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HomeMy WebLinkAboutCT 79-10; La Costa South Unit 1; Soils Report Preliminary; 1968-03-08OF .,.,.‘.,, ~,. _pli.” ., j ~,,_. ; .,*.~ ?‘~,; I ~.< c7 7 9-10 -79 -II BENTON ENGINEERING. INC. APPLIED SOIL MECHANICS ~ FOUNDATlONP 674, EL CAJON BOULEVARD S&N DIEGO. C*LIFORNI* 82115 PHILIP HENKING BENTON PrlFSIDEHT CIWL ENGINEER Rancha La Costa, Inc. Route 1, Box 2550 Encinitas, California March 8, 7968 Subject: Project No. 68-2-2C Preliminary Soils Investigation La Costa South Unit No. 1 East of the intersection of La Costa Avenue and El Camino Real San Diego County, California Gentlemen: SAN DIEGO: SS9.5654 L& MESA: aso-5654 CONCLUSIONS It is concluded from the field invertbation and laboratory tests results that: 1. Generally the existing natural soils which are to receive fill and/or one and two story residential dwellings are suitable for the safe support of the proposed loads. How- ever, the results of field density tests taken in alluvial soils existing in certain drainage channels and low areas indicate that these upper soils are relatively soft or loose and would be considered unsuitable for the support of the proposed filled ground and dwellings. It is recommended that these soft or loose soils be removed under the direction of the soils engineer and the compacted filled ground placed on suitable supporting natural soils. Any loose or soft natural soils existing in shallow cut areas should also be removed and replaced with filled ground uniformly compacted to at least 90 percent of maximum dry density. ?. Calculations, based an the results of the shear tests performed an undisturbed natural soils determined to be suitable for structural support, give a safe allowable bearing pressure of at least 2000 pounds per square foot for one foot wide footings founded at a depth of 1 foot below the undisturbed natural ground surface. 3. It is ccncluded from the results of the load-consolidation tests that the settle- ment of a one foot wide continuous footing loaded to 2000 pounds per square foot and founded on suitable firm natural soils is estimated to be less than l/8 inch, 4. It is concluded from the results of the expansion tests that the silty clay and sandy clay soils encountered 01 the site would be considered to have sufficient expansion ENGINEERING DEPT. LIBRARY City of Carl&ad 2075 Las Palmas Drive Carl&ad CA 92009-4859 Project Uo. 68-2-2C La Costa South Unit t\lo. I -2- March 8, 1968 potential to require special design of foundations and slabs. Either during or upan com- pletion of grading an inspection should be made of each lot to determine whether “expansive” soils exist in the upper 3 feet below fininshed grade. Where expansive soils exist for thick- nesses enough to cause adverse differential movemenbthen special recommendations will be presented for the construction of houses on these “expansive” soils. Conventional type foot- ings may be used where nonexpansive soils exist in the upper 3 feet below finished grade. It may be desirable to specify and provide for this condition during grading. 5. All of the soils may be satisfactorily compacted in the fill areas and, when compacted to at least 90 percent of maximum dry density, have a safe bearing capacity of 1510 pounds per square foot for one foot wide footings placed 1 foot below the compacted ground surface. The settlement of a cne foot wide continuous footing placed on fill soils uniformly compacted to 90 percent of maximum dry density is estimated to be an the order of l/8 inch. It is recommended that all soft or loose soils existing in proposed campocted filled ground areas be removed as required by the soils engineer and the compacted filled ground be placed an firm natural soils. Based an the results of the field investigaticn and laboratory tests the depths of this required removal would be 1.2, 4.5, 6.0 and 5.5 feet, respectively, at Pits 1, 2, 3 and 4. / Recommendations for the placement of filled ground are presented in the attached “Standard Specifications for Placement of Compacted Filled Ground, ” Appendix AA. 6, A. Preliminary plans indicate that cuts an the order of 50 to 60 feet in height are to be made on the south side of La Costa Avenue in the general vicinity of Borings 3, 4 and 5. It is concluded from the field investigation and the test date that these cub be made no steeper than a slops mtio of 2 horizontal ta 1 vertical . Relatively shallow cuts are indicated on the lot areas and these may be excavated on a 1 l/2 horizantal to 1 vertical for heights not to exceed 20 feet. B. The fill soils, when uniformly compacted to ot least 90 percent of maximum dry density in accordance with the approved specifications, will be stable with an adequate factor of safety when constructed on a I l/2 horizontal to I vertical slope. The maximum heights of fill slopes are estimated to be approximately 33 to 37 feet. If any soil types are encountered during the grading operatian that were not tested in this investigation, odditional laboratory tests will be conducted in order to determine their physical characteristics, and supplemental reports and recommendations will automatically become a part of the sfzecificatians. The data presented on the attached pages are a Fart of this report. Respectfully submitted, ‘BENTON ENGINEERING, INC. &flip K.Bentan, Civil Engineer BY -#.d?&&sxw R. C. Rsmer Dish: (4) Addressee (2) Mclntire 8 Quirce, Inc. Atten ticn: Mr. Gary Cumbey BLNTON ENOINELRIN.3. INL. (1) Rick Engineering Project No. 6ii-2-2C La Costa south unit No. 1 -3- tdarch 8, 1363 DISCUSS I ON A preliminary soils investigation has been completed on the proposed La Costa South Unit No. 1 located east of the intersection of La Costa Avenue and El Camino Real in San Diego County, California. The obiectives of the investigation were to determine the existing soil conditions and physical properties of the soils in order that engineering recommendations could be made for the grading and construction of houses an this unit. In order to accomplish these objectives, three borings were drilled with a truck-mounted drill rig ond seven pits were excavated using a backhoe, field density tests were taken, undisturbed and loose bag samples were obtained, and laboratory tests were performed on these samples. The site is located on the south side of the valley extending easterly from the Batiquitos Lagoon northeast of Encinitas, California. The southerly portion of the site may be described as gently rolling terrain while much of the north portion is located cn the steep sloping sides of the valley. Much of the upper land has been cultivated. The upper soils in the volley ond lower slope areas in the north portion of the site ore described by the U .S . Department of Agriculture as Alviso loam and Huerhuero fine sandy loam. The major soil types encountered in the exploration borings and pits were silty sond, clayey sand, sandy clay, and silty clay. Field Investigation Three borings, Numbers 3, 4 and 5, were drilled with a truck-mounted rotary bucket-type drill rig and seven exploration pits were excavated using a backhoe. The borings were drilled during the same period as Borings 1 ond 2 an La Costa Avenue between El Camino Real and La Costa South Unit No. 1. The opproximate locations of the borings and pits on La Costa South Unit No. 1 are shown an the attached Drawing No. I, entitled “Location of Test Borings and Exploraticn Pits,” The borings were drilled to depths pf 46 to 51 feet below the existing ground surface and the depths of the exploration pits varied from 4 to 15.5 feet. A continuous lag of the soils encountered was recorded at the time of excavation and is shown imdetail on Drawing Nos. 2 to IO, inclusive, each entitled “Summary Sheet.” The soils were visually classified by field identificatian procedures in accordance with the Unified Sail Classification Chart. A simplified description of this classification system is presented in the attached Appendix A at the end of this report. Undisturbed samples were obtained in the borings at frequent intervals in the soils ahead 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 overage drop wos 12 inches. The general procedures used in field sampling are described under “Sampling” in Appendix B. In-place field density tests were taken in Exploration Pits 1, 2, 3 and 4, using the sand dis- placement method, in order to evoluate the suitability of the soils in these areas for the support of fi I led ground. BLNTON ENOINEERWG. INC. Project No. 68-2-2C La Costa South Unit No. 1 -4- March 8, 1968 Laboratory Tests Laboratory tests were performed on all undisturbed samples of the soils in order to determine the dry density and moisture content. The results of these tesk are presented on Drawing Nos. 2 to 10, inclusive. Consolidation tesk were performed on representative samples in order to determine the load-settlement characteristics of the soils. The results of these tests are presented an Drawing ~Vos. 11 and 12, each entitled “Consolidation Curves .I’ In addition to the above laboratory tesk, expansion tests were performed on some of the clayey soils encountered to determine their volumetric change chamcteristics with change in moisture canten t . The recorded expansions of the samples are presented as follows: San Diego County Method Percent Expansion Lbtder Percent Expansion Under Depth of Unit Load of 144 Pounds Unit Load of 500 Pounds Boring Sample Sample, Soi I per Square Foot from Opti- per Square Foot from No. No. in feet Description mum Moisture to Saturation Air Dry to Soturotion 3 7 35.0-35.5 Silty clay 6.19 4 4 15.5-16.0 Silty clay 7.23 4 6 25.5-26 .O Clayey fine sand 1.27 5 6 20.0-20.5 Silty clay 7.15 3 2.0- 3.0 Silty clay 7.30 Pit 5 21 1 .O- 2 .O Fine to medium 6.12 sandy clay Pit 5 Bag 2 4.0- 5.0 Silty clay 5.90 Direct shear task were performed on saturated and drained samples in order to determine the minimum angle of internal friction and apparent cohesion of the soils. The results of these tesk are presented in the following tabulation: Normal Load in kips/sq ft Boring 3, Sample 7 0.5 Depth: 35.0-35.5 feet 2.0 Boring 4, Sample 8 0.5 Depth: 35.5-36.0 feet 1.0 2.0 Boring 4, Sample 11 0.5 Cbpth: 50.5-51 .O feet 1 .o 2.0 * Indicates reduced value. Angle of Shearing Internal Apparent Resistance Friction Cohesion Kipe/sq ft Degrees Ib/sq ft I .26 28 1000 2.06 1.55 40* 400 2.69 5.07 1.08 40* 370 2.24 3.22 BENTON ENGINEERING. INC. Project No. 63-2-2C La Costa South Unit No. 1 Boring 5, Sample 5 Depth: 15.5-16.0 feet Boring 5, Sample 11 Depth: 40.5-41 .O feet Boring 3, Bag Sample 2** Depth: 6.0-7.0 feet Boring 5, Bag Sample l** Depth : 38.0-39 . 0 feet Pit 5, Bag Sample 2** Depth: 4.0-5.0 feet Pit 6, Bag Sample 4** Depth: 9.0-10.0 feet -5- March 8, 1962’ Normal Shearing Load in Resistance kips/sq ft Kit&q ft 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1 .o 2.0 0.5 1.0 2.0 0.5 1.0 2.0 1.07 1.45 1.69 Angle of Internal Friction Des reef 22.5 Apparent Cohesion Ib/sq ft 860 2.65 3.34 5.45 0.82 1.08 1.30 0.59 1.02 1.69 2.76 2.34 3.14 40’ 17.5 3.5 14 400* 660 250 1000* 0.43 0.92 1.41 33.3 100 * indicates reduced value. ** Indicates test sample compacted to 90 percent of maximum dry density. The general procedures used for the preceding laboratory tests are described briefly in Appendix B . Compaction tesk were performed on representative samples of the soils to establish compaction criteria. The soils were tested according to a modified A.S .T.M. D 1557-587 method of compactiar which uses 25 blows of a 10 pound hammer dropping 18 inches on each of 5 layers in a 4 inch diameter l/30 cubic foot meld. The results of the tesk are presented as follows: Boring Bag Depth Soil No. Sample in Feet Description 3 1 2.0- 3.0 Silty clay 3 2 6.0- 7.0 Silty clay 4 1 4.0- 5.0 Silty fine sand 5 1 38.0-39.0 Silty fine sand Continued on page six. Maximum Optimum Mois- turc Content Dry Density Ib/cu ft % dry wt 114.8 14.1 110.6 15.7 116.0 13.2 119.0 12.0 BENTON ENOINECRIWGb I,. _‘~ Project No. 68-2-2C La C&a South Unit No. I Pit kJ Depth No. Sample in Feet 1 1 2.0-2.5 2 2 4.0-4.5 3 1 2.0-2.5 4 1 2.0-2.5 1.0-2.0 4.0-5.0 1.0-2.0 9.0-10.0 -6- March 8, 1968 Maximum Soil Dry Density Description lb/cu ft Silty clay 118.0 Fine sandy clay 120.2 Clayey fine to medium 128.0 sand Clayey fine ta medium 131.8 sand Fine to medium sandy clay 125 .O Silty clay 118.8 Silty fine sand 103.6 5 i I ty fine sand 113.0 Optimum Mois- ture Content % dry wt 13.6 12.2 8.4 7.4 10.5 12.1 15.5 13.2 Atterberg Limlt terk were performed on a representative sample of the silty clay soil in accordance with A.S.T.M. D 42361T and D 424-59. The results of these tesk are presented as follows: Boring Sample Depth Liquid Plasticity Group No. No. in Peat Soil Description Limit lndax Symbol 5 5 15.5-16-O Silty clay 58.7 32.6 CH Unconfined compression tests were performed on representative samples of the silty clay soils and the results are presented balow: Cohesica Ib/sq ft Boring Sample D8Pth (T/2 Unconfined No. No. in Peet Compressive Strength) 3 10 40.5-41.0 1380 5 7 20.5-21.0 670 5 13 45.5-46.0 4650 Using th8 tower values of internal angle of friction and apparent cohesion, and the Terraghi Formula for local shear faiture,the safe allowable bearing pressures for the soils are deter- mined as follows: Local Shear Formula: cY=2/3~N’,+yDfN’~+yBN’y Assumptions: (1) Continuous footing 1 foot wide = 28 (2) Depth of footing = 1 foat = Df Continued on page seven PCNTQN CNCilNLCRING. INC. bOi8Ct No. 6&2-2C La Costa South Unit No. 1 -7- March 8, 1968 Undisturbed natural soils 0 = 22.5” c = 86Olb/sq ft y = 120 Ib/cu ft N’, = 13.5 Nlq = 6.0 N’Y = 3.3 Q’ = (2,‘3 x 860 x 13.5 + 120 x 1 x 6.0 + 120 x 0.5 x 3.3) = 8,660 Ib/sq ft Q’ Safe = Q’+ 3 (Factor of Safety) = 2,880 lb/sq ft Fill soils compacted to 9wO of maximum dry density 0 = 330 c = 100 Ib/sq ft y = 120 Ib/cu ft NIc 21.5 N’q = 12.0 N’Y =7.5 Q’=(2/3x 100x21.5+120x Ix 12.0+120x0.5x7.5)=3323lb/sqft Q’ Safe = Q’+ 2.2 (Factor of Safety) = I510 Ib/sq ft BCNTON LNGINELIING. INC. ; ! SUMMARY SHEET BORING NO. 3 ELEVATION 169’ * Brown, Moist, Loose, Some Rook, Topsoil SILTY FINE Yellow-brown, Moist, Medium i SAND c ,ompact 4 - r ~l.Pi12 ! , ,7.9’11 ! ! 13.4 12 SILTY CLAY ( 19.5 ! i !32.5 I L IL?-- ,- 20- - 22- - 24- - 26- - 28- - 30- Cemenkd Sandstone Yellow-gray, Moist, Very Firm, Lenses of Highly Cemented Continued / T 1 1 c 2 12.5 18.1 4 IO.0 11.9 c -. - I jl: SILTY FINE SAND Drawing No. 3 cl - Indicates Loose Bq Sample 0 - Indicates Undisturbed Drive Sample * - The elevations presented for Borings 3, 4 and 5 were furnished by Ranch0 La Costa PROJECT NO. 68-2-2C BENTON DRAWING NO. ENGINEERING, INC. 2 I z ii:: SUMMARY SHEET IL :if 2: BORING NO.3t.j E $2 Lzrxlen ted Sands kxlL~ ow-brown, Slightly Moist, Yellow Brown Some Cemented Lenses j: I Z9.2 18.C 12 .? $121, SILTY FINE SAND J SILTY CLAY ~-__. CEMENTED SANDS TONE -1 PROJECT NO. DRAWING NO. 68-2-2C BENTON ENGINEERING, INC. 3 ; : ti 1;;; i p E ! 1 FT 1 SUMMARY SHEET BORING NO. 4 ELEVATION 128’ SILTY CLAY CLAYEY FINE -AAND- (Merges) low-brown, Moist, Medium 6 Lenses at 5.0 Feet 8 Dip = 5” to N20” W SILTY FINE SAND 13.1 I.0 p.4 II L t / 12’ 1.1 !.5 ?.O -- 5.4 5.4 tl SILTY CLAY il 3i c CLAYEY FINE SAND -~~(t&+i- Very Very .: “. a rcrm . :-..* .-.I xl *. 1.7 1.7 19 .! Thin Silty Clay Lens SILTY FINE SAND - . . 28 -1.: - 24 .* : *. . . :‘. 3 -.. _ Continued on Drawing No. 5 PROJECT NO. 68-2-2C BENTON DRAWING NO. ENGINEERING, INC. 4 z z:: SUMMARY SHEET IL :: 22 BORING NO.-QCmt.) : z$t dray-brown-Moist, Very - Thin Silty Clay Lenses Coarse Grains of Sand j;>y>i’: 42 ,::y;;k : ..y~:; .;[y~;:. .,:%.:.x:: :. ::-< ,sj : ~~~ @$ ,yp:; lb.>;< :;: yg;:+. ,;; 3::;;” 5 ,,.:.~~:..- .:y .::a.; 5 , :.” , ‘>, SILTY FINE SAND SLIGHTLY SILTY INE TO MEDIUM SAND 65, 50. 50. 50. - .8 18.t 27. - PROJECT NO. 68-2-2C BENTON DRAWING NO. ENGINEERING, INC. 5 SUMMARY SHEET BORING NO. 5 ELEVATION 191’ 6 Light Olive-green, Streak of 8 Thin Silty Fine Sand Lens SILTY CLAY Yellow-brown, Moist, Very Firm, Slightly Silty Fine to Medium Sand Lenses and Some Coarse Sand Grains Below 24.0 Feet ---I Thin Silty Clay Lenses Cemented Sandstone Lenses SILTY FINE SAND Continued on Drawing No. 7 . I I 14.6 19.6 16.2 20.9 11.4 19.5 17.3 17.5 11.1 75.0 i : ; . . T ) ; 1 > : ; 07.1 39.E M.C 11.8 19.6 II I PROJECT NO. 68-2-2C BENTON DRAWING NO. ENGINEERING, INC. 6 ! SUMMARY SHEET : ek ,&CC BORING NO.-..&(&nt.) { 22;; 2; uu y z YS”ru 0, > ~OO>ti GE z< = 2 0 0 0 -,n I 4” E ‘.. rcfl Yellow-brown, .O . Moist, Very Olive-green, Moist, Very Firm, Dip = 2” to N40’ E Gray-brown, Moist, Very Compact, Some Coarse 62.5 ilLTY FINE SAND (Continued) 157.5 SILTY CLAY 158.3 I SILTY FINE TO i MEDIUM SAND 110.2 22.1 iI: 8.9 i109.9 IL 20.2 108.8 I - PROJECT NO. DRAWING NO. 68-2-2C BENTON ENGINEERING, INC. 7 . ~I j I? ;, ,, $ SUMMARY SHEET PIT NO.- ELEVATION AD’ * i 2 - PIT NO. 2 ELEVATION 88.0’ i 2 FINE SANDY 4 5 PIT NO. 3 ELEVATION 34.0’ Scattered Gravel and Pea Gravel &own, Very Moist, Very Firm ,lLTY FINE SAND SILTY CLAY CLAYEY FINE TO MEDIUM SAND FINE SANDY CLAY (Mew2s) SILTY CLAY 78. 82. - n - Indicates location of in-place field density test 0 - Indicates loose bag sample * - The elevations shown for the exploration pits were determined by interpolating between the contours shown on the grading plans prepared by Mclntire 8 Quiros, Inc. PROJECT NO. 68-2-2C BENTON DRAWING NO. ENGINEERING, INC. 8 z 25 SUMMARY SHEET I- 5% Pm ii” $$ PIT NO.4 0 ELEVATION 34.0’ -’ I b Brown, Very Moist, Loose, 1 CLAYEY FINE TO 1 MEDIUM SAND Brown, Very Moist, /CLAYEY FINE TO MEDIUM SAND - ..I \ Dark Brown, Very Moist, Locae, 4 ii;,“,“3 RebFravel and Gravel CLAYEY FINE TO 1 MEDILJ&s,,$DY Brown, Very Moist, Very Firm SILTY CLAY I PITNO. 5 ELEVATION 76 .O’ 2 own, Moist, Firm, Scattered Gravel, Some Medium to Coarse 4 Sand Grains, Fleck of Rust and White at 1 .O Foot, Slightly Moist and Very Firm Below 2.0 6 Feet, Same Gravel Below 3.0 SILTY FINE SAND FINE TO MEDIUM SANDY CLAY I I -. 13.6 106.1/ 80.; - - PROJECT NO. DRAWING NO. 68-2-2C BENTON ENGINEERING, INC. 9 SUMMARY SHEET PIT NO.6 Silty Fine Sand Lenses - -~~---- SILTY FINE SAND 1 PIT NO. 7 ELEVATION aO, lt Brown-ray, Moist, Firm, F&bred, Very Firm Below 1 .O Foot, Yellow Streaks at 2 .O Feet Rust Streaks at 3.0 Feet Light Brown, Moist, Very Firm, Gray, Slightly Silty Fine Sand Lenses With Rust Streaks SILTY FINE SAND SLIGHTLY SILTY FINE SAND SILTY FINE SAND - - - PROJECT NO. 68-2-2C BENTON DRAWING NO. ENGINEERING, INC. IO CONSOLIDATION CURVES LOAD IN KIPS PER SOUARE FOOT T- I,6 0.8 1.0 2 4 6 6 10 16 ! I Bormg 3 / , / Bag 1 L 1 Death 2-3’ emolded to 9C% / 7 +3 L fk ( km -r L la, imum Dry ii 1 I I 1 I wing 4 ‘, ‘cl 1 \ aeoth 4-5’ ed to 900/r, PROJECT NO. 68-2-2C o Indicates percent consol idotion at field moisture l Indicates percent consolidation after soturotion DRAWINQ NO. BENTON ENGINEERING, INC. 11 CONSOLIDATION CURVES LOAD IN KIPS PER SQUARE FOOT PROJECT ND. 68-2-2C o Indicates percent consolidation at field moisture e Indicates percent consolidation after saturation DRAWINQ NO. BENTON ENGINEERING, INC. 12 13.2 .A/?4 ?> 3 -/.7-i : :‘Z I; 1.7;; 2, 7 . ,‘,, - ” 3 i- --.-~~ ~~.- k. :’ / ‘\ ‘\ $ 3 a : “k-. Q _ ‘.., .~f/.+$f i/&V ->. -’ 7 , ‘\, I . 5,. ,‘f, c/J<, ‘\ ‘\ ” \ I -1~ F / ;3 \ I ‘k_ I 4 5;~ ,.- .t-Acd Y \T--~,\ I / \ I _,~ x : 5 , ~’ :\ ~ i ” L- _,_;i St li, C,‘dY j “X 3 3 7 ,. 80: ‘~ ‘_ . Y.3 + ,ci -~~ 7 J-u 5iT - _ A ft: &Xc7YA// x /.I’ i 17 /2-o ,a. JO73 w, /o. R//d 0 + ; x. 2,’ 3. w, * 123 a+~~j x ; i?B./OO id, 2 80 ” dl;, ‘3 > 3i’ 303 A-0, 030 $,I 5j b+$y i w(~Le!YL”8-‘lzL~~ x ” 5-f /‘JJ .24,idJ M/s : 7(.fz y .“-6) x ‘I /8< 630 5,929 M 2 /3. 7f&py x p 3 3j 329 Y, 3UD w/ I & x 3 3. y x /3.0 x ‘~’ #2d,#l3 -13 3 .COO~. 10 5, / ro ,y; s&5TZd T /Y5’ /35.2’ /+;I’ c(4f@=oj J?s;/oo 5 7J.& /‘3 5: k ---- ./4/b w N ran 4 2-n GCP “3/s, ,6.//J-& :: Y2”- 5~0OU~7-” ‘/Do- u2,003 ecyy c ,n ///7j r/ur = ( :‘jJo /D s, /‘7D ‘-J fl~JOOXJ~ yr&o’ 96,600 ,?C‘,~f.w “3~rus,63~ ‘5B,500 i//3.42 ;m [jj. ,d:/ c,, z<: ._ .T..~. ~~~.~. ~..~._~...._ ..-. _.._ PROJECT NO. BENTON ENGINEERING, INC. DRAWING NO. LB-J-2 c b’. i ’ ./’ i* 7 \ . -\,, . ‘.. / Y’? Bsl’ -Lb /y = *%#.dS-*- /2 y /.a?.5 = /$7YO $ ; /Y(J’l.< t :rrj < ’ s .37,/3D a’ W’ ( LwJp) t ) - /9,5m w,: B(.L’/A~) d ’ 3 9.DL)3 n;. ‘9(.7y6)~ ” j 4,800 :1,/r, C,Gy ~_ 5;. Sand -is /J.BGO i 3,739 6.203 ,- -S ; / 56 ‘, D. K PROJECT NO. DRAWING NO. 68-J-.2 c BENTON ENGINEERING, INC. j-, ,‘/ * 9 .d - --_ 2 + Q ‘\\ - ;; .y;; F ,&it, c-/I& ‘\ AC-:, ../ .4 , Cl .%n‘f 81. 5,: .C,,d 1, ,‘\ \\\. ‘$ \* \ “1~ “k~,,. i \\~ JO 3.9405 ---~-- PROJECT NO. DRAWING NO. d&--Z-Z C BENTON ENGINEERING, INC. BENTON ENGINEERING, INC. APPLIED SOlI. MECHANICS - FOUNDATIONS 6’117 CONVOY CO”RT SAN DIEGO. CALIFORNIA 82111 PHlLlP HENKING BENTON P”L,IDENI CIY,L EHGIHECR TELEPHONE (714, 56s.rBss APPENDIX AA STANDARD SPECIFICATIONS FOR PLACEMENT OF COMPACTED FILLED GROUND 1. General Description. The objective is to obtain uniformity and adequate internal strength in filled 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 compaction of the filled oreas to conform with the lines, grades, and slopes as shown on the accepted plans. The owner shall employ o qualified soils engineer to inspect and test the filled ground as placed to verify the uniformity of compaction of filled ground to the specified 90 percent of maximum dry density. Th-s ti soils engineer shall advise the owner and grading contractor immediately if any unsatisfactory conditions ore observed to exist and shall have the authority to reject the compacted filled ground until such time that corrective measures ore 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, and 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 oreos to be filled free of vegetation and debris. Any soft, swampy or otherwise unsuitable oreas shall be corrected by draining or removal, or both. (b) The natural ground which is determined to be satisfactory for the support of the filled ground shall then be plowed or scarified to o depth of at least six inches (6’7, 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. (c) Where fills ore made on hillsides or exposed slope areas, greater than 10 percent, horizontal benches shall be cut into firm undisturbed natural ground in order to provide both lateral and vertical stability. This is to provide o horizontal base so that each layer is placed and compacted on o 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 eleva- tion of the toe stoke placed at the natural angle of repose or 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 (d) After the natural ground has been prepared, it shall then be brought to the proper mois- ture content and compacted to not less than ninety percent of maximum density in accordance with A.S.T.M. D-1557-66T method that uses 25 blows of a 10 pound hammer folliw from 18 inches on each of 5 layers in o 4” diameter cylindrical meld of a 1/30th cubic foot volume. 3. Materials and Special Requirements. The fill soils shall consist of select materials so graded that at least 40 oercent of the material oasses a No. 4 sieve. This mav be obtained from I the excavation of banks, borrow pits of any other approved sources and by mixing soils from one or more sources. The material uses shall 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, rock, 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 the soils ewineer. 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. (4 (b) Cc) (4 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 throughly mixed during the spreading to insure uniformity of material and moisture in each layer. When the moisture content of the fill material is below that specified by the soils ewineer, water shall be added until the moisture content is near optimum as specified by the soils engineer to assure thorough bonding during the compacting process. Men the moisture content of the fill material is above that specified by the soils ewineer, 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 er\gineer. After each layer has been placed, mixed and spread evenly, It shall be thoroughly compacted to not less than ninety percent of maximum density in accordance with A. 5. T .M. D-1557-66T modified as described in 2 (d) above. Compaction shal I 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 shal I be of such design that they wi II be able BENTON CNOINLLIINO. INC. 5. 6. 7. 8. (e) 0-l (!A APPENDIX AA -3- to compact the fill materiol to the specified density. Rolling shall be accomplished while the fill material is at the specified moisture content. Rolliw 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 areas to be filled shall be compacted. 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 elevation gain or by other methods produciw satisfactory results. Field density tests shall be taken by the soils engineer for approximately each foot in elevation gain after compaction, but not to exceed two feet in vertical height between tests. Field density tests may be taken at intervals of 6 inches’in elevation gain if required by the soils evineer . Th e ocation of the tests in plan shall be so spaced to I give the best possible coverage and shall be taken no farther apart than 100 feet. Tests shall be token on corner ond terrace Iok for each two feet In elevation gain. The soils engineer may take additional tests as considered necessary to check on the uniformity of compaction. Where sheepsfoot rollers are used, the tests shall be taken in the corn- pacted maMaI below the disturbed surface. No additional layers of fill shall be spread until the field density tests indicate that he specified density has been dbtained. The fill dperotion shall be continued in six Inch (6”) compacted layers, as specified above, until the fill has been brought to the flnlshed slopes and grades as shown on the accepted plans. ?I@- Sufficient itispection by the soils eqineer shall be maintatned during the fi illg and compacting operations so that he can certify-that the fill was constructed in accordance with the accepted specifications. Seasonal Limits. No fill material shall be placed, spread, or rolled if weather conditions increase the moisture content above permissible limits. When the work Is Interrupted by rain, fill operations shall not be resumed until field tejk by the soils ewineer indicate that the moistvre content and density of the fill are as previously specified. Limitirg Values of Nonexpansive Soils. Those soils that expand 2.5 percent or less from air dry to saturation under a unii load of 500 pounds per square foot are consldered to be nonexpansive. All recommendations presenteci in the “Conclusions” section of the attached report are a part of these specifications. BENTON ENGINEERING, INC. APPLIED 8QIL MECHANICS - FOUNDATION* 6717 CONVOY COURT *AN DIEL3O. CALIFORNIA e211, PHUJPHENKINO BENTON ,“l,ID.WI ClYlL LNDlWIL” APPENDIX A Unified Soil Classification Chart* SOIL DESCRIPTION GROUP SYMBOL I. COARSE GRAINED, More than half of material is &than 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 More than half of coarse fraction is smaller 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, 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 grovel- sand-cloy 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, poorly graded sand-silt mixtures. Clayey sands, poorly graded sond-cloy 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, gravelly clays, sandy clays, silty clays, lean clays. Organic silts and organic silty-clays of low plasticity. Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts. inorganic clays of high plasticity, fat clays. Organic clays of medium to high plasticity PT Peat and other highly organic soils. TYPICAL NAMES TELL,“ONT ,714, ses-,*ss * Adooted by the Corps of Engineers and Bureau of Reclamation in January, 1952. PHILIP HENKING BENTON CIISIDIWT CIY,L EHG1NIE.I BENTON ENGINEERING. INC. APPLIED SOIL MECWANICS - FO”NDATIONS 6717 CON”OY CO”R1T SAN DIEGO. CALIFORNIA 8211, TELEP”ONF ,714, ?l(i*.1sss APPENDIX B Sampling The undisturbed soil samples ore obtoined by forcing o 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 o steel barrel 3.0 inches outside diameter, with a special cutting tip on one end and o double ball valve on the other, ond with a lining of twelve thin brass rings, each one inch long by 2.42 inches inside diameter. The sampler, connected to o twelve inch long waste barrel, is either pushed or driven approximately 18 inches into the soil ond a six inch section of the center portion of the sample is taken for laboratory tests, the soil being still confined in the brass rings, after extraction from the sampler tube. The samples are taken to the loboratory in close fitting waterproof containers in order to retain the field moisture until completion of the tests. The driving energy is calculated OS 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 o direct shear machine of the strain control type in which the rate of deformation is approximately 0.05 inch per minute. The machine is so designed thot the tests are mode without removing the samples from the brass liner rings in which they are secured. Each somple is sheared under o normal load equivalent to the weight of the soil above the point of sampling. In some instances, samples ore sheared under various normal loads in order to obtain the internal angle of friction and cohesion.. Where considered necessary, samples are saturated and drained before sheoring 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 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 apparatus. A unit load of 500 pounds per square foot is then applied to the upper porous stone in contact with the top of each sample. Water is permitted to contact both the top and bottom of each sample through porous stones. Continuous observations are made until downward movement stops. The diol reading is recorded and expansion is recorded until the rote of upward movement is less than l/10000 inch per hour.