Application of geophysical methods to detect lateral stress in bridge foundations

Abstract

Understanding the process of distribution of stress on foundations of bridges, structures and monuments is interest of structural, geotechnical, archaeological specialists as well as urban managers. Today in big cities to solve the traffic jam and connectivity of different parts therein more than thousand of bridges are constructed and economical and technical supervising for their exploitation is very vital. In this regard, geophysical methods are non destructive tools that can be evaluate and monitor the vulnerability during exploitation. In this research seismic, electrical sounding and geoelectrical tomography methods are used to assess distribution of strength of foundations, site classes, layering conditions and petrophysical characteristics of the underlying soil. The bridge is built on alluvial sediments of the Haraz River in Mazandaran province. The bridge consists of two lateral and three intermediate bases. The Haraz River passes through the eastern and adjacent intermediate base. This investigation indicates that: 1based on seismic studies the average shear wave velocity to a depth of 30 meters at the western base of the bridge is significantly more than that of the eastern base. Therefore the stiffness, loading capability and reflection factor of bridge in both bases of the bridge are different, 2-geoelectrical sounding show that the eastern side of the bridge, most likely composed of silt and clay and there is a possibility of subsidence at the east side of the bridge, 3electrical resistivity tomography maps in EW section is asymmetric and shows lateral changes of soil structures along bridge. In other words, distribution of stress on eastern and middle basis of the bridge with considering mentioned reasons is stirred with probably subsidence in the last few decades utilization, and 4existing defects in the body of the bridge agrees with the available results of research.