Research on the Stability of the Cofferdmas with Geotextile Bags Filled with Sand on Soft Soil Foundation
|School||South China University of Technology|
|Keywords||Bag cofferdam Strength reduction method Limit equilibrium method The ultimate bearing capacity of foundation|
In the pearl river delta region of guangdong province, the foundation soil is in the majority with soft soil and groundwater is abundant, it increased the difficulty to construct cofferdam. Because the earthwork fabric has good function of water draining, isolation and the filtration in application aspect of the soft soil ground, it may enhance the structure stability in the soft soil ground. So people put forward into the method of building into the cofferdam which sewing geotextile to bag type, making use of hydraulic to fill sand into bag. Such cofferdam type calls the bag cofferdam.This paper mainly studies the method of stability analysis of bag cofferdam. Currently there are three kind methods of slope stability analysis: the limit equilibrium method, the limit analysis and the strength reduction method. This paper mainly studied the difference of the slope stability analysis result which is based on the limit equilibrium method and the strength reduction method, and combining the ultimate bearing capacity of foundation when under complex loading, obtaining the strength reduction method is a more appropriate stability analysis method of the bag cofferdams, and for the soft soil foundation under complex loading the method of the ultimate bearing capacity of foundation is more convenient for engineering ues.Firstly, building modle for no back berm slope and back berm slope to analyse stability based on the limit equilibrium method and the strength reduction method through numerical simulation, comparing two methods from two aspects of safety coefficient and the presplit face potential sliding wich is searched out by two methods, the results show that for no back berm slope, two kinds of methods’calculation results are almost identical; For back berm slope, two kinds of methods’difference is very big. Then according to the ultimate bearing capacity of foundation under the complex load which is proposed by YangGuangHua professor, to research the Engineering cases. Comparing the result of three kinds of methods, obtains the corresponding scope respectively. Considering the back berm impact on the slope stability, the strength reduction method’s results show that with the increase of back berm’s width, safety factor growth is nonlinear regressive, eventually growth rate to zero.Secondly,considering reinforced geotextile impact on slope stability, regarding geotextile as element which is only by tensile cannot be bended, the safety factor result of added reinforced geotextile contrasting without reinforced geotextile does increase, the increase of the strength reduction method’s result is obvious, but the limit equilibrium’s result increased less. Finally, analysing the actual project cases respectively based on the strength reduction method and the limit equilibrium method, the results can prove strength reduction method is actually a reliable analysis method for bag cofferdam, Foundation limit load method is suitable for soft soil foundation, moreover due to the limit equilibrium method is based on the assumption, so it own existence deficiency, the result can not be a good reaction of actual situation.