Geological Disaster Models In The Mined-out Subsidence Area In The Mountainous Areas Of Northern Hebei And Their Hazard Mechanisms

The damage by ground movement and deformation in old goaf is the main threat to ground buildings.Therefore,how to ensure that urban construction is not affected by the goaf and the safety of ground buildings are extremely important.The paper takes Yingshouyingzi diggings in mountain area of North Hebei as an example to analyze and evaluate the mechanism of geological hazards in gob collapse and the site adaptability in resource-exhausted cities,adopting the comprehensive technical means of data collection,field geological survey,in-situ monitoring,numerical simulation and theoretical analysis,and what has been achieved is as following:(1)According to the formation mechanism and distribution characteristics of geological hazards induced by coal mining in Yingshouyingzi mining area,the damage and disaster-causing patterns of old goaf site in the coal mine of mountain area are divided into four categories: sliding disaster-causing pattern,tension disaster-causing pattern,subsidence disaster-causing pattern and collapse disaster-causing pattern,which are controlled by rock types and properties,coal seam dip angle,fault and terrain and Quaternary loose layer of the study area.(2)The compaction creep test of different lithological falling objects in the goaf was designed and carried out,and the characteristics of the compaction and creep structure change process of the fallen and broken rock in the old goaf were revealed.The results of the compaction test of falling objects in the goaf show that the compaction creep process of broken rock can be divided into three stages: the rapid compaction stage,the slow compaction stage and the stable consolidation stage.The creep characteristics of broken rock are affected by the load,the lithology and the rock particle size.The larger the load is,the larger the creep deformation is and the longer the creep time is;the creep deformation and time of broken mudstone is the largest,followed by the sand mudstone mixture,and sandstone is the smallest.In the creep process,the change degree of rock particle size is affected by lithology and load size.The larger the load is,the lower the rock strength is and the larger the change of particle size is.(3)The fuzzy comprehensive evaluation method can be used to evaluate the ground stability of goaf,and the exploration area can be divided into four regions:unstable area,less stable area,relatively stable area and relatively more stable area.Subsequently,the distribution of ground fissures and the damage of houses in the exploration area were used to verify the results.It was found that the length,width and number of ground fissures and the damage rate of buildings increased gradually from relatively more stable area,relatively stable area,less unstable area to unstable area,which means that the fuzzy comprehensive evaluation method is reliable and the corresponding evaluation results are effective.(4)The paper employed numerical simulation method to calculate the surface subsidence,inclined value,curvature value and horizontal deformation of the study area and evaluate the ground stability of coal motor industrial park.Moreover,the residual displacement and deformation of the area and the “activation” of the overlying strata were calculated and distinguished by simulating loading the ground.And then the site adaptability evaluation was carried out for the study area,which was divided into site adaptability level I,site adaptability level ?,site adaptability level ?and site adaptability level ?.The region of site adaptability level I is located at the northwest and northeast points of exploration and evaluation area;the region of site adaptability level ? is surrounded by Laoyi Road,Dongfengyan,sandstone pile and Nanhuan Road;the region of site adaptability level ? is mainly surrounded by the area of the north of outcrop location of four coal seam and Xifengyan and the south of Zhongfengyan,and the area surrounded by the southwest of Yanying recreation machinery factory and the north of exploration and management area;the region of site adaptability level ? is mainly sited at the north of Nanhuan Road and the south of the outcropping position of the fourth coal seam.This treatise contains 94 figures,25 tables and 237 references.