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HomeMy WebLinkAbout; 5580 El Camino Real Industrial Park; Soils Report; 1971-02-22BENTON ENGINEERING. INC. APPLIED SOlI. MECHANICS - FOUNDAT,ON* 6741 EL CAJON BOULE”ARD SAN DIEGO. CALIFORNIA 07.11, PHIL,P IiENKINO BENTON P”~IID~NT. ClVlL L*O4*Ll!” February 22, 1971 srrr OILGO: !Ja3-?Ies. LA MIS*: .6S.,SS. Mr. Ralph Palmer P. 0. Box 1111 Carl&ad, California 92008 Subiect: Project No. 71-l-18E Preliminary Soils Investigation Car&d Industrial Pork I East side of El Camino Real North of Polomar Airport Road Carl&ad, Colifomia Gentlemen: - This is to present the results of a soils investigation conducted at the site of a proposed addition to the office for Magnadyne, Inc. 5580 El Comino Real, Carl&ad, California. This parcel is more particularly described as o portion of Lot 8, Ranch0 Aqua Hediondo, Mop No. 823, City of Carl&d, San Diego County, California. It is our undentonding that the proposed building oddition will be concrete tilt-up single story construction approximately 14 feet in height, with wall Icads estimated to be no more than 2670 pounds per lineal foot. - The objectives of the investigation were to determine the existing soil conditions ond physical properties of the soil and, through observation and laboratory testing, to determine the various physical pammeten of the soils so that recommendations could be made for the design of safe and economical foundations. In order to accomplish these obioctives, two borings were drilled and representative undisturbed samples were obtained for labomtory testing. ,- Field Investigation The borings were drilled, 24 inches in diameter, uring a truck-mounted rotary bucket-type drill rig ot locations inside the limits of the proposed building addition. Borings were drilled to depths of 6 and 7 feet below the existing ground surface. A continuous log of the soils encountered in the borings was recorded at the time of drilling and is shown in detail on Draw- ing No. 1, entitled “Summary Sheet.” The soils were visually and textumlly classified by field identification pra&dures in accordance with the Unified Soil Claaifieotion Chart. A simplified description of this classification system is presented in the attached Appendix A, at the end of this report. ENGINEERING DEPT. LIBRARY - City of Cartsbad 2075 Las Palmas Drive Cartsbaa CA 92009459 .- - - .- - - - - -~ - Undisturbed samples were obtained at frequent intervals in the soil ohead of the drilling. The drop weight used for driving the sampling tube into the soils was the “Kelly” bar of the drill rig which weighs 1623 pounds, and the average drop was 12 inches. The geneml proc- edures used in field sampling are described briefly under “Sampling” in Appendix 8. Labomtory Tesh Labomtory tests were performed on all undisturbed samples in order to determine the dry density, moisture content ond shearing strength. The results of these tests are presented on Dmwing No. 1. Consolidation tests were performed on representative samples in order to determine the laod-settlement characteristics of the soils. The results of these tests ore pre- sented on Dmwing No. 2, entitled “Consolidation Curves.” In order to determine the safe allowable soil bearing value,a saturated and drained direct shear test was performed ori a representative sample of the upper soils and the rdh are listed below: Boring No. 1, Sample No. 2 Depth: 2.5 feet Normal Load in kips/sq ft 0.5 1 .o 2.0 Minimum Maximum Angle of Shear Internal Apparent Load in Friction Cohesion kips/sq ft Degrees Ib/sq ft 1.54 12 1280 1.79 1.83 In oddition to the above labomtory tesk, an expansion test was performed on some of the clayey soils encountered to determine their volumetric change characteristics with change in moisture content. The recorded expansion of the sample is presented as follows: Percent Expansion Under Unit Lwd of Depth of 150 Pounds per Squore Boring Sample Sample, Soil Foot from Field No. No. in Feet Description Moisture to Soturation 2 1 1.5 Brown clay 0.42 The geneml procedures used for the labomtory tests ore described briefly in Appendix B. Discussion Soil Stmta Boring No. 1 - Cloy was encountered to a depth of 2.8 feet being soft in consistency to 2.0 feet and firm between 2.0 and 2.8 feet. This was underlain by very firm, silty claystone between 2.8 and 7.0 feet, the limit of the explomtion. BENION ENGINEERING. INC. Boring No. 2 - Clay was encountered in Boring No. 2 to a depth of 3.0 feet being soft in consistency ta 2.0 feet, firm between 2.0 and 2.5 feet and very firm between 2.5 and3.0 feet. This was underlain by very firm silty claystone between 3.0 and 6.0 feet, the bottom of the excavation. No free ground water was encountered in either of the two holes. Conclusions Based on the field investigation and the results of the lobomtory testing,it is concluded that the notuml soils ore competent load bearing strota that will adequately support the proposed build- ing without detrimental differentiol settlemenk. Consolidation task do indicate however, that the soil is sufficiently expansive to require special precautions in the design of footings for build- ings located where these expansive soils occur within three feet below the final ground surface. Recommendations It is recommended that the fallowing design procedures, which should minimize any damaging effeck due to soil expansiveness, be observed wherever the above-described expansive soils exist within the upper 3 feet below the final ground surface: 1. 2. 3. 4. 5. 6. 7. 8. Avoid the use of isolated interior piers. Use continuous footings throughout, and place these at a minimum depth of 16 inches below the lowest adjacent exterior final ground surface. Reinforce and interconnect continuously with steel bars all interior and exterior footings with one y5 bar at 3 inches obove the bottom of oil footings and one 15 bar placed 1 l/2 inches below the top of the stems of the footings. Exercise every effort to assure that the soil under the foundations and slabs has a uniform moisture content at least 1 ta 3 percent greater than optimum through- out the tap 3 feet below finished gmde at the time of placing the foundations and slabs. Reinforce oil concrete slabs with 6 x 6 - lO/lO welded wire fabric. Provide a minimum of 4 inches of clean sand or 6 inches of decomposed granite beneath all concrete slabs. provide a moisture vapor barrier 2 inches below slobs. Provide positive dminage away from all perimeter footings to a horizontal distance of at least 6 feet outride the building walls. Continuous footings embedded as recommended may be designed for dead plus live loads of up to 2500 pounds per square foot. BENTON ENOINEERING. INC Dtawing Nos. 1 and 2 and Appendices A and B are a part of this report. Respectfully submitted, BENTON ENGINEERING, INC. - BY . William G. Catlin, Civil Engineer - Distr: (4) Addressee (1) City of Carlsbod - Attention: Mr. Ray Green - - -- - - - _- - - - sENTON ENGINEERING. INC, - - - - - .- - - - - EORING NO.1 Qi I I q Brown, Moist, Soft 2oEl 1 Firm Gmy-brawn and Brown, Moist, Very Firm BORING NO. 2 Brown, Moist, Soft CLAY (Merges) SILTY. CLAYSTONE CLAY SILTY CLAYSTONE 3 0 - Indicates Undisturbed Drive Sample u&n g ti 0 - 0.8 6.5 - 16.2 8.2 - 0.8 23.6 98. 0.85 T-l- 24.71 W.{ 1.541 23.8 100.0 1.04 II 22.4 103.2 3.24 23.1 101.0 3.11 - PROJECT hu. 71-l-18E BENTON ENGINEERING, INC. DRAWING NO. 1 -- - - - - - ‘ - I - - OLIOATION CURVES LOAD Ill KIFS ?Ell SQUARE FOOl OQp 0.4 0.6 0.6 1.0 3 +3 E Y =+2 u z +1 !!I r" a 0 $ 1 5 s g2 : z i ! 0 INDICATE6 FERCENT CONSOLIOAlION AT FIELD MOISTURE . INDICATE6 ?ERCCNT CONSOLl0AlION AFTER SAlUI1AllON ORAWINQ NO. 71-l-18E - - - - - - - - - - - - - ,- BENTON ENGINEERING, INC. APPLIED SOIL MECHANICS ,- FOUNDATlONS e,*, EL CAJON BOULEYARD SAN DIEGO. CALIFORNIA 92115 PHlLlP “ENKING BENTON PRLIIDE+4,. ClVlL ENGINICI1 APPENDIX A Unified Soil Classification Chart” SOIL DESCRIPTION GROUP SYMBOL I. COARSE GRAINED, More than half of material is larger t&m No. 200 sieve size.** - GRAVELS CLEAN GRAVELS s half of coarse fraction is larger than No. 4 sieve size but smallerGRAVELS WITH FINES than 3 inches SANDS man half of coarse fraction is smol ler than No. 4 sieve size (Appreciable amount of fines) CLEAN SANDS SANDS WITH FINES (Appreciable amount of fines) II. FINE GRAINED, More than half of material is smaller than No. 200 sieve size.** SILTS AND CLAYS Liquid Limit Less than 50 SILTS AND CLAYS Liquid Limit Greater than 50 - Ill. HIGHLY ORGANIC SOILS GW GP GM GC Well graded gravels, gravel-sand mixtures, I ittle a no fines. Poorly graded gravels, gravel-sand mixtures, little or no fines. Silty gravels, poorly graded gravel- sand-silt mixtures. Clayey gravels, poorly graded grovel- sand-clay mixtures. SW SP SM SC Well graded sand, gravelly sands, little or no fines. Poorly graded sands, gravelly sands, little or no fines. Silty sands, pocsly graded sand-silt mixtures. Clayey sands, poorly graded sand-clay mixtures. ML CL OL MH CH OH Inorganic silts and very fine sands, rock flour, sandy silt or clayey-silt-sand mixtures with slight plasticity. Inorganic cloys of low to medium plas- ticity, gmvelly clays, sandy clays, silty clays, lean clays. Organic silts and aganic silty-clays of low plasticity. lnaganic silts, micoceous or diatuna- ceous fine sandy OT silty soils, elastic silts. lnaganic clays of high plasticity, fat clays. Orgclnic clays of medium to high plasticity. PT Peat and other highly organic soils. TYPICAL NAMES 8LN 0IcT-J: Sa%(16S. I.* MLS.: 409.,es. * Adopted by the Corps of Engineers and Bureau,of Reclamation in January, 1952. ** All sieve sizes on this chart are U.S. Standard. - - - BENTON ENGINEERING. INC. APPLlED SOIL MECHANlCS FO”ND*T,ONS 6744 EL CAJON BOULEVARD SAti DIEGO. C.4LIFORNIA 921,s - - .- - - - - .~ - - PHILIP “ENKING BEN~TON PITSIDLNT CIVIL LNGINELII Sampling APPENDIX B SAN DIICO: ,83-56Sl LA LIL,*: 4se.sss. The undisturbed soil samples are obtained by forcing a special sampling tube into the undisturbed soils at the bottom of the boring, at frequent intervals below the ground surface. The sampling tube consists of a steel barrel 3.0 inches outside diameter, with a special cut- ting tip on one end and a double ball valve on the other, and with a lining of twelve thin brass rings, each one inch long by 2.42 inches inside diameter. The sampler, connected to a twelve inch long waste barrel, is either pushed or driven approximately 18 inches into the soil and a six inch section of the center portion of the sample is taken for laboratory tesk, the soil being still confined in the brass rings, after extraction from the sampler tube, The samples are taken to the laboratory in close fitting waterproof containers in order to retain the field mois- ture until completion of the tesk. The driving energy is calculated as the average energy in foot-kips required to force the sampling tube through one foot of soil at the depth at which the sampie is obtained. Sheor Tests The shear tests ore run using a direct shear machine of the strain ccntrol type in which the rate of deformation is approximately 0.05 inch per minute. The machine is so designed that the tests are made without removing the samples from the brass liner rings in which they are se- cured. Each sample is sheared under a normal load equivalent to the weight of the soil above the point of sompl ing . In some instances, samples are sheared under various normal loads in order to obtain the internal angle of friction ond cohesion. Where considered necessary, samples ore saturated and drained before shearing in order to simulate extreme field moisture conditions. Consolidation Tesk The apparatus used for the consolidation tests is designed to receive one of the one inch high rings of soil OS it comes from the field. Loads are applied in several increments to the upper surface of the’ test specimen and the resulting deformations are recorded at selected time intervals for each increment. Generally, each increment of load is maintained on the sample until the rate of deformation is equal to or less than l/10000 inch per hour. Porous stones are placed in contact with the top and bottom of each specimen to permit the ready addition or release of water. Expansion Tests One inch high samples confined in the brass rings are permitted to air dry at 105°F for at least 48 hours prior to placing into the expansion apporotus. A unit load of 500 pounds per square foot is then applied to the upper porous stone in contact with the top of eclch sample. Water is permitted to contact both the top cmd bottom of each sample through porous stones. Continuous observations ore made until downward movement stops. The dial reading is recorded and expansion is recorded until the rate of upward movement is less than l/10000 inch per hour.