The Significance Of The Research On Adoption Displacement Vector Angle To Predict Instability Of Foundation Pit With Soil Nailing

The research contents of the Thesis based on the projects of the National Natural Science Foundation of China and the projects of the Youth Science Foundation, carrying out research and analysis of numerical calculation on the safety of foundation pit slope,using non-linear finite element method according to the deformation characteristics, through the analysis of the results of numerical simulation to explore the relationship of the monitoring displacement vector Angle of foundation pit slope and the safety of foundation pit.The specific contents are as follows:1、From the points of dynamics, analyzing the limitation of the single information that only depending on the displacement or displacement rate in the process of evolution of foundation pit slope destruction, and illustrating the research significance of displacement vector Angle and its dynamic characteristics, introducing the basic structure of foundation pit slope surface displacement vector Angle and space-time evolution characteristics.2、Put forward three foundation pit slope stability criterion:(1) the displacement vector angle in the bottom of foundation pit slope will become smaller suddenly, that in the top of foundation pit slope will become bigger suddenly and that in the middle part of of foundation pit slope will increase gradually with time goes on;(2) According to the basic principle of mathematical statistics, we can adopt mean square error as criterion to judge wether the abnormal changes of displacement vector angles of oundation pit slope is mutation, namely regarding wether change values of the displacement vector Angle fluctuate in range of mean and variance of multiples as a criterion of slope displacement vector Angle abnormal changes;(3) The minimum mutation value of displacement vector Angle in bottom of foundation pit should be compared with the dip angle of foundation pit slope, if that is greater than the dip Angle of foundation pit slope, shows that foundation pit moves fall within the scope of the shear strength of soil,without the possibility of a cut out damage; if that is less than the dip Angle of foundation pit slope,shows the foundation pit soil move outside the foundation pit with trend of cut slope going to be instability. 3、According to the function mechanism of soil nailing, the soil nail and the foundation pit slope soil plays a skeleton role in space combination, so as to improve the integral rigidity of soil and structural integrity, and the soil nailing belongs to the passive restriction mechanism.4、Considering the changing rule of the displacement vector Angle evolution process of foundation pit slope in two situations about the absence of supporting conditions and the soil nailing conditions, putting forward and verifying the criterion of displacement vector Angle in the foundation pit slope stability.5、According to the criterion of displacement vector Angle to foundation pit slope stability under the the condition of simple soil, discussing the influence of seepage along with extreme rainfall to safety of foundation pit slope with soil nailing support,and using the prediction results of foundation pit slope stability under the absence of supporting conditions and the soil nailing conditions as criterion.