| Summary: | 碩士 === 國立臺灣海洋大學 === 河海工程學系 === 99 === During the process of wave transmitting into the seabed, the internal seabed soil was induced the dynamic pressure under wave loading. While the wave pressure was transmitted into the internal seabed, the seabed soil was subjected to the interaction of vertical stress, horizontal stress, pore water pressure and torsional stress at the same time. It was led to the seabed failure due to the seabed soil be in the unstable condition.
This research in order to discuss the natural condition of the soil under the wave of the process that dynamic pressure transmitted to the soil of seabed. It integrates the earlier developed triaxial cyclic testing system with torsion shear stress function analysis. It can set any kinds of the control model for various stress condition including axial,confining pressure,back water pressure and torsional shear stress by the computer. This system can simulate completely the situations of four stresses when the wave acting on the seabed. We can change the system from semi-automatic control mode to full-automatic control mode and direct input the data of torsional moment to do the tests. The results of simulating the force under the horizontal shear stress more approach to the real condition of seabed under forces.
In this study, mainly discuss how to use cyclic axial and torsional system to operate testing simulations with same initial wave conditions in different sea depth. It includes axial tests,torsional tests,and axial combined with torsional shear stress tests . Under these three kinds of test we can analyse the variation and difference of pore pressures.
The analysis for test results of the typhoon breaking point simulated with axial, torsional,and axial combined with torsional shear stress systems reference with the paper researches discussing pore water pressure build-up modes by Seed(1976) and Chang(2004).We indicated that the axial simulation can effectively predict the pore pressure for both modes. The initial predictions of pore water pressure build-up with torsional,and axial combined with torsion shear stress systems have significant differences. It made by the operating testing simulations without considering the factor of torsional shear stress. If the active threshold of pore water pressure build-up based on the cyclic torsional test results, the triaxial test results with this study could get the maximum underestimated value approach to 10% .The results of cyclic triaxial and torsional tests could get the maximum underestimated value approach to 26% .
This study proposes the simulation results and establishes the cyclic triaxial testing system(TCTS) combined cyclic torsional system to simulate the actual seabed condition. We hope it could contribute to the study of the seabed soil under the wave loading.
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