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HomeMy WebLinkAbout; 5580 El Camino Real; Soils Report; 1967-02-21PHlLlP HENKING BENTOW c”Lo,oI*r. CIY,‘ L*GI*nc” February 2 I, 1967 SAN DIIT.a s.,.?Ies. LA MC**: .ee-,#I‘ Remlap, Ltd. P. 0. Box 1111 Carl&ad, California Subject: Project No. 67-I-13DE Preliminary Soils Investigation Unit ho. 1 of the Proposed Carlsbad industrial Park ENGINEERING DEPT. LIBRARY El Camino Zeal, north of City of Carlsbad Palomar Airport Road 2075 Las Patmas Drive Carlsbod, California Car&act CA 92009-4859 Gentlemen: This is to present the results of a preliminary soils investigation conducted ot the subject site. The obiectives of the investigation were to determine the existing soil conditions and to perform certain field and laboratory tests in order that engineering recommendations could be made for the development of the site. Field Investigation Four pits were excavated by hand@ depths of 3:3_ta3~.3 feet below the existing ground surface at the locations shown on the attached Drawing ‘%-~T;-entifIed “Location of Test pits . I’ Field density tests were taken in Pik 1, 2 and 3 and loose representative bag samples were obtained from Borings 2, 3 and 4 for laboratory testing. The soils were visually class- ified by field identification procedures in accordance with the Unified Soil Classification Chart? A continuous log of the soils encountered in the pits was retarded at the time of excavation and is presented below: LOG OF TEST PITS Pit Depth Group No. in Feet Symbol Soil Classification 1 o-3 .o CL Brown to dark brown fine sandy clay (moist and loose to OS’, then very moist and medium firm) 3.0-3.3 SC Yellow brown and brown clayey very fine sand (moist, firm) * A simplified description of this classification system is presented in the attached Appendix A at the end of this report. - Pit No. - 2 3 - 4 - - - - LOG OF TEST PITS (CONT.) Depth Group in Feet Symbol o-2.9 CL 2.9-3.2 SC Soil Classification Brown fine sandy clay (very moist, medium soft to ‘2 .O feet, then medium firm) Yellow brown and gray brown clayey very fine sand (moist, firm) o-2 5 CL 2.5-3.0 CL o-3.3 CL (Proposed Borrow Area) Brown fine sandy clay with few scattered pea gravel (very moist, medium soft to 1 .8 feet, then medium firm) Yellow brown very fine sandy cloy (moist, firm) Brown fine sandy clay (moist, ‘soft to 1 .O foot, then medium firm to firm) Yellow brown clayey very fine sand encountered ot 3.3 feet The resutk of the field density tests are presented in the following tabulation: Depth of Maximum Test Below Fie Id bY bY Pit Exist. Surface Moisture Density Density No. in Feet % dry wt Ib/cu ft Ib/cu ft 1 1.0-1.5 20.8 98.9 108.0 2 1.0-1.5 28.2 90.2 108.0 2 2.0-2.5 25.1 95.7 108.0 3 1.0-l .5 24.0 96.9 108.0 Laboratory Tests * Percent Compaction 91.5 83.5 88.6 89.6 Compaction tests were performed on representative samples of the soils in order to establish compaction criteria. The soils were tested according to a modified A .S , T .M. D698 method of compaction which uses 26 blows of a 10 pound hammer dropping 18 inches on each of 3 layers in a 4 inch diameter l/30 cubic foot meld. The results of the tests are presented as follows: Maximum Optimum Mois- Pit Depth Dry Density ture Content No. in Feet Soi I Description Ib/cu ft % dry wt 2 1.0-l .5 Fine sandy clay 108.0 17.1 3 2.5-3.0 Very fine sandy clay 107.9 18;O 4 2.0-2.5 Fine sandy clay 111.0 15.4 * The general procedures used for the laboratory tests are described briefly in Appendix 8. BENTON &wNEERING. INC. Expansion tesk were performed on representative samples of the soils encountered to determine their volumetric change characteristics with change in moisture content. The recorded expan- sions of the samples are presented as follows: - - - Pit No. 1 2 3 3 ‘4 Depth of Sample, in Feet 1.0-1.5 1.0-I .5 1.0-1.5 2.5-3 .o 2.0-2.5 Soi I Description Fine sandy clay (Sample remolded to in-place field density) Fine sandy cloy (Sample remolded to 93% of maximum dry density) Fine sandy cloy (Sample remolded to in-place field density) Fine sandy clay (Sample remolded to 92% of maximum dry density) Fine sandy clay (Sample remolded to 91% of maximum dry density) Percent Expansion Under Unit Load of 500 Pounds per Square Foot from Air Dry to Saturation 4.27 3.94 6.20 5.65 5.66 A load-consolidation test was performed on a sample of the soil between 1 .O and 1.5 feet in Pit 2 remolded to the in-place field density. The results of this test are presented graphically on Drawing No. 2, entitled “Consolidation Curve.” Discussion and Recommendations A. It is concluded from the results of the expansion tesk that nearly all the soils encountered in the investigation would be considered as “expansive” with respect to volumetric change with change in moisture content. Therefore, in order to minimize possible detrimental effects of these soils, it is recommended the either Alternate 1 be followed, or the following special design and precau- tions in Alternate 2 be included in any design of foundations for structures. Alternate 1 . Import select nonexpansive silty sand or sand soils to the site and compact these to at least 90 percent of maximum dry density to a depth of 3 feet below finish- ed grade and to a horizontal distance of 5 feet outside the buildings. If this procedure is adopted, then special footing and slab design would not be required. Alternate 2. If the on site “expansive” soils are to remain or to be placed and compacted within the upper three feet below finished grade, then the following, on pcge 4, is recommended: BENTON ENGINEERING. ,NC. -. - -- -. .~~ ..- .- -, 1. Use continuous footings throughout and place these at a minimum of 1.5 feet below the lowest adjacent final ground surface. 2. Reinforce and interconnect continuously with steel bars all interior and exterior footings with one #5 bar at 3 inches above the bottom of the footing and one #5 bar placed 1 l/2 inches below the top of the stem of the footing. 3. Reinforce all concrete slabs with 6” x 6” by #IO x #IO woven wire mesh. 4. Place a minimum of 4 inches of clean sand beneath all concrete slabs and also provide o waterproof membrane 1 inch below the top of this sand layer. 5. Separate the floor slabs from the footings by l/2 inch thickness of construction felt or equivalent to allow independent movement of the slab relative to the footings. 6. Provide positive droinoge away from all perimeter footings to a horizon- tal distance of at least 6 feet beyond foundations. B. Footings placed on either the medium firm to firm natural soils or on filled ground, consisting of the on-site soils uniformly compacted to at least 90 percent of maximum dry density, may be designed using an allowable bearing value of 2,000 pounds per square foot. It is concluded from the load-consolidation test data that the settlements of one foot wide footings placed at 1.5 feet that are designed as recommended and founded in either the medium firm to firm natural soils or in prop- erly compacted fill soils are estimated to be less than l/8 inch. C. All filled ground should be placed and uniformly compacted to at least 90 per- cent of maximum dry density in accordance with the attached “Standard Spec- ifications for Placement of Compacted Filled Ground,” Appendix AA. It is recommended that the “expansive” sandy clay soils be placed and compacted at moisture contents 3 to 5 percent wetter than optimum moisture in order to reduce their potential expansion. If any soils types are encountered during the grading operation that were not tested in this investigation, additional laboratory tests will be conducted in order to determine their physical characteristics, and supplemental reports and recommendations will automatically become a part of the specifications. Respectfully submitted, BENTON ENGINEERING, INC. By&C?& Distr: (4) Addressee R. C. Remer (1) Donald Holly BENTON ENGINEERING. INC. - -~ - - - - - - - - - - - I LOCATION OF TEST PITS PROJECT NO. I BENTON I DRAWING NO. 67-I-13DE ENGINEERING, INC. 1 - -. - - - - -. ..- - - - .- .- LOAD IN KIPS PER SQUARE FOOT 92.1 lb/w fi 92.1 lb/w fi o Indicates percent consolidation at field moisture l Indicates percent consol idotion after saturation PROJECT NO. 67-l-13DF DRAWINQ NO. BENTON ENGINEERING, INC. 2 - - - ,- - - PWl‘lP HENKING BENTON P”lSIDm4T. ClYlL lNC,NrL” BENTON ENGINEERING. INC. APPLIED SOlL MECHANICS - FO”ND*TIONs (17.1 El. CAJON .O”LEYARD SAN DIEGO. C*LIFcRNI* DPIIS APPENDIX AA STANDARD SPECIFICATIONS FOR PLACEMENT OF COMPACTED FILLED GROUND 1. General Description. The objective is to obtain uniformity and adequate internal strength rn frlled ground by proven engineering procedures and tests so that the proposed structures may be safely supported. The procedures include the clearing and grubbing, remOval of existing structures, preparation of land to be filled, filling of the land, the spreading, and compacticn of the filled areas to conform with the lines, grades, and slopes as shown on the accepted plans. The owner shall employ a qualified soils engineer to inspect and test the filled ground as placed to verify the uniformity of compaction of filled ground to the specified 5Q percent of maximum dry density. The soils engineer shall advise the Owner and grading cartractor immediately if any unsatisfactory conditions are observed to exist and shall have the authaity to reject the compacted filled ground until such time that carective measures are taken necessary to comply with the specifications. It shall be the sole responsibility of the grading contractor to achieve the specified degree of compaction. 2. Clearing, Grubbing, ond Preparing Areas to be Filled. (a) All brush, vegetation and any rubbish shall be removed, piled, and burned or other- wise disposed of so as to leave the areas to be filled free of vegetation and debris. Any sdt, swampy Q otherwise unsuitable areas shall be corrected by draining or re- moval, or both. (b) The natuml ground which is determined to be satisfactory fa the support of the filled ground shall then be plowed or scarified to a depth d at least six inches (6’9, and until the surface is free from ruts, hummocks, or other uneven features which would tend to prevent uniform compacticn by the equipment to be used. (c) Where fills are made cn hillsides or exposed slope areas, greater than IO percent, horizantal benches shall be cut into firm undisturbed natural ground in arder to pro- vide both lateral and vertical stability. This is to provide a horizontal base so that each loyer is placed and compacted on a horizontal plane. The initial bench at the toe of the fill shall be at least 10 feet in width on firm undisturbed natural ground at the elevation of the toe stake placed at the natural angle of repose ar design slope. The soils engineer shall determine the width and frequency of all succeeding benches which will vary with the soil conditions and the steepness of slope. - - APPENDIX AA -2- - - - - - - - - - - (d) After the notural ground has been prepared, it shall then be brought to the proper mois- ture content and comljocted to not less than ninety percent (90%) of maximum density in accordance with A.S.T.M. D-698 method modified to use 26 blows of o lo-pound hammer falling from 18 inches on each of 3 layers in a 4” diameter cylindrical mold of o 1/3Oth cubic foot volume. 3. Materials and Special Requirements. The fill soils shall consist of select materials so graded that at least 40 percent of the material passes a No. 4 sieve. This may be obtained from the excavation of banks, borrow pits of any other approved sources and by mixing soils from one or more sources. The material used shal I be free from vegetable matter, and other de- leterious substances, and shall not contain rocks or lumps of greater than 6 inches in diameter. If excessive vegetation, rocks, or soils with inadequate strengthor other unctc- ceptable physical characteristics are encountered, these shall be disposed of in waste areas OS shown on the plans or as directed by the soils engineer. If during grading operations, soils not encountered and tested in the preliminary investigation are found, tests on these soils shall be performed to determine their physical characteristics. Any special treatment recommended in the preliminary or subsequent soil reports not covered herein shall become an addendum to these specifications. The testing and specifications for the compaction of subgrade, subbase, and base materials for roads, streets, highways, or other public property or rights-of-way shall be in accordance with those of the governmental agency having jurisdiction. 4. Placing, Spreading, and Compacting Fill Materials (a) The suitable fill material shall be placed in layers which, when compacted, shall not exceed six inches (6”). Each layer shall be spread evenly and shall be thoroughly mixed during the spreading to insure uniformity of material and moisture in each layer. (b) When the moisture content of the fill material is below that specified by the soils engin- eer, water shall be added until the moisture content is near optimum cts specified by the soils engineer to ctssure thorough bonding during the compacting process. (c) When the moisture content of the fill material is above that specified by the soils engineer, the fill material shall be aerated by blading and scarifying or other sotis- factory methods until the moisture content is near optimum as specified by the soils engineer. (d) After each layer has been placed, mixed end spread evenly, it shall be thoroughly compacted to not less than ninety percent (9%) of maximum density in accordance with A.S.T.M.,D-698 modified as described in 2(d) above. Compaction shall be accomplished with sheepsfoot rollers, multiple-wheel pneumatic-tired rollers, or other approved types of compaction equipment, such as vibratory equipment that is specially designed for certain soil types. Rollers shall be of such design that they will be able --U3v.Y .Yr_l~..-.Ym I.“- - - APPENDIX AA -3- - - - - - - - to compact the fill material to the specified density. Rolling shall be accomplished while the fill material is at the specified moisture content. Rolling of each layer shall be continuous over ik entire area and the roller shall make sufficient trips to insure that the desired density has been obtained. The entire areas to be filled shall be compacted. (e) Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equip- ment. Compacting operations shall be continued until the slopes are stable but not too dense for planting and until there is no appreciable amount of loose soil on the slopes. Compacting of the slopes shall be accomplished by backrolling the slopes in increments of 3 to 5 feet in elevation goin or by other methods producing satisfactory resulk. (f) Field density tests shall be made by the soils engineer for approximately each foot in elevation gain after compaction, but not to exceed two feet in vertical height between tesk. Field density tests may be taken at intervals of 6 inches in elevation gain if required by the soi Is engineer. The location of the tests in plan shal! be so spaced to give the best possible coverage and shall be taken no farther apart than 100 feet. Tests shall be taken on corner and terrace Iok for each two feet in elevation gain. The soils engineer may take additional tesk as considered necessary to check on the uniformity of compaction. Where sheepsfoot rollers are used, the tesk shall be taken in the com- pacted material below the disturbed surface. No additional layers of fill shall be spread until the field density tests indicate that the specified density has been obtained. (9) The fill operation shall be continued in six inch (6”) compclcted layers, as specified above, until the fill has been brought to the finished slopes and grades as shown on the accepted plans. 5. Supervision. Sufficient inspection by the soils engineer shall be maintained during the filling and compacting operations so that he can certify that the fill was constructed in accordance with the accepted specifications. 6. Seasonal Limits. No fill material shall be placed, spread, or rolled if weather conditions - - increase the moisture content above permissible limits. &hen the work is interrupted by rain, fill operations shall not be resumed until field tests by the soils engineer indicate that the moisture content and density of the fill are as previously specified. - 7. Limiting Values of Nonexpansive Soils. Those soils that expand 2.5 percent or less from air dry to saturation under a unit load of 500 pounds per square foot are considered to be nonexpansive. - 8. All recommendations presented in the “Conclusions” section of the attached report are a part of these specifications. - mLN?oN LNOINLLIINO. INC. - - - - - - - .- - - - - - - - - - - BENTON ENGINEERING, INC. APPLIED 801L MECHANICS - FOUNDATIONS 87.1 EL CWON BOULEVARD SAN DIEGO. CALIFORNIA 82113 PHlLlP “ENKINa BENTON P”1S101?41. ClVlL EYTINl!II APPENDIX A Unified Soil Classification Chart* SOIL DESCRIPTION GROUP SYMBOL I. COARSE GRAINED, More than half of material is larger than No. 200 sieve size.** GRAVELS CLEAN GRAVELS m half of coarse fraction is larger than No. 4 sieve size but SmallerGRAVELS WITH FINES than 3 inches (Appreciable amount of fines) SANDS CLEAN SANDS -than half of coarse fraction is smaller than No. 4 sieve size SANDS WITH FINES (Appreciable amount of fines) II. FINE GRAINED, Mere 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 grovels, gravel-sand mixtures, little cr no fines. Poorly graded gravels, gravel-sand mixtures, little or no fines. Silty gravels, poorly graded gravel- sand-silt mixtures. Clayey gravels, poorly graded gravel- sand-cloy mixtures. SW SP SM SC Well graded sand, gravelly sands, little or no fines. Poaly graded sands, gravelly sands, little or no fines. Silty sands, poaly 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, sondy silt or clayey-silt-sand mixtures with slight plasticity. Inorganic clays of low to medium plas- ticity, gravelly clays, sandy cloys, silty clays, lean clays. Organic silts and organic silty-clays of low plasticity. lnaganic silts, micaceous cr diatuno- ceous fine sandy or silty soils, elastic silts. lnaganic cloys of high plasticity, fat clays. Organic cloys of medium to high plasticity. PT Peat and other highly organic soils. TYPICAL NAMES SAH OILTO: *a,-se,. LA MIS.: *se-sss. * Adcpted by the Corps of Engineers and Bureau of Reclamation in January, 1952. ** All sieve sizes on this chart are U.S. Standard. - - - - - - - - - - - ,- - - - - PHlLlP HENKING BENTON .“ISIDINI CIVIL LHOI”.zL” BENTON ENGINEERING, INC. APPLIED 501L MEC”&NICS - FO”NDATlON* 6741 EL CAJON BOULEVARD SAN DIEGO. C*LIFORNI* 92115 SAN DIIGO: sa.%s6s, LA MI*A: 46D.s*s. APPENDIX B Sampling 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 artside diameter, with a special cut- sting 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 token fcr laboratory tests, 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 tests. 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 sample is obtained. Shear Tests The shear tests are run using a direct shear machine of the strain control type in which the rate of defwmation is appra*imately 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 sampling. In some instances, samples are sheared under various normal loads in ader to obtain the internal angle of friction and cohesion. Where considered necessary, samples are saturated and drained before shearing in order to simulate extreme field moisture conditions. Consolidation Tests The apparatus used for the consolidation tests is designed to receive one of the one inch high rings of soil as it canes from the field. Loads are applied in several increments to the upper surface of the test specimen and the resulting defcrmotions are recorded at selected time intervals for each increment. Generally, each increment of load is maintained cn the sample until the rate of deformation is equal to or less than l/lOOoO inch per hour. Porous stones are placed in contact with the tcp 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 fa at leost 48 hours prior to placing into the expansion apparatus. A unit Iwd d 500 pounds per square foot is then applied to the upper porous stone in contact with the tap of each somple. Water is permitted to cantact both the top and bottom of each sarrple through porous stones. Continuous observations are made until downward movement stops. The dial reading is recorded and expansion is recorded until the rote of upward movement is less than l/10000 inch per haur.