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HomeMy WebLinkAbout; Elm Avenue Sta 42+94 - 115+20; Soils Report; 1966-04-14SOILS INVESTIGATION Proposed E Im Avenue Sta . 42+94 to Sta . 115+20 Corlsbad, California For the City of Corlsbad Project NO. 66-I-28F April 14, 1966 ENGINEERING DEPT. LIBRAflY City of Carlsbad 2075 Las Palmas Drive Car&bad CA 92009459 BENTON ENGINEERING. INC. BENTON ENGINEERING, INC. APPLIED 501L MECHANICS ~ FOUNDATIONS 6741 EL CAJON BOULE”*RD SAN DIEGO. CALIFORNIA 8211!l SAN DILCO; se3-*(Is. LA Iltsr\: .es.ses. PHILIP HENKINO BENTON PRESIDENT ClVlL LNOINELR Introduction SOILS INVESTIGATION This is to present the results of tests and findings of a soils investigation performed for the proposed Elm Avenue between Sto. 42+94 and Sta. 115+20 in Carlsbad, California. The obiectives of the investigation were to determine the existing soil conditions to depths of 5 feet or more below the proposed pavement elevation and to perform laboratory tests required for the design of the structural section of the roadway and also to determine the allowable slope ratios for both cut and fill areas. In order to accomplish these.objectives, nine borings were drilled at the designated locations, both undisturbed and loose representative bag samples were obtained, and loboratory tests were conducted on these samples in order to provide data upon which to base recommendations D Field Investigation Nine borings were drilled with a truck-mounted rotary bucket-type drill rig ot thedesignated locations. The borings were drilled to depths of 5 to 39 feet below the existing grourd surface. A continuous log of the soils encountered in the borings was recorded at the time of drilling and is shown in detail on Drawing Nos. 1 to 7, inclusive, each entitled, “Summary Sheet”. The approximate location where each boring was drilled is described by Station Number on each applicable “Summary Sheet”. The soils were visually classified by field identification procedures in accordance with the Unified Soil Clossificotion Chart. A simplified description of this classification system is -2- presented in the ottoched Appendix A at the end of this report. Undisturbed samples were obtained 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 1100 pounds, and the average drop was 12 inches. The general procedures used in field sampling are described under “Sampling” in Appendix B. Laboratory Tes k 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 tests are presented on Drawing Nos. 1 to 7, inclusive. Consolidation tesk were performed on represenative samples in order to determine the load-settlement characteristics of the soils. The resuik of these. tests are presented on Drawing No. 8, entitled, “Consolidation Curves”. Direct shear tests were performed on both undisturbed and remolded soil samples that were saturated and drained prior to testing in order to determine the minimum angle of internal friction and apparent cohesion of the soils. The results of these tests were as follows: Boring 4, Bag Sample 2 (Remolded to 90% of maximum dry density) Depth: 4.5-5.5 ft. Boring 6, Sample 3 Depth: 12.5-13.0 ft. Boring 7, Sample 4 Depth: 18.5-19 .O ft. Normal Load Kips/sq ft. 0.5 1 .o 2.0 0.5 1 .o 2.0 0.5 1 .o 2.0 Angle of Minimum Internal Apparent Shear Load Friction Cohesion Ki ps/sq f t . Degrees Ib/sq . ft. 0.32 34 0 0.69 I .36 1 .20 39 800 1.57 2.45 1.54 37 1160 1.93 2.68 BENTON ENGINEERING. INC, -3- Norma I Minimum Load Shear Load Kips/sq ft. Kips/sq . ft. Boring 9, Sample 6 0.5 3.77 Depth: 28.5-29.0 ft. 1 .o 2.22 2.0 3.59 Boring 9, Sample 8 0.5 0.72 Depth : 38 S-39 .O ft. I .o 2.24 2.0 2.80 Angle of Internal Friction Degrees 20”* 29”* Apparent Cohesion Ib/sq. ft. 1840* 440* * Due to variations in cementation and density in these samples the shear results did not vary in direct proportion to the normal loads. The values presented are suggested for design purposes. In addition to the above laboratory tests, expansion tests were performed on some of the representative soils encountered to determine their volumetric change characteristics with change in moisture content. Th e recorded expansions of the samples are presented as follows: Percent Expansion Under Depth of Unit Load of 500 Pounds Boring Sample Sample, per Square Foot from Number No. in Feet Soi I Description Air Dry to Saturation 1 1 0.8- 1.3 Sandy clay 4.66 2 2 5.5- 6.0 Silty sand -1.37** 4 2 10.5-11 .O Silty sond with slight 0.31 amount of clay binder 8 1 4.5- 5.0 Sandy clay 0.82 9 7 33.5-34.0 Silty clay 9.42 ** Indicates consolidation The general procedures used for the preceding laboratory tests ore described briefly in Appendix 6. Compaction tests were performed on a representative sample of the soils to be excavated and used in the deeper fill area in the vicinity of Sta. 75+00. The soi I was tested according to a modified A .S .T.M. D698-58T method of compaction which used 26 blows of a 10 pound hammer BENTON ENGINEERING. INC. -4- dropping 18 inches on each of 3 layers in a 4 inch diameter 1/30th cubic foot meld. The resulk of the tests are presented OS follows: Maximum Optimum Mois- Boring Bag Depth Soil Dry Density ture Content Number Sample in Feet Description Ib,‘cu ft % dry wt 4 2 4.5-5.5 Silty sand withy slight 127.1 10.5 clay binder Mechanical analysis tests were performed on representative samples of the various soil types in accordance with A.5 .T.M. Designation D422-61T. Atterberg Limit tests were also performed on these samples in accordance with A.S .T.M. Designations D423-59 and D424-61T. The resutk of the tests and the soil classifications are presented in the following tabulation: U.S. Sieve Size No. 4 10 30 40 60 100 200 Boring 2 Boring 5 Boring 7 Bag 2 Bag 1 Bag 2 (9’- 10’) (0.51-l .5’) (28’-29’). 100.0 100.0 98.5 99.9 99.8 91.5 97.7 94.8 48.8 85.0 82.2 40.2 45.8 48.2 31.8 29.4 29.5 27.2 21 .6 19.7 23.2 Boring 9 ;:‘-229’) 100.0 99.9 99.4 98.7 91 .7 89.7 86.4 Lrquid Limit 20.4 48.8 41.1 Plasticity Index Non-Plastic Non-Plastic 32.7 22.8 Group Symbol SM SM SC CL Soil Classification Silty Sand S,i I ty Sand Clayey Sand Silty Clay California Bearing Rotio tesk were performed on representative samples of the proposed s&grade soils. The tesk were performed in accordance with Section 6 of the Standard ‘Specifi- cations of the Division of Highways, State of California, dated January, 1949. The test resulk are presented on the following page. Melded Dry Boring Depth Density No. in Feet [b/a ft 1 2 9-10 o-1 125.7 126.5 4.5-5.5 128.3 13.5-14.5 123.0 0.5-l .5 121 .o 19-20 125.5 28-29 127.0 Initial Moisture Content % dry WI 11.5 10.5 11.4 10.0 9.9 10.3 10.9 -5- Pene- tration Inch 0.1 0.2 0.3 0.4 0.5 0.1 0.2 0.3 0.4 0.5 0.1 0.2 0.3 0.4 0.5 0.1 0.2 0.3 0.4 0.5 0.1 0.2 0.3 0.4 0.5 0.1 0.2 0.3 0.4 0.5 0.1 0.2 0.3 0.4 0.5 Load in Pounds on 3 Sq. In. Plunger Percent C .B . R. Expansion O/r of Std. 244 8.1 444 9.9 591 10.4 679 9.8 783 10.0 1150 38.3 2610 58.0 2800 49.2 2960 42.9 3070 39.4 930 31.0 1630 36.2 2020 35.4 2330 33.8 2600 33.3 980 32.6 1750 38.9 1850 32.4 2080 30.1 2320 29.8 1010 33.7 2200 48.9 2610 45.8 2730 39.1 2690 34.5 1500 50.0 2600 57.8 2770 48.6 2770 40.1 2830 39.1 287 9.6 548 12.2 740 13.0 900 13.0 1010 12.9 During Soaking 2.48 Per,:ent Moisture After Penetration 14.2 0.32 11.2 0.82 12.2 0.63 10.4 0.09 10.5 0.63 12.0 2.49 13.6 BENTON ENOINEERI~G. INC. Earing Depth No. in Feet a 4-5 9 28-29 9 35-36 -6- Melded Initial Load in Percent bY Moisture Pene- Pounds on C.B.R. Expansion Density Content tration lb/w ft % dry v/t Inch 3sq. In. % of Plunger Std. During Soaking 4.38 127.3 11.2 0.1 131 4.4 0.2 152 3.4 0.3 174 3.1 0.4 174 2.5 0.5 239 3.1 120.6 15.2 0.1 242 8.1 0.2 280 6.2 0.3 372 6.5 0.4 435 6.3 0.5 480 6.2 122.2 13.2 0.1 590 19.7 0.2 1000 22.2 0.3 1200 21.1 0.4 1320 19.1 0.5 1460 18.7 4.25 2.56 Moisture After Penetration 16.7 20.2 16.6 Tests were performed on representative samples of the various soil types to determine the R-value of the soils. These tests were performed by Testing Engineers, Incorporated, and the results are presented below: Boring Depth NO. in Feet Soil Classification “R” Value 4 13.5-14.5 Silty fine to medium sand 51 7 28-29 Clayey fine to medium sand 11 9 28-29 Silty clay 4 DISCUSSION AND RECOMMENDATIONS Soi I Conditions The soils encountered in Borings 2 (Sta. 58+85), 4 (Sta. 70+95), 5 (Sta. 90+64), and 6 (Sta. 93+OO), consisted generally of silty sands and silty sands with varying amounts of clay binder to the depths of exploration of 14.5, 18.0, 5.0, and 24.0 feet, respectively. BENTON ENGINEERING. INC. -7- One foot of clayey fine sand topsoil was underlain in Boring 1 (Sta. 51+70) by fine sandy clay to a depth of 4.0 feet and by clayey sand between 4.0 and 5.0 feet. A lean sandy clay was encountered to a depth of 1.7 feet in Boring 3 (Sta. 631-42) and was underlain by clay to 6.0 feet. A clayey fine to medium sand was found beneath 3.5 feet of silty sand in Boring 7 (Sta . 99+55) and to the depth of exploration at 33 .O feet. Sandy clay was encountered to a depth of 7.0 feet in Boring 8 (Sta. 105+96) and was underlain by clayey sand between 7.0 and 8.0 feet. A fine sandy clay in Boring 9 (Sta. 110+65) was underlain at a depth of 4.8 feet by clayey fine sand to 13.0 feet, silty claystone between 13.0 and 34.3 feet and finally by a silty very fine to fine sand between 34.3 and 39.0 feet. The area between Sta. 72+00 and Sta. 88+00 was not accessible to the drill rig. However, visual observations of cut slopes and deeply eroded areas revealed the soils on this portion of the project to be primarily silty sands and silty sands with clay binder, similar to .those soils encountered in Borings 2 (Sta. 58+85), 4 (Sta. 70+95), 5 (Sta. 90+64), and 6 (Sta . 93+00). Free ground water was not encountered in any of the exploration borings. Grading It is concluded from the findings in Borings 2, 4, 5 and 6, that the majority of the soils on this portion of the project would be desirable for use as subbase or subgrade under the base course. Where clayey soils exist within two feet of finished subgrade, these could be overexcavated and replaced with the more suitable silty sand soils. The soils encountered in the vicinity of Borings 1 and 3 and east of approximately Sta. 95+00 may be expected to BENTON ENGINEERING. INC. -a- have low values for pavement design. If economically feasible, it is recommended that the silty sand soi Is be hauled to these areas and be placed and compacted as subbase over the clayey type soi Is. Loose or soft soils should be removed from areas to receive fill and the filled ground should be placed on firm natural soils. All filled ground should be uniformly compacted to at least 90 percent of maximum dry density in accordance with approved specifications. It is concluded from the test data that the proposed cuk up to 35 feet in height may be safely excavated on a ratio of 1 horizontal to 1 vertical provided drainage benches and/or brow ditches are provided to control erosion. The deepest fill on the project is estimated to be approximately 46 feet in height at Sta. 75+00. If it is assumed that this fill will be constructed primarily of silty sand soils from adjoining cut areas then it is concluded from laboratory tests that these soils will be stable for the planned height on a 1 l/2 horizontal to 1 vertical when uniformly compacted to at least 90 percent of maximum dry density in accordance with the approved specifications. Compacted fills constructed using primarily the clayey soils in the eastern portion of the project, will be stable for heights up to 25 feet at ratios of i l/2 horizontal to 1 vertical. For heights of fill greater than 25 feet, where the clayey soils areused, it is recommended that the slope ratio be no steeper than 2 horizontal to 1 vertical. Pavement Sections It is understood that the pavement section is to be designed using a Traffic Index of 6.5. Using an R-value of 50 for the silty sands and silty sands containing clay binder and the design methods on pages 26 to 29, inclusive, of the “Test Method No. Calif. 301-F”, in the Materials Manual of the State of California, Department of Public Works, Division of Highways, a satisfactory pavement section would beas presented on the following page. BENTON ENOINEERING. INC. -9- Thickness Material 3” Asphalt Concrete 6” Bose (R-value = 70) In areas where clayey soils exist near the proposed finished subgrade, the required pavement section, using an R-value of 4 for the s&grade soils and an R-value of 50 for the on-site silty sands to be used as subbase, the pavement section would be as follows: Thickness Material 3” Aspho It Concrete 6” Base (R-value = 70) 11” Subbase (R-value = 50) This would mean the hauling of the more select silty sand soils from cut portions west of Stu . 95+00 to provide subbase for al I areas east of S ta. 95+00. If a design wheel load of 12,000 pounds is used with the “California experience for medium heavy traffic” and the s&grade is a si Ity sand having o C .B. R. of 31, the required combined thickness of pavement and base over the silty sand s&grade would be 6 inches. It is concluded from correlation of the test results that the pavement sections determined for the assigned R-values would be adequate for the proposed roadway. Respectfully submitted, By &&‘&+c.ez/ R. C. Remer Reviewed b mp H. B&f&n, Civil Engineers’ BENTON ENGINEERING. INC. z YZ SUMMARY SHEET IL Lk! $2 BORING NO. 1 zi 3s Station 51+70* / ;2$%$ ; I”‘O$ Y- -*ai “$ CL (8’ North of ‘$) Fill 2.0’ a -=oL Brown to Light Brown, Motst, CLAYEY FINE Loose to Medium Firm SAND TOPSOIL , 1.1 9.7 109.1 SC Grov/Brown, Moist. Medium Firm FINE SANDY CLAY CL I I I I I I Red Brown, Moist, Very Firm CLAYEY FINE SAND I SC BORING NO.2 Station 58+85 (46’ South of Q Cut 8.4’ Contains only slight cloy Binder 8 SILTY FINE TO MEDIUM SAND 1.1 5.5 - 6.8 8.7 - 33.1 36.5 * According to the “Elm Avenue, Improvement Plan and Profile” provided by the City of Carl&ad. 0 lndicotes undisturbed drive sample q Indicates Loose represenotive bag sample 1 SM PROJECT NO. 66-l-28F BENTON DRAWING NO. ENGINEERING, INC. 1 BORING NO. 3 Station 63+42 rk Groy, Moist, Medium BORING NO.4 Stotion 7095 (On Centerline) Cut 12.7’ “FA Brown, Moist, Loose Firm, Cloy Binder, Fine to Medium Sand Contains only slight Cloy Binder Below 5.5’ SILTY FINE TO MEDIUM SAND I I I 2.2 16.2 100.0 4.4 18.3 107.5 l-r I I I - 2.2 4.4 9.4 9.3 1 ; 1 - 19 08 - L: Ij i.. J: xc 3; - Cl ct - Stb - PROJECT NO. BENTON ENGINEERING, DRAWING NO. 66-l-28F INC. 2 BORING NO. 5 Stotion 90+64 SILTY FINE TO MEDIUM SAND BORING NO .6 S totion 93+00 (On Centerline) Cut 18.2’ Very Firm, with Interbedded Layers of Cloyey Sand Less Cloy Content From Slight Increase in Cloy Content Below 13’ SILTY FINE TO MEDIUM SAND SLIGHTLY SILTY FINE TO MEDIUM SAND SILTY FINE TO MEDIUM SAND 9.9 1.0 7.6 - 5.7 3.c 3.E 9.: 19.a 13.2 14.7 SM - ‘M - SM - iNl - PROJECT NO. DRAWING NO. 66- 1-28 F BENTON ENGINEERING, INC. 3 SUMMARY SHEET BORING NO. 7 St0 tion 99+55 Very Moist IL 16 1; Occasional Grovel to 2” From6.c-7.5’ Light Brown Less Clayey Below 10’ No &arse Groins or Grovel From 15 .O’ - 16 S’ Contains Scattered Coarse Groins and Grovel to 2” Below 16.5’ 7.3’ SILTY FINE TO MEDIUM SAND CLAYEY FINE TO MEDIUM SAND 3.3 8.8 17.2 15.0 !3.1 z! i;; :2’ : - K-l 1 .t 0.6 0.C ‘0.t I8 .! 13.’ 20.: 19 .: 16 .s 6i.i :Z izs :“; ‘GE =x - - - SM - CC PROJECT NO. DRAWING NO. 66-l-28F BENTON ENGINEERING, INC. 4 z SUMMARY SHEET $6 ttlk E? zc; Et! 22 BORING NO. 8 zi:: E $2 Station 10996 5: n (On CenterIine)Cut 3.3’ g:: Moist, Firm, Few ins rises of Cloyey Fine Sand From 3 .O’-4.5’ FINE TO MEDIUM SANDY CLAY MEDIUM SAND PROJECT NO. DRAWING NO. 66-l-28F BENTON ENGINEERING, INC. 5 2- 4 6.. 8- lo- 12- 16- 18- 20- 22- 24- 26 28 30- 32, YE 2: $2 (50’ south of Q cu ---..__, Dark Groy Moist, Soft SUMMARY SHEET BORING NO. 9 Station 1 lo+65 14.0’ light Brown, Slightly Moist. Lenses of Silty Fine to Medium Sand and Silty Clay Light Gray Brown, Moist, Very Firm Lime Cemented Lenses Between 18.8’ ond 19 .O’ Less Clay Content Between 22.7’ and 32 .O’ FINE TO MEDIUM SANDY CLAY CLAYEY FINE SAND SILTY CLAYSTONE 5; Zk 5:: “E 2 5’ 3 - 3.3 12.1 4.3 16.5 !8.0 8.3 4.4 - ; ; L : 1 - , ; ! - 03 - 06 - I6 ?3 18 17 j6 ;z v) - CL - iC 3L Continued on Drawing No. 7 PROJECT NO. DRAWING NO. 66-I-28F BENTON ENGINEERING, INC. 6 i iG YE SUMMARY SHEET I=; :: $2 BORING NO.-%-- : 2: Station 1 10+65 (50’ South of Q Cut 34.0’ SILTY FINE TO MEDIUM SAND 19.2 - 11.61116.9 . PROJECT NO. DRAWING NO. 66-l-28F BENTON ENGINEERING, INC. 7 I CONSOLIDATION CURVES LOAD IN KIPS PER SPUARE FOOT 1.0 2 4 6 o Indicates percent consolidation at field moisture l Indicates percent consolidation after saturation I lorlong 3 iample 2 joring 5 iample 1 +h 1 .5’ PROJECT NO. 66- 1-28 F BENTON ENGINEERING, INC. I DRAWING NO. 8 BENTON ENGINEERING. INC. APPLIED SOIL MECH*NIC* - FOUNDATIONS 6741 EL CAJON BOULEVARD S&N DIEGO. CALIFORNIA 82115 PHlLlP HENKING BENTON eIE81oIHT CIYIL ENG,NEER APPENDIX A Unified Soil Classification Chart* SOIL DESCRIPTION GROUP SYMBOL I. COARSE GRAINED, More than holf of material is larger than No. 200 sieve size.** GRAVELS CLEAN GRAVELS s half of coarse fraction is larger thon No. 4 sieve size but SmallerGRAVELS WITH FINES than 3 inches (Appreciable omount of fines) SANDS CLEAN SANDS -than half of ,- coarse fraction is smaller thon No. 4 sieve size 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 MH Liquid Limit Greater than 50 ,-- Ill. HIGHLY ORGANIC SOILS GW GP GM GC SW SP SM SC ML CL OL CH OH PT TYPICAL NAMES Wel I graded gravels, gravel-sand mixtures, little a no fines. Poorly graded gravels, gmvel-sond mixtures, little or no fines. Silty gravels, poorly graded grovel- sand-silt mixtures. Clayey gravels, poorly graded grovel- sand-clay mixtures. Well graded sand, gravelly sands, little or no fines. Poorly graded sands, gravelly sands, little cr no fines. Silty sands, poaly graded sand-silt mixtures. Clayey sonds, poorly graded sand-cloy mixtures. Inorganic silts and very fine sands, rock flour, sandy silt or clayey-silt-sand mixtures with slight plasticity. Inorganic clays of low to medium plos- ticity, gravelly clays, sondy cloys, silty clays, lean clays. Organic silts and agonic silty-clays of low plasticity. lncrgonic silts, micoceous cr diotcmo- cecus fine sandy or silty soils, elastic silts. Inorganic clays of high plasticity, fat cloys. Organic cloys of medium to high plasticity. Peot and other highly organic soils. * 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. APPLIED SOIL. MECHANICS - FO”NDATIONS 6741 EL CAJON sOUIE”*RD SAN DIEGO. CALIFORNIA 92115 ,r- PHlLlP HENKlNG BENTON PRESIDENT. ClVlL ENCCNEER SAN DIEGO: s*3.s65. LA ME**: 468.S6S. APPENDIX B Sampling The undisturbed soil somples are obtained 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 cutside diameter, with o special cut- ting tip on one end and a double ball valve on the other, and with o lining of twelve thin bross rings, each one inch long by 2.42 inches inside diometer. 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 loboratory tests, the soil being still confined in the brass rings, after extraction from the sampler tube. The samples are taken to the laborotory in close fitting waterproof containers in ader to retoin the field mois- ture until completion of the tests. The driving energy is calculated OS the overoge 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 ore run using o direct shear machine of the stmin control type in which the rote of deformation is approximately 0.05 inch per minute. The machine is so designed that the tests ore made without removing the samples from the brass liner rings in which they ore 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 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 shearing in order to simulate extreme field moisture conditions. Consolidation Tests The appomtus used for the consolidation tests is designed to receive one of the one inch high rings of soil os it comes from the field. Loods ore oppl ied in sever01 increments to the upper surface of the test specimen ond the resulting deformations ore recorded at selected time intervals for each increment. Generally, each increment of load is mointoined on the sample until the rote of deformation is equal to or less than l/l0000 inch per hour. Porous stones ore placed in contact with the top and bottom of each specimen to permit the reody addition or release of woter. Exponsion Tests One inch high samples confined in the brass rings ore permitted to air dry ot 105°F for ,- at least 48 hours prior to placing into the expansion opporotus. A unit Iood of 500 pounds per square foot is then opplied 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 mode until downward movement stops. The diol reading is recorded and expansion is recorded until the rate of upward movement is less than l/l@)00 inch per hour.