Research On Time-dependent Mechanical Behavior Of Strong Structured Clay In Zhanjiang Area

Based on the strong-structured soft clay in Zhanjiang area and the advanced GDS triaxial testing system, the research on time-dependent mechanics behavior of strong-structured clay in Zhanjiang area have been investigated systematically in this paper, in which the evolutionary process of soil structure damage is taken into account and the mechanics behavior of the structured soft clay under various shearing strain rate and creep conditions of one dimension or triaxial are systematically studied. Tentatively, the mechanism of deformation is explained from the angle of micro-scale.Firstly, The effects of shearing strain rate on mechanics behavior of Zhanjiang strong structured clay have been investigated systematically by means of triaxial test. It is discovered that the strong structured clay has special mechanics effect of shearing strain rate, (and) the CU shear strength increases at first then decreases with the increase of strain rates, and a critical rate exists. The effect of strain rate on pore pressure is not so significant under the low confine pressure condition, whereas with the increase of confine pressure, the effect gradually becomes significant. Furthermore, the cohesion and the internal friction angle entirely decreases and increases with the increase of strain rate, respectively, which show turning points when the strain rate increases to a certain value, but the latter lags behind to the former. These phenomena are resulted from the breakage behavior of clay structure related to the strong and weak structure of soil, which provides a help to understand the engineering properties of structured clay further.Secondly, The characteristics of deformation of soft clay under different loading are studied by means of one-dimension consolidation creep test in which two kinds ways of loading are applied. The axial strainεis linear with ln t in most conditions except that the increment of loading is very small when the style of stage loading is applied under whichε= A( ln t)~B. The constitutive equation is derived by analyzing experimental data and comprised a index parameter that reflect the change of structure of clay recessively.Thirdly, The research on the triaxial drained creep is investigated systematically under different cell pressure. The volume change increases and reduces by turns when the cell pressure is lower than the structure yield stress, while as the cell pressure arrives to the structure yield stress, the volume change develops with time linearly. The law that Lgεis linear with ln t is confirmed by analyzing the experimental data and the constitutive equationε= ( D_r - T )t n/S(T,S are constants)that is similar to the Mesri model in form aspect is derived. The time effect index n is a parameter that reflects the change of structure of strong structured clay recessively. The rule that the long-term intensity decreases with the increase of time is verified by using Mohr envelope. In addition, the relationship betweenε- t ofε= at~3 + bt~2+ ct + d in the phase of rupture is suggested.Finally, The mechanism of creep deformation is analyzed from the angle of microscale that provides a possible direction for further research, that is to say that the research in microstructure should be strengthened. The deformation mechanism of structured clay should be investigated by means of multi-disciplinary analysis to recognize the mechanics effect of the structural clay in an all-round way.