Monitoring Data Fusion And Hydrogeological Interpretation Of Urban Land Subsidence In Zhengzhou City

Zhengzhou city is confirmed as national center city by the national development and reform commission on December 26,2016.And it is currently in large-scale urbanization.Zhengzhou city is divided into the two parts by the beijing-guangzhou railway,the east part is the yellow river alluvial plain,the regional geological structure are mainly thick Cenozoic strata;the west part is priority the alluvial-proluvial plain,its deposit consists of Holocene stratum.In the geological environment,groundwater level dropping will be caused by the urban construction process such as high-rise building foundation pit excavation,the subway construction and so on,and further cause the development of urban land subsidence and concealed fault and other issues.The long-term development of the ground settlement will cause fracture of the urban water supply and gas supply pipeline,urban pavement cracking and buildings cracking.This is a potential safety hazard.This paper comprehensive study of modern geodesy techniques,such as level,GNSS,InSAR monitoring theory and method,and the settlement of multi-source data fusion theory.This data is analyzed and resolved by the geological structure data and fault data,the groundwater exploitation of Zhengzhou area.This is very important and urgent needs for safety monitoring of large cities and urban construction,security evaluation.From 2007 to 2010,with the rapid development of Zhengzhou,north and northeast of the city gradually formed two typical ground subsidence funnel.This paper has chosen 35 ASAR data covered the whole city,then the rate of land subsidence is obtained used to SB AS time-series analysis technique.According to the obtained monitoring data and the settlement of deep groundwater funnel,settlement of shallow groundwater funnel,we analyze and obtain that the land subsidence of north and northeast region is related to deep groundwater funnel,and the land subsidence of west region is related to shallow groundwater funnel,but the western land subsidence is closely related to between deep groundwater funnel and shallow groundwater funnel.The analysis results of InSAR monitoring results and geological structure show that there are significant differences in north of Lao ya-chen fault,its northern data of land subsidence is about 25mm/y,its rate of land subsidence after crossing the fault increase rapidly,its value is nearly 60mm/y;the western rate value is greater than eastern rate of the nanyangzhai fault-chaan fault's north,its value is about 10mm/y.The northern rate of western Shangjie fault is about 15mm/y?20mm/y,its value decrease to less than 10mm/y through the fault.And other fault in the small sedimentation rate area is not observed near fault.Base on InSAR monitoring data and the stratum,the largest areas of sedimentation is mainly in the alluvial plain,its maximum subsidence rate reached 70mm/y,the sedimentation rate of the former alluvial plains and aeolian dune and sandy is around 30mm/y,the sedimentation rate of flood fan is about 20mm/y,the sedimentation rate of the former diluvial plain and loess tableland can rarely be monitored,its maximum subsidence rate is generally less than 12mm/y.This paper collected the sedimentation data of leveling,GNSS and InSAR,but these data on the spatial and temporal resolution is not completely consistent,and the fusion data is uncertainty.In the future to ensure the consistency of fusion data,as well as the reliability of the fusion data,this paper examined consistency of the InSAR data,leveling data and GNSS data,using Bland-Altman consistency test,the results show that 93%of observations passed consistency test.This paper fuse passed data,and obtained the result of fusion,its result will be analyzed the geological structure and hydrological change.The related geological parameters such as pore water pressure,aquifer depth and thickness in the land subsidence model is obtained by drilling samples test and certain assumptions.But there are differences between the results and actual monitoring value because of the complexity soil.The ground subsidence model is restrained by monitoring settlement value,and then the parameters of model are inverted.It is closer using constrained parameters than using tested data in the settlement model.This paper inverted parameters using InSAR monitoring data,then calculate the settlement values using inverted parameters.It will be closer actual monitoring value using constraint parameters by comparing with the monitoring data.It is more reliable data using settlement calculated by the constraint parameters than these parameters tested by experiment data in the laboratory.