Some remarks on the assessment of P-wave velocity in laboratory tests for evaluating the degree of saturation

This work stems from the need to validate a technique for a reliably measurement of the degree of saturation (S-r) in deposits composed of sandy soils to improve their liquefaction resistance. The estimation of the degree of saturation of soil can be conducted by assessing the P-wave velocity (V-p), due to it values sharply increase near to the full saturation condition. P-wave measurements are comparable for in situ and laboratory procedures, offering prominent advantages for practical implementation. This paper presents a series laboratory results obtained from bender element tests conducted on a partially saturated monogranular sand. As a first approach, these tests were interpreted in the time-domain, showing how the interferences among the generated waves can significantly affect results and mask the actual degree of saturation in the specimen. However, a new processing of the output signal was carried out in the frequency-domain to accurate identify the wave propagation time. Moreover, results are discussed to investigate the mutual relationships between the V-p with S-r and Skempton's B parameter. Finally, an experimental correlation between V-p and S-r is obtained, considering the strain level dependency of the soil behaviour, which can be adopted to interpret the results of in situ tests.

Automated summary

This study validates a technique for measuring the degree of saturation in sandy soil deposits and investigates the relationship between P-wave velocity and saturation degree through laboratory tests.