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Home My WebLink AboutCT 74-21; Carlsbad Crossroads Phase I; Soils Report; 1987-04-15IJr 2. 2% 50 /-- - - - - - - - .- SAN DIEGO GEOTECHNICAL CONSULTANTS, INC. SOIL ENGINEERING 8 ENGINEERING GEOLOGY ApriL 15, 1987 Ninteman Construction Company 1465 Morena Boulevard San Diego, California 92110 Attention: Mr. Mat Reno Job No. 05-6983-001-00-10 Log No. 7-1418 SUBJECT: SOILS COMPACTION REPORT Precise Grading Completed - Building Pads Only Carlsbad Crossroads, Phase I Buildings A,B.C, and D Carlsbad, California References: (1) San Diego Geotechnical Consultants, Inc., November 20. 1986, "Foundation Investigation, Carlsbad Oaks Business Center, Lots 3-6, Carlsbad, California," Job No. 30065-00 (2) San Diego Geotechnical Consultants, Inc., February 19, 1987, "As-Graded Geotechnical Report, Final Report of Mass Grading, Carlsbad Oaks Business Center, Carlsbad Tract 74-21, Carlsbad, California" Job No. 05-l 079-002-00-l 0 Gentlemen: This report p~resents the results of our testing and observation performed during precise grading at the above referenced site. Field density test locations are shown on the Plot Plan, Plate 1. test results are tabulated on Table I, "Results of Compaction Tests." The purpose of-the grading and compaction was to: (1) precise grade the building pad and (2) perform remedial grading overexcavation and moisture conditioning within the building pad - area. ENGINEERING DEPT. LIBRARY City of Carlsbad 2075 Las Palmas Drive - . Carlsbad CA 92009-4859 6455 NANCY RIDGE DRIVE . SUITE 200 l SAN DIEGO, CALIFORNIA 92121 l (6191587-0250 - - - - - - .- - Ninteman Construction Company April 15, 1987 Job No. 05-6983-001-00-10 Log No. 7-1418 Page 2 1.0 PREVIOUS GRADING The site consists of two previously rough graded lots within the Carlsbad Oaks Business Center. The lots were rough graded using the observation and testing services of San Diego Geotechnical Consultants, Inc. The As-Graded Geotechnical Report for the mass grading on this subject is referenced above. Up to 55 feet of compacted fill was placed during rough grading. The fill materials varied from silty sands to clayey silts and clays. The contact between fill and bedrock materials at the surface is shown on Plate 1. 2.0 OVEREXCAVATION OF BUILDING AREA Due to the variable fill depths and transition conditions on the site, individual recommendations were provided for each building pad to address specific conditions. On all buildings the upper two feet of the recompacted fill material was moisture conditioned to at least five percent over optimum moisture content during placement. Over- excavation of the bedrock portion of the building pad was performed as described in the following paragraphs. The lateral extent of all overexcavations was five feet outside of all footings. 2.1 Building A The maximum depth of fill below Building A was estimated at 11 feet. Because Building A was placed across a cut-fill transition, the building area was overexcavated to a depth of three feet below the bottom of proposed footings. This resulted in a total depth of excavation of five feet. . - - - - - - - 2.3 Buildings C and D - - - - - - Ninteman Construction Company April 15, 1987 Job No. 05-6983-001-00-10 Log No. 7-1418 Page 3 2.2 Building B The maximum expected depth of fill underlying Building B was five feet. Because Building B also crossed a cut/fill transition, cut materials were removed to a depth of three feet below lowest adjacent finish grade and replaced as a uniformly compacted fill. Since Buildings C and D were not placed over transition areas, no overexcavation below footing elevation was considered necessary. These two buildings were over- excavated two feet below slab elevation to perform moisture conditioning. 3.0 PREPARATION OF EXPOSED GROUND The exposed subgrade soil in areas of the overexcavation was scarified 8 to 12-inches, brought to near optimum moisture conditions and compacted to at least 90 percent relative compaction. 4.0 SOIL TYPES The soils encountered during grading generally consisted of silty sands and clays. During excavation for the eastern portion of-,building A, very hard bedrock was encountered. The ripping and removal of this material required the use of a D8L Dozer. Oversized rock removed during grading was broken down to less than 12-inch maximum diameter prior to placement or stockpiled for later use in non-structural . - - - - .- - - - - - - - - Ninteman Construction Company April 15, 1987 Job No. 05-6983-001-00-10 Log No. 7-1418 Page 4 areas. The soil types used as fill are tabulated in Table 11, "Laboratory Test Results." All fill materials were derived from the area of overexcavation. 5.0 FILL PLACEMENT Fill soils were placed in 6 to 8 inch lifts, brought to the proper moisture content and compacted to a minimum of 90 percent of the maximum density as determined by ASTM D1557-78. The equipment used for removal and recompaction consisted of one John Deere 860 Scraper, one 613 Scraper, one 126 Grader, one D6 Dozer, one D8L Dozer, and one 915 Trackloader with sheepsfoot drum compactor. Grading operations were started and completed to fine grade during the period covered by this report, March 26 to April 10, 1987. Density tests were made in accordance with ASTM D2922-81 (Nuclear Gauge Method). Results of the density tests made during the recompaction of the fill are tabulated in Table I. Results of the maximum density and optimum moisture determination of the various soils encountered are tabulated in Table II, "Laboratory Test Results". - - ,- .- .- .- .- .- - Ninteman Construction Company April 15, 1987 Job No. 05-6983-001-00-10 Log No. 7-1418 Page 5 6.0 CONCLUSIONS AND RECOMMENDATIONS 6.1 Compaction Based on the results of the observations and testing noted herein, it is our opinion that the grading and compaction was performed in general accordance with our recommendations and the requirements of the City of Carlsbad. 6.2 Moisture Conditioning The results of our testing and observations indicate that the upper two feet of slab subgrade within building areas have been moisture conditioned to at least five percent over optimum moisture content. In order to maintain this moisture content, periodic sprinkling of the building pad is recommended. Prior to construction, moisture testing should be performed by the geotechnical consultant to confirm that moisture conditions are as recommended. 6.3 Foundation and Slab Recommendations 6.3.1 General The results of our testing and observation indicate that the existing surface soils exhibit a high to very high expansion potential (see Reference). The following recommendations are provided for the design of footings and slabs based on the expansion potential of the soils presently at the site. ,- -, ..- .- .- -- .- ~,- - .~- Ninteman Construction Company April 15, 1987 Job No. 05-6983-001-00-10 Log No. 7-1418 Page 6 Our recommendations are considered generally consistent with the Standards of Practice. The potential for favorable foundation performance can be further enhanced by maintaining uniform moisture conditions throughout the Life of the structure. The footing configurations and reinforcement recommendations herein should not be considered to preclude more restrictive criteria by the governing agencies or by structural consider- ations. A Structural Engineer should evaluate configurations and reinforcement requirements for structural loadings, shrinkage and temperature stresses. 6.3.2 Foundations It is anticipated that a shallow foundation should be suitable to support the proposed structures. All footings for building should be founded entirely in the recompacted fill. Based on soil conditions, continuous footings should be reinforced with at least two No. 5 bars placed one at the top of the stemwall and one at the bottom of the footing. Footings should have a width of at least 12-inches, and should be founded at Least 24-inches below lowest adjacent finish subgrade. Footings may be designed for an allowable dead plus live load bearing pressure of 2,000 pounds per square foot with a one-third increase for ..- - - - _ Ninteman Construction Company April 15, 1987 Job No. 05-6983-001-00-10 Log No. 7-1418 Page 7 short-term wind or seismic loads. Where footing are located adjacent to utility trenches, they should extend below a one-to-one plane projected upward from the inside bottom corner of the trench. 6.3.3 Slabs We recommend that slabs be constructed a minimum of four inches in actual thickness and be rein- forced with at least 6x6/10-10 welded wire mesh placed at mid-height of the slab. Actual design of on-grade slabs may be based upon a modulus of subgrade reaction of 200 pounds per cubic foot. We recommend that slabs be underlain by at least four inches of crushed rock or clean washed sand to act as a capillary break. If a moisture membrane is used, we recommend that it be overlain by at least two inches of sand to decrease the likelihood of curing problems. 6.3.4 Lateral Load Resistance Lateral loads against buildings may be resisted by friction between the bottom of footings and the supporting soils. An allowable friction coefficient of 0.30 is recommended. Alter- natively, passive pressure equal to an equivalent fluid weight of 215 pounds per cubic foot acting against the footings may be used, provided the footings are poured tight against undisturbed soils. This value includes a factor of safety of 1.5. .- .- .- .- .- __ ,- Ninteman Construction Company Job No. 05-6983-001-00-10 April 15, 1987 Log No. 7-1418 Page 8 6.3.5 Expected Settlement For footings supported on the properly recompacted fill and sized for the recommended bearing pressures, total and differential settlements are not expected to exceed one inch and three-quarters of an inch, respectively. 6.4 Drainage The performance of foundations is highly dependent upon maintaining adequate surface drainage both during and after construction. The ground surface around structures should be graded so that surface water will be carried quickly away from the building without ponding. The minimum gradient within ten feet of the building will depend upon surface landscaping. In general, paved or lawn areas should have a minimum gradient of five percent. Roof drains should he carried across all backfilled areas and discharged at least ten feet away from structures. Planters should be constructed so that moisture is not allowed to seep into the foundation areas or beneath slabs and pavements. 6.5 Retaining Walls The active earth pressure for the prevailing on-site soil may be based on an equivalent fluid pressure of 40 pounds per cubic foot. The active earth pressure should be used for retaining walls which are free to yield at the top (unrestrained). For retaining walls which are braced at the top, an equivalent fluid pressure of 60 pounds per cubic foot should be used, . .,.~. - .- .- .- _- .- - .- - - - Ninteman Construction Company April 15, 1987 Job No. 05-6983-001-00-10 Log No. 7-1418 Page 9 based on the at-rest soil condition. The above values should he modified to take into account any surcharge loads, sloping backfill or other externally applied forces. Passive pressures used for design of retaining walls were presented previously in Section 6.3.4, "Lateral Load Resistance." 6.6 Trench Backfill Utility trench and/or wall backfill consisting of the on-site material types should be placed by mechanical compaction to a'minimum of 90 percent of the laboratory maximum density. 6.7 Foundation Observations 6.8 All excavations should be observed by the geotechnical consultant prior to placement of forms, reinforcement or concrete, for verification of conformance with the intent of these recommendations. All excavations should be trimmed neat, level, and square. All loose or sloughed material should be removed prior to the placement of concrete. Materials from footing excavations should not be spread in slab-on-grade areas unless compacted to a minimum relative compaction of go-percent. Reactive Soils The results of sulfate testing performed on soils obtained in our borings indicate that Type 11 cement should be used for concrete which will he in contact - - - - Ninteman Construction Company April 15, 1987 Job No. 05-6983-001-00-10 Log No. 7-1418 Page 10 with the on-site soils. Results of these sulfate tests are included in Table B-3. 6.9 Temporary Excavations Temporary construction excavations may be made vertically without shoring to a depth of 5 feet below the adjacent surrounding grade. For deeper cuts, the slopes should be properly shored or sloped back at least 1 :l (horizontal:vertical) or flatter. The exposed slope face should be kept moist (but not saturated) during construction to reduce local sloughing. No surcharge loads should be permitted within a horizontal distance equal to the height of cut from the toe of the excavation unless the cut is properly shored. Excavations that extend below an imaginary plane inclined at 45 degrees below the edge of any nearby adjacent existing site facilities should be properly shored to maintain the foundations support of the adjacent structure. All excavations and shoring systems should meet the minimal requirements given in Article 6 of the State of California Occupational Safety and Health Standards. 7.0 SUMMARY Our description of grading operations, as well as observations and testing services herein, have been limited to those grading operations performed between March 23, and April 10, 1987. No representations are made as to the quality or extent of materials not observed, or for any subsequent changes made to this site. Ninteman Construction Company April 15, 1987 Job No. 05-6983-001-00-10 Log No. 7-1418 Page 11 Elevations and test locations noted in the attached Table I and Plate 1 are estimated from field surveys done by others. Based upon our observations and testing, it is our opinion, as aforementioned, that the work performed has been accomplished in accordance with our recommendations as well as the requirements of the regulating agencies. This report should be considered subject to review by the controlling authorities. Professional judgements represented in this report are based partly on our evaluations of the technical information gathered, our understanding of the proposed construction, and our general experience in the geotechnical field. Our engineering work and judgments rendered meet or exceed the standard of care of our profession at this time. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. .~- .- _- .~- .- _- ..- -. Ninteman Construction Company April 15, 1987 Job No. 05-6983-001-00-10 Log No. 7-1418 Page 12 The opportunity to be of service is appreciated. If you have any questions, please call. Very truly yours, SAN DIEGO GEOTECHNICAL CONSULTANTS, INC. Erik 3. Nelson Staff Engineer LfJJJk W. Lee Vanderhurst, C.E.G. 1125 Reeistration Ex Chyef Geologist' Regist;ati& Expires: 3-31-91 Chief Engineer EJN:WLV:AFB:m,pb Attachments: Plot Plan, Plate 1 Tables I and 11 Distribution: (6) Addressee TABLE I RESULTS OF COMPACTION TESTS 05-6983- 08 NO.: 001 -00-10 NAME: Carlsbad Crossroads DATE: April 87 MOISTURE UNIT DRY EST NO. DATE RELATIVE EfEyATTy;N COW$NT “;p”c”:;Y COMPACTION so’L (96) TYPE 1 03-26-87 367.5 19.4 103.2 91 1 2 03-26-87 368 19.1 102.6 90 1 3 03-26-87 367 24.0 95.8 92 2 4 03-26-87 367 20.4 101.8 87 3 Retest on #5 5 03-26-87 367 19.1 105.5 90 3 6 03-26-87 368 19.5 102.8 90 1 7 03-26-87 368 19.0 104.1 91 1 a 03-30-87 369 24.2 95.1 92 2 9 03-30-87 369 24.5 94.5 91 2 10 03-30-87 370 21.8 99.5 87 2 1 Retest on /I12 11 03-30-87 370 19.8 102.2 90 1 12 03-30-87 370 20.4 102.5 90 1 13 03-30-87 369 25.0 95.7 92 2 14 03-30-87 370 24.5 97.2 94 2 15 04-01-87 371 17.5 104.5 92 1 Retest on F23 16 04-01-87 371 17.6 105.3 93 1 Retest on f/24 17 04-01-87 370.5 17.0 105.9 93 1 Retest on #34 18 04-01-87 371 18.1 102.5 90 1 19 04-01-87 370 18.5 103.3 91 1 20 04-01-87 370 17.9 102.8 90 1 21 04-01-87 369 19.1 106.1 91 3 22 04-02-87 371.5 18.0 104.3 90 3 23 04-02-87 371.5 19.3 102.7 90 1 24 04-02-87 371.5 19.0 103.8 91 1 25 04- 12-87 371.6 19.6 102.6 90 1 26 04-02-87 369 19.5 103.4 91 1 27 04-02-87 368 19.7 107.1 90 4 28 04-02-87 370 19.2 104.1 90 3 29 04-02-87 368 18.4 102.5 90 1 30 04-02-87 369 19.3 103.6 91 1 31 04-02-87 369 19.1 100.5 88 2. : Retest on H32 32 04-02-87 369 16.9 105.3 93 33 04-02-87 370 18.7 107.4 92 3 34 04-02-87 370.8 19.2 106.2 91 3 35 04-02-87 370 20.2 102.2 90 1 36 04-03-87 a~368 19.3 103.5 91 1 37 04-03-87 368 19.4 104.1 92 1 38 04-03-87 369 18.9 105.4 90 3 SEE PLAN FOR TEST LOCATIONS ‘SAND-CONE TEST, ALL OTHERS NUCLEAR DENSITY TESTS ‘TEST FAILED, SEE RETEST SAN DIEGO GEOTECHNICAL CONSULTANTS. INC. - .-, ~~. .~- .~~. ..- ,~- - - - - - TABLE I RESULTS OF COMPACTION TESTS 05-6983- OS NO.:- - - NAME: cn l-l..& EST NI 39 )4-03-B' 370 19.4 103.4 91 1 40 )4-03-8' 370 19.9 102.4 90 1 41 )4-03-B. 370 19.5 106.3 91 3 42 14-03-B 369 18.8 107.0 92 3 43 )4-07-8. 367 14.9 109.8 92 4 44 14-07-B 368 15.4 110.1 92 4 45 )4-07-B' 367 15.6 106.4 91 3 46 14-07-8 368 13.7 107.5 90 4 47 14-07-B' 368 14.7 107.0 90 4 48 14-07-B 369 19.4 102.5 90 1 49 14-07-B' 369 18.7 103.7 91 1 50 14-08-B 370 19,l 103.5 92 1 51 14-08-B' 370 25.6 97.6 94 2 52 14-08-B 370 28.6 94.5 91 2 53 14-08-B 364 17.4 115.4 97 4 54 14-08-B 364 18.3 107.2 90 4 55 14-08-B' 366 20.2 105.2 93 1 56 14-08-B 366 19.7 104.0 92 1 57 14-10-8' 372 18.6 106.3 94 1 58 14-10-B 372 ,19.3 101.9 90 1 59 14-10-B 372 18.9 106.9 93 1 DATE DEPTH/ iLEVATl0 hOISTlJF CoxT:N UNIT OR’ OENSIT’ (PCF) Cl-OSSrO< . _ RELATIVE :OMPACTIO (%) SEE PLAN FOR TEST LOCATlONS SAND-CONE TEST. ALL OTHERS NUCLEAR DENSITY TESTS TEST FAILED, SEE RETEST - - SOlI rypi - - ATE: April 87 SAN OIEGO GEOTECHNICAL CONSULTANTS. INC. .- TABLE II LABORATORY TEST RESULTS 05-6983-001-00-10 OS NO.: NAME: Carlsbad Crossroads SOIL TYPE CLASSIFICATION 1 Light silty SAND gray green 2 Black to medium brown silty CLAY 3 Medium greenish brown silty CLAY 4 Light brown silty SAND orange DATE: April 1987 MAXIMUM OPTIMUM “:E::y MOISTURI (%) 113.5 13.5 103.4 19.2 116.5 12.9 118.9 13.2 SAN OlEGO GEOTECHNLCAL CONSULTANTS, IN<