12 02/18 blocks should be poured on and against undisturbed soil or soil tamped to 95% proctor density. Thrust blocks shall be installed using a concrete having a compressive strength of not less than 3,000 psi minimum ultimate 28 days compressive strength, air entrained, with water reducing admixture. Where the soil bearing value is less than 1,000 pounds per square foot, Thermal Pipe System, Inc. will make the necessary calculations and recommendations as to how the fitting should be thrusted. Where special thrust provisions are needed, Thermal Pipe System, Inc. will recommend the necessary design. The table on the following page gives the thrust load at any fitting in lbs. at 100 psi* pressure. Size (in.) 90º Elbow 45º Elbow Tee 2 510 276 361 3 1,187 642 839 4 2,025 1,096 1,432 6 4,458 2,413 3,152 8 7,763 4,201 5,489 10 11,922 6,452 8,430 12 16,750 9,065 11,844 *For pressure other than 100 psi increase loads proportionately (example: for 150 psi multiply by 1.5; for 200 psi multiply by 2.0: etc.) NOTE: Dead End and Anchor loads are equal to TEE shown above. The approximate safe bearing loads of various soils given in the following table are for horizontal thrusts when the depth of cover over the top of the pipe exceeds two feet. These loads are estimates only. Actual soil and safe bearing loads should be determined by the Design Engineer. SOIL SAFE BEARING LOAD lbs./sq. ft. Muck, Peat etc.* 0 Soft Clay 1,000 Sand 2,000 Sand & Gravel 3,000 Sand & Gravel Cemented with Clay 4,000 Hard Shale 10,000 * All thrusts are resisted by piles or tie rods to solid foundations, or by removal of muck or peat and replacement with ballast of sufficient stability.