This study presents the details of a site specific investigation and drilled shaft foundation study for a site in Tremonton, Utah, which is along PacifiCorp's constructed 345 kV transmission line extending from Ogden, Utah to Downey, Idaho. This study is based off of a three part investigation previously submitted to PacifiCorp, and its objectives to evaluate the shear strength and deformation characteristics of a granular, transitional soil for the proposed construction of laterally loaded drilled shafts.;The primary goals of this research project are as follows: (a) Perform detailed geological and geotechnical investigations in order to define the variability of the shear strength and deformation behavior of the subsurface soils using the various field and laboratory test methods performed on the soils from the transitional material site; (b) identify and compare the strengths and weaknesses of the various test methods and evaluate their applicability to the characterization of the transitional materials at the subject site; (c) evaluate and compare the load vs. deformation (i.e., P-y) curves determined for the design structural loading condition(s) using the shear strength properties obtained from each test method (d) recommend additional studies that will result in improvements to the foundation design in similar subsurface conditions.;The first task undertaken to achieve these objectives was to perform a detailed geological investigation at each site. Surficial geological units were determined for the site, and several types of geological hazards were investigated and analyzed.;Geotechnical investigations were then conducted for the site, according to the predominant types of subsurface materials present. The subsurface materials consist primarily of transitional granular-cohesive soils with significant amounts of gravel and larger size particles.;The results from the geological and geotechnical investigations were used to estimate appropriate engineering parameters for the analysis and design of drilled shaft foundations at the site. The computer program, LPILE ™ was used for the analyses and designs. Comparisons of the designs were made between the actual foundation constructed at the Tremonton site and those determined using parameters obtained in this research project.;Major recommendations regarding future research and training are summarized as follows: (a) full-scale load tests at the subject site investigated in this research project should be performed to determine the accuracy and reliability of the various methods used for analysis; (b) several additional triaxial compression tests be conducted to validate results determined in this study.
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