Loadings on Foundations

Examples of marine foundation types—(a) t) cal piled steel jacket structure, (b) typical gravity structures (i) Co eep and (ii) Howard-Doris, (c) hybrid sted gravity structure (i) RDL hybrid and (ii) sandpooL (Continued) 

Examples of marine foundation types—(d) typical tension leg structure and (e) guyed tower structure. (From Gibson, R.E. and Dowse, B.E.W., Canadian Geotech. /, 18 171-178,1981. Reprinted with permission of Canadian Geotechnical Journal.) 

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The above discussion on foundation settlement is equally applicable to upward movement of foundations. Upward movement of foundations can be due to heave of the foundation soil or upUft of the foundation. Heave of shallow foundations occurs due to increase in the volume of expansive soils when additional moisture is introduced into these soils. Heave usually is only a concern for lightly loaded foundations and not for most bridges, because their foundations are generally heavily loaded. Uplift movements of foundations occur due to the externally applied upward (or tensile) load on foundations. Bridge foundations, in particular shallow foundations, are not usually allowed to be subjected to service level or sustained uplift forces. Thus, uplift movement is generally not a design concern for shallow foundation used to support bridge structures. 

Depending on bearing characteristics of the soil, strata depths and prospective loadings on foundations, piling may be necessary. There are many varieties of pile and piling techniques available. However, we can divide them into two broad categories ... 

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