Study On The Stability Of The Large Size Fabriform Sand Cofferdam On Soft Soil Foundition

Since the theoretical analysis and experimental research on fabriform sand cofferdam still lag far behind the engineering practice, there is an urgent need to give more reasonable solutions of questions that are related to fabriform sand cofferdam in engineering practice. Nowadays, there are plenty of papers that are related to fabriform sand cofferdam. However, most of those studies are restricted to mechanical properties of a single filling bag or multiple filling bags, or the introduction of its construction technology. The slope stability analysis method is adopted to calculate its safety factor of stability, under conditions that the fabriform sand cofferdam is equivalent to homogeneous soil, when Study on the stability of fabriform sand cofferdam. This method can still meet the engineering requirement when the foundation soil is hard enough. However, the limit state of fabriform sand cofferdam in soft soil is shown as the lateral extrusion of the foundation soil. The essence of this phenomenon is instability of the foundation soil, continue using the slope stability analysis method is biased. Therefore, the stability of the large size fabriform sand cofferdam on soft soil was studied in this paper by using numerical analysis methods, based on the bearing capacity of foundation and the strength reduction theory.Summarized the research status quo of the fabriform sand cofferdam at both home and abroad, as well as problems that need to be studied in this field. Then, the research subject and research methods of this paper were put forward.The numerical model of large size fabriform sand cofferdam on soft soil foundation was established by using the finite element analysis software-ABAQUS. Firstly, the deformation characteristics and stability of the soft soil foundation were analyzed, based on the strength reduction theory. And then the difference in the limit state between the large and small size fabriform sand cofferdam on soft soil was compared. Then, through sensitivity analysis, the influence of cofferdam slope ratio and silt foundation thickness on the stability of cofferdam foundation were studied. A series of conclusions were obtained through the above analysis.The stable regularity of the large size fabriform sand cofferdam under three different reinforcement methods was analyzed, by using the numerical model of anti pressure platform, cement mixing pile and vacuum preloading combined with surcharge loading by fabriform sand.The calculation formula of ultimate bearing capacity of large size fabriform sand cofferdam on natural soft soil foundation was derived,based on the limit equilibrium theory and combined with the characteristics of large size fabriform sand cofferdam(Since the section of the cofferdam is large, the width of the rigid core under the cofferdam foundation is smaller than the equivalent width of the large size fabriform sand cofferdam, the average value of the top width and the bottom width of the fabriform sand cofferdam,when the whole sliding shear failure occurs).Finally, the approximate analytical solution of the maximum bending tensile stress of fabriform in large size fabriform sand cofferdam on soft soil foundation was derived, based on the theory of finite length elastic foundation beam.