Numerical Analysis Of The Consolidation’s Effect Of Upstream Sedimentation And The Stability Of Dam Improved By Vertical Drainage Plate

"Upstream sedimentary heightening fill" is one of the main methods for reinforcement project of dams in south region of Ningxia. For a long time this method is stuied by experiences but little theoretical perspective. And there has exposed some problems and deficiencies during the long-term usage. Directed towards these problems, take the Yashigo reservoir of PengYang as object, a method which based on the old one and added vertical drainage plate in the soft foundation has been studied and analyzed by the PLAXIS finite element software in this thesis. The main researchs and conclusions are as follows:(1) Based on test and investigation research, established a two-dimensional finite element numerical model which picked Yashigou reservoir as the prototype. Accuracy of this model has been checkout by comparing the consolidation settlement which acquired by simulation and the monitor data in a specific period. Result shows that the consolidation deformation process of Yashigou project could be truly reflected and the model meet the requirements of simulation.(2) The variation of consolidation’s rate were simulated by finite element numerical model, and the contribution of adding vertical drains to original method made to consolidation’s effect was analyzed. And the permeability coefficient of sedimentation in the model was adjusted to search the differences of contribution which vertical drains made to consolidation’s effect in varied permeability coefficient. Result shows that:①When heightening fill the upstream sedimentary, the biggest excess pore water pressure in sedimentation foundation appeared after one of soil layers filling finished, and this moment the sedimentation foundation has smallest effective stress and worst stability;②Adding vertical drains has a remarkable effect to raise the rate of consolidation, it can reduces about 70% construction period under ideal conditions;③Adding vertical drains has more engineering significance when the permeability coefficient of sedimentation is smaller.(3) The dam and foundation’s stability were simulated by finite element numerical model and the contribution of adding vertical drains to original method made to stability was analyzed. And the safety factor of each construction stage has been studied as well. Result shows that:①The maximum shear strain of project is distributed in the areas between the old dam and soft foundation and the areas of new dam’s upstream slope toe;②Adding vertical drains has a remarkable effect to stability of project, the maximum shear strain of soft foundation could reduces about 40%;③ Adding vertical drains has a remarkable effect to raise the safety factor of each construction stage, particularly the second and third stages of loading process.