-inch diameter continuous flight augers powered by a truck- mounted CME-458 ddll rig. The borings were logged by a representative of F{-PlKumar. Sarnples of the subsoils were taken with a 2 inch I.D. spoon sampler. The sampler was driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is sirnilar to the standarcl penetration test described by ASTM Method D-1586. The penetration resistance values are an indication of the relative density or consistency of the subsoils. 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. SUBSUR.FACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The subsoils encountered, below about I foot of organic topsoil, consisted of about 10 to 14 feet of medium dense, silty to very silty clayey sand with scattered gravel overlying about 5 to L3V2feet or more of very stiff, sandy to very sandy clay with scattered gravel. Below depths of about 20 and 23 feet in Borings I and 2, respectively, medium dense, clayey, silty to very silty sand with scattered gravel was encountered. The sandy to very sandy clay soils extended down to the depth drilled in Boring 3 of 26 feet. H-PVKUMAR Project No. 18-7-202 -3- Laboratory testing performed on samples obtained from the borings included natural moisture content and density, and percent finer than sand size gradation analyses. Results of swell- consolidation testing performed on relatively undisturbed drive sampies, preserrted on Figures 4 through 6, indicate low to moderate compressibility under conditions of loading and wetting. The samples typically showecl nil to minor hydro-compression potential. One sample (Boring 2 at 10') showed a low swell potential when wetted under a constant i,000 psf surcharge. The laboratory testing is summarizecl in Table 1. No free water was encountered in the borings at the time of drilling ancl the subsoils were slightly moist. F'OUNÐ,A.TTON EEAR.ING CONDITTOI\{S The soils at assumed excavation subgrade possess low bearing capacity and some settlement potential, especially when wetted. Lightly loaded spread footings bearing on the natural soils appoar feasible for foundation support of the buildings with some risk of settlement. The risk of settlement is primarily if the bearing soils were to become wetted and precautions should be taken to prevent wetting. The low expansion potential encountered in one of the samples is believed to be an anomaly and can be neglected in the foundation design. A lower risk of settlement would be to remove and replace a depth (typically 3 feet) of the on-site soils as compacted structural fill below the footings, or use a helical pier or screw pile foundation system. Provided below are recommendations for spread footings. If recommendations for structural fill below the footings or for a helical pier or screw pile foundation system are desired, we should be contacted. DESIGN R.ECOMMENDATIO¡{S FOUNDA,TIONS Considering the subsurface conditions encountered in the exploratory borings and the natule of the proposed construction, we believe the building be founded with spread footings bearing on the natural soils with some risk of settlement. H.P+KUMAR Project No. 18-7-202 -4- The design and construction criteria plesented below should be observed fol a spread footing foundation system. 1) Footings placed on the r-rndisturbed natural granular soils should be designed for an allowabie bearing pressure of 1500 psf. The shop buiiding footings can be designed for an allowable soil bearing pressure of 2,000 psf. Basecl on experience, we expect settlement of footings designed ancl constructed as discussed in this section will be about 1 inch. Some additional settlement could occur if the bearing soils rvere to become wetted. 2) The footings should have a minimum width of 18 inches for continuous walls and 2 feet for isolated pads. 3) Exterio¡ footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundatiorls at least 36 inches beiow exterior grade is typically used in this atea. 4)Continuous fonndation walls should be well 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 repofi. All existing fill, topsoil and any loose or disturbed soils should be removecl and the footing bearing level extended down to the firm natural soils. The exposed soils in footing area shouìd then be moistened and compacted. A representative ofthe geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. 5) FOUNDATION 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 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 buildings and canbe expected to deflect sufficiently to mobilize the full active earth pressure condition should 6) H.PryKUMAR Project No. 18-7-202 5 be clesigned for a lateral earth pressure computed on the basis of an equivalent fluid unit weight .of at least 45 pcf for backfill consisting of the on-site soils. The backfill should not contain topsoil or rocks 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 prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lifts and compacted to at least 95Vo of the maximum standard Proctol density at a moistttre content near optimum. Backfill in pavement and walkway areas should be compacted to at least 95Vo 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. The lateral resistance of lbunclation or retaining wall footings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth pressnre against the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated based on a coefficient of friction of 0.35. Passive presslrre 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 strength. Suitable factors of safety should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads can consist of the on-site soils compacted to at least 957o of the maximum standard Proctor density at a moisture content near optimum. FLOOR. SLABS The natural on-site soils, exclusive of topsoil, are suitable to suppoft lightly loaded slab-on-grade construction. There could be some slab settlement or heave if the subgrade were to become H-PÈKUMAR Project No. 18-7-202 6- wetted. Providing a depth (typically lVzto 2 feet) of road base such as CDOT Class 2, 5 or 6 agglegate base course below the slabs could be done to reduce the risk of movement. We should observe the slab subgrade conditions at the time of construction fo determine if subexcavation of potentially expansive or other unsuitable soils and replacement with road base is needed. 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 rcduce 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 6 inch layer of snad and gravekl road base should be placed beneath floor level slabs for support and to facilitate drainage. This material should consist of minus 2 inch aggregate with at least 50Vo retained on the No. 4 sieve and less than 1ZVo passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 957o of maximum standard Proctor density at a moisture content near optimum. Required fitl can consist of the on- site soils devoid of topsoil and oversized (plus 6 inch) rocks. UNDERDRAIN SYSTEM It is our understanding the proposed finished floor elevations at the lowest levels is at or above the surrounding grade. Therefore, a foundation dl'ain system is not required. It has been our experience in the arca and where clayey soils are present that local perched gronndwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can also create a perched condition. We recommenci below-grade construction, such as retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an undordrain and wall drain system. If the finished floor elevation of the proposed structure is revised to have a floor level below the surrounding grade, we should be contacted to provide recommendations for an underdrain system. All earth retaining structures should be properly drained, H-PVKUMAR Projeci No. 18-7-202 -7 - SURFACE DRAINAGE Positive surface drainage is an important aspect of the project to prevent wetting of the bearing soils. The following drainage precautions should be observed during construction and maintained at all times after the residence and shop have been completed: 1) Inundation ofthe foundation excavations and underslab areas should be avoided during construction. 2) Exterjor backfill should be adjusted to near optimLlm moisture and compacted to at least 957o of the maximum standard Proctor density in pavement and slab areas and to at least 9OVo of the maximum standard Proctor density in landscape areas. 3) The ground surface sulrounding the exterior of the buildings 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 unpaved areas and a minimum slope of 3 inches in the first 10 feet in paved areas. 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 10 fèet from foundation walls. N.IMTTATXONS This str-rdy has been conducted in accorclance with generally accepted geotechnicai engineering principles and plactices 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 from the exploratory borings drilled at the locations indicated on Figure 1, the proposed type of construction and our experience in the area. Our services do not include determining the presence, prevention or possibility of rnold 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 ihe exploratory borings and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered H.PVKUMAR Project No. 18-7-202 -8- during construction appear different from those described in this report, we should be notified so that re-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to verify thai 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 fill by a representative of the geotechnical engineer. Respectfully Submitted, H-P+ KUMAR -þ** James H. Parsons, E.I. Reviewed by David A. Young, P JHP/kac ,:"1 6, H.PÑKUM¡/AR Project No.18-7-202 I Ê I: : toT l ccP SuBDlvtstoN PARCEL #21810s101293 BORING_"--_a_,.{ l I 3Jry E&*ÈrJ Ësrô4r.]Bteur& -*'*_ç.I PROPOSED RES IDENCE BORIN G 2 L to @N ô o t-z fo O ..æryi* PROPO D SHOP BUILDI B l,.eFd 5¡e Id åftC ldúbñ nè 4âg IRFøþff¿. ¡5¡221 ,1 (,/ú'rúl 25 0 0 APPROXIMATE SCALE-FETT 18-7 -202 H-PryKUMAR LOCAÏION OF TXPLORATORY BORINGS Fí9. 1 ¡ s I I Ê I BORING 1 BORING 2 BORING 3 0 0 21/12 WC=5.1 DD=97 -2OO=46 16/ 12 tNC=7.5 DD=1 1 0 35/12 WC=4.0 DD=119 5 53s/12 WC=6.5 DD= 1 06 36/12 46/12 WC=3.1 DD= 1 0B -200=27 10 33/12 102s/12 WC=8.4 DD=1 17 21/12 WC=5.5 DD=1 13 F LiJ LJ L! I-t-fLtJÕ 15 t.) FL¡ LJ LL I-F L L¡(f 25/12 WC=3.5 DD=1 27 41/12 32/12 WC=9.6 DD=118 20 15/ 12 48/ 12 WC=4.9 nñ- r to -200=66 20 1B/ 12 ZJ 33/12 252e/12 16/12 30 SHOP BUILDING R ESI DENC T 30 18-7 -202 H-PryKUMAR LOGS OF EXPLORATORY BORINGS Fig. 2 I ı ¡ I Ê ñ LEGEND TOPSOIL; ORGANIC SILTY CLAYEY SAND, FIRM, MOIST, DARK BROWN SAND (SM-SC); SILTY TO VERY SILTY, TYPICALLY CLAYEY, SCATTERED GRAVIL AND SMALL COBBLES, MEDIUM DENSE, SLIGHTLY MOIST, BROWN. CLAY (CL); SANDY TO VERY SANDY, SCATTERED GRAVEL AND SMALL COBBLES, VERY STIFF, SLIGHTLY MOIST, BROWN. RELATIVELY UNDISTURBED DRIVE SAMPLE; 2-INCH l.D. CALIFORNIA LTNER SAMPLE t1 /11 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 21 BLOWS OF A 140-P0UND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE THE CALIFORNIA OR SPT SAMPLER 12 INCHES. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON APRIL 2, 2O1B WITH A 4_INCH DIAMETER CONÏINUOUS FLIGHT POWER AUGER. 2, THE LOCATIONS OF ÏHE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 5. THE ELEVATIONS OF THE EXPLORÄTORY BORINGS WERE NOT MTASURED AND THE LOGS OF THE EXPLORATORY BORINGS ARE PLOTTED TO DEPTH. 4. THE EXPLORATORY BORING LOCATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5. ÏHE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWTEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWAÏER WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING 7. LABORATORY ÏEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSITY (PCf) (ASTM D 2216); -2Oo= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1 140) 18-7 -2A2 H-PryKUMAR LEGEND AND NOTES Fig.3 SAMPLE OF: Silly Cloyey Sond Grovel FROM:Boringl@5' WC = 6.3 %, DD = 106 pcf with ii i-? \ not b. reproduc.d, wilhoúl the wdttèn opp.ovol of ond ßsociotes. lnc Ssell Coñsolidolion te3ting pedormed in occordonce w¡lh Æru D-4546. ¡ I I I I I f I I I i,t. I l I I I i.l- li -i- i -liil i'lli ll I i l -,+ii tii, l: Iitti I l I I I l I i j I I ,1 i : l I 1 I i I i I l i i '1 ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING i I I I I i r I I I i I -..1. I lt' I I I I l I i I I -i I ¡ 1 i f, I I i I I ,l l I I lr rl I -r f l l ,i o JJ LJ =Ø -l z z tr Õ Jo(n z.o -6 -7 .0 APP t0 18-7 -2A2 H-PryKUMAR SWILL-CONSOLIDATION TEST RTSULTS li9. 4 E I SAMPLE OF: Sondy Cloy with Grovel FROM: Boring 1 @ 15' WC = 3.5 %, DD = 127 pcÍ I I I I l I I I l NO MOVEMENT UPON WETTING { L I I \l \r t\ l i I I .i. I Ì à( JJ trl =(n I zo t-- of (nz UO J JU =tn I zo F- ô:oazoO 0 -1 -z _J 0 -l -2 2 -J 1.0 APPLIED PRESSURE _ KSF 100 SAMPLE OF: Silty Cloyey Sond wilh Grovel FROM:Boring2e^2.5' WC = 7.5 %, DD = 110 pcfI I I I I I j I l II I ! I l: i l I I .t J l l I l I I I 'i'.- Ì I ij';-'' ' i- i- ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING Kùmar ond bsociot.s, lnç.swell Consôlidolioh tcst¡ñ9 pêdormêd ¡n occo¡donc. with Añ D-4546. full, *ithout thc vriH¿n opprovol of 1.0 100 18-7 -202 H-PryKUMAR SWELL-CONSOLIDATION TEST RTSULTS Fig. 5 9 É l l I i I l SAMPLE OF: Sondy Cloy with Grovel FROM: Boring2@ 1A' WC = 8.4 %, DD = 117 pcf Ì I]__ I I I EXPANSION UNDER CONSTANT PRESSURE UPON WETTING \ l l I l I I I I ì ì I I I I -l l l 2 0 -1 _L _z -4 0 -1 _z JJ t¡J =tn I z.o Ê o =o(n z. O --JJ Lil =TN z t- Õ Jo(nz O 1.0 APPLIED PRESSURE - KSF APPLIED PRESSURE - KSF 10 10 100 SAMPLE OF: Siliy Cloyey Sond with Grovel FR0M: Boring 5 @ 10' WC = 5.5 %, DD = 113 pcf I I l I l I I I l i L I I l l l ì I l l i 1 I i li ii i I I I l i I I I l i ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING :l li l l I I l lhes. tcs! resuhs opply oñly to th. soñplês t¿ded. lh¿ tlsìi¡g rcpod sholl not bc r¿produccd, cxccpt in flrl, without th€ w.iRcñ opprovol of Xúmor ond Associolcs, lnc. Swcll Consolidotioñ t6sti¡9 p¿do.med iñ occordaÀc. w¡ü ASM 0-4546. I l _A 1.0 100 18-7 -202 H-PryKUMAR SWTLL_CONSOLIDATION TTST RTSULTS Fis.6 FI-HÈKUIVIAH TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Pnoject f$o. '! 8-7-202 UNCONFINED COMPRESSIVE STRENGTH SOILTYPE Very Silty Clayey Sand with Gravel Silty Clayey Sand with Gravel Sandy Clay with Gravel Silty Clayey Sand with Gravel Sandy Clay with Gravel Sandy Clay Silty Clayey Sand with Gravel Silty Clayey Sand with Gravel Silty Clayey Sand with Gravel Sandy Clay with Gravel ATTERBERG LIMITS PLASTIC INDEX (%l LIQUID LIMIT (%l NATURAL DRY DENSITY GRADATION GRAVEL (%) SAND (%) PERCENT PASSING NO.200 SIEVE 46 66 27 91 106 r2l 110 1t7 129 119 108 113 118 LOCATION NATURAL MOISTURE CONTENTBORINGDEPTH 5 I 6.3 3.5 7.5 8.4 4.9 4.0 3.1 5.5 9.6 zYz 5 I 5 2Vz 10 20 2V2 5 10 1 5 I 2 3