One- and Two-Dimensional Active MASW Survey for Subsurface Profiling of Jia Bharali River Bed, Assam, India, for a Proposed 1.2-Km Road Bridge

摘要

This article describes the active multichannel analysis of surface waves (MASW) survey conducted at the Jia Bharali River Bed, Tezpur Assam, to identify the shear-wave velocity profile of the subsurface at the site. A new 4-lane (approximately 1.2 km) carriageway bridge construction is proposed over River Jia Bharali, a tributary of River Brahmaputra, intending to connect two national highways NH-52A and NH-37. The site consists of sand and silt deposits, intermingled with pebbles, gravels, and perched hard strata formations. The proposed bridge consists of 24 piers and 2 abutments, each separated by an interval of 48 m. Active MASW surveys were conducted at the pier and abutment locations, along with roll-along mode in-between the piers. Multiple sledgehammer shots were used at each location and dispersion image stacking is used to generate higher resolution dispersion images. Automated extraction of dispersion curve was attained with the aid of image processing techniques employing an integration of Surfseis version 5.0 and Matlab version R2019a software packages. The one-dimensional (1D) shear stiffness profile was determined at each of the test locations, which is further used to decipher the two-dimensional (2D) shear-wave velocity profile along the bridge alignment. The outcome of the analysis could clearly identify the perched hard strata that prevented the progress of borehole driving at specific locations in the site. The bearing stratum could be properly located, which would serve as the foundation depth for the well foundations. The thicknesses of the top erodible sediment deposit, the intermediate soft soil stratum, and the deep-seated bedrock were also effectively recognized. The findings of the survey can aid in effective bridge foundation planning for construction and design.