Determination of the Dynamic Material Properties of Soils from the Result of Static Shear Tests

At the present time, the only reliable methods for directly determining the material property relationships required for dynamic analysis are geophysical exploration and laboratory cyclic shear testing. Only through laboratory testing can one reliably obtain properties in the intermediate to high shear strain range. In many parts of the world, the sophisticated equipment required to perform these laboratory tests is not available. Furthermore, even when the necessary equipment is available, the expense of performing cyclic tests may be difficult to justify, particularly for preliminary analysis. The only alternative currently available is the use of empirical correlation such as those proposed by Hardin and Drnevich and Seed and Idriss. Several recently developed general constitutive relationships for soils offer the possibility of evaluating dynamic material properties from the results of static shear tests. Static test facilities are much more widely available than cyclic facilities, and for many sites information on static shear behavior is already available.

This paper reviews the applicability of several of the recently developed elasto-plastic and endo-chronic constitutive theories for predicting dynamic soil behavior with parameters determined from static shear tests. Based on this review, a simple procedure for predicting equivalent linear shear modulus and the fraction of critical damping from the results of triaxial compression tests with an unload-reload cycle is developed. The applicability of this procedure is demonstrated on two different soils, Crystal Silica sand and San Francisco Bay mud.

The results show the procedure may be useful for preliminary analysis and in situations where more sophisticated testing apparatus are not available.