Experimental Study And Numerical Analysis On Failure Mode Of Soft Soil Foundation Under Sand Bag Cofferdam

Large size sand bag cofferdam is the plane on the tens of meters or even hundreds of meters of large size film bag laid on the soft soil foundation,the use of hydraulic filling gravel,layer by layer to build a high degree of cofferdam.The large size cofferdam has the advantages of fast construction speed,low construction cost and strong adaptability to soft soil foundation,and has been widely used in the field of reclamation of the sea or the construction of offshore sluices and seawalls for more than 10 years.However,in the process of construction,the collapse of large size sand bag cofferdam is still happening,which shows that the theory,design and construction technology of the cofferdam are still to be improved.In this paper,the application and research status of large size sand bag Cofferdam at home and abroad are investigated.On the basis of this,the optimum design method of large size sand bag cofferdam is discussed.The main results are as follows:(1)in the film width of sand bag cofferdam size is small,the shape of the foundation deformation and failure: membrane bags sand foundation center field soil cofferdam subsidence displacement,uplift,crack appeared at the foot of the soil surface,soil foundation failure.Based on the analysis of displacement vector,this paper puts forward the division of the soft soil foundation under the flexible load of the sand bag cofferdam.(2)when the film width of sand bag cofferdam large size,the foundation is not possible overall damage,there will only be a local sliding failure in cofferdam slope,causing the sand cofferdam is pulled off,eventually developed into the overall sliding soil slope failure.In this case,only in accordance with the requirements of the specification for sliding stability check,not for the calculation of the bearing capacity of the foundation.(3)when the width of the bottom of the sand bag cofferdam is certain and the stiffness increases,the integrity of the cofferdam is improved,and the lateral deformation of the foundation soil is restrained.(4)the influence of cofferdam stiffness deformation and failure mode of sand foundation based on the proposed new design method of "ship design method",which is made of high strength of geosynthetics in sand bag cofferdam bottom reinforcement,improve the integrity,to ensure that the geotextile and geogrid is not broken,in the foundation of large settlement,cofferdam like a ship just increase the "draft",but not the slide of slope.