Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
ANALYSIS FOR LATERALLY LOADED SINGLE DEEP FOUNDATION
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| 6 ANALYSIS FOR LATERALLY LOADED SINGLE DEEP FOUNDATION ELEMENTS This chapter presents methods for analyzing single laterally loaded deep foundation elements, including simplified methods and more complex methods requiring computer software. 6.1 INTRODUCTION The interaction between a vertical deep foundation element and surrounding soil when the foundation element is subjected to a lateral load, P t , applied at the top is schematically illustrated in Figure 6-1. Horizontal pressures are uniform around the foundation element at a depth, Z, before lateral loads are applied. After the load is applied, the foundation element deflects away from the load with a magnitude, y 1 , at depth Z 1 , and the existing soil pressure distribution is modified. In the upper part of the foundation element, pressures in front of the foundation element increase as shown in Figure c. If the applied load is large enough, the pressures may approach the passive Limit State. Conversely, pressures on the back of the foundation element decrease and may approach the active Limit State, or may even approach zero if the element moves away from the soil. The stress distribution may reverse its sign in the lower portion of the foundation element. The foundation element will tend to rotate if it is relatively short and stiff, resulting in a condition close to passive wedge failure, whereas if the foundation element is relatively long, it will deflect and bend but will not deflect enough to reach the passive state (see Error Reference source not found. Shear stresses, not shown in Figure 6-1, are also mobilized on the sides of the deep foundation element. The net effect is a soil resistance, p 1 , corresponding to a deflection, y 1 , at depth Z 1 as shown in Figure c. The relationship between soil resistance, p, and displacement, y, is referred to as the “p-y” relationship. The p-y relationship changes with depth, soil type and other factors (McClelland and Focht 1958; Reese and Matlock 1956). The p-y concept captures most aspects of the soil-foundation interaction under lateral loading. Download 6.03 Mb. Share with your friends:
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