INSTRUMENTATION FOR DETERMINING SHEAR WAVE VELOCITY IN SANDS
Determination of shear wave velocity in sands is necessary for safety of various civil engineering structures. Usually, resonant column, cyclic triaxial and torsional shear tests are employed to determine this parameter. However, most of these methodologies are indirect, extremely cumbersome to adopt, employ especially designed apparatus and cost-intensive instrumentation, and necessitate trained manpower. Apart from this, tests are usually conducted on undisturbed and reconstituted samples of sands, which are difficult to obtain.
These problems can be overcome by resorting to the application of bender elements, which are capable of yielding shear wave velocity in sands directly, easily and quite rapidly. Though, bender elements can easily be fitted in any conventional test setup, they employ sophisticated and costly circuitry, which makes them beyond the reach of many. This calls for development of an instrumentation for determining shear wave velocity in sands, which is simple, cost effective, easy to use and non-invasive.
Though, shear wave velocity in sands has already been shown to be mainly dependent on its type, state of compaction and the confining stress, not many efforts have been made by the researchers to investigate the influence of morphological parameters on it. With this in view, investigations were conducted to determine shear wave velocity in different types of granular materials (sands, glass beads and cenospheres). Results were used to develop generalized relationships that can be used for computing the shear wave velocity in sands just by inputting their mean grain size, morphological characteristics, confining stress, under dry and saturated states. The utility and efficiency of these relationships has also been demonstrated.
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