3003 W CASINO RD BLDG 40-58 Geotech Report 2022-10-25

3.7 BUILDING FOUNDATIONS Due to variable depths to the top of glacial till, variable conditions within the existing fill, expected column working loads on the order of several thousand kips, and an expected tolerance for column-to-column settlement of an inch or less, we anticipate that drilled shafts are the most appropriate foundation type for support of the building superstructure. The building layout includes west-east rows of columns along the north and south walls,plus an interior row about midway between the north and south rows. We present four simplified west-to-east subsurface profiles broadly summarizing the subsurface conditions encountered during exploration. We expect that drilled shafts at the site will need to be drilled at least two shaft diameters into consistently very dense soil underlying the existing fill layer. To reduce or eliminate downdrag loads on the shafts, we recommend that shaft construction occur after site filling activities are complete. Alternatively, drilled shafts could be drilled prior to or during earthwork operations and designed to accommodate downdrag loads. 3.7.1 AXIAL CAPACITY (The axial capacity of shafts will be evaluated and presented in the draft version of this report) 3.7.2 LATERAL LOADING OF DRILLED SHAFTS (Lateral loading of drilled shafts will be discussed in the draft version of this report) 3.7.3 DRILLED SHAFT CONSTRUCTION CONSIDERATIONS Support for drilled shafts will be derived from friction developed around the shaft circumference and from end-bearing. Development of shaft friction and end-bearing is influenced by shaft excavation practices,equipment,contractor experience,concrete placement method,soil and groundwater conditions, as well another factors. Drilled shaft subcontractors who participate on this project should be required to demonstrate that they have suitable equipment for this project and adequate experience in the construction of shafts with similar subsurface conditions. Recent drilled shaft construction experience (May 2014) at the nearby Building 40-27 encountered generally medium dense to very dense drilling conditions. Drilling through very dense glacial till at depth has been a challenge, and wet zones near the fill/till soil contact and at isolated locations within the till created caving conditions which have required a wet drilling method. Contractors should anticipate that drilling 'in the wet' may be necessary at some or all shaft locations within the 40-58 footprint. (This section will be expanded in the draft version of this report.) 5/16/14 P:\1423\002\010\FileRm\R\Draft Bldg 40-58 Report\Bldg 40-58_draft rpt.docx INTERIM DRAFT 3-6