Slope Deformation Analysis And Reliability Study Based On The Material Point Method

As the most common geological environment for human activities,slopes have been one of the research hotspots in the field of geotechnical engineering for many years.Once a landslide is caused by slope instability,it will pose a great threat to the safety of people’s lives and properties.At present,most of the research mainly focuses on the slope instability stage,but less on the landslide damage process after instability.The traditional grid-based numerical methods often encounter grid distortion when dealing with such problems,resulting in computational failure.The emerging material point method,which is less dependent on the grid,provides a promising opportunity for this purpose.This paper adopts the material point method to carry out static and dynamic analysis of slopes,and to study the reliability of slopes under the stochastic ground motion,revealing the mechanism of slope instability and damage,presenting the whole process of slope movement after instability,and providing a reference and basis for disaster prevention and mitigation.The main contents of the thesis are as follows.1.The theory related to the material point method is described and numerical simulations of large deformations for slopes are implemented based on the source program.Firstly,the equations of motion,the intrinsic structure model,the contact algorithm and the generalized interpolation material point method are introduced in detail.Then,the numerical simulations of dry aluminium bar collapse,sand and clay large deformation are carried out to verify the effectiveness of the material point method source procedure for modelling slope large deformation problems.Finally,for a simple slope,the influence of grid size,internal friction angle and cohesion on the sliding distance of the slope is studied.The cohesion and internal friction angle are negatively correlated with the sliding distance of the slope,both of which play a crucial role in the stability of the slope.Moreover,the slope inclination has a great influence on the sliding distance,which should not be underestimated for the stability of the slope.2.The material point method procedure is improved so that it can simulate the process of earthquake-induced landslides.Firstly,motion damping,local damping and the gravity increment model are introduced to obtain the initial stresses and strains required for dynamic analysis.Then,the effect of soil strength on slope instability under sinusoidal excitation is investigated to lay the foundation for the subsequent stochastic dynamic analysis.Finally,based on the measured ground motion data,the Chiu-fen-erh-shan landslide induced by the 1999 ChiChi earthquake in Taiwan is reproduced using the material point method,and the simulation results are compared with those of other numerical methods to verify the effectiveness of the improved procedure.3.Study of slope safety under the action of stochastic ground motions.Firstly,based on the frequency non-smooth power spectrum model and the idea of spectral expression-random function,the stochastic ground motion is synthesized artificially.Then,the study is carried out on a simple slope and an actual engineering embankment slope.The influence law of random earthquakes on the sliding distance of slopes are analyzed.With the increase of peak ground acceleration,the sliding distance of the slope gradually increases,and the variation interval becomes wider and wider,and the uncertainty of ground motions becomes more and more obvious.Combined with the cumulative distribution function curve,the degree of slope safety is studied.The cumulative distribution function curve of the sliding distance of the slope can represent the degree of slope safety.When the sliding distance is greater than the safety distance,the degree of slope safety decreases with the increase of the peak ground acceleration.The spacing of the cumulative distribution function curve represents the difference in slope safety,the greater the spacing,the greater the difference in safety.