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HomeMy WebLinkAboutSP 182; ELM GARDEN OFFICES; GRADING OBSERVATION AND FIELD DENSITY TEEST; 1984-01-19• rD GEOTECHNICAL EXPLORATION, INC; ' =-- SOIL & FOUNDATION ENGINEERING U . GROUNDWATER • GEOPHYSICS • ENGINEERING GEOLOGY •19 January 1984 . . Mr. Bill Seargeant . . JOB NO. 82-2358 LUSARDI CONSTRUCTION COMPANY . . I . 1570 Linda Vista Drive . San Marcos, CA 92069 . . I . Subject: Final Report of Grading Observation and Field Density Testing Elm Gardens Office Complex . Northeast of the Intersection of E Camino Real and Elm Avenue I . . Carlsbad; California . Dear Mr. Seargeant: . I In accordance with your request, Ceotechnical Exploration, Inc., hereby submits the following report summarizing our work and test results, as well as our conclusions and I .. . recommendations concerning the subject project. Our firm has inspected the grading -. operation and tested the fill soils that were removed and recompacted during the preparation Of, the. Elm Gardens office complex sitc at the above subject address. GENERAL SITE INFORMATION The property, consisting of approximately six acres, is situated northeast of and I .adjacent to te corner of Elm Avenue and El Camino Real. The portion of the site recently developed for construction is located at the southern portion of the site. I This portion of the site slopes gently toward the northwest and southwest, with a large buttressed and retained slope along the eastern property boundary. Elevation of I the building pad area is approximately ±138 feet above mean sea level (M SL). Survey Information concerning actual elevations was not available at the time of our testing and observation services. The property is legally described as: A portion of Lot J of the Rancho Aqua Hedonla, I Map No. 832, City of Carlsbad, County of San Diego, State of California. I 1 8145 RONSON ROAD, SUITE H • SAN DIEGO, CALIFORNIA 92111-2081 • (619) 560-0428 Elm Gardens Office Complex Job No. 82-2358. 18 January 1984 Page 2. Existing vegetation prior to grading consisted of a moderate to heavy growth of low shrubs and weeds. The majority ,of the vegetation was removed prior to grading operations. The site has currently been prepared to receive'a bank structure at the southernmost building pad, which will' be a maximum Of two stories in height. It is our understanding that ,the building will be constructed in conformance with the Uniform Building Code, utilizing conventional-type foundations, footings and conventional-type building materials. Grading operations have taken place across the entire site extending from, the rec*.ii: completed southernmost building 'pad to the northern property boundaries. The on-site operations also include the construction and backfilling of a cribwall retaining structure at the face of the stability fill. Additicaal grading 'resulted in finish-grading of proposed parking areas surrounding the bank structure currently under construction and the remainder of the site to the north. ,A plot plan, illustrating' the approximate location of all materials which were recompacted throughout the grading. operation, is enclosed as Figure No. I. Previously issued reports pertinent to the recent site development include: -' 1. Report of Soil Investigation, dated August 9, 1982. Report of Field Density Testing, dated January 14, 1983. Slope Stability Analysis, dated 'January 17, 1983.' ' Report of Field Density Testing, dated 27 April 1983. ' MATERIALS AND PLACEMENT The soils utilized in the grading operation were from on-site excavations and consisted I primarily of mixtures of clayey sands, silty sands, and sandy clays. These till materials were placed in layers not exceeding eight inches in compacted thickness and compacted to at least 90 percent of Maximum Dry Density, while maintaining a moisture content at, or near, the optimum. Compaction was reached by means of rubber-tired, track, and drum rolling with heavy construction equipment such as Caterpillar D-6 and 0-9 I dozers and loaded scrapers. Backfill compaction within the stability fill crib walls and underground drain and improvement trenches was reached utilizing hand-operated I . pneumatic compactors. ' ' ' ' . . . ' ' '' Elm Gardens Office Complex Job No. 82-2358 18 January 1984 0 Page 3 TESTS Field density tests were performed in accordance with A.S.T.M. D-1556. Expansion potential tests were performed in accordance with the County of San Diego Test for Expansive Soils. Maximum density determinations were performed in accordance with A.S.T.M..D-1557, Method A. The relative compaction results, as summarized on Figure No., II, are the ratios of the field densities to the laboratory Maximum Dry 'Densities, expressed as percentages. CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations are based'upon our analysis of all the data available from the testing of the soils compacted on this site. Our visual inspec- tion of the grading operation (while in progress), field and laboratory testing of the typical bearing soils, and our general knowledge and experience with the natural- ground soils and recompacted fill soils on this site were utilized in conducting our services. ,. 'The soils utilized in the grading operation were from existing on-site soils which were removed and recompacted. The soils primarily consisted of variable mixtures of clayey sands, silty sands, and sandy clays. Soils of this type are considered moderately-expansive, as measured by the County of San Diego Test for Expansive Soils as approved by the City of Carlsbad Standard Specifications. Unless properly dealt with, the moderately expansive characteristics of the sandy clays (described above) can cause significant damage to the structures arid associated improvements (such as those planned for the subject property). In order to reduce significantly the potential for such damage, the recommenda- tions herein must be followed: 0 2.1 The continuous foundations and spread footings shall extend a minimum depth of 18 inches into the firm natural ground or compacted fill. The continuous foundations shall be reinforced with two No. 4 steel bars; one bar shall be located near the top of the foundations and one bar near the bottom. V Elm Gardens Office Complex Job No. 82-2358 18 January 1984 Page 4 2.2 Prior to construction of footings and foundations, and prior to placement of floor slab base sections, the clayey soils shall be thoroughly watered such that they approach their maximum potential for expansion. 2.3 Concrete floor slabs, if used, shall be founded on.at least four inches of sand overlying one 6 mil sheet of visqueen. The slabs shall be reinforced with 6 x 6 - 10/10 steel wire mesh. 2.4 It is recommended that all 'nonstructural concrete slabs (such as patios, driveways, sidewalks, et cetera), and all parking areas, be founded on at least four inches of non-expansive soils. During the grading operation, the natural-ground soils were exposed (where necessary) and properly prepared to receive the fill soils. The fill soils were properly placed, watered and then compacted to at least 90 percent of Maximum Dry Density, in accordance with the requirements of the City of Carlsbad Grading Ordinance. The maximum depth of fill soils placed on the building pad portions of the site at the time of the grading operation monitored by this firm was not in excess of 36 feet in vertical thickness. Utilizing an Angle of Internal Friction of at least 25 degrees, and a minimum cohesion of 300 pounds per square foot. (with the appropriate Terzaghi Equa- tion), the maximum safe soil bearing value of the compacted fill soils placed on the site is at least 2,000 pounds per square foot. Using an Angle of Internal Friction of 25 degrees, and a cohesion of 300 pounds per square foot (with the same Terzaghi Equation), the safe soil bearing value of the natural ground is at least 2,000 pounds per square foot. This soil bearing value may be increased one third for design loads that include wind or seismic analysis.. Additionally, .,these bearing values rnay be utilized in the design of foundations and footings of the proposed structures when founded a minimum of 18 inches into the firm natural ground or compacted fill for single-story (or equivalent height) structures, 24 inches for two-story (or equivalent height) structures. 5 Elm-Gardens Office Complex . Job No.. 82-2358 18 January 1984 . . . Page 5 It should -be noted that changes of surface and subsurface hydrologic condi- tions, plus irrigation of landscaping or significant increases in rainfall over the 'accepted average-annual' rainfall for San Diego County for the past ten years,. may result in the appearance of minor amounts of surface or near-surface water, at locations where none existed previously. The damage from such water is expected to be minor and cosmetic in nature, if corrected immediately. Correc- tive action should be taken on a site-specific basis if, and when, it becomes necessary. The on-site, slightly clayey sands and silty sands are highly conducive to rapid erosion if drainage is allowed to cross slope faces uncontrolled. . . . Following placement of concrete floor slabs, sufficient drying. time' must be allowed prior to placement of floor coverings. Premature placement of floor coverings may result in degradation of adhesive materials and loosening of the finish floor materials. . 7 . Natural-ground cut slopes of maximum inclinations of 1.5 horizontal to 1.0 vertical, and compacted fill slopes of maximum inclinations of 2.0 horizontal to 1.0 vertical, -shall be stable and free from deep-seated failures for materials native to the site and utilized in compacted fills. . . 8. Although the compacted fill soils have been verified to a relative compaction of 90 percent of Maximum Dry Density or better, the compacted fill soils that occur . within five feet of-the face of a fill slope possess, poor lateral stability. The proposed structures and associated improvements (such as walls, fences, patios, sidewalks, swimming pools, driveways, asphalt paving,.et cetera), that are : located within five feet of the face of compacted fill slopes, could suffer. differential movement as a result of the poor lateral stability of these soils. The foundations and footings of the proposed structures, fence posts, walls, et * cetera, when founded five feet and further away from the top of compacted fill slopes, may be of standard design in conformance with the recommended soil value. If proposed foundations and footings are located closer than five feet Elm Gardens Office Complex Job No. 82-2358 18 January 1984 Page 6 Inside the top of compacted fill slopes, they shall be deepened to one foot below a line beginning at a point five feet horizontally inside the fill slopes and projected, outward and downward, parallel to the face of the fill slopes (see Figure No Ill). . The active earth pressure (to be utilized in the design of walls, et .tera), shall be based on an Equivalent Fluid Weight of 50 pounds per cubic foot (for level backf ill only). . The passive earth pressure of the encountered natural-ground soils and well-compacted fill soils (to be used for design of building foundations and footings to resist the lateral forces) shall be based on an Equivalent Fluid Weight of 350 pounds per cubic foot. This passive earth pressure shall only be- -considered valid for design if the ground adjacent to the foundation structure is essentially level for a distance of at least three times the total depth of the foundation. A Coefficient of Friction of. 0.35 times the dead load may be used between the bearing soils and concrete wall foundations or structure foundations and floor slabs. If the coefficient of friction is to be used in conjunction with the passive earth pressures, the coefficient shall be reduced to 0.3. It is recommended that all compacted fill., slopes and natural Cut slopes be planted with an erosion-resistant plant, in conformance with the requirements of the City of Carlsbad Grading Ordinance. Planter areas and planter boxes shall be sloped to drain away from the founda- tions, footings and floor slabs. Planter boxes shall be constructed with a sub- surface drain, installed in gravel, with the direction of subsurface flow away from the foundations, footings and floor slabs, to an adequate drainage facility. Elm Gardens Office Complex Job No. 82-2358 18 January 1984 Page 7 14. Any backfill soils. placed adjacent to swimming pool excavations, in. utility trenches, or behind retaining walls, which support structures and other improve- ments (such as patios, sidewalks, driveways, pavements, et cetera), other than landscaping shall be compacted to at least 90 percent of Maximum Dry. Density. Ceotechnical Exploration, Inc. will accept no liability for damage to structures that occurs as a result of improperly backfilled trenches or walls. 15. Adequate measures shall be taken to properly finish grade the site after the structures and other improvements are in place. Drainage waters from this site and adjacent properties are to be directed away from foundations, floor slabs and footings, onto the natural drainage direction for this area or into properly designed and approved drainage facilities. Proper subsurface and surface drairr' age will help prevent waters from seeking the level of the bearing soils under the foundations, footings and floor slabs. Failure to observe this recommenda- tion could result in uplift or undermining and differential settlement of the structures or other improvements on the site. • 16. Pools and appurtenances and/or subsurface structures, that are founded in any potentially expansive, clay soils, shall be properly designed by a structural engineer and/or soils engineer. SLJ4MARY Based on our field testing and grading observation, it is our opinion that the grad operation was performed in conformance with the City of Carlsbad Grading Ordinance, and the compacted fill soils and natural-ground soils will safely support the proposed structures and other improvements. All statements in the report are applicable only for the grading operation inspected by our firn and are representative of the site at the time our report was prepared. The • firm of Geotechnical Exploration, Inc. shall not be held responsible for future slope construction, or, for fill soils placed at any future time, or subsequent changes to the site by others, which directly or indirectly cause poor surface or subsurface drainage and/or water erosion altering the strength of the compacted fill soils. C C~s 4 D AI no Elm Gardens Office Complex Job No. 82-2358 18 January 1984 S . Page 'B' Our services Consist of professional opinions and recommendations made in accord- ance with generally accepted' geotechnical engineering, principals and practices. . This warranty is in lieu of all other warranties, either expressed or implied. Thank you for this opportunity to be of service. Should any questions arise concern- ing this report, please do not hesitate to contact us. Reference to our Job. No'.' 82-2358 will expedite response to your inquiries. • • S ' • Respectfully submitted, S , • • , S • • • CEOTECHNICAL EXPLORATION, INC. • S S iohjØv. Reed, Staff Engineer 99 CliffordLa Monte, R.C.E.25241 JWR/CWL/pj S Enclosures • • OD . S •• • iri Compaction Test Results Depth Moisture Field Soil Relative Test Date Location Fill Density Type Compaction 1 " 12/16/82 refer to plot plan 6' 12 119 pcf I 92.2% 2 .12/1E/82 refer to plot plan 6 17 118 pcf I 91.4% 3 12/17/82 refer to plot plan 16' 14 124 pcf. I 96.1% '4 12/17/82 refer to plot plan 6' 14 117 ptf I. 90.6% 5 12/17/82 refer to plot plan 6' 16 117 pcf I 9.6% 6 12/20/82 refer to plot plan , 2' 11 113 pcf Ill . , 90.4% 7 12/20/82 refer to plot plan 4' 11 116 pcf II . 92.0% -8 1Z/2P/ 2,referjo.p 4cf WIN 9 12/20/82 refer to plot plan retest #8 9 .116 pcf ' III 92.8%. 10 12/20/82 refer to plot plan 8' .. 8 111 pcf IV . 92.5' 11 12/21/82 refer to plot plan 2' . ' 6 109 pcf IV ' 90 .8% 12 12/21/82 refer to plot plan 3' 9 ' 116 pcf I . 90.0,4; 13 12/21/82' refer to plot plan 5' , .11 118 pcf . , II 94.4% 14 12/22/82 refer to plot plan 7' . ' 6 111 pcf IV '92.5% 15 12/22/82 refer to plot plan 9' 6 113 pcf . IV 94.1% 16 12/22/82 refer to plot plan 2' ' 8 112 pcf " IV 93.3 17 12/22/82 refer to plot plan 4' 7 . 113 pcf IV 94.1% 18 12/22/82 refer to plot plan 6' 10 119 pcf I' 92.2% 19 12/22/82 refer to plot plan '8' 9 112 pcf II 90.0% 20 12/22/82 refer to plot plan 2' 9 , 113 pcf . II 90.4% 21 12/22/82 refer to plot plan 10' 9 116 pcf ' lI 92.8%'' 22 12/22/82 refer to plot plan , 12' 8 . 113 pcf II ' 90.4% 23 12/27/82 refer to plot plan is, 8 118 pcf II . . 94.4% CONTINUED Job No. 822358 QD Figure No,. Ila /O Compaction Test Results Test Date Location Depth Fill Moisture 010 Field Density Soil Type Relative Compaction 24 12/27/82 refer to plot plan .17' . 8 120 pcf I 93.0% 25 12/28/82 refer to plot plan 2' 8 116pcf Ill 92.0% 26 12/28/82 refer to plot plan 2' 9 120 pcf Ill 95.2% 27 . 12/29/82 refer to plot plan 2' 9 124 pcf I 96.1 % 28 12/29/82 refer to plot plan 4' . 9 124 pcf I 96.1% 29 .12/29/82 refer to plot plan 7' 9 122.pcf I 30 12/29/82 refer to plot plan 9' 9 116 pcf I 90.0 31 12/29/82 refer to plot plan 11' 6 119 pcf I 92.2% 32 12/30/82 refer to plot plan 14' 13 119 pcf I 33 12/30/82 refer to plot plan 17' 9 117 pcf Ill 92.6% 34 12/30/82 refer to plot plan 21' 13 122 pcf I 94.5% 35 1/5/83 refer to plot plan 4' 11 122 pcf I 36 1/5/83 refer to plot plan 19' 8 121'pcf . I 93.7% 37 1/6/83 refer to plot plan 21' 9 119-pcf I 92.2% 38 1/6/83 refer to plot plan 23' 6 121 pcf I 93.7% 39 1/6/83 refer to plot plan 25' 8 118 pcf I 91.4% 40 1/7/83 refer to plot plan 28' 8 116 pcf I 90.0% 41 1/7/83 refer to plot plan 27' 7 123 pcf I . 95.3% 42 1/7/83 . refer to plot plan 19' 10 125 pcf I 96.8% 43 1/7/83 refer to plot plan 30' 11 117 pcf I 90.6% 44 1/7/83 refer to plot plan 33' 13 124 pcf I 96.1% 45 1/8/83 referto plot plan 35' 9 118 pcf I 91.4% 46 1/8/83 refer to plot plan 32' 8 122 pcf I 94.5% CONTINUED Job N 82-2358 UCAMO Figure No. I I b - I Compaction Test 'Results ' 1. I --~s dD b J N 82-2358 MO Figure No.IC I Compaction Test Results I Job No. 822358 I - /3 Compaction Test Results I. Depth Moisture Field . Soil Relative Test Date Location . Fill Density Type Compaction 93 1/20/83 referto plot plan 5' 7 .115 pcf II 92.0% 94 1/20/83 refer to plot plan 2' 10 114 pcf II 91.2% 95 1/20/83 refer to plot plan 44 9 121 p0 I 93.7% 96 1/20/83 refer to plot plan 4' 11 116 pcf I 90.0% 97 1/20/83 refer to plot plan 3' 7 116 pcf I. 90.0% 98 4/15/83 refer to plot plan 3' F.G. lu 122 pcf I 94.5% 99. 5,19/83 refer to plot plan . 2' F.C. 12 118 pcf 1 91.4% 100 5/20/83 refer to plot plan 2' F.G. 9 113 pcf II 90.4% 101 5/20/83 refer to plot plan 2' F.C. 11 123 pcf I 95.3% 102 5/21/83 . refer to plot plan 4' F.G. 10 .116 pcf . 1 90.0% 103 5/21,'83 refer to plot plan 3' F.G. 11 114 pcf . II 91.2% 104 7/6/83 refer to plot plan 2' F.G. 8 127 pcf I .98.4% 105 7/6/83 refer to plot plan . 15' F.G. 9 128 pd I 99.2% 106 7/6/83 reter to plot plan 1' F.G. 9 126 pcf I 97.6% 107 7/6/83 refer to plot plan . 24' F.C. 9 121 pcf I 93.7% These test results r,ve been used in our previously -released report dated January 14, 1983. CONTINUED U Compaction Test Results SOIL CLASSIFICATION . I TYPE DESCRIPTION OPTIMUM MOISTURE MAXIMUM DRY DENSITY . . I Light-brown to gray-brown, slightly clayey, . I . fine to medium silty sand intermixed with brown, sandy clay and gray to white, silty . I . fine sand. . . . 10.1% 129 pcf II Light-brown to gray-brown, slightly clayey, silty, fine to medium sand. 11.1% 125 pcf I III Gray to white, silty, fine sand. . 11.0% 120 pcf I I IV Gray to white, silty, fine sand. .. . . . 11.0% . . 120 pcf I I. I. I I.. . . . . ..: . . ... . H . .., I . . ... I Figure Job No 82258 No. I