Experimental Research On Dynamic Behavior Of Saturated Calcareous Sand Under Wave Loading

Calcareous sand is a special marine geotechnical medium, which has unexpected physical and mechanical properties due to its origin and fabric. Wave loading is a primary loading in oceanic engineering. So it is very important to investigate the dynamic behavior of calcareous sand for promoting the mechanical properties research level, guiding the analysis of sea bed stabilization, directing the design and construction of practical projects. Many researchers have investigated the dynamic properties of calcareous sand. But because of the testing condition limiting, they generally carried out their tests with the conventional triaxial test apparatus and torsion shear apparatus. So they did not consider the effect of the rotation of principal induced by wave loading on their testing results. In order to stimulate the wave loading, and investigate the dynamic behavior of calcareous sand under wave loading, a series of triaxial-and-torsional coupling cyclic shear tests were carried out in a new universal triaxial and torsional shear apparatus of Dalian University of Technology in this paper. The main work can be concluded as follows:Firstly, 11 groups tests with on calcareous sand with a relative density of 30 % under isotropic consolidation and third-directional anisotropic consolidation were performed to study its dynamic strength and liquefaction properties subjected to wave loading. The effect of the initial angle of principal stress on the dynamic strength of calcareous sand was analyzed, and an empirical formulation, which considering the initial angle of principal stress effects on dynamic strength of calcareous sand, was deduced. In the other hand, the liquefaction mechanics of calcareous sand was also analyzed fully.Second, the behavior of residual pore pressure and residual shear strains was studied based on the tests mentioned above. Effects of the rotation of principal stress and the initial angle of principal stress on pore pressure and shear strains were explored detailed. According to initial consolidation condition, different residual pore pressure increase model and residual shear strain predicted models were established.Third, in order to investigate the dynamic modulus and damping behavior of calcareous sand, 14 groups tests were carried out on calcareous sand with a relative density of 30 % and 55%. The influence of relative density and initial consolidation condition to the dynamic modulus and damping ratio was analyzed detailed.Then, the dynamic behavior of calcareous sand and a kind of quartz sand were compared, some divisions were concluded.Finally, the achievements of the research in this paper were concluded, and the direction of this thesis was also presented based on the shortcoming of the author's research.