Experimental characterization of monotonic, cyclic, dynamic and streaming potential poromechanics of water-saturated soils.

摘要

The city of Venice, Italy is joined with the Adriatic Sea to the east via three inlet channels. Storm events, originating from the Adriatic, have historically raised water levels in the Venice lagoon, flooding the city. The city has decided to construct retractable flood gate structures in each of the three inlets in order to temporarily mitigate floodwater levels during storm events. A vibratory plate system, 3 meters in length by 3 meters in width, was constructed to perform compaction of the saturated, structural fill used for the gates' foundations along the seafloor. Successful compaction requires that the structural layer achieve a certain design stiffness for proper performance. A real-time performance evaluation model was developed to monitor stiffness during underwater compaction using on-board, vibratory plate instrumentation, i.e., accelerometers. The model was successful, but suffers limitations in that it does not account for dynamic, excess pore water pressures generated during underwater vibratory loading. The research presented here indicates that monitoring pore water pressure accumulation, enabling application of an effective stress model, would assist in avoiding significant plastic yielding and cyclic mobility induced failure during vibratory loading. Accumulation of plastic volumetric strain, and consequently excess pore water pressure, can be significant during undrained cyclic loading. Accumulation of excess pore water pressure during vibratory loading is consistent with results from cyclic testing. This dissertation presents the results of both a detailed experimental investigation into fundamental, cyclic (i.e., <0.2 Hz) and dynamic (i.e., 1-30 Hz) soil behavior as well as a study on the policy environment surrounding innovative technology diffusion as it pertains to the US Highway Construction Industry. Additionally, this research investigates the use of surficial, electric potential (self-potential) measurements to monitor the streaming potential phenomenon to infer subsurface, dynamic pore water pressure generation induced during vibratory loading.