Comparison between pressuremeter modulus (EPMT) and shear wave velocity (Vs) in silty clay soil

Abstract

Pressuremeter Test (PMT) and shear wave velocity (Vs) are two important in-situ tests for determining soil deformation characteristics in different strain levels. The PMT is an expensive and time-consuming test that can measure pressuremeter modulus (EPMT) of soil and rock. The Vs is a low-cost test for determining soil deformation through the seismic method. So finding the relationship between PMT and Vs can be useful and cost-saving for cross-checking the parameters obtained by these two methods.In this study, 94 PMT and Vs tests were carried out on silty clay and clay soil from 3 sites in Iran, and the relationship between EPMT and Vs was investigated using regression analysis. Finally, the best statistical model for relationships was proposed according to the highest value of adjusted R2 and Fisher coefficient (F) and a minimum value of significance (Sig.). The results showed that there is a direct relationship between EPMT, Vs, and N60 with depth then the soils with higher relative density are at the deeper layers. On the other hand, there is a linear significant relationship between EPMT and Vs for each site with R2 > 0.79. When the data for all three sites are considered together, R2 decreased to 0.62 but the overall trend of the data is similar. Due to the similarity of the soil of the three sites in terms of classification, minor differences in plasticity index and water content ranges in the three sites can be a reason to reduce the R2. The comparison between estimated EPMT based on proposed equations in the present study and measured EPMT shows that the normalized consistency ratio is generally close to zero (−0.09 < CR < 0.06) so the equations are valid and reliable.A comparison of the results of the present and a previous study showed that the change rates of EPMT and VS were similar so that the CR values are generally close to zero (−0.09 < CR < 0.09). The minor difference between the EPMT and Vs in each site in the present study and the previous research is due to the soil type and plasticity specifications.