Experimental Research Of Dynamic Characteristics Of The Reclaimed Sand In Beibu Gulf Under The Conditions Of Cyclic Loading For A Long Period Of Time

Along with our country taking more and more attention to the using of the coastal area, a large number of reclamation epeirogenic project has been built in the Guangxi Beibu gulf. Because of its unique effect on the choosing by the hydraulic power, leading to the formation of a unique layered geotechnical structure, which is loose on the first layer and soft on the following. Namely the substratum is the marine soft soil layer which is four to five meters, overlying the reclaimed sand of six to seven meters. And compared to stratum which is formatted by sedimentation naturally after a long time, it has the unique engineering properties, for example, large differences in the distribution of compactness in time and space, continuous change of the predominant period in the site. In addition, it is located in the intersection of the land and sea, where the earthquake is very active, having a high risk of far field earthquake. So, related researching in the dynamic characteristics of the reclaimed sand on the coastal area during the land reclamation construction and the subsequent construction is particularly necessary, providing guidance for the plot in the earthquake resistance and disaster mitigation.In this thesis, the reclaimed sand collected from reclamation area nearly the Beibu gulf avenue of Fangchenggang of Guangxi as the research object, mainly by layered packing as the sample preparation methods for the triaxial specimen. From the relative compactness, the vibration frequency, consolidation pressure, clay content, consolidation ratio five aspects, simulating the changes in the physical state of reclaimed sand during the reclamation process. Carry out some research work of the soil dynamics test by the GDS dynamic triaxial apparatus, and at the same time, the corresponding static triaxial test and direct shear test are carried out for the strength comparison analysis.The main research contents and results are as follows.1. Hysteresis curve and backbone curve of reclaimed sand are described and analyzed, it shows hysteresis and nonlinear characteristics, having some relationship with the vibration frequency, compactness, clay content and other factors. Backbone curve presents the development trend of hyperbolic, however, hysteresis curve is more and more plentiful with the increase of earthquake time, but closed performance is worse and worse.2. By the dynamic triaxial test of step by step loading for the reclaimed sand, to study the relationship between the dynamic elastic modulus and dynamic damping ratio with the vibration frequency, the compactness, consolidation ratio and clay content and other factors. Think that the development of the dynamic elasticity modulus is conform to the hyperbolic model, and the empirical formula is presented. Dynamic damping ratio has little relationship with the vibration frequency, sandy soil compactness and other factors, having irregular development, only associated with the development of strain.3. Under the condition of large strain the dynamic strength test of reclaimed sand has been finished, test results show that the dynamic strength increases with the decrease of the vibration frequency, the increase of the compactness, the confining pressure, the consolidation ratio, but the correlation with the clay content is not obvious, then the empirical formula is presented. Dynamic pore water pressure also has relationship with the vibration frequency, the compactness, the consolidation ratio, the clay content and other factors.4. The results which is got by the direct shear test were compared with the results of the dynamic strength test, from which we can get the simple mathematical relationship between the dynamic strength and static strength, providing certain reference basis for the project which has a unconditional for the dynamics test.