Study On Ground Subsidence Of Unconsolidated Strata Of No.3Jining Coal Mine In Porous And Low Pressure Water Injection Process

With the development of our science and technology progress, underground engineering quantity increases day by day, and the scale expands.So the surface settlement becomes more and more obvious, many of our cities caused by surface settlement problems.East China universal distributes deep cenozoic loose water-bearing stratum, because of the mining the water of the cenozoic loose in the mining lossed a lot.Thus the formation stress increases, the aquifer produced compression deformation, ground settlement caused shaft wall damage. In order to improve this situation,we injected water on the dehydration layer to replenish water, and we used the advanced Fiber Bragg Grating monitoring technology to monitor the formation of settlement, grasped and predicted the settlement state and settlement law.Based on this situation, we analysis ed the dehydrate deformation properties of the loose layer on theoretic,improved settlement computing method of the loose layer because of water loss,established the relationship formula between the drawdown of water level, the amount of compression and strain strata,provided more accurate calculation of settlement for a good theoretical basis.In order to improve the No.3jining coal mine shaft and stratum settlement status,they proceed the water injection experiment and long-term water supply project.They proceed the joint injection at four different positions of the water injection holes using tap water pressure,to supply aquifer under the loose layer,ease the stratum subsidence trend, and protect well bore not damaged. According to the monitoring to water level, water pressure, water injection rate, injection rate and optical fiber grating strain information,we summed up strain change law in the process of water injection in loose layer.We calculated stratum settlement of the No.3jining coal mine in the process of water injection,and the optical fiber grating monitoring results were compared and analyzed, found an improved calculation method and loose layer strain monitoring results,and verified the accuracy of the optical fiber grating settlement monitoring method to the water loss of loose layersResearch shows that under small amplitude of the injection pressure,the water injection quantity of loose layers basic increased linearly.Water level with water injection process changed from uplift to the smooth.The long-term water injection scheme will be able to reduce and control the water level decline of loose layer. Fiber Bragg Grating sensor changes of the loose layer and the same horizon level change trend had good synchronization relationship.The lower of the water level of loose aquifer showed compression deformation,Fiber Bragg Grating suffered compression stress effect,and the corresponding wavelength value reducted. The increase of the water level of loose aquifer showed compression deformation relief,the compression stress reduced,and the corresponding wavelength value increased.Therefore, the long-term water injection is a method to inhibitor of loose layer water loss settlement, water injection had certain effect to prevent the stratum subsidence.But how to protect water, we need to explore.The strain monitoring system of Fiber Bragg Grating of loose layers can realize the high precision real time monitoring.