Simulation Analysis Of The Sliding Process Of A Piedmont Gentle Slope Under The Action Of The Temporary Groundwater In The Confined Aquifer In Nanjing

According to the traditional view,the gentle slope in front of the mountain is equivalent to the counter pressure road,which is conducive to the overall stability of the mountain.However,in recent years,extreme heavy rainfall occurred frequently in Nanjing areas,and the intensity and duration of rainfall increased and lengthened.For example,the annual rainfall in 2015 and 2016 is about 1800 mm.Affected by this,many large-scale landslides occurred on the gentle slopes in Nanjing.Through geological investigation,it was found that a series of landslides,including a series of gentle slope sliding in front of the mountain,mostly occurred after heavy rainfall,and showed intermittent creep characteristics.There were two large-scale landslides in zhutoushan Mountain,Pukou District,Nanjing city in 2003 and 2007,which did not attract enough attention at that time.In 2015 and 2016,two large-scale landslides occurred in some parts of the mountain affected by heavy rainfall,which attracted the attention of engineering and scientific researchers.In this paper,the formation mechanism of the landslide is studied by theoretical analysis,numerical simulation and monitoring system arrangement after in-depth analysis of the characteristics of the mountain stratum structure and hydrogeology.At the same time,the instability process of the slope under the influence of rainfall is comprehensively analyzed by using Geo Studio numerical simulation software.The main contents and results of this paper are as follows:(1)Through geological investigation and analysis,it is found that the landslide in the study area is an intermittent creep landslide.According to the deformation characteristics of the landslide,the deformation process can be divided into creep deformation accumulation stage,sliding deformation temporary sliding stage,accelerated deformation failure stage and repeated creep sliding stage.(2)Based on the special geological background and sedimentary environment in Nanjing area since Cenozoic,the formation and evolution process of the Piedmont gentle slope in the study area is inverted.The special stratum structure of Piedmont gentle slope is analyzed in terms of stratum distribution,stratum lithology and related stratum physical and mechanical properties.It is found that "temporary groundwater in the confined aquifer" is easy to form under the control of its unique stratum structure and hydrogeological conditions.(3)In this paper,the rainfall infiltration process of Piedmont gentle slope under the influence of heavy rainfall is analyzed,the seepage equation suitable for different groundwater types of Piedmont gentle slope is derived,and the formation process of temporary groundwater in the confined aquifer and its influencing factors in the slope under the condition of heavy rainfall are simulated,and the rainfall conditions causing sudden change of pressure head are mainly studied.On this basis,the formation mechanism of the piedmont gentle slope in the study area are analyzed.(4)For this kind of intermittent creep landslide,the seepage,deformation and stability of the slope are analyzed by Geo Studio numerical simulation software.At the same time,the monitoring scheme suitable for this kind of landslides is designed and applied to the monitoring of landslides in the study area.By analyzing the long-term and short-term displacement and groundwater monitoring data,the relevant laws of intermittent creep of piedmont gentle slope are obtained,the sliding mechanism of this type of landslides is verified,and the prevention and control suggestions are put forward for this kind of landslides.