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Home My WebLink AboutMS 01-08; KELLY CORPORATE CENTER; KELLY RANCH CORPORATE CENTER SIT AND OFFSITE IMPROVEMENTS AND BUILDING 2A EAST ENTRANCE; 2001-07-105W' 7-25 MS 0/— og ROBERT PRATER ASSOCIATES Consulting Geotechnical Engineers & Geologists JUL 11 2001 July 10, 2001 543-iD-1, 01-129 OciA1ES The Allen Group 2141 Palomar Airport Road, Suite 300 Carlsbad, California Attention: Mr. Harve Filuk Re: Kelly Ranch Corporate Center Site and Offsite Improvements and Building 2A East Entrance - Aviara Parkway Carlsbad, California Gentlemen: Robert R. Prater, C.E. 1942-1980 Wm. David Hespeler, CE., G.E. RECEIVED JUL 20 2001 ENGINEERING DEPARTMENT In accordance with your request, we are providing this letter regarding the proposed driveway entrance off Aviara Parkway along the east side of the subject site. We previously performed a geotechnical investigation for the Kelly Ranch Corporate Center, the results of which were presented in our report dated April 30, 1997. The results of our earthwork observation, testing and as-built geology services associated with the previous mass grading operations at the subject site were presented in our report dated April 12, 2000. An update geotechnical reconnaissance letter dated March 23, 2001, was also issued for the subject project. According to the improvement plans, Sheet 17 of 27, an unknown type retaining wall is apparently indicated at the toe of a proposed fill slope which is located at the top of a rip rap lined drainage channel. It is our understanding that the wall would be a reinforced earth wall (geogrid) up to about 7-1/2 feet in height with a proposed 2(horizontal) to 1(vertical) fill slope extending up about 6 feet in height from the top of the wall to the drive. In light of the proximity of the channel to the proposed wall, we recommend that the proposed wall not be constructed at the base of the fill slope. An alternative to the retaining wall at the bottom of the slope would be to steepen the fill slope to a 1-1/2 to 1 inclination and, if needed, build a small retaining wall at the top of the slope. Based on our previous work and current analysis, it is our opinion that a proposed 1-1/2 to I fill slope that will have a maximum, composite height of 20 feet will have a safety factor in excess of 1.5 against mass and surficial instability. Attached are our stability calculations. In order to protect the toe of the proposed fill slope, we recommend that a key be excavated at the toe a minimum of 4 feet deep and 8 feet wide. Prior to the placement and compaction of the fill, a 4125 Sorrento Valley Blvd., Suite B, San Diego, California 92121 • (858) 453-5605 FAX: (858) 453-7420 r cP12 July 10, 2001 543-ID-1,01-129 Page 2 geotextile fabric such as Mirafi 500X or better should be placed across the bottom of the key and against the rip rap so as to separate the new fill from the rip rap. It is imperative that proper compaction be achieved to the face of the slope during construction. In the event a reinforced earth wall is required at the top of the slope, we recommend the following soil parameters be used in the design: Angle of Internal Friction: 28 degrees for the reinforced, retained, and foundation zones. Cohesion: 400 pounds per square foot for the reinforced, retained, and foundation zones. Moist Unit Weight: 120 pounds per cubic foot for the reinforced, retained, and foundation zones. In addition, we recommend that the gravel base consist of compacted aggregate base or compacted gravel completely enveloped in filter fabric. No passive pressures in front of the wall should be used. Temporary cut slopes should be no steeper than 3/4 horizontal to 1 vertical. Our services consist of professional opinions and recommendations made in accordance with generally accepted geotechnical engineering principles and practices. This warranty is in lieu of all other warranties either express or implied. If you have any questions, please call. Very truly yours, ROBERT PRATER ASSOCIATES Wm. D. Hespeler, G.E. WDH:jb Attachment Copies: Addressee (2) Reno Contracting, Attn: Messrs. Dan Swartzer and Steve Hon (2) Crosby, Mead, Benton and Associates, Attn: Mr. Bruno Callu (2) * * ******* * **** * ** XSTABL Slope Stability Analysis using the Method of Slices Copyright (C) 1992-96 Interactive Software Designs, Inc. Moscow, ID 83843, U.S.A. All Rights Reserved Ver.5.200 96-1358 Problem Description: Kelly, SE Corner 1.5 to I with water SEGMENT BOUNDARY COORDINATES ----------------------------------------------------- 5 SURFACE boundary segments Segment x-left y-left x-right y-right Soil Unit No. Uft Lfi.'I (-ft) Uft Below Segment 1 .0 72.0 14.0 72.0 1 2 14.0 72.0 26.0 79.0 1 3 26.0 79.0 42.5 90.0 2 4 42.5 90.0 42.6 93.0 2 5 42.6 93.0 80.0 93.0 2 8 SUBSURFACE boundary segments Segment x-left y-left x-right y-right Soil Unit Lfi Below Segment 1 26.0 79.0 26.5 74.5 1 2 .0 68.0 15.5 68.0 3 3 15.5 68.0 26.5 74.5 3 4 26.5 74.5 34.5 74.5 3 5 34.5 74.5 35.0 79.5 3 6 35.0 79.5 46.0 80.0 3 7 46.0 80.0 46.1 82.0 3 8 46.1 82.0 80.0 84.0 3 ISOTROPIC Soil Parameters 3 Soil unit(s) specified Soil Unit Weight Cohesion Friction Pore Pressure Water Unit Moist Sat. Intercept Angle Parameter Constant Surface (pcf) (deg) 1 110.0 130.0 .0 38.00 .000 .0 1 2 130.0 135.0 800.0 31.00 .000 .0 1 3 120.0 130.0 400.0 28.00 .000 .0 1 1 Water surface has been specified Unit weight of water = 62.40 (pcf) Water Surface No. 1 specified by 4 coordinate points PHREATIC SURFACE, * **** *** ** * * * Point x-water y-water fi) 1 .00 77.00 2 26.50 77.00 3 29.00 74.50 4 80.00 68.00 A critical failure surface searching method, using a random technique for generating CIRCULAR surfaces has been specified. 6400 trial surfaces will be generated and analyzed. 80 Surfaces initiate from each of 80 points equally spaced along the ground surface between x = 3.0 ft and x = 25.0 ft Each surface terminates between x = 45.0 ft and x = 60.0 ft Unless further limitations were imposed, the minimum elevation at which a surface extends is y = .0 ft * * * * * DEFAULT SEGMENT LENGTH SELECTED BY XSTABL * * * * * 3.0 ft line segments define each trial failure surface. ------------------------------------ ANGULAR RESTRICTIONS ------------------------------------ The first segment of each failure surface will be inclined within the angular range defined by: Lower angular limit = -45.0 degrees Upper angular limit = (slope angle - 5.0) degrees The following is a summary of the TEN most critical surfaces Problem Description: Kelly SE Cor 1.5 to 1 with water wp Correction Initial Terminal Modified Factor x-coord x-coord JANBU FOS ift) £Ik) 2.461 1.076 5.51 56.48 2.462 1.077 4.11 55.71 2.462 1.076 6.90 55.80 2.462 1.075 4.39 56.61 2.462 1.076 6.06 56.82 2.463 1.076 .6.62 55.31 2.464 1.078 5.51 55.40 2.464 1.075 6.34 56.82 2.464 1.075 7.46 56.86 2.465 1.077 4.67 57.65 * * * END OF FILE * * * Available Strength 5.095E+04 5.039E+04 4.893E+04 5.056E+04 5.109E+04 4.809E+04 4.992E+04 5.018E+04 4.990E+04 5.445E+0 543-104 7-09-.. 17:29 110 100 91 90 91 UI x 80 >- 70 60 0 Kelly SE Car 1.5 to I with water wp 10 most critical surfaces, MINIMUM JANBU FOS = 2.461 10 20 30 40 50 60 70 80 X-AXIS (feet) V SURFICIAL STABILITY CALCULATIONS Slope faceiIii1 F.S.= C+TbdCOSPthflI d sin 3 cos 3 Potential Failure Surface Where + = angle of internal friction C = apparent cohesion = saturated unit weight = bOUyant unit Weight P = slope angle d = depth to potential failure surface F.S. = Factor of Safety Boring Depth + c No. (ft) (degrees) (psf) 31 400 31 400 31 400 Y s Y b (pcf) (pcf) (ft) F.S. 135 72.6 1 6.6 135 72.6 2 3.4 135 72.6 3 2.4