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HomeMy WebLinkAbout; Knob Hill; Soils Report; 1969-02-12SOIL ‘l‘L:S:l’IxG I‘.uwILiTORU OF NORTH COUNTY INC. \ra .,: 423 HALE AVE. - 4 ESCONDIDO, CALIF. 92025 ESCONDIDO-746.2333 OCEANSIDE-722-2125 February 12, 1969 D. A. Gannon Company -1 /0~3 A. Pi++-@ San Clemente, California Re: Job No. 69-20 Preliminary Soils Investigation Knob Hill, Carlsbad, California Dear Mr. Gannon: i . x,, In accordance with your request, we have completed the soils investigation of the subject property located NortherIy of Falcon Hills Subdivision, in Carlsbad, California. This report des- cribes the results of the investigation and inckdes the recomm- endations for the foundation design of the proposed structures. Respectfully submitted, SOIL TESTING LABORATORY OF NORTH COUNTY, INC. / / ,- ,’ ,, / D. A. GANNON CO. .“ILOI”* . DIYIL0.C”. D. A. (DON) OANNON I I J E. Brian Smith’ RCE 13, 817 EBS:ce TELEPHONES IO8 B. “IRWc5A SAN CLEMENTE. CILIC. WR OFF. tn.> de* 111, *es. tn4 .w lo74 ESCOND,DO PROJEDT 014 4s za*. :, . ; .- ENGINEERING DEPT. LIBRARY ciiy ol carlsbad 2075 Las Palmas Drive Girlsbad CA 92999-4859 APR 1 d 1369 CITY OF CARLSBAD EnglWW ,hwtment PRELIMINARY SOILS INVESTIGATION KNOB HILL CARLSBAD, CALIFORNIA JOB NO. 69-20 FOR D. A. GANNON COMPANY * /03E, /Y‘+“//n~~~ San Clemente, California BY SOIL TESTING LABORATORY OF NORTH COUNTY, INC. FEBRUARY 12, 1969 SOIL TESTING l~ABOl~A’J’Ol1Y OF NORTH COUNTY INC. TABLEOFCONTENTS - I. General Information II. Purpose of Investigation III. Field Investigation A. Surface Conditions B. Test Holes C. Soils Encountered IV. Laboratory Tests v. Conclusions VI. Recommendations . . . . . . . . . . . . . . . . . . . APPENDIX Locations of Test Borings . . . Logs of Borings . . Unified Soil Classification Chart Specification for Construction of Controlled Fills PAGE 1 1 1 i 1 2 2 2&3 &4 4 4&5 PLATE 1 2-6 SOIL TESTISG LABORATORY OF NORTH COUNTY INC. SOIL ‘l’~S;TING LAE0I~fYFOI~Y OF NORTH COUNTY INC. I. 423 XALE AVE. . ESCONDIDO, CALIF. 92025 ESCONDIDO-746.2333 PRELIMINARY SOILS INVESTIGATION OCEANSIDE-722-2125 KNOB HILL CARLSBAD, CALIFORNIA GENERAL INFORMATION: A preliminary soils investigation has been completed on the proposed subdivision site in Caslsbad. California. It is understood that the property is to be developed into a residential ! subdivision. Future drainage of the residential lots will be directed / into the streets and storm drains. The Tentative Map indicates that cut and fill slopes will have maximum heights of less than 20 feet, and probable maximum slope ratios of& horizontal to 1 vertical for cut slopes and 2 horizontal to 1 vertical for fill slopes. - II. PURPOSE OF INVESTIGATION: The purpose of this investigation was to determine the soil conditions and make recommendations concerning the following: I. Grading, including the stability of proposed cut and fill slopes. 2. Disposition and treatment of any potentially expansive soils. 3. Availability of select fill material. 4. Allowable bearing pressures for foundations in natural undisturbed ground and compacted filled ground. 5. Most suitable type and the required depth of the proposed foundations. III. FIELD INVESTIGATION: A. Surface Conditions: The site is situated on the Northerly slope of a small North-South trending ridge. The elevation of the site ranges from approximately 262 feet in a draw on the Northerly property line to a maximum of approximately 290 feet at the top of the ridge on the Southerly pro- perty line. Vegetation consists generally of a sparce covering of grass. -l- B. Test Holes: In order to accomplish the objectives, five exploratory test holes were made with a backhoe on January 30, 1969, at the approximate locations indicated on Plate No. 1 entitled, “Location of Test Holes. ” Samples of the soils excavated were obtained for laboratory analysis. A continuous log of the soils encountered in the test holes was re- corded in the field. The Logs of Borings shown on Plates 2 to 6 inclusive, are based on the field logs, an inspection of the samples, and on the laboratory test results. The test holes were located in the field with the aid of a Tentative Map dated December 6, 1968, prepared by Roy L. Klema Engineers, Inc. Field density tests were performed in the test holes at various depths to determine the moisture content and dry density of the soils. The vertical position and results of each test is shown on the Logs of Borings. C. Soils Encountered: The soils underlying the site, as indicated by the test holes, consist generally of 1 to 3 feet of silty fine to medium sand (topsoil) underlain by firm to dense, clayey silty fine to medium sand to the depths ex- plored, being a maximum of 10 feet below the existing ground surface. Loose topsoil was encountered to depths of 3 feet and 1 foot in Test Holes 3 and 5 respectively. No expansive soil was encountered dur- ing this investigation. No ground water was encountered in the Test Holes during the ex- cavations. The soils were visually classified by field identification procedures in accordance with the Unified Soil Classification Chart. A simplified description of this classification system is presented in the Appendix to this report. IV. LABORATORY TESTS: The samples obtained in the test holes were visually classified and evalu- ated with respect to strength and expansive characteristics. In order to substantiate the classification,mechanical sieve analysis tests were performed in accordance with A. S. T. M. Designation D422-61T. The results of these tests are tabulated as follows on Sheet 3. SOIL TESTISG I.ABOKATOI<Y OF NORTH COUNTY INC. 7 Percent Finer By Weight U.S. Std. Soil Type Soil Type Soil Type Soil Type Sieve Size No. 1 2 3 4 4 100.0 100.0 100.0 100.0 10 100.0 100.0 100.0 97.2 40 80.2 85.0 79.5 56. 8 200 21.7 37,0 37.0 27.2 Soil Description Brown silty Reddish-Brown Reddish-Brown Grey, silty fine to med. clayey, silty, fine silty, clayey clayey med. sand to med. sand fine to med. sand to fine sand An expansion test was performed on one of the clayey soils encountered to determine its volumetric change characteristics with change in moisture content. The recorded expansion of the sample is presented below: Boring Bag Depth Soil Percent Expansion Under No. Sample In Feet Description Unit Load of 150 Pounds per Square foot from Air Dry to Saturation 4 3 2.5 Reddish-Brown 1. 5 clayey fine to medium sand Direct shear tests were performed on saturated and drained~’ samples in order to determine the minimum angle of internal friction and apparent cohesion. The test results and calculated angle of internal friction and apparent cohesion are presented below: Soil Type Normal Shearing Angle of Apparent Load In Kips/ Resistance Internal Cohesion Sq. Ft. Kips/Sq. Ft. Friction lb/sq.ft. 2 Degrees 1. 0 I. 09 30 480 1. 5 1. 35 2. 0 1. 66 4 1. 0 1. 00 31 400 1. 5 1.18 2. 0 1. 62 Laboratory compaction tests were performed on representative samples of the soils expected to be excavated to establish compaction criteria. The soils were tested according to A. S. T. M. D1557-64T method which uses 25 blows of a 10 pound hammer falling from a height of 18 inches on each of 5 layers in a 4 inch diameter l/30 cubic foot compaction cylinder. SOIL TI~STING LABOl~A1’01<Y OF NDRTH COUNTY INC. The results of the tests are presezted as follows: Boring Bag Depth Soil Max. Dry Optimum No Sample In Feet Description Density Moisture Con- lb/ cu. ft. tent, % Dry Wt. 2 1 0 to 1.0 Brown silty fine 126. 5 9. 5 to med. sand 2 2 3. 0 to 10. 0 Reddish-Brown 120. 0 13. 5 Clayey, silty, fine to med. sand 4 3 2.0 to 3.0 Reddish-Brown 128. 5 10.3 silty, clayey, fine to med. sand v. CONCLUSIONS: The ground which will receive fill and/or residential structures will have an adequate bearing capacity to safely support the proposed residential structures when treated as described in the recommendations and the “Specifications for Construction of Controlled Fills” contained in the Appendix to this report. Footings for residential structures placed on non-expansive undisturbed, firm native soil or properly compacted r.on- expansive fill may be designed for a bearing pressure of 1500 pounds per square foot for l-foot wide contimous footings founded at least I- foot below the lowest adjacent ground surface. The existing soils expected to be used in the fills have low volume change characteristics and may, in our opinion, be classified as non-expansive. Loose soil encountered in the draw area (Test Hole 3) on the Northerly side of the site will require removal. It is concluded that cuts may be safely excavated at slope ratios of 2 horizontal to 1 vertical. Fill slopes, when uniformly compacted to not less than 90 percent of the maximum dry density, will be stable, in our opinion, at slope ratios of 2 horizontal to 1 vertical. i IV. RECOMMENDATIONS: It is recommended that all loose soils not removed by the grading opera- tion be excavated to firm native ground. The maximum depth of loose soil as found in Test Hole 3 was approximately 3 feet. The actual depth of compaction should be controlled in the field by a qualified Soil Engineer upon visual examination of the exposed soil. SOIL TESTING LABOH~TOl~P OF NORTH CCIUNTY INC. -A- No expansive soil was encountered during this investigation however, if expansive soil is encountered during the grading operation laboratory tests should be performed to determine the strength and expansive characteristics. It is recommended the upper 2 feet of fill on all lots be constructed of non-expansive soil. Recommendations for the placement of filled ground are presented in the attached “Standard Specifications for Placement of Compacted Filled Ground. ” If any soil types are encountered during the grading of the site that were not tested in the process of this investigation> additional labora- tory tests shall be conducted in order to determine their physical characteristics. Supplemental reports and recommendations will auto- matically become a part of the specifications. The data presented in the attached Appendix are a part of this report. Respectfully submitted, SOIL TESTING LABORATORY OF NORTH COUNTY, INC. ,/ I .t.. ,, -+/ ,,. ~, I’ E. Brian Smith RCE 13, 817 EBS:ce Enclosure SOIL TESTIKG LABOICATOICY OF NORTH COUNTY INC. -E- I \ b \ \ & 5 \ VA \ r ----- 7 0 1 x s I o- APPROX. LOcA?-/ON OF ?-EST HOLE SOIL TBST~N~ EABQDATQQY \ OF NORTH COUNTY INC. \ 69-20 P-/2-69 - LOGS OF BORINGS BORING NO 1 ELEVATION 242.5* Brown silty fine to med. sand. FIRM SOIL TYPE # 1 Reddish-brown clayey, silty fine to med. sand. IlENSE SOIL TYPE # 2 O- Indicates moisture/density test sample n- Indicates bag sample + Elevations determined by interpolation of the contours shown on the tentative map, entitled “Knob Hill” dated December 6, 1968, prepared by Roy L. Klema Engineers, Inc. : --c Ii jM jM, AC, 3. 8 ,2. I 1 16.2/ ~96. I / , ! I 15.5 ~ 96.: I L 18.71 ~93. I I I ~ Dote: I-30-69 KNOB HILL Job No. 69-20 _ By: Jennings CARLSBAD, CALIFORNIA Plate No. 2 Sc)IL TESTING LADORATC)RY OF NORTH COUNTY INC. LOGS OF BORINGS z ” 2” BORING NO 2 Y :cj z 2 ELEVATION 275. 0% Brown silty fine to med. sand. FIRM SOIL TYPE # 1 . ..a... . ‘. . ‘. * Reddish-brown clayey, silty fine to ! j::::::: med. sand FIRM !...e... , *...... SOIL TYPE # 3 3 .,..... 1 .,..... i . ,. . . . . j ~ I / 1 I..“.‘. I 7. .a... DENSE I I...... . . . . . . . ~ .,..I.. . . . . . , . . .._\ ,...,.. .O ‘.......i SOIL TYPE #2 Date: I-30-69 KNOZ HILL Job No. 69-20 ~~ By: Jennings CARLSBAD, CALIFORNIA Plate No. 3 §0lL TESTING LADQRATQRY OF NORTH COUNTY INC. - LOGS OF BORINGS / z $5 ” 2’: BORING NO 3 IL! 2 n ! ELEVATION 266+ Brown silty fine to med. sand LOOSE SOIL TYPE #l Grey silty, clayey med. to fine sand. DENSE SOIL TYPE # 4 Dote: I-30-69 KNOB HILL Job No. 69-20 By: Jennings CARLSBAD, CALIFORNIA Plate No. 4 SQIL TESTING LADORATQRY OF NORTH COUNTY INC. - -41 LOGS OF BORINGS BORING NO 4 ELEVATION 2 8 8 0 :‘: Brown silty fine to med. sand FIRM ! SOIL TYPE # 1 / ! Reddish-brown clayey, silty fine to / SM- 12. 4~113.6~ ; q 3:: med. sand. FIRM 3 , . . . ‘. . ., “’ .‘. ,, ‘4. ,,. . . .! Reddish-brown silty, clayey 4 - ,. I / (. 8 . ..I SOIL 1_: fine to med. sand DENSE , . # . . . , . . . 1 ! 1 I 1. . . 3 i”“‘. ~, ,. . . 8 i,...: . . . . . I” a.., I. ,. . . 9 SOIL TYPE # 2 ! 1 i i i I I Date: l-30-69 KNOB HILL Job No. 69-20 By: Jennings CARLSBAD, CALIFORNIA Plate No. 5 J SORK TESTING LADODATORY OF NORTH COUNTY INC. - LOGS OF BORINGS z ” gi 22 BORING NO L g ,z ELEVATION 270. 5+ Brown silty fine to med. sand LOOSE 1 SOIL TYPE NO. 1 I ,a “’ l:P:#: : Tan fine to med. sand 4 CLEAN - FIRM 2 /‘oh * a Cobbles up to 4” lkameter / Grey silty, clayey med. to fine sand DENSE 6 SOIL TYPE # 4 ! I Date: I-30-69 KNOB HILL Job No. 69-20 By: Jennings CARLSBAD, CALIFORNIA Plate No. 6 §QlL TBSTIING LARQRATQRY OF NORTH COUNTY INC. Sc)IL TESTING LABORAlXlRY OF Wok,” COUNTY INC. 423 HALE AVE. ESCONDIDO, CALIF. 92025 ESCONDIDO-746.2333 OCEANSIDE-722.2125 UNIFIED SOIL CLASSIFICATION CHART SOIL DESCRIPTION GROUP TYPICAL SYMBOL NAMES 1. COARSE GRAINED, More than half of material is larger than No. 200 sieve size. GRAVELS CLEAN GRAVELS GW More than half of coarse frac- GP tion is larger than No' 4 sieve GRAVELS W/FINES size but smaller GM than 3 inches. (Appreciable amt. of fines.) GC SANDS CLEAN SANDS SW More than'half of coarse frac- SP tion is smaller than No. 4 sieve SANDS WITH FINES SM size. (Aaareciable amt. o>-fines) 11. FINE GRAINED, More than half of material is smaller than No. 200 sieve size. SILTS & CLAYS Liquid Limit Less than 50 SILTS & CLAYS Liquid Limit Greater than 50 111. HIGHLY ORGANIC SOILS SC ML CL OL MH CH OH PT Well graded gravels, gravel- sand mixtures, little or 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-clay mixtures. Well graded sand, gravelly sand, little or no fines. Poorly graded sands, gravelly sands, little or no fines. Silty sands, poorly graded sand- silt mixtures. Clayey sands , poorly graded sand-clay mixtures. Inorganic silts and very fine sands-, rock, flour, sandy silt or clayey-silt-sand mixtures with slight plasticity. Inorganic clays of low to med- ium plasticity, gravelly clays, sandy clays, silty clays, lean clays. Organic silts, and organic silty- clays of low plasticity. Inorganic silts, micaceous or ditomaceous fine sandy or silty soils, elastic silts. Inorganic clays of high plasticity, fat clays. Organic clays of medium to high plasticity. Peat and other highly organic soils. S(>IL TESTING LABORATORY OF NORTH COUNTY I N c. 423 HALE AVE. ESCONDIDO, CALIF. 92025 ESCONDIDO-746.2333 OCEANSIDE-722.2125 SPECIFICATIONS FOR CONSTRUCTION OF CONTROLLED FILLS -- GENERAL DESCRIPTION: This item shall consist of all clearing and --7---- grubbing, removal of existing structures and foundations, prepara- tion of land to be filled, excavation of earth and rock from cut areas, filling of the land, spreading, compaction and control of the fill, and all other subsidiary work necessary to complete the grading of the fil- led areas to conform with the lines, grades and slopes as shown on the accepted plans. CLEARING, GRUBBING AND PREPARING AREAS TO BE FILLED: ----- (a) All timber, logs, trees, brush, vegetation and other rubbish shall be removed, piled and burned or otherwise disposed of so as to leave the areas that have been disturbed with a neat and finished appearance free from unsightly debris. (b) Any soft, swampy or otherwise unsuitable areas shall be corrected by draining or removal, or both, to the depths indicated on the plans or as directed by the soils engineer. _- (c) The natural ground which is determined to be satisfactory for the support of the filled ground shall then be plowed or scarified to a depth of at least six inches (6"), and until the surface is free from ruts, hummocks, or other uneven features which would tend to prevent uniform compaction by the equipment to be used. (d) Where fills are made on hillsides or exposed slope areas, greater than 5 per cent, horizontal benches shall be cut into firm undisturbed natural ground in order to provide both lateral and vertical stability. This is to provide a horizontal base so that each layer 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. 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. (e) After the natural ground has been prepared, it shall be brought to the proper moisture content and compacted to not less than 90% of max- imum density in accordance with A.S.T.M. D1557-58T. MATERIALS: 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 appro- ved sources and by mixing soils from one or more sources. The material used shall be free from vegetable matter, and other deleterious substances, and shall not contains rocks or lumps greater than 6 inches in diameter. If excessive vegetation, rocks, or soils with inadequate strength or other unacceptable physical characteristics are encountered, these shall be disposed of in waste areas as shown on the plans or as directed by -- l-- .I- the soils engineer. If during grading operations, soils not encount- ered and tested in the preliminary investigation are found, tests on these soils shall be performed to determine their physical character- istics. Any special treatment recommended in the preliminary or sub- sequent soil reports not covered herein shall become an addendum to these specifications. No material of a perishable, spongy, or otherwise improper nature shall be used in the fills. PLACING, SPREADING AND COMPACTING FILL MATERIAL: -- --- (a) The selected 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 blade 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 speci- fied by the soils engineer, water shall be added until the moisture con- tent is near optimum as specified by the soils engineer to assure thor- ough bonding during the compacting process. (c) When the moisture content of the fill material is above that speci- fied by the soils engineer, the fill material shall be aerated by blading and scarifying or other satisfactory methods until the moisture content is near optimum as specified by the soils engineer. (d) After each layer has been placed, mixed and spread evenly, it shall be thoroughly compacted to not less than the specified maximum density in accordance with A.S.T.M. D1557-58T. Compaction shall be by means of tamping or sheepsfoot rollers, multiple-wheel pneumatic-tired rollers or other types of rollers. Rollers shall be of such design that they will be able to compact the fill to the specified density. Rolling of each layer shall be continuous over its entire area and the roller shall make sufficient trips to insure that the desired density has been obtained. The entire area to be filled shall be compacted to the specified density. (e) Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. 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 clcvation gain or by other methods producing satisfactory results. (f) Field density tests shall be made by the soils engineer for approx- imately each foot in elevation gain after compaction, but not to exceed two feet in vertical height between tests. The location of the tests in plan shal:l be so spaced to give the best possible coverage and shall be taken no farthcr than 100 feet apart. Tests shall be taken on corner and terrace lots for each two feet in elevation gain. The soils engineer may take additional tests as considered necessary to check on the uniform- --*-- SOIL TESTING LABORATGRY OF NORTH COUNTY INC. ,_- ity of compaction. Where sheepsfoot rollers are used, the tests shall be taken in the compacted 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. (g) The fill operation shall be continued in six inch (6") compacted layers, as specified above, until the fill has been brought to the fin- ished slopes and grades as shown on the accepted plans. SUPERVISION: Supervision by the soils engineer shall be made during the --- fill and contracting operations so that he can certify that the fill was made in accordance with accepted specifications. SEASONAL LIMITS: No fill material shall be placed, spread or rolled whileit is frozen or thawing or during unfavorable weather conditions. When the work is interrupted by heavy 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. In the event that, in the opinion of the engineer, the soils unsatis- factory for grading purposes are encountered, they shall not be incor- porated in the grading and disposition will be made at the engineer's discretion. --3-- Sc)IL TESTING LABQRATORY OF NORTH COUNTY INC.