The purpose of this paper is to present the results of a study which involves the prediction of the static bearing capacity of a pile from a wave equation analysis of piling behavior. Recently developed soil parameters including point damping, friction damping and quake are used in the computer solutions of the wave equation analysis. Also, the wave equation program is modified so that velocity may be raised to a power less than 1 in order to insure constant damping effects.
Curves of total static soil resistance at the time of driving vs pile penetration resistance in blows per foot are developed. Different curves are generated for different distributions of total soil resistance between the side of the pile and the tip and for varied soil parameters. These curves are compared with similar curves developed using E. A. L. Smith's recommended soil parameters.
Using the computed curves and the knowledge of pile penetration resistance during the last foot of driving, the static bearing capacity of the pile is predicted. These values of pile capacity are compared to actual values determined full-scale static load tests made in the field.
In 1960, Smith7 presented a mathematical model to simulate pile-soil interaction. At the same time he proposed a numerical method for analysis of piling behavior based upon the one-dimensional wave equation. Smith' s model idealized the pile as a series of masses and springs as shown in Fig. 1. The load deformation characteristics of the soil as shown in Fig. 2 are described the parameters Ru, Q, J, J1 and V, where
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The total soil resistance mobilized during dynamic loading was given by Smith as:
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Research personnel at Texas A&M later modified Smith's original equation so that the velocity term is raised to a power [N]. 3,4,6 Eq. 1 is rewritten as:
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When Smith's paper was presented in 1960, factual information concerning the magnitudes of the damping constants and J1 were virtually unavailable smith recommended parameters of 0.15 and 0.05 for J and J1, respectively. He also recommended a value of 0.10 for the parameter Q. Smith based his recommendations mainly on the strength of his own field experience with the piling behavior problem.
Recent research conducted at Texas A&M has resulted in What is believed to be more representative values for the parameters Q, J1 and J.3,4,6 The values obtained are presented in Table 1. There values are based mainly on the work of Korb,4 which involved small-scale dynamic and static pile loading tests in a variety of soils.
The computer program for solving the one-dimensional wave equation is used to generate a curve relating total static soil resistance at the time of driving to the driving resistance expressed in blows per foot.
