System Reliability Evaluation Of Long Embankment Slopes Considering Seismic Risk With Design Service Period

Embankment slope is an important part of railway and other line engineering foundation,and the slope instability induced by earthquake is one of the main forms of embankment disaster.Local sliding at any position along the road can cause serious consequences,and the reliability analysis method of long embankment slope system under seismic risk is in urgent need of research.Based on seismic risk and slope reliability analysis theory,carry out the analysis of slope stability under earthquake risk in design service,the K/N system was used to study the system reliability of long embankment slopes under different allowed number of unstable subunits.A method for system reliability evaluation of long embankment slopes under seismic risk in design service is established.Combined with a long embankment slope of a railway project,an example is given to analyze the application process of the proposed method.The main understandings and conclusions are as follows:(1)Based on the poisson distribution model of seismic time and exceeding probability principle of three levels of the aseismatic standards under different design reference period,Seismic fortification intensity and acceleration under different design reference period is studied.Using the extreme value distribution model of earthquake intensity,the exceeding probability and occurrence probability of any earthquake intensity in different time window can be calculated.In order to facilitate the practical application of the project,the fortification intensity and acceleration of three types of subregions in the country with reference period of 50 and 100 years,and the exceeding probability and occurrence probability of each seismic intensity with time window of 50 and 100 years are provided.(2)According to the statistical analysis results of peak acceleration data under different seismic intensities,the seismic peak acceleration obeys Gumbel distribution,and the influence law of the variation of seismic peak acceleration on the calculation results of slope stability reliability is analyzed.The results show that the slope failure probability increases non-linearly with the increase of the variation coefficient of seismic acceleration.Therefore,the variation characteristics of peak acceleration should be considered in the reliability analysis of slope stability under seismic conditions.(3)According to the seismic zoning site information and the intensity distribution function,the occurrence probability of earthquake intensity is calculated.Considering the uncertainty level of slope soil strength parameters and the tvariability of peak ground acceleration,using the pseudo-static method and Monte Carlo method,failure probability of slope under each seismic intensity.Then,the failure probability of slope is obtained by using the total probability formula with the probability of occurrence of intensity,and the reliability analysis method of slope under seismic risk in the service period is proposed.(4)According to the most probable local instability length along the longitudinal road of the embankment slope,the embankment slope of the long section is divided into several independent subunits.The failure probability of the subunit slope under seismic risk during the service period is calculated by pseudo-static method and Monte-Carlo simulation.The K/N voting system is used to obtain the reliability of long section embankment slope system under different allowed number of instability subunits,and the reliability evaluation method of long embankment slope system under seismic risk during the design service period is established.(5)Taking a 5 km continuous embankment slope of a railway as an example,the reliability of the slope system under the three levels of fortification in different design base period is analyzed and compared,and the stability reliability level of the embankment slope system under the seismic risk during the design service period is evaluated.The example shows that the failure probability of the slope system decreases non-linearly with the increase of the allowaed instability number during the design service period of 100 years.When the number of allowaed instability subunits is 0,the failure level of the slope system is high,so attention should be paid and effective measures should be taken to deal with the low reliability subunits,and risk monitoring should be strengthened.When the number of allowable instability subunits is greater than 0,the failure level of the slope system decreases significantly.