Study On Damage Degree Of Overhead Permanent Prime Farmland In Coal Mine Goaf

Permanent prime farmland is the permanent protection of high-quality cultivated land.Related regulations stipulate that permanent prime farmland cannot be damaged by any unit or individual.All-round protection of permanent prime farmland is one of the effective ways to achieve the steady growth of agricultural products in our country,solve the contradiction between human and land,and food security.This article adheres to the principle that permanent prime farmland cannot be damaged.Determining the zone and extent of damage to permanent prime farmland by underground mining under natural conditions through the evaluation of the damage level of permanent prime farmland.And explore economically reasonable governance measures to achieve the purpose of underground mining without damaging permanent prime farmland.This article takes an underground mine in Sichuan Province as an example,and establishes a corresponding simplified numerical model.The FLAC^3D software is used to simulate the ground movement and deformation caused by the underground mining of the mine.The simulation results show that after mining C11 coal seam,Tensile plastic failure zone appears,and tension cracks are created.The fracture zone will reach the surface,destroying the permanent prime farmland on the surface,and causing large movement deformation on the surface;Continue to mine the C13 coal seam will basically not have an additional impact on the plastic area above the goaf of the C11 coal seam,but it will increase ground movement and deformation.The damage degree and scope of the permanent prime farmland on the surface of the mine were determined through the evaluation of the damage degree of the permanent prime farmland.The evaluation results show that compared with the mining of C11and C13 coal seams,the scope and area of permanent prime farmland damage increased by13.35%.It can be seen that repeated mining will aggravate the damage of permanent prime farmland.In terms of exploring measures to prevent permanent prime farmland damage,it is a more reasonable plan to obtain indwelling coal pillars,and to find reasonable coal pillar sizes through numerical simulation experiments.The results show that:When conducting the first set of experiments,that is,mining only the C11 coal seam,at least a natural coal pillar with a width of 4m needs to be retained to avoid the impact of underground mining on permanent prime farmland;When the second group of experiments is performed,that is,the C13 coal seam is continued to be mined on the basis of the first group of experiments,if the coal pillars are not left in the C13 coal seam,all the schemes of the second group of experiments will affect the permanent prime farmland on the surface;When conducting the third set of experiments,that is,leaving coal pillars in the goafs of C11 and C13 coal seams,natural coal pillars with a width of more than 8m need to be placed in all the goafs to prevent the damage of permanent prime farmland by underground mining.Considering the factors of maximizing the economic benefits of the mine,the width of the coal pillars should be set at 8m in all the goafs.