ABSTRACT:

Single anchor and anchor-pedestal foundation pullout tests were performed for cometion of tower foundations on a new 500 kV electrical transmission line. Hard soil and weak rock shear capacities determined from testing were compared to geotechnical data that included seismic wave refraction surveys to determine correlations. Test data, analysis, comparative models, and design results are presented.

INTRODUCTION

The Mead-Phoenix Project is a 1300 MW electric transmission system, including a 500 kV alternating current transmission line extending approximately 415 km from the proposed Marketplace Substation southwest of Boulder City, Nevada, to the proposed Perkins Substation just northwest of Phoenix, Arizona (see Figure 1). The line route crosses numerous geologic conditions and physiographic features. Designs for transmission line tower foundations in mountainous terrain conditions incorporate a combination socket-anchor option.

Obtaining undisturbed samples in the weathered and fractured rock and calcareous soil conditions of the transmission line route is very difficult and uneconomical. Results obtained from traditional laboratory testing of these samples are often doubtful. Therefore, as part of a fi?11 scale foundation load test and geotechnical exploration program, 27 single anchors and 4 drilled pier anchor-pedestal foundations were installed at six weak rock and calcareous soil sites, load tested in uplift conditions, and correlated with seismic wave refraction data for design purposes.

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