Study On Stability And Evaluation Of Safety Influencing Factors Of Reinforced Embankment Under Heavy Rainfall

In recent years,since ground transportation network is constructed more and more frequently in southwest,which can form lots of artificial high-filled embankment slopes,it would affect the normal operation of traffic if slope is failure.So it has attracted attention in engineering.There are some reinforcement methods for embankment slope,such as retaining wall,reinforced,but the failure mode and mechanism of reinforced artificial embankment slope under the extreme conditions,especially rainstorm,are rarely reported.Therefore,the research on the risk and failure mode of reinforced embankment slope under storm conditions important theoretical basis and engineering value for the disaster prevention and mitigation.In this paper,four rainfall intensity of 14mm/h,28mm/h,42mm/h and 70mm/h are defined as "strong rainfall",of which 14mm/h is heavy rain,28mm/h is rainstorm,42mm/h is heavy rainstorm,70mm/h is torrential rain.Based on saturation-unsaturated flow theory,the paper regarded rainfall intensity,slope grade,reinforcement density as the main factors and carried out the experiment of artificial reinforced embankment slope failure model device under heavy rain state,the evolution laws of wetting peak,pore water pressure and earth pressure were analyzed,the risk inoculation and failure modes of artificial reinforced embankment slope were deeply analyzed,and the following research results were obtained:(1)There was an artificial reinforced embankment slope rainstorm failure model test device,which included automatic rainfall control system,slope displacement monitoring system,pore water pressure and soil pressure monitoring system.The test tank was made of transparent toughened glass,which can achieve monitoring displacement successive.(2)By analyzing the final width,the top depth and slope gullies at the end of the test,It was found that the width and ditches depth at the top of the slope were the best,regardless the slope grade under coupling effect of band density and slope.However,the width and gullies depth on the top of the slope strengthened by 4 layers of reinforcement were the worst.It showed that the higher the gradient and the greater the rainfall intensity,the better the development of the gully width.Under the interaction of rain intensity and slope,no matter how steep the slope was,with any kind of reinforcement conditions,the slope with the effect of 70mm/h rain intensity was the best in the width and ditches depth at the slope top.While the width and gullies depth at the slope top are worst when the rainfall intensity is 14mm/h.(3)Analysed the failure history of artificial fill embankment before reinforcement was found to destroy the slope surface: formed gully at slope surface after rainwater infiltration?gully developed through the shoulder-slope and slope foot progressively ?gully became wider and deeper ?gully ran through the whole slope?slope occurred large scale failure.The failure evolution process for the slope top was: tensile failure of sloping shoulder under rainwater infiltration ?formed a gully at shoulder-slope,the development of gully was the back edge of slope top ? the gully at shoulder-slope and slope top became wider and deeper?gully ran through the whole slope ?after that gully changed wider and deeper.At the same time,the damage evolution process of embankment before and after reinforcement was compared and analyzed,it was showed that the evolution process of reinforced embankment failure was similar to the no reinforced embankment,but the slope of reinforced embankment would produce pitting before large scale failure occured.(4)There were three stages for the variation of pore water pressure in the whole experimental process: a period of rapid development,slow growth phase,stabilization process.the pore water pressure was the closer to the foot of the slope,shoulder-slope,the more pressure increased;There were 4 stages of the earth pressure changes: a period of rapid development,slow growth phase to the peak stage,rapid decline stage,slow decline stage;in the same depth,when they were the closer to the position shoulder-slope,the more earth pressure was greater.The mean infiltration rate of humid peak,pore water pressure and earth pressure increased with rainfall intensity increasing and decreased with reinforcement belt density decreasing.Meanwhile,with the increase of the slope,the average infiltration rate of humid peak,pore water pressure and earth pressure decreased gradually.(5)Orthogonal analysis method was used to systematically analyze the influence of safety factors such as rainfall intensity,slope ratio and density of ribs on wetting peaks,pore water pressure,and earth pressure.The effect of safety factor levels on experimental indexes was analyzed.The safety factor A(rainfall intensity)was found to be positively related to the average infiltration rate of the wet peak,pore water pressure,and earth pressure,while the safety factor B(slope ratio)and safety factor C(strand band density)are inversely related to the average infiltration rate of wet peaks,pore water pressure,and earth pressure.At the same time,it is also found that the influence of rainfall intensity on the pore water pressure,the wet peak and the earth pressure is far greater than the rib zone density and the slope ratio.