2009-192A - Laserfiche WebLink

Home Browse Search

A. M . ENGINEERING AND TESTING, INC. - Geotechnical Exploration Indian River County Parks Maintenance Complex, IRC Project No . 0710 A . M . Engineering Project No. PSL 1825 - 1 Floor Slabs A conventional slab-on- grade can be used for the ground floor of the structures . The upper one foot of subgrade below the floor slabs should be compacted to 98 percent of the modified Proctor maximum dry density (ASTM D 1557) prior to placement of the concrete. An estimated modulus of subgrade reaction of 200 pounds per cubic inch (pci) can be used for design of the slab-on- grade. The floor slabs should have a minimum thickness of four inches. Control joints should also be incorporated in the slabs at intervals (in feet) of two to three times the thickness of the slab (in inches) to control shrinkage cracks . The joints should be sawn as soon as the slabs can support loads, but not so soon as to cause raveling of the concrete surface and aggregate during sawing. Typically the cuts need to be made within two to eight hours after placement of the concrete (before shrinkage cracks can begin). The minimum saw-cut depths should be one quarter of the slab thickness. A moisture barrier is recommended beneath the floor slabs to prevent moisture migration from the underlying soil resulting indampnessof the slab. SITE PREPARATION RECOMMENDATIONS i Stripping, Proof-rolling and Proof-compaction The construction area should be stripped of all surface vegetation, top soil , trees, roots, debris and other deleterious matter within and at least five feet beyond the perimeter of the proposed buildings and in all paved areas . Any areas to receive fill should be likewise stripped. The depth of the stripping will vary from 6 to 24 inches across the site. A 2 foot thick layer of sand with surface organics and organic.silt was encountered in borings AB-7 , AB-8 and AB- 11 . The cleared areas should then be proof-rolled and compacted with a 15-ton (minimum) vibratory roller operating at a "slow walk" speed. The vibratory compactor should make at least eight overlapping passes over the entire cleared area, four passes in one direction and four more at a right angle to the first four passes. Proof-rolling helps to detect any soft or loose zones and buried debris. If unstable areas are encountered, the project engineer or the geotechnical consultant should be advised, the matter investigated and the problem resolved. Because the initial proof-rolling is very critical, we recommend that a representative of A. M. Engineering and Testing, Inc. monitor the operation. { After proof-rolling, the cleared areas should be compacted until the upper 2 feet of soil achieve a density of at least 95 percent of the modified Proctor maximum dry density (ASTM D 1557) . A representative of A. M. Engineering and Testing, Inc. should check the compaction with field density tests prior to placing any fill 5