| Land subsidence is a major geological environmental problem facing major urban areas in the world.The occurrence of land subsidence will pose a serious threat to urban construction facilities,social and economic development,human life safety and living environment.Excessive extraction of groundwater can easily cause surface subsidence and other land subsidence problems.With the rapid development of globalization,human society's demand for water resources continues to increase,which promotes the continuous enhancement of human beings' ability to extract water resources and the intensity of utilization.Water resources,especially groundwater resources,have long faced the problem of unreasonable exploitation.The drop of groundwater level caused by over-exploitation of groundwater resources will lead to the deformation of underground aquifer structure,which in turn will cause elastic or permanent deformation of the ground surface.Permanent deformation of the ground surface will cause a series of geological and environmental problems such as ground subsidence.At the same time,with the rapid economic growth of karst areas,the increasing demand for groundwater resources is also likely to cause land subsidence problems such as karst collapse.Therefore,it monitors the changes in surface subsidence in karst areas and analyzes the characteristics of subsidence changes.At the same time,it conducts dynamic monitoring of groundwater changes in subsidence areas,analyzes the relationship between groundwater dynamic changes in karst areas and changes in surface subsidence,and explores and understands surface subsidence changes and their effects in karst areas.Factors are of great significance.Taking Guiyang City as the research area,this paper aims to study the relationship between groundwater dynamic changes and land subsidence in karst areas,and analyzes the impact of groundwater changes on land subsidence by combining InSAR technology and GRACE dynamic monitoring of groundwater changes.Since its development,InSAR technology has increasingly become the main technical means for surface deformation monitoring at home and abroad due to its all-weather,all-day,large-scale,and short-period advantages.It has also revolutionized the shortcomings of traditional deformation monitoring technology to a certain extent.Its continuously improved monitoring technology provides a variety of methods and models to choose from for the development of different monitoring programs.Among them,the PS-InSAR method and the SBAS-InSAR method,as the two more commonly used InSAR deformation monitoring technologies,have become important methods widely used in urban settlements,mine deformations,earthquakes and landslides and other geological disasters.In practical applications,the algorithmic improvement of these technologies is still in the stage of continuous exploration.In this paper,by combining the PS-InSAR method and the SBAS-InSAR method,the advantages of the two are used to reduce the error of the SBAS-InSAR method subjectively selecting the control point by introducing the PS point,thereby improving the deformation estimation accuracy and monitoring the settlement changes in the study area.Since its development,GRACE gravity satellites are not affected by topography,climate and other factors,and have the advantage of inverting changes in land water reserves with a uniform observation scale,making GRACE data widely used in the field of groundwater dynamic monitoring.At the same time,GRACE data in the field of monitoring groundwater changes makes up for the long-term pains and difficulties faced by traditional groundwater monitoring technologies,such as high cost,uneven spatial distribution,easy data loss,and long cycle.It greatly reduces the cost of groundwater monitoring and improves it to a certain extent.Improve the monitoring efficiency of regional groundwater dynamic changes.In this paper,the changes in land water reserves retrieved by GRACE data,and post-processing methods such as improved Gaussian filtering are selected through experiments to improve the accuracy of GRACE data to monitor the long-term sequence of groundwater reserves changes in the study area,and provide efficient,true and reliable groundwater reserves for the study area.Change information.The main research content of this paper is to monitor the land subsidence of the study area from 2015 to 2016 by using the SBAS-InSAR method with the introduction of PS points,combined with the groundwater level yearbook data of the study area,and use GRACE data to monitor the time series of groundwater reserves changes in the study area during the same period.From point to face ratio,the relationship between groundwater storage changes and land subsidence is analyzed,and the influence of groundwater changes on land subsidence is discussed.The research results are as follows:1)From 2015 to 2016,the more obvious settlement areas in the study area were distributed in the main urban area of Guiyang and the southwest area,where the minimum settlement rate was-3mm/a,and the maximum settlement rate was-28mm/a;time In terms of changes,the settlement increase in Qingzhen City,Baiyun District,and Guanshan Lake District is relatively large,while the regional settlement changes in Xifeng County and Kaiyang County are not obvious;in addition,Nanming District,Wudang District,and Huaxi District have changed over time.Obvious funnel settlement;at the same time,the results of comparing the settlement volume of the study area with the measured control points show that this paper adopts the SBAS-InSAR method that introduces the PS feature points to monitor the ground settlement in the study area.2)From 2015 to 2016,the groundwater reserves in the study area showed a slow downward trend as a whole.Among them,the dynamic change of groundwater reserves has a minimum value of-80 mm and a maximum value of 60mm;the changes in groundwater reserves in the study area have obvious seasonal characteristics,GRACE data The monitored karst groundwater changes are consistent with the precipitation characteristics of the study area;in addition,the changes in groundwater reserves monitored by the GRACE data in the study area are generally consistent with the historical actual situation published in the Guizhou Water Resources Bulletin in 2015 and 2016;therefore,it shows that the improved Gaussian used in this article The filtering method and other post-processing methods have improved the accuracy of GRACE data to a certain extent,and can well reflect the changes of groundwater resources in the study area.At the same time,this paper uses the measured station water level data to verify the GRACE Rl-06 data to monitor groundwater reserves in the study area.The feasibility of change.3)Through comparative analysis of the relationship between groundwater changes and land subsidence changes,the drop of groundwater level at monitoring sites in the study area has a significant impact on land subsidence.The groundwater change trend of GRACE data and the average subsidence change trend of the study area basically show a downward trend.It can be seen that from the change of groundwater level in the monitoring site area to the dynamic change of groundwater reserves in the entire study area monitored by GRACE,groundwater changes and surface subsidence changes and trend changes have obvious correlation,indicating that excessive groundwater consumption is caused by the ground One of the important reasons for settlement.Therefore,rational exploitation of groundwater resources is not only a necessary measure for the sustainable management of water resources,but also a necessary means for the prevention and control of land subsidence disasters. |
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