Investigation into ground pressure control within the two-step stope of the staged mining method
To mitigate the displacement of the upper wall rock mass in the two-step mining of the block chambering method,a common practice involves cutting a slot in the middle of the stope and mining towards both sides of the upper and lower walls.This approach aims to minimize the exposed time of the stope and consequently reduce the displacement of the upper wall rock mass.When the ground pressure reaches rheological conditions,simply minimizing the exposed time of the stope may not effectively control rock movement failure.Therefore,employing the Fast Lagrangian Analysis of Continua in 3 Dimensions(FLAC3D)to simulate the ground pressure of the upper wall of the stope,along with rheological analysis,becomes crucial.In this approach,the roof of the upper wall is supported by low relaxation prestressed large diameter steel strand anchor ropes.This strategy aims to alleviate the ground pressure on the upper wall,thus enabling the mitigation of stress conditions that lead to rheological deformation.The research indicates that applying support resistance to the upper wall rock mass can mitigate or eliminate flow deformation caused by high ground pressure.It was found that the displacement of the upper wall rock mass is significantly reduced when the roof of the upper wall is supported by utilizing 7 rows of 7.0 m long anchor cables,with 6 cables in each row.However,it was observed that the anchoring force of the top row anchor rope in the second layer and the local anchor rope in the third layer of the stope exceeds the design value.By implementing 8 rows of 7.0 m long anchor cables,comprising 7 ropes in one-step stope and 6 ropes in two-step stope,to support the roof of the hanging wall,the anchoring force of the anchor ropes remains below the designed value even after mining the bottom pillar.Monitoring results indicate that the displacement of the upper rock wall is generally reduced to less than 6 mm following the installation of large diameter steel strand anchor ropes.Practical application demonstrates that the use of low relaxation prestressed large diameter steel strand anchor rope not only prevents cracks and subsidence of the roadway outside the upper wall vein in the two-step mining of the block chambering method but also significantly reduces the construction cost of upper wall excavation.
safety engineeringmine safetyblock chambering methodtwo-step miningrheological analysisFast Lagrangian Analysis of Continua in 3 Dimensions(FLAC3D)anchor ropedeformation monitoring
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