The URL can be used to link to this page

Home My WebLink AboutSubsoils Study for Foundation Designi' I"¡r*.rrtir -P,-.'lak L,-eorechnical. i nc 50lir Ct'urrtr R.r¡J l5i Gicrrç...:.ì Sl.¡in.gs, CLrl.rraclo S l60l f 11.1¡-¡s' ; !) j ¡-t- !:l i - l!)$'\ HEPWORTH - PAI/VLAK GEOTECHNICAL Fnt, ,(.17t-94í-S"{i4 erìail: h¡.gec@h¡.getrtech.ct-rtr-t ST'BSOIL STT]DY FOR T'OUNDATION DESIGN PROPOSED RESIDENCE LOT 9, BLOCK 7, TIIE RESERVE AT BATTLEMENT CREEK VILLAGE MEADOW CREEKDRTVE BATTLEMENT MESA, COLORADO JOB NO.106 0987 NO\/EIìdBER 30,2006 PREPARED FOR: TRA\rIS PREBLE 78 PROMONTORYPLACE PARACIIUTE, COLORADO 8I.635 H Pirrker 3tr3-841-7119 o Colorar{oSprings 719-633-5567 r Sih'ertirorne 970-468'i989 TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PR.OPOSED CONSTRUCT]ON. SITE CONDITIONS FIELD EXPLORATION...... SUBSURFACE CONDIT]ONS.. DESIGN RECOMMENDATIONS............ FOUNDATIONS FLOOR SLABS SURFACE DRAINAGE ......"....... LIMTTATIONS .--..-......... FIGURE 1 - LOCATION OF EXPLORATORY BORING FIGURE 2 -LOG OF EXPLORATORY BORING FIGURE 3 - LEGEND AND NOTES FIGURES 4 AND 5 - SV/ELL-CONSOLIDATION TEST RESULTS TABLE I- SUMMARY OF LABORATORY TEST RESULTS -1 a-L- -2- J 3 4 5 5 PURPOSE AND SCOPE OF STUDY This report presents rhe results ofa subsoil study for a proposed residence to be located on Lot 9, Block 7,The Reserve at Battlement Creek Village, Meadow Creek Drive. Battlement Mesa, Colorado. The project site is shown on Figure l. The pulpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with our agreement for geotechlical engineering services to Travis Preble dated November 20,20A6. An exploratory boring was drilled on the lot to obtain information on the general 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 {ield exploration and laboratory testing were analyzedto develop recommendations for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained dwing this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered' PROPOSED CONSTRUCTTON The proposed residence will be a single story, wood frame stmcture with an attached garcge. Ground floor will be structural over a crawlspace for living areas and slab-on- grade in the garage. Grading for the structure is assumed to be relatively minor with cut depths berween about 3 to 4 fcet. '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' iobNo. l0ó0987 cå8tecn -2- SITE CONDITIONS The site was vacant al the time of our field exploration- The ground surface is relatively l'lat with a gentle slope down to the north. There is about 2 to 3 feet of elevation difference across the lot. Vegetation consists of sagebrush, grass and weeds. FIELD EXPLORATION The field exploration for the project was conducted on November 22,2006. Ane exploratory boring was drilled at the location shown on Figure I to evaluate the subsurface conditions. The boring was advanced with 4 inch diameter continuous flight augers powered by a truck-mounted CME-458 drill rig. The boring was logged by a representative of Hepworth-Pawlak Geotechnical, Inc- Samples of the subsoils were taken with 1% inch and 2inch I.D. spoon samplers. The samplers were driven into the subsoils 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-t 586. 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 Log of Exploratory Boring, Figure 2- The samples were returned to our laboratory for review by the project engineer and testing. ST'BSIJRFACE CONDITIONS A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The subsoils consist of about I foot of topsoil overlying stiff to hard, slightly sandy to sandy silt and clay. Dense basalt fragments up t0 boulder size in a sandy silt and clay matrix was encountered beneath the silt and clay at a depth of about 12 feet. JobNo- 1060987 cåFtecrt J- Laboratory testing perfbrmed on samples obtained from the boring included natural moisture content, density and finer than sand size gradation analyses- Results of swell- consolidation testing performed on relatively undisturbed drive samples of the silt and clay, presented on Figures 4 and 5, generally indicate low to moderate compressibility under conditions of loading and '*'etting. The sample from Boring 1 at 5 feet showed a minor collapse potential (settlement under constant load) when wetted. The sample from Boring 1 at l0 feet showed a low expansion potential when wetted under a constant light surcharge. The laboratory testing is summarized in Table l. No free 'water was encountered in the boring at the time of drilling and the subsoils were slightly moist. DESIGN RECOMMENÍDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural subsoils. The design and construction criteria presented below should be observed for a spread footing foundation system - 1) Footings placed on the undisturbed natural subsoiis should be designed for an allowable bearing pressure of 1,500 psf. Based on experience, we 3) expect settlement/heave of footings designed and constructed as discussed in this section will be about I inch or less- Addítional movement could occur if the bearing soils become wetted. The footings should have a minimum width of l8 inches for continuous walls and 2 feet l'or ísolated pads. Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for liost protection. 2) .lob No. 106 0987 cåEtecrt -4- 4) Placemenl of foundations at least 36 inches below exterior grade is typically used in this area. Continuous foundation \ilalls should be reinf-orced top and botlom to span Iocal anomalies such as by assuming an unsupported length of at least l2 feet. Foundation walls acting as retaining structures should also be designed to resist a lateral earth pressure colresponding to an equivalent fluid unit weight of at least 50 pcf for the on-site soils as backfill. The topsoil and any loose or disturbed soils should be removed and the footing bearing Ievel extended down to the firm natural soils. The exposed soils in fboting area should then be moistened and compacted. A representative ofthe geotechnical engineer should observe all footing excavations prior to conclete placement to evaluate bearing conditions. 5) 6) FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to suppon lightly loaded slab- on-grade construction. The silt and clay soils are typically compressible when wetted and precautions should be taken to prevent wetting of the subgrade soils. 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 minimttm 4 inch layer of sand and gravel, such as road base, should be placed beneath interior slabs-on-grade for subgrade support. This material should consist of minus 2 inch aggegate with at least 500/o retained on the No. 4 sieve and less fhan 12Yo passing the No. 200 sieve. AII fill materials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a moisture content near optimum. Required hll can consist of the on-site soils devoid of vegetation, topsoil and oversized rock. Job No. I0ó 0987 eåEtecn -5- SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: I) Inundation of the foundation excavations and underslab areas should be avoided during conslruction. 2) Exterior backfill should be adjusted to near oprimum moisture and compacted to at least 95% of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proclor 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 recolnmend a minimum slope of 6 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) Irrigation sprinkler heads and landscaping which requires regular heavy irrigation, such as sod, 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 ât 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 boring drilled ât the location 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 mold or other biological contaminants (MOBC) developing in the future, If the client is concerned aboul MOBC, then a professional in this special fìeld of practice should be consulted. Our findings include extrapolation of the subsurface conditions identified at lobNo.1060987 cåEtecn -6- the exploratory boring and variations in the subsurfäce conditions may not become eviclent until excavation is performed. If conclitions cncountered during construction appear different from those described in this reporl, we should be notifìed 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 ínterpretations by others of our information. As the project evolves, we should provide continued consultalion and fìeld services during construction to review and monitor the implementation of our recommendations, and to verífy that the recommendations have been appropriately interpreted. Signifìcant 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 fìll by a repr esentative of the geotechnical engineer. Respectfully Submitted, HEPWORTH - PAWLAK G Jordy Z. Adamson, Jr-, P Reviewed by INC S*ñ-"^* Steven L. Pawlak, P.E JZAlksw JobNo- 1060S87 cåFtecL APPROXIMATE SCALE 1 " :30t LOT 10 BENCH MARK: GROUND AT PROPERTY CORNEH; ELEV. = 100.0', ASSUMED. I I LOT 9 BLOCK 7 BATTLEMENT CREEK VILLAGE UJ E,ô \¿ul LU(r CJ =oo tl-l BORING 1 o LOT 8 MEADOW CREEK DRIVE Figure 1LOCATION OF ËXPLORATORY BORING1 06 0987 BORING 1 ELFy'.: 101' 105 105 100 100 24112 wc:6.8 DD:108 95 14112 WC:3.6 DD=98 -2flD:82 95 o)ot! co (ú ot 90 43112 WC:6.9 DD=117 90 o) 0)LL co.Fñ o ul 85112 85 B5 3511 80 80 NOTE: Explanation of symbols is shown on Figure 3. 106 0987 LOG OF EXPLORATORY BORING Figure 2 LEGEND TOPSOIL; sandy silt and clay, organics, roots, firm, moist, slightly moist, dark brown- CLAY AND SILT (CL-ML); stightly sandy to sandy, stiff to hard, slightly moist, brown, slightly to moderately calcareous. ffi BASALT GRAVELAND COBBLES (GC); in a sandy silt and clay matrix, dense, slightly moist, brown F I Relatively undisturbed drive sample; 2-inch l.D. California liner sample. 24112 Drive sample; standard penetration test (SPT), 1 3/8 inch LD. split spoon sample, ASTM-1586. Drive sample blow count; indicatesthat 24 blows of a140 pound hammer falling 30 inches were required tô drive the Galifornia or SPT sampler 12 inches. Depth at which boring caved following drilling.-+ NOTES: i. The exploratory boring was drilled on November 22,2AO6 with a 4-ínch diameter continuous flight power auger. 2. Theexploratory boring location was rneâsured approximately by pacing from features shown on the site plan provided. O. The exploratory boring elevation was measured by instrument level and refers to the Bench Mark shown on Figure 1 4. The exploratory boring location and elevation should be considered accurate only to the degree implied by the method used. S. The lines between materials shown on the exploratory boring log represent the approximate boundaríes between materialtypes and transítions 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 Resulis: WC : Water Content (7.) +4 = Percent retained on the No.4 sieve -200 : Percent passing No. 200 sisre 106 0987 LEGEND AND NOTES Figure 3 0 òe Co'6a(l)o ÊoO 1 2 3 0.1 1.0 10 100 APPLIED PRESSURE - ksf 0 ès1 co'ı Øt(l)ã Eoo3 4 0.1 10 100 APPLIED PRESSURE - ksf Moisture Content : 6.8 Dry DensitY = i08 Sample of: $¿¡6y Silt and Clay From: Boring 1 at 2 Feet percent pcf t 'No movement upon wetting Moisture Content : 3.6 Dry DensitY = 98 Sample of: $a¡fly $i¡ From: Boring 1 at 5 Feet percent pcf .Compression upon wetting I ) 1.0 106 0987 SWELL-CONSOLI DATION TEST RESU LTS Figure 4 Moisture Content: 6.9 Dry DensitY : 117 Sample of: Sandy Silty Clay From: Boring 1 at 10 Feet percent pcf Expansron upon wetting ì rOo\co'6c(s o-Xu Ico'6 at(¡) o- Eo C) 1 0 'l 2 0.1 10 100 APPLIED PRESSURE - ksf 1.0 106 0987 SWELL-CONSOLI DATION TEST RESU LTS Figure 5 HEPWORTH-PAWLAK GEOTECHNICAL, INC,TABLE 1SUMMARY OF LABORATORY TEST RESULTSJob No. 106 0987SOIL ORBEDROCK TYPESandy Silt and ClaySandy SiltSandy Silty CIayUNCONFiNEDCOMPRESSIVESTRENGTH(PSF)ATTERBERG LIMITSPLASTiCINDEX(o/o\LIQUIDUMIT(o/o)PERCENTPASSINGNO, 200SIEVE82GRADATIONSAND(%)GRAVEL(o/o)NATURALMOISTURECONTENTNATURALDRYDENSTIVi0898lt76.83.66.9SAMPLE LOCATIONDEPTHlft)2510BORINGI