Study On The Influence Of Rapid Drawdown Of Water Level On The Stability Of Quay Wall

At present,there is still insufficiency in the understanding of the quay wall’s stability in the case of rapid drawdown of water level in front of the wall.This is mainly due to the fact that the study of the relationship between the water level infront and behind the wall during the rapid drawdown of water level is not deep enough.For simple one-dimensional and two-dimensional seepage model,there is a lack of a convenient analysis method that can be used in engineering design.And the analysis of the three-dimensional seepage effect is insufficient.Therefore,a comprehensive analysis of the impact of the three-dimensional seepage caused by rapid drawdown of water level can help to make a more accurate judgment on the stability of the quay wall.In response to above problems,the main research work in this paper is as follows:(1)In this paper,MATLAB is used to write a one-dimensional seepage difference program based on previous researches,and the reliability of the program is verified through the model test and numerical simulations.The program is then used to analyze the effects of each parameter on seepage.(2)A large self-made model box is applied to two sets of rapid drawdown of water level tests under different drainage conditions,and the test results of each group are compared to analyze..(3)Use ABAQUS software to build the numerical model of the test model,compare the results of the numerical model and the test model in order to verify the accuracy of the numerical model.(4)A numerical model of caisson in prictical engineering is developed by ABAQUS,which is used for three-dimensional seepage analysis.Calculate two different conditions(rapid drawdown of water level and typical tidal water level)respectively,compare the results of different permeability coefficients of foundation and distance between cracks.(5)The seepage / stress coupling analysis of the above caisson model is carried out using ABAQUS,then the strength reduction method is introduced to analyze the stability of the caisson during the rapid drawdown of water level.The effects of drawdown rate,permeability coefficient of soil and foundation,distance between cracks on the stability of caisson are analyzed.Based on the above research,this study developped a MATLAB code that can be used to analyze one-dimensional seepage and two-dimensional seepage model on highly permeable foundation.Then the water level difference between the front and back of the wall under three-dimensional seepage are discussed in this thesis.The water level difference between the front and back of the wall increases continuously with the drop of the water level in front of the wall,and the setting of joints between cassions can effectively reduce the difference of water level during rapid drawdown of water level.At last,the strength reduction method is used to analyze the stability of the caisson model under the rapid drawdown of water level,which helps to find the variation law of stability:as the water level in front of the wall decreases,the stability of the wall decreases first and then increases.Among the parameters of this study,the permeability of soil has the largest impact on the stability of the quay wall.The greater the permeability coefficient,the better the stability.The most unfavorable water level of caisson stability will also change according to the change of the parameters.