Study On Deformation And Stability Of Landslide Based On InSAR And Surface Monitoring

The mountainous area in southwestern China is one of the most frequent geological disasters due to its complex terrain and strong tectonics.Especially after the "5.12" Wenchuan earthquake in 2008,a large number of landslides were triggered,and a lot of potential landslides caused by cracks and earthquakes after the earthquake have caused significant losses to people’s lives and property.The use of time series In SAR technology can realize landslide identification and deformation monitoring in a large area over a long time series.It is of great impact and significance for the "gateway forward" of landslide disaster prevention and reduction.However,its monitoring accuracy,applicable conditions and whether the surface deformation can reflect the overall deformation characteristics of the landslide body.It has always been the limiting factor affecting the wide application of In SAR technology in landslide deformation monitoring.This article is based on field and literature research.Taking Hongmeicun landslide and Qinglongsi landslide as research objects,Based on monitoring data such as ground rainfall,groundwater level,pore water pressure,inclinometer,and multi-slope survey;Deformation monitoring of Hongmeicun landslide using PS-In SAR technology,Deformation monitoring of Qinglongsi landslide using SBAS-In SAR technology;The geological models of Hongmeicun landslide and Qinglongsi landslide were established by taking typical landslide profiles.Dividing the rainfall in the landslide area into multiple rainfall processes to numerically simulate the deformation of the landslide;Based on ground monitoring data,The accuracy evaluation of In SAR monitoring results was performed.Comparing the results of numerical simulation with the results of In SAR monitoring and ground monitoring,Based on the comparison of three kinds of deformation data,the deformation characteristics of the landslide are analyzed and discussed.Finally,the Morgenstern-Price method was used to analyze the stability of the landslide.Combined with the deformation characteristics of landslide,the landslide stability change law is analyzed.The main conclusions are as follows:(1)The processing of ground monitoring data shows that there is a significant difference between the rainy season and the dry season of Hongmeicun landslide and Qinglongsi landslide.Rainfall is mainly concentrated in the rainy season;the response of groundwater level and pore water pressure is high.The landslide deformation showed a certain change law with seasonal rainfall.(2)The deformation rate monitored by In SAR in the Hongmeicun landslide area is in the range of-19.31mm/a to 22.45mm/a.The areas with obvious deformation are located at the toe of 1# landslide and 3# landslide;The deformation rate of the Qinglongsi landslide area is distributed in the range of-15.14mm/a to 3.43mm/a.The area with a large amount of deformation is mainly located at the trailing edge of the landslide and the southeast part.(3)Simulation of the landslide shows that under the action of rainfall,the infiltration of rainwater into the landslide body increases the water content of the landslide volume.Under the action of rainfall,the deformation of the leading edge of the Hongmeicun landslide is relatively large.Under the action of Qinglongsi landslide,the deformation position of the landslide is mainly the rear edge of Qinglongsi1 # landslide and Qinglongsi 2 # landslide.Exponential fitting of rainfall and deformation during rainfall,The rainfall and deformation index of Hongmeicun landslide and Qinglongsi 1 # landslide fit well,and their fitting degree is between 0.62-0.76.(4)The surface monitoring was used to evaluate the accuracy of the In SAR of the Hongmeicun landslide and Qinglongsi landslide,and compared with the accuracy in related literature,it was shown that the monitoring accuracy of the In SAR of the Hongmeicun landslide and Qinglongsi landslide was high.Using ground monitoring data,In SAR monitoring data and numerical simulation for comparison,the landslide deformation tendency of the three methods is strong.The landslide deformation is compared.The Hongmeicun landslide has the characteristics of a traction landslide,and the Qinglongsi 1 # landslide has the characteristics of a sliding landslide.Combining improved tangent angle and landslide evolution law,the Hongmeicun landslide is in the stage of constant velocity deformation,and the Qinglongsi landslide is in the initial deformation stage.(5)The stability of Hongmeicun landslide is calculated.In the natural state of Hongmeicun landslide,the stability factor is 1.23,which is in a stable state.The stability factors of light rain,moderate rain and heavy rain are 1.23,1.17,1.12 in stable or basically stable state under different rainfall conditions.The stability factor of rainstorm is 1.05 and it is in an unstable state.The stability factor of heavy rainstorm and extremely heavy rainstorm is 0.99 and 0.94 are not stable state.Under the condition of daily rainfall,the stability coefficient is distributed between 1.0382-1.3482.The lagging effect of the landslide rainfall is not obvious.In the natural state of Qinglongsi 1 # landslide,the stability factor is 1.33 and it is in a stable state.The stability factors for light rain,moderate rain,heavy rain and rainstorm are 1.33,1.20,1.13 and 1.05.The stability factor of extremely heavy rainstorm is 0.98,and it is in an unstable state.Under the condition of daily rainfall,the stability coefficient is distributed between 1.0382-1.3482.The lagging effect of landslide rainfall is obvious.(6)Using Spaceborne SAR data,the data collection frequency is limited by the satellite revisit period,which can realize long-term sequence and large-area landslide deformation monitoring.Hongmeicun landslide and Qinglongsi landslide have severe short-term deformation during the rainy season.Using Spaceborne SAR data does not reflect this kind of severe deformation obviously.Spaceborne SAR data can be used to identify the continuous deformation body in the area,and the recognized deformation can be continuously monitored by professional surface monitoring technology to make up for In SAR.(7)The stability of Hongmeicun landslide and Qinglongsi 1 # landslide are similar.The larger the deformation,the greater the stability coefficient decreases.When the deformation is small or no deformation occurs,the stability of the landslide gradually returns to its original stability.Linear fitting of landslide deformation and stability coefficient,the linear correlation is not high.However,generally speaking,landslide surface deformation and landslide stability show a negative correlation trend,landslide surface deformation(ground deformation monitoring,In SAR monitoring)can indirectly reflect the landslide stability changes,and provide a reference for further judgment of landslide stability status.