Study On The Cause Of Formation And Hazard Zonation Of The Ground Fissure In The Topographic Map Area Of XuZhuang Town Of Dali County

As a kind of special geological hazard of linear spreading,ground crack is the main feature of surface fracture deformation,Ground fissures are distributed in many countries,causing damage to farmland,roads,buildings and all kinds of infrastructure,and to the safety of planned and proposed facilities.Based on the field field investigation of the crack in xuzhuang town,Dali county of the research area,the geological background of the research area was identified by combining with the collected data and indoor processing.And from ground fissure and geological background and the engineering point of view of environmental background relationship found out the characteristics of spatial distribution characteristics and profile,and then through the finite difference software FLAC3D to establish a typical model for numerical simulation of the collapsibility loess ground fissures and structural ground fissures.According to the field exploration,field test and numerical simulation results,the genetic mechanism of two kinds of fissures is generalized.Finally,AHP is used to set up an evaluation index system to carry out risk zoning for the ground fissure in the study area.The main research results obtained in this paper are as follows:1.Through field investigation,46 ground fissures have been identified in the study area.The main causes of the ground fissure are structural causes and loess collapsibility.The main geomorphologic units of the ground fissure are the Loess Tableland and the three terrace.The trend of ground crack is mainly N and NWW,But the overall trend is disorderly.The plane shape of the Loess collapsible ground fissure is straight line,and the profile type is a single trumpet like crack on the upper and lower width.The plane shape of the structural ground fissure is linear and polygonal,and is exposed in the form of pinch and reappearance.The profile form is a series of ladder shaped faults with the same tendency.The genetic mechanism is generalized to vertical seepage stage,horizontal seepage stage and differential settlement stage.2.Based on the exploration data,in-situ experimental data and FLAC3d numerical simulation results,the generalizing models of two typical types of ground fissures are summarized.The cause of typical loess collapsible ground fissure is mainly related to seepage of the canal.According to the results of numerical simulation and field test,the influence radius of the canal seepage is 18m and the depth 7.5m is affected.The cause of the typical tectonic ground cracks is mainly related to the ShuangQuan-Linyi fault activity below.The genetic mechanism is generalized to the deep main fracture control seam,the shallow secondary fracture initiation,the surface runoff expansion joint.3.This paper selected the landscape category,landscape boundary,the distance from the fracture,the size of the ground fissures,the density of the ground fissures,ground fissure activity,the annual average precipitation,ground subsidence rate and distance from the channel 9 evaluation factor,and the analytic hierarchy process(AHP)is used to establish the risk assessment system for cracks.In Arcgis,the above evaluation factors are superposed by natural discontinuity method.The danger zone is divided into four zones,which can be divided into extremely high danger zone,high danger zone,intermediate danger zone and low danger zone.The result shows that the area of low risk area is about 152.35km~2,accounting for 36.0%of the total map area.The area of the dangerous area is about 149.91km~2,accounting for 35.4%of the total map area.The area of high risk area is about 117.55km~2,accounting for 27.8%of the total map area.The extremely high risk area is about 3.11km~2,accounting for 0.7%of the total area of the study area.Will risk regionalization results and practical activity of ground fissures in the study area for comparison,the result has good consistency,determine the risk regionalization result has good scientific and reliability.In this paper,the resulting ground fissure hazard regionalization results in the study area can be applied to the area in the future construction plan reference and guide for disaster prevention and mitigation of ground fissures,as well as for other similar ground fissure disaster risk zoning activity areas to provide the reference.