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Valley R Center-CS 890920RE: ,ii tJl(l!:l-II HI '1'1 !(I. V~L.t.,~',f" ~.4qk.tC.~ c.~t4-r~--e COMM. NO.: ARE SENDING YOU HEREYVITH THE FOLLOVVING COPIES SUBJECT: ! DATE: REMARKS: URBAN ARCHITECTURE-- DALLP6 BY: CC,; URBAN ARCHITECTURE--DALLAS 7001 PRESTON RD. SUITE 210 L.B. 12 DALLAS, TEXAS 75205 {214J 522-8494 VALLEY RANCH CENTRE D08.03 UAD #84437 08.03-89 URI3AN ARCHITECTURE--DALL/~S 7001 PRESTON RD. SUITE 210 L.B. 12 DALLAS, TEXAS 75205 (214) 522-8494 It is recommended that the existing clay soils in drive and parking areas be excavated to achieve final subgrade elevation. The exposed surface of the clays should be scarified to a depth of at least 6 inches and mixed with an estimated 5 to 7 percent of hydrated lime (by dry unit weight) in conformance with Texas Highway Department Item 260. The actual amount of lime required should be determined by additional laboratory tests. Results of a lime series reported by Southwestern Laboratories indicate that 6 percent of hydrated lime will be required at this 'site. The soil-lime 'mixture should then be compacted t© at least 98 percent of Standard Proctor maximum dry density (ASTM D 698) at or slightly above the optimum moisture content. In all areas where hydrated lime is used to stabilize the subgrade soils, routine Atterberg-limit tests should be performed to assure that the resulting plasticity index of the soil-lime mixture is at or below 15. Texas this soils Triaxial Classification tests have not been performed for specific project, but our previous experience with similar indicates that the Texas Triaxial value for lime stabilized clay will be about 1.0. The Texas Triaxial value for the natural untreated clay will be about 6.0. using the above values, and assuming normal traffic for a 15-year project life, we provide the following pavement recommendations for the parking.and drive areas. An asphaltic concrete pavement section constructed upon a lime stabilized subgrade could consist of at least 5.0 inches of asphaltic concrete, composed of 3.5 inches Page 16 · the light cover for r equ i r ed. of binder under 1.5 inches of surface course in light duty (automobile) traffic areas. In areas where heavy truck traffic is expected, 6 inches of asphaltic concrete (4.5 inches of binder and 1.5 inches of surface course) should be adequate. In the event concrete pavements are used, the above recommended procedure for mechanical lime stabilization would also be required due to the highly plastic soils encountered near the surface and the fact that the pavements are Subject to flooding. Pavements could then consist of 5 inches of adeqdately reinforced concrete in both light duty.and heavy truck traffic areas~,- Theoretically, a thinner pavement section is possible in traffic area, however, to provide adequate concrete the reinforcing steel., a 5 inch pavement section is All concrete for pavements should have. a 28-day design strength of at least 3,000 psi. The calculations used to determine the required pavement thickness are based on only physical and engineering properties of the materials and conventional thickness determination procedures. Related civil design factors such as subgr ade drainage, shoulder support, cross-sectional configurations, surface elevations, reinforcing ste el, joint design and environmental factors will significantly affect the service life and must be included in the preparation of the constructed drawings and specifications. Page 17