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Home My WebLink AboutCT 14-09; UPTOWN BRESSI RANCH; LIME/CEMENT-TREATED PAVEMENT SECTION RECOMMENDATIONS; 2017-07-21RECEIVED. Shea Homes JUL 212017 9990 Mesa Rim Road - San Diego, California 92121 LAND DEVELOPMENT ENGNEERI.NG . Attention: Mr. Greg Ponce Subject LIME/CEMENT-TREATED PAVEMENT SECTION RECOMMENDATIONS UPTOWN BRESSI RANCH RETAIL LOTS 29 THROUGH 3 CARLSBAD, CALIFORNIA 2 Reference Update Report and Chazge of Geotechnical Engineei of Record Bressi Ranch Lots 29 through 32 Carlsbad California prepared by Geocon Incorporated, dated April 24, 2017. Dear Mr. Ponce: In accordance with your request, we.have performed supplemental geotechnical services to evaluate alternative pavement recoiimendatins for the roadways at the subject site Based on recent laboratory testing and our experience with similar soil, ye expect in-situ R:values to range between 0 and 10 Based on recent discussions regarding alternative pavement designs, 've understand that a lime or cement-treated pavement section is bbing c\onsidered as an alternative to a conventional pavement section considering the low sub grade support characteristics The scope of our services included obtaining representative subgrade soil samples and performing laboratory tests to aid in determming the appropriate lime or cement-treated pavement qesign sfibgrade soils in the area are predominately clayey sands, sandy clays and clays and typically exhibit relatively low R-Value characteristics Laboratory soluble sulfate content testing was performed in accordance with California Test Method 417 and the test results are presented in Table I These tests were perfohiied to.-determine the feasibility of using lime or cement as an additive to stabilize the existing clayey subgrade soils TABLEI SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE CONTENT TEST RESULTS CALIFORNIA TEST METHOD 417 e N Samplo Water-Soluble Sulfate Content (%) 2016 CRC Classification S 1 0 063 Not Aplicable (SO) S_`2 .0.100_"Moderate (S1)( 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 (PT) tests at different lime and cement contents until the P1 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 LABORATORY PLASTICITY INDEX VS. QUICK LIME CONTENT TEST RESULTS ASTMD43I8 Sample Plasticity Index 0% 2% 4% 6% 8% S-i ' 36- 37 22 9 NP S-2 33 26 12 12 NP NP = Non-Plastic TABLE III SUMMARY OF LABORATORY PLASTICITY INDEX VS. CEMENT CONTENT TEST RESULTS ASTMD43I8 Sample Plasticity Index 0% 2% 4% 6% 8% 10% S-I --- 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. / TABLE IV SUMMARY OF LABORATORY R-VALUE TEST RESULTS CALIFORNIA TEST METHOD 301 Sample No. Geologic Unit No Additive R-Value .7% Quick Lime by 11-Value 7% Cement by Dry Dry Weight ' Weight S-i Santiago Formation . --- --- . 51 S-2 ' Santiago Formation --- . 57 Project No. G2108-32-01 . . . -2- . ' . July 21,017 Traffic indices ranging between 4.5 and 7.0 were used to evaluate the pavement sections presented in Table V. Based on the above information 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-1 7, Structural Section of Streets and Alleys. These recommended pavement recommendations should be considered preliminary with final sections to be approved by the City, of Carlsbad. Based on the above information, the following pavement recommendations are proyided 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 PAVEMENT SECTION RECOMMENDATIONS QUICK-LIME OR CEMENT TREATED SUBGRADE SOILS AT 7% BY DRY WEIGHT Location Traffic In ' R-Value Asphalt Concrete (inches) Aggregate Base (inches) Depth of Lime- Treated Subgrade' - Soil (inches) Cul-de-Sac 4.5 50 4 4 12 - Local 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 - with ASTM D 2726 The lime/cement-treated subgrade soils should be placed and compacted in accordance with the recommendations contained in Section 27 of the Caltrans Manual and Section 301 of the Standard SpecifIcations for 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 Caltrans 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 likelyr. result in pavement distress and subgrade failUre. To reduce the occu'rrence of such situations,. 'we recommend that a minimum 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 within open areas adjacent to the curb/gutter areas FCC PAVEMENT RECOMMENDATIONS A rigid 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. G2108-2-0I :' ' ' -3 u1y 21, 2017 I rigid pavement section in general conformance with the procedure recommended by the American Concrete Institute report ACI 330R-08 Guide for Design and Construction of Concrete Parking Lots using the parameters presented in Table VI. The parameters preented below are,, considered 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 Traffic Category, TC A and C Average daily truck traffic, ADTF 10 and 100 Based on the criteria presented herein, the PCC pavement sections should have a minimum thickness as presented in Table VII'. TABLE VII RIGID PAVEMENT RECOMMENDATIONS Location . Portland Cement Concrete (inches) Automobile Parking Areas (TC=A) 5.0 Heavy Truck and Fire Lane Areas (TCC) 6.5 The PCC pavement should be placed over subgrade soil 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-thick 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 control 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 maximum spaCing of 1,2.5 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 ACI 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 soil compacted to a dry density .of'at least 95 percent of Project No:'G2108-32-01 ' . ' . ' -4- . . July 21, 2017