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HomeMy WebLinkAboutCDP 92-03; ARMY & NAVY ACEDEMY; REPORT OF GRADING OBSERVATION AND FIELD DENSITY TESTING; 1992-10-30pp q03 REPORT OF GRAONG OBSERVATION AND FIELD DENSITY TESTING Proposed Crean/Atkinson Hall Northwest of Cypress Avenue and Garfield Street Carlsbad, California JOB NO. 92-6190 30 October 1992 Prepared for: Mrs. Mary Lipps ARMY AND NAVY ACADEMY ME1 GEOTECHNICAL EXPLORATION, INC. SOIL & FOUNDATION ENGINEERING • GROUNDWATER HAZARDOUS MATERIALS MANAGEMENT • ENGINEERING GEOLOGY 30 October 1992 ARMY AND NAVY ACADEMY P.O. Box 3000 Carlsbad, CA 92008 Attn: Mrs. Mary Lipps Job No. 92-6190 Subject: Report of Grading Observation and Field Density Testing Proposed Crean/Atkinson Hall Northwest of Cypress Avenue and Garfield Street Carlsbad, California Dear Mrs. Lipps: In accordance with your request, Geotechnical Exploration, Inc., hereby submits the following report summarizing our work and test results, as well as our conclusions and recommendations concerning the subject project. A representative of our firm observed the recent grading operation and tested the fill soils that were removed and recompacted during the preparation of the building pads for the subject buildings (see Plot Plan, Figure No. I). The grading described herein consisted of removing and recompacting on-site loose fills and undercutting to provide a layer of compacted fill within the building envelopes. The grading was observed and/or tested between October 22 and October 28, 1992. SCOPE OF WORK The scope of work of our services included: Observations during rough grading of the site. Performing field density tests In the placed and compacted fill. 7420 TRADE STREET • SAN EIEGO, CALIFORNIA 92121 • (619) 549-7222 • FAX: (619) 549-1604 Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 2 3. Performing laboratory tests on representative samples of the fill material. 14 • Providing professional opinions, conclusions, and recommendations regarding the observed grading and the pending work. GENERAL SITE INFORMATION The building site, consisting of approximately 4,000 square feet, is located at the northwest corner of Cypress Avenue and Garfield Street, in the City of Carlsbad, California. The property is bordered on the north and east by the Army and Navy Academy complex, on the south by Cypress Avenue, and on the west by Ocean Street. Prior to grading, the new building area sloped gently to the west, with varying slopes on the west and east sides, with elevations ranging from 52 feet above mean sea level (MSL) to 1414 feet above MSL. Mapped survey information concerning actual elevations after grading was not available at the time of this report preparation. Existing structures on the site prior to grading included three buildings and surrounding improvements which were demolished to provide room for the new buildings. Existing vegetation prior to grading consisted of lawn grass, shrubs, several large pine trees and iceplant groundcover on the slopes. The site has been prepared to receive the foundations and slab-on- grade of two buildings, which will be a maximum of two stories in height. It is our understanding that the buildings will be constructed in conformance with the Uniform Building Code, utilizing conventional- type foundations, footings, and building materials. A Plot Plan illustrating the approximate location of all our tests taken throughout the grading operation is enclosed as Figure No. I. Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 3 Work that remains to be completed at the site and that will require our observations and/or testing include any retaining wall backfill, trench backfill, and final subgrade and base preparation of areas to be paved. FIELD OBSERVATIONS Periodic tests and observations were provided by a representative of Geotechnical Exploration. Inc. to check the grading contractor's compliance with the drawings and job specifications. The presence of our field representative at the site was to provide to the client a continuing source of professional advice, 'opinions, and recommendations based upon the field representative's observations of the contractor's work, and did not include any superintending, supervision, or direction of the actual work of the contractor or the contractor's workers. Our visits were made on request of the contractor's representative (Mr. Russ Beilby, Wermers Construction). The grading operation was observed to be performed in the following general manner: Prior to placing any compacted fill, the areas to be graded were cleared of surface trash, miscellaneous debris, and/or vegetation, and temporarily stockpiled on the property. Uncompacted fills, soft or disturbed materials, and/or unsuitable soils were removed to expose competent ground. The removed material in the building pad areas was extended to a depth of at least 5 feet below finish grade and to at least 10 feet beyond the perimeter building lines. Undercut was provided to create a uniform layer of fill under the entire pad. In west fill areas, the slope was rebuilt from elevation £40 MSL. 0 AM Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 4 The exposed ground surface was scarified at least 12 inches and uniformly recomp acted to at least 90 percent of the laboratory Maximum Dry Density, prior to placement of compacted soil. Areas to receive compacted fill were, in general, observed and evaluated by our field representative prior to placing compacted fill. Soils approved for use in the compacted fill were placed in hori- zontal layers not exceeding approximately 10 inches •in loose thickness. Fill material was watered or dried at or near optimum moisture content, and mixed prior to compaction. The soils utilized in the grading operation were from on-site and consisted primarily of silty sands. Fill materials were tested and found to be compacted to at least 90 percent of Maximum Dry Density at the specific test, locations. Compaction was achieved by drying or wetting the soil, mixing it and rolling it with heavy construction equipment such as a Cat D6- H dozer. The method used to compact the slope fill surface consisted of track-walking it with the D6 dozer. Field density tests were taken at the approximate locations shown on the plot plan (Figure No. I). Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 5 TESTS Field density tests were performed in accordance with ASTM D1556. Maximum density determinations were performed in accordance with ASTM D1557, 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 data available from the testing of the soils compacted on this site. Our observations of the grading 'operation (while in progress), our 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. A. General Grading The soils utilized in the grading operation were from existing on- site soils that were removed and recompacted, and imported materials that were placed and recompacted. The soils' consisted primarily of brown silty sands. Soils of this type are considered non- to' low-expansive, per simple visual inspection. During the grading operation, the natural-ground soils were exposed (where necessary), undercut and properly prepared to receive the 'fill soils. The fill soils were placed, watered, compacted, and then tested, and were found to be compacted to at least 90 percent of Maximum Dry Density, in accordance with the requirements of the City of Carlsbad. The maximum depth of fill Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 6 soils placed on this site at the time of the grading operation monitored by this firm was not in excess of 7 feet in vertical thickness. Any surplus, loose, stockpiled soils remaining at the property should be removed and hauled off the site. The area of stockpile observed during our last visit 'was on the location of one of the demolished buildings (on the east-west direction). Grading work that needs to be completed and performed under our observations and testing include any retaining wall backfill, trench backfill, and finish subgrade and base preparation in the areas to receive pavement. B • Foundations and Slabs On-Grade The continuous foundations and spread footings shall extend a minimum depth of 18 inches into the firm natural ground or properly compacted fill, and have a minimum width of 12 inches. The continuous foundations shall be reinforced with at least four No. 4 steel bars; two bars shall be located near the top of the foundations and two bars 3 inches from the bottom. Concrete floor slabs shall be founded on at Jeast 3 inches of sand overlying a 6-mil visqueen. The slabs shall be reinforced with at least 6 x 6 - 6/6 steel welded-wire mesh or No. 3 steel bars placed on 18-inch centers. Any steel, reinforcement should be placed in the middle of the floor slab section. Proper supports should be used to keep the steel reinforcement separated from the base or soil subgrade. It is recommended that all nonstructural concrete slabs (such as patios, sidewalks, etc.), be founded on at least 2 inches of sand on nonexpansive, properly prepared soils. Proper shrinkage joints Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 7 (sawcuts) should be provided and spaced no farther than 8 feet or the width of the slab, whichever is less. The sawcuts should be performed no later than 24 hours after pouring, or as soon as the concrete is set. Sawcuts should be deepened to at least one- quarter of the thickness of the slab. If steel reinforcement (such as 6 x 6 - 6/6 welded-wire mesh) is provided for the slabs, the control joints may be spaced up to 15 feet apart. All concrete (flatwork) slabs or rigid improvements should be built - on properly -,compacted and approved subgrade and/or base material. Geotechnical Exploration, Inc. will accept no liability for damage to flatwork or rigid improvements built on untested or unapproved subgrade or base material. C. Foundation Design Parameters The recommended allowable bearing value of the property compacted fill soils placed on the site is 2,000 pounds per square foot. The recommended allowable bearing value of the competent natural ground is 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 may be utilized in the design of foundations and footings of the proposed structures when founded a minimum of 12 inches, into the firm natural ground or compacted fill for single-story structures, 18 inches for two-story structures. For on-site conditions, it is expected that the maximum settlement will not exceed 1.0 inch, and the maximum differential angular rotation will not exceed 1/300. 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 300 pounds per cubic Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 8 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, the soil is properly compacted fill or natural dense material, and the concrete is poured tight against the walls of the excavation. A Coefficient of Friction of 0.40 times the dead load may be used to calculate the total friction force between the bearing soils and the bottom of concrete wall foundations, or structure foundations, or floor slabs. D. Retaining Wall Design Parameters The active earth pressure (to be utilized in design of cantilever walls, etc.) shall be based on a Equivalent Fluid Weight of 38 pounds per cubic foot (for level backfill only and nonexpansive or low-expansive, on-site native soils). In the event that the cantilever retaining wall is surcharged by sloping backfill, the design active earth pressure shall be based on the appropriate Equivalent Fluid Weight presented in the following table: Height of Slope/Height of Wall* Slope Ratio 0.25 0.50 0.75 1.00(+) 2.0 to 1.0 L$Z$ 48 50 52 *To determine design active earth pressures for ratios inter- mediate to those presented, interpolate between the stated values. Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 9 In the event that a retaining wall is to be designed for a restrained condition, a uniform pressure equal to 8xH (eight times the total height of retained soil, considered in pounds per square foot) shall be considered as acting everywhere on the back of the wall, in addition to the design Equivalent Fluid Weight. The design pressures presented above are based on utilization of an uncontrolled mixture of expansive or low-expansive soil native to the site used in backfill operations. ' In the •event that imported, clean, granular fill soils or approved, on-site, clean sands are to be utilized as backfill material, this firm should be contacted for possible reduction of design pressures -due to level backfill, sloping backfill, or restrained wall conditions. Additional surcharge •pressures to be considered in the wall design include any loads applied within the failure block retained by the wall. E. Cut and Fill Slopes 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. 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 5 feet of the face of the fill slope may posses poor lateral stability. If not properly founded, the proposed structures and associated improvements (such as walls, fences, patios, sidewalks, driveways, asphalt paving, etc.) [1 CAR Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 10 that are located within 5 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, etc., when founded 5 feet and farther 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 5 feet inside the top of compacted fill slopes, they shall be deepened to at least .1.5 feet below a line beginning at a point 5 feet horizontally inside the fill slopes, and projected outward and downward, parallel to the face of the fill slopes (see Figure No. Ill). 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. F. Drainage 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, footings, and slopes, onto the natural drainage direction for this area or into properly designed and approved drainage facilities. Roof gutters and downspouts should be installed on all structures, and the runoff directed away from the foundations via closed drainage lines. Proper subsurface and surface drainage will help minimize the potential for waters to seek the level of the bearing soils under the foundations, footings, and floor slabs. Failure to observe this recommendation could result in uplift or undermining and differential settlement of the structures or other improvements on 11 the site. Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 11 Proper subdrains shall be installed behind all retaining and restrained retaining walls, in addition to proper waterproofing of the back of the walls. The drainage of said subdrains shall be directed to the designed drainage for the project or the natural drainage for, the area. It should be noted that changes of surface and subsurface hydrologic conditions, plus irrigation of landscaping or significant increases in rainfall over the "accepted average-annual" rainfall for San Diego County for the past 10 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. Corrective action should be taken on a site-specific basis if, and when, it becomes necessary. Planter areas and planter boxes shall be sloped to drain away from the foundations, footings, and floor slabs. Planter boxes shall be constructed with a sealed bottom, and be provided a subsurface drain installed in gravel, with the direction of subsurface and surface flow away from the foundations, footings, and floor slabs, to an'adequate drainage facility. Any backfill soils placed adjacent to or close to foundations, in utility trenches,. or behind retaining walls, that support structures and other improvements (such as patios, 'sidewalks, driveways, pavements, etc.), other than landscaping In level ground, shall be compacted to at least 90 percent of Maximum Dry Density. It is recommended that Geotechnical Exploration. Inc. observe and test the backfill 'during placement. Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 12 Geotechnical Exploration, Inc. will accept no liability for damage to structures that occurs as a result of improperly backfilled trenches or walls, or as a result of fill soils pl?ced without our observations and testing. G. Miscellaneous Recommendations 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 degration of adhesive materials and loosening of the finish-floor materials. 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. The remaining soil work to be completed at the site (such as any trench or retaining wall backfill, and final subgrade preparation of areas to receive improvement or pavement) should be performed under .our observations and testing. It is also recommended that all footing excavations be observed by a representative of this firm prior to placing concrete, to verify that footings are founded on satisfactory, soils for which the recommendations expressed in the soil investigation report remain. applicable. SUMMARY Based on our field testing and grading observation, it is our opinion that the grading operation described herein, in general, was performed in conformance with the City of Carlsbad Grading Ordinance. It is to Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 13 be understood that our test results and opinion of general acceptance do not guarantee that every cubic yard of compacted fill has been compacted to specification since not every cubic yard has been observed or tested. Our test results indicate the measured compaction degree obtained at the specific test location. We can only guarantee that our tests and observations have been made in accordance with the care and current professional standards in our field. All observed or tested work done during the grading operation appears, in general, to have been performed in accordance with the soil investigation report for this site, issued by our firm and dated March 11, 1992 (Job No. 92-6190). The grading described herein was observed and/or tested between October 22 and October 28, 1992. All statements in the report are applicable only for the grading operation observed by our firm, and are representative of the site at the time of our final site visit before the report was prepared. The firm of Geotechnical Exploration, Inc. shall not be held responsible for fill soils placed without our observations and testing at any other time, or for subsequent changes to the site by others, which directly or indirectly cause poor surface or subsurface drainage, water erosion, and/or alteration of the strength of the compacted fill soils. In the event that any changes in the nature, design, or location of the buildings or improvements are planned, the conclusions and recommen- dations contained in this report shall not be considered valid unless the changes are reviewed and the conclusions of this report modified or verified in writing. 0 Professional opinions presented herein have been made based on' our tests, observations, and experience, and they have been made in accordance with generally accepted current geotechnical engineering principles and practices. This 'warranty is in lieu of all other warranties, either expressed or intended. 0 Army and Navy Academy Job No. 92-6190 Carlsbad, California Page 14 Thank you for this opportunity to be of service. Should any questions arise concerning this report, you may contact the undersigned. Reference to our Job No. 92-6190 will help to expedite a reply to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. Jaime K.rros,RC.. 34422/G.E. 2007 W No. 002 07 Senior Geotechnical Engineer cc: Addressee (2) 'FC' Mr. Russ Beilby, Wermers Construction (2) F] VAN SCALE: i = 30 VICINITY MAP LEGEND STRUCTURE lATE UMITS RK AREA 22 FIELD DENSITY TEST A13 LOCA1ON OF SLOPE PROP)SED LOCATION OF WALL P LOT PLAN OCEAN STREET NOTE: This Plot Plan is not to be used for legal REFERENCE: THIS PLOT PLAN WAS PREPARED FROM AN purposes. Locations and dimensions are approxi— EXISTING GRADING PLAN BY DOUGLAS BENDER AND mate. Actual property dimensions and locations of utilities may be obtained from the Approved ASSOCIATES AND FROM ON—SITE FIELD RECONI\4JSSANCE Building Plans or the "As—Built' Grading Plans. PERFORMED BY GE!. OCTOBER 1992 PROPOSED BUILDING ADDITIONS ARMY/NAVY ACADEMY Northeast Corner OCEAN STREET and CYPRESS AVENUE CARLSBAD, CA. FIGURE NUMBER I JOB NUMBER 92-6190 Vic Compaction Test Results Test Date Location Elevation of Fill Moisture Field Density Soil Type Relative Compaction 1 10/22/92 Bldg I east 43.0 8.4 110 pcf I 90% 2 10/22/92 Bldg I east 43.0 9.7 110 pcf I 90% 3 10/23/92 Bldg I east 45.0 10.5 111 pcf I 91% 4 10/23/92 Bldg I middle 43.0 13.0 116 pcf I 95%. 5 10/23/92 Bldg I middle 45.0 11.7 112 pcf I 92% 6 10/23/92 Bldg I middle 45.0 111 112 pcf I 92% 7 10/23/92 Bldg I west 41.0 10T7 113 pcf I 92% 8 10/23/92 Bldg I west 41.0 10.7 113 pcf I 92% 9 10/23/92 Bldg I west 43.0 13.7 117 pcf I 96% 10 . 10/23/92 Bldg I west 43.0 12.9 . 114 pcf I 94% 11 10/26/92 Bldg I west 45.0 9.1 111 pcf I 91% 12 10/26/92 Bldg I west 45.0 11.4 111 pcf I 91% 13 10/27/92 Bldg II south 43.0 12.1 119 pcf I 98% 14 10/27/92 Bldg II south 43.0 11.4 112 pf I 92% 15 10/28/92 Bldg II south 45.0 11.7 116 pcf I 95% -16 10/28/92 Bldg II south 45.0 11.1 114 pcf I 94% 17 10/28192 Bldg II north 43.0 9.9 115 pcf I 94% 18 10/28/92 Bldg II north 43.0 9.9 115 pcf I 94% 19 . 10/28/92 Bldg II north 45.0 12.1 . 116 pcf I 95% 20 10/28/92 Bldg II north 45.0 10.1 116 pcf I 95% 21 10/28/92 Bldg Feast S.G. 13.5 111 pcf I 91% 22 10/28/92 Bldg I east S.G. 13.7 . 114 pcf I 94% 23 10/28/92 Bldg I middle S.G. 13.9 116 pcf I 95% 24 10/28/92 Bldg I middle S.G. 14.1 117 pcf I 96% 25 10/28/92 Bldg I west S.G. 11.7 116 pcf I 95% 26 10/28/92 Bldg I west S.G. 11.4 114 pcf I 94% 27 10/28/92 Bldg II south S.G. 11.3 115 pcf I 94% 28 10/28/92 Bldg II south S.G. 11.7 110 pcf I 90% 29 10/28/92 Bldg II north S.G. 12.9 116 pcf I 95% 30 10/28/92 Bldg II north S.G. 11.7 118 pcf I 97% CONTINUED Job No. 92-6190 Figure No. Ha CAN Compaction Test Results Depth Moisture Field Soil Relative Test I Date Location I Fill Density Tvoe I Compaction SOIL CLASSIFICATION TYPE DESCRIPTION OPTIMUM MOISTURE MAXIMUM DRY DENSITY I Orange-brown, silty, fine to medium sand. 11.0% 122 pcf Job No. 92-6190 Figure No. llb CIRO n FOUNDATION REQUIREMENTS NEAR SLOPES PROPOSED STFAXTURE CONCRETE FLOOR SLAB SETBACK - 10 ------ 5' 4 • I444 44qP • • .4. p • • 4 4 2 N . S •• 44 REINFORCEMENT OF N FOUNDATIONS AND FLOOR 444 4 . N e SLABS FOLLOWING THE , RECOMMENDATIONS OF THE ARCHITECT OR STRUCTURAL ENGINEER • • 44 4, , •4 CONCRETE FOUNDATION ., . • 180 MINIMUM OR AS DEEP AS QUID FOR LATEML STABILITY TOP OF COMPACTED FILL SLOPE (Any loose soils on the slope surface shall not be considered to provide lateral or vertical strength for the footing or for slope stability. Needed depth of ieent shall be measured from competent soil.) COMPACTED FILL SLOPE WITH NAXINIM INCLINATION AS PER SOILS REPORT. TOTAL DEPTH OF FOOTING MEASURED FROM FINISH SOIL SUB-GRADE COMPACTED FILl. N OUTER MOST FA1'- 5' OF FOOTING TYPICAL SECTION (SHOWING PROPOSED FOUNDATION LOCATED WITHIN 5 FEET OF TOP OF SLOPE) 18' FOOTING/ 5' SETBACK TOTAL DEPTH OF FOOTING 1.5:1.0 SLOPE J 2.0:1.0 SLOPE 0 58' 48' 510 42 42' 36' 34• 306 41 260.24' 5' 18' W S when applicable FIGURE NUMBER lIE. JOB NUMBER 92-6190 I I =rPHEN