9 First American Way - Soils Report

Home Browse Search

Lutzky Associates Development. LP - Geotechnical Investigation MACTEC Project 4953-03-2631 September /8.2003 The electronic files of the modified orthogonal horizontal components of acceleration time histories are included in the enclosed CD-ROM disk, attached as Appendix C. 6.7 FLOOR SLAB SUPPORT It is not expected that the base isolated building will have floor slabs supported on grade. However, if there are any floor slabs to be supported on grade, this section contains the recommendations. The subgrade should be prepared as recommended in Section 7.11, Grading. Construction activities and exposure to the environment can cause deterioration of the prepared subgrade. Therefore, we recommend our that our field representative observe the condition of the final subgrade soils immediately prior to slab-on-grade construction, and, if necessary, perform further density and moisture content tests to determine the suitability of the final prepared subgrade. I f vinyl or other moisture-sensitive floor covering is planned, we recommend that the floor slabs be underlain by a capillary break consisting of a vapor-retarding membrane over a 4-inch-thick layer of gravel. A 2-inch-thick layer of sand should be placed between the gravel and the membrane to decrease the possibility of damage to the membrane. A suggeited gradation for the gravel: Sieve Size Percent Passing 1/4,90-100 No. 4 0-10 No. 100 0-3 A low-slump (3 inches or less) concrete should be used to facilitate the curing process and to minimize possible curling of the slabs. A 2-inch-thick layer of coarse sand may be placed over the membrane to reduce slab curling. If this sand bedding is used, care should be taken during the placement of the concrete to prevent displacement of the sand. The concrete slabs should be allowed to cure properly before placing vinyl or other moisture-sensitive floor covering. 25