The URL can be used to link to this page

Home My WebLink AboutCT 14-09; Uptown Bressi Ranch; Lime/Cemet Treated Pavement Section Recommendations Lots 29-32; 2017-07-21GE OCON I NCORPORATED GEO T EC HNI CAL • Project No. G2 108-32-0 I July21,2017 Shea Homes 9990 Mesa Rim Road San Diego, Califo rnia 92121 Attention: Mr. G reg Ponce L RECORD COPY . I ebrJ,, Dae . LG Subject: LIME/CEMENT-TREATED PAVEMENT SECTION RECOMMENDATIONS UPTOWN BRESSI RA CH RETAIL LOTS 29 THROUGH 32 CARLSBAD, CALI FORNIA Reference: Update Report and Change o.f Geotechnical Engineer o.f Record, Bressi Ranch, Lots 29 through 32, Carlsbad, California, prepared by Geocon Incorporated, dated April 24, 20 17. Dear Mr. Ponce: In accordance with your request, we have performed supplemental geotechnical services to evaluate alternati ve pavement recommendations for the roadways at the subject site. Based on recent laboratory testing and our experience with sim ilar soil, we expect in-situ R-values to range between O and 10. Based on recent discussions regarding alternative pavement designs, we understand that a lime or cement-treated pavement section is being considered as an alternative to a conventional pavement section considering the low subgrade support characteristics. T he scope of our services included obtain ing representative subgrade soil samples and performing laboratory tests to aid in determining the appropriate li me or cement-treated pavement design. Subgrade soils in the area are predominately clayey sands, sandy clays and clays and typically exhibit relatively low R-Value characteristics. Laboratory sol uble su lfate content testi ng was performed in accordance w ith California Test Method 4 17 and the test results are presented in Table I. These tests were perfom1ed to determine the feasibili ty of using lime or cement as an additive to stabilize the existing clayey subgrade soils. TABLE I SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE CONTENT TEST RESULTS CALIFORNIA TEST METHOD 417 Sample No. Water-Soluble Sulfate Content(%) 2016 CBC Classification S-1 0.063 Not Applicable (SO) S-2 0.100 Moderate (S 1) 6960 Flanders Drive • San Diego, California 9212 1-297 4 • Telephone 858.558.6900 • Fax 858.558.6 159 .o £D (l) ca .i:::. 0 ·-~ The laboratory tests indicate that the subgrade soils have a water-soluble sulfate content of less than 5,000 parts per million (ppm). Therefore, using lime or cement as an additive to the clayey soils is feasible. Resistance Value (R-Value) tests were performed on subgrade soils utilizing lime and cement as an additive. The amount of lime or cement content needed to stabilize the clayey subgrade soil was determined by the Texas Method, which consists of performing a series of plasticity index (PI) tests at different lime and cement contents until the PI generally stabilizes at its lower bound. The test results are presented in Tables II and III. Based on the results of our testing, we recommend a lime or cement content of approximately 7 percent by weight or greater. R-value testing was performed at quick lime and cement contents of 7 percent to evaluate the treated R-Value characteristics. The laboratory R- value tests results are presented in Table IV. TABLE II SUMMARY OF LABO RA TORY PLASTICITY INDEX VS. QUICK LIME CONTENT TEST RES UL TS ASTM D4318 Sample Plasticity Index 0% 2% 4% 6% 8% S-1 36 37 22 9 NP S-2 33 26 12 12 NP NP = Non-Plastic TABLE Ill SUMMARY OF LABO RA TORY PLASTICITY INDEX VS. CEMENT CONTENT TEST RES UL TS ASTM D4318 Sample Plasticity Index 0% 2% 4% 6% 8% 10% S-1 ---34 26 26 18 NP S-2 32 30 23 24 27 NP NP= Non-Plastic The R-Value samples treated with lime or cement contents of 7 percent by dry weight yielded R- Values ranging between 51 and 57. Laboratory R-Value tests were performed in accordance with ASTM D 2844-07 (California Test Method No. 301) and the test results are presented in Table IV. Sample No. S-1 S-2 TABLE IV SUMMARY OF LABORATORY R-VALUE TEST RESULTS CALIFORNIA TEST METHOD 301 R-Value R-Valne Geologic Unit No Additive 7% Quick Lime by Dry Weight Santiago Formation ------ Santiago Formation ---57 Project No. G2108-32-01 -2- R-Value 7% Cement by Dry Weight 51 --- July 21, 2017 Traffic indices ranging between 4.5 and 7.0 were used to evaluate the pavement secti ons presented in Table V. Based on the above informati on and laboratory testing, we recommend the lime or cement- treated pavement sections indicated on Table V. Pavement section presented below utilized the City of Carlsbad's Standard Drawing GS-17, Structural Section of Streets and Alleys. T hese recommended pavement recommendations should be considered preliminaiy with final sections to be approved by the City of Carlsbad. Based on the above information, th e following pavement recommendations are provided in Table V. An average R-Value of 50 with a lime or cement content of 7 percent by weight was used for design purposes. TABLE V PAVEMENT SECTION RECOMMENDATIONS QUICK-LIME OR CEMENT TREATED SU BG RADE SOILS AT 7% BY DRY WEIGHT Traffic Asphalt Aggregate Depth of Lime- Location Index R-Value Concrete Base (inches) Treated Subgrade (inches) Soil (inches) Cul-de-Sac 4.5 50 4 4 12 Loca I Street 5.0 50 4 4 12 Collector 6.0 50 4 6 12 Light Industrial 7.0 50 4 6 12 We recommend that the lime or cement-treated subgrade and aggregate base be moisture conditioned, and compacted to a minimum of 95 percent relative compaction based on ASTM D 1557. Asphalt concrete should be compacted to at least 95 percent of the laboratory Hveem density in accordance w ith ASTM D 2726. The lime/cement-treated subgrade soil s should be placed and compacted in accordance with the recommendations contained in Section 27 of the Ca/trans Manual and Section 30 I of the Standard Specifications/or Public Works Construction. The subgrade stabilization should be observed and tested by Geocon Incorporated to verify that the project specifications discussed above have been met and the typical stabilization procedures provided in Section 27 of the Ca/trans Manual and Section 301 of the Standard Specifications for Public Works Construction were achieved . The performance of pavement is highly dependent on providing positive surface drainage away from the edge of the pavement. Ponding of water on or adjacent to the pavement will likely result in pavement distress and subgrade fa ilure. To reduce the occurrence of such situations, we recommend that a m inimum drainage gradient of one percent be maintained for pavement surfaces. Drainage from landscaped areas should be directed to controlled drainage structures. It is very important to prevent any ponding and/or excessive landscape irrigation w ithin open areas adjacent to the curb/gutter areas. PCC PAVEMENT RECOMMENDATIONS A ri gid Portland cement concrete (PCC) pavement section should be placed in driveway entrance aprons and trash bin loading/storage areas. The concrete pad for trash truck areas should be large enough such that the truck wheels will be positioned on the concrete during loading. We calculated the Project No. G2 I 08-32-0 I -3 -July21.2017 ri gid pavement section in general co nformance with the procedure recommended by the American Concrete Institute report ACI 330R-08 Guide for Design and Construction of Concrete Pad"ing Lots using the parameters presented in Table VI. The parameters presented below are conside red appropriate considering a lime/cement treated subgrade soils exhibiting laboratory R-values of 50 or greater. TABLE VI RIGID PAVEMENT DESIGN PARAMETERS Design Parameter Design Value Modulus of subgrade reaction, k 200 pci Modulus of rupture for concrete, MR 500 psi Traffi c Category, TC A and C Average daily truck traffic, ADTT 10 and 100 Based on the criteria presented herein, the PCC pavement sections should have a minimum thickness as presented in Table VI I. TABLE VII RIGID PAVEMENT RECOMMENDATIONS Location Portland Cement Concrete (inches) Automobile Parking Areas (TC=A) 5.0 . Heavy Truck and Fi re Lane Areas (TC=C) -0.5 The PCC pavement should be placed over subgrade so il that is compacted to a dry density of at least 95 percent of the laboratory maximum dry density near to slightly above optimum moisture content. This pavement section is based on a minimum concrete compressive strength of approximately 3,000 psi (pounds per square inch). A thickened edge or integral curb should be constructed on the outside of concrete slabs subjected to wheel loads. The thickened edge should be 1.2 times the slab thickness or a minimum thickness of 2 inches, whichever results in a thicker edge, and taper back to the recommended slab thickness 4 feet behind the face of the slab (e.g., a 7-inch-thick slab would have a 9-inch-thi ck edge). Reinforcing steel will not be necessary within the concrete for geotechnical purposes with the possible exception of dowels at construction joints as discussed herein. To contro l the location and spread of concrete shrinkage cracks, crack-control joints (weakened plane joints) should be included in the design of the concrete pavement slab. Crack-control joints should not exceed 30 times the slab thickness with a maxim um spacing of 12.5 feet and 15 feet for the 5.5-and 7- inch-thick slabs, respectively, and should be sealed with an appropriate sealant to prevent the migration of water through the control joint to the subgrade materials. The depth of the crack-control joints should be determined by the referenced AC I report. Concrete curb/gutter should be placed on soil subgrade compacted to a dry density of at least 90 percent of the laboratory maximum dry density near to slightly above optimum moisture content. Cross-gutters should be placed on subgrade so il compacted to a dry density of at least 95 percent of Project No. G2108-32-01 -4 -July21.2017 - the laboratory maximum d1y density near to slightly above optimum moisture co nte nt. Base materials should not be placed below the curb/gutter, cross-gutters, or sidewalk so water is not able to migrate from the adjacent parkways to the pavement sections. Where flatwork is located directly adjacent to the curb/gutter, the concrete flatwork shou Id be structural ly connected to the curbs to help reduce the potential for offsets between the curbs and the fl atwork. If you have any questions regarding this letter, or need additional information, please contact the undersigned at you r conveni ence. Ve1y truly yours, GEOCO (e-mail) (2/pkup) IN CORPORA TED Addressee Ri ck Engineering Attention: Mr. John Goddard Project o. G2 I 08-32-0 I -5 -July 21. 2017