Study On Cofferdam Stability Of Dredging Silt Yard Based On Straw Rope Reinforcement

Our previous studies have focused on capacity expansion of dredged soil stockyard,but the use of straw rope to reinforce the cofferdam is rarely discussed.In order to solve the longterm land occupation problem of dredged soil stockyard and make rational use of straw resources,this paper proposes to weave straw rope into straw grid and put it into cofferdam for reinforcement of cofferdam.In order to study the reinforcing effect of the straw ropes on cofferdam,a tensile test and a pull-out test are carried out.The tensile property and interface friction characteristics of the straw ropes under different degradation degrees in the soil are analyzed.The finite element software ABAQUS was used for simulation,and Design Expert was used for response surface analysis to further study the influencing factors and sensitivity of cofferdam stability.The following conclusions are obtained in this paper.1.When the straw rope is nearly destroyed by tension,the fracture of the internal straw fiber starts from the secondary fiber and gradually transfers to the main fiber.The stress mode of straw rope is that the main fiber and the secondary fiber are stressed together.The longer the straw rope is buried in the soil,the more obvious the stress mode is.2.Straw buried in the soil,straw softening,cross section changes and produce some pores,soil particles are squeezed into the pores of fiber,the reinforced soil interface area increases,the interfacial shear strength also increases.With the increase of degradation time,the degradation degree deepens,the fiber on the surface of the straw rope peels off,the reinforced soil interface area decreases,and the interfacial shear strength also decreases.3.Straw grid reinforcement can well inhibit the formation of plastic zone and prevent the plastic zone from extending upward from the slope toe.Although it cannot significantly change the position of plastic zone,it disperses the plastic strain of cofferdam soil to a certain extent and improves stability of the cofferdam.4.Reducing the slope ratio,reducing the cofferdam height,increasing the reinforcement length and reducing the reinforcement spacing will increase the cofferdam stability,but the influence degree of each factor is different.With the degradation of straw,the stability of cofferdam decreases,but it can meet the engineering needs within the construction period.This study provides a theoretical support for the rational use of straw resources to solve the long-term land occupation problem of dredged soil stockyard.