The Analysis Of Cofferdam's Stability In Vaal River In South Africa

South Africa's Vaal River water diversion project on the background of a brief introduction, a detailed description of the structural characteristics of cofferdam, indicating that the selection order of removal from the bottom to anchor block, the bottom ring beam, the beam, the top ring beam removal program reasons.Describes the stability of sub-cofferdam method should be used on the arch cantilever method and limit equilibrium method of the simplified calculation of a detailed description of the principle, the final finite element method is recommended because it can get the exact solution does not require over-simplification of the structure, and makes the results more practical projects.The above methods were applied to the calculation of the stability of the cofferdam, the cofferdam first simplified into a slab structure, the structure of the seepage as a pile arranged in an arched plate, and then look at three arch into a continuous beam supported at the board the following board structure. The first dimension according to the structure and structural reinforcement to calculate the shear and bending capacity of the structure, and then remove the process into four steps, four cases were calculated corresponding to the maximum shear and maximum bending moment, and then structure the resistance and the maximum shear and maximum bending moment than the safety factor calculated structure. whichever is minimum.Analogy with the way the project will be done as a dam structure. The arch dam in the general cantilever method of calculation applied to the top of the cofferdam. Because the cofferdam and the rock ends and the lower phase is a statically indeterminate structure several times, the horizontal point of view is the level of one arch superimposed together, the vertical point of view is received by a number of cantilever together. So the first arch cantilever method with their respective calculated load distribution, and then calculate their stress and strain, and then, and the structure can withstand the extreme stress and strain compared to determine their safety.Introduces the modeling of finite element model, a segment of the four simulated steps, each step in turn compared to the displacement of upper and lower down the river, river to the vertical displacement of the maximum principal stress, minimum stress, plastic zone obtained their stress-strain laws of the displacement and plastic zone development. Finally, strength reduction of the cofferdam around the reduced strength of rock mass. Left rear does not converge, or by calculating the plastic zone through the zero bound to get a value, is the safety factor of cofferdam.Through various methods of the above structure is found using this segment of the program is feasible and safe removal.