Midway Evaluation in Civil Engineering - Elín Ásta Ólafsdóttir

Title: Multichannel Analysis of Surface Waves for soil characterisation

Doctoral candidate: Elín Ásta Ólafsdóttir

Doctoral committee:

Bjarni Bessason, Professor, Faculty of Civil and Environmental Engineering, University of Iceland
Sigurður Erlingsson, Professor, Faculty of Civil and Environmental Engineering, University of Iceland
Amir M. Kaynia, Prófessor, Department of Structural Engineering, Norwegian University of Science and Technology.

Abstract: 

Knowledge of the geotechnical properties of subsoil sites and man-made fillings is essential in various civil engineering projects. The shear wave velocity profile is a fundamental parameter in soil dynamics and geotechnical earthquake engineering.

Multichannel Analysis of Surface Waves (MASW) is a relatively new method to evaluate the shear wave velocity profile of near-surface soil materials by utilizing the dispersive properties of surface waves in a heterogeneous medium. The MASW method is an environmentally-friendly technique as the data acquisition is conducted on the soil surface without requiring heavy machinery nor leaving lasting marks at the site. The method is further time and cost efficient and can be applied at a wide variety of soil sites, including locations where conventional invasive techniques (e.g., penetration tests) are problematic to apply.

The aim of the project is threefold; (i) to develop an open software to acquire, process and analyze MASW field data, (ii) implement and adapt the MASW technique for analysis of the stiffness properties of Icelandic soil sites and man-made fillings, and (iii) validate and calibrate the field observations by comparison with results obtained by other measurement techniques.

To date, MASW measurements have been carried out at different locations in Iceland, ranging from sites characterized by peat and loosely compacted sand to cemented soil materials and soft rock, and, where available, the results compared to data from existing in-situ measurements. The method has further been successively used for characterization of large earth dams.

In order to benchmark results obtained by the new software, field measurements were carried out at several well-characterized geotechnical research sites in Norway. The results show that the shear wave velocity profiles obtained by the new software are very comparable to those obtained from invasive measurement techniques, thus verifying the performance of the set of data acquisition and analysis tools that have been developed.