Experimental research of seepage characteristics caused by coal floor rock full of stress and strain process, operated by No.5 Taiyuan group

摘要

To explore chenghe main coal seam permeability characteristics of the mine rock bottom.In this paper the No.5 Dongjiahe coal seam floor which was representatively formed by mudstone, gritstone, siltstone and limestone was chosen as study case.By using MTS electro-hydraulic servo system, rock mechanics test is full of stress state-behavior of permeability contrast test.According to the test results of rock samples obtained four complete stress-strain process and penetration with stress and strain curves corresponding changes, combined with the destruction of the permeability of rock samples before-the relationship between stress analysis of its associated features.The results reflect the specimen deformation under conditions of complete stress-strain process permeability of the soft rock and hard rock showed a greater difference, soft rock strain softening stage in a sharp decrease in the permeability of the phenomenon, after the peak of the rock sample poor permeability;rather coarse sandstone, siltstone and limestone of the three samples representing a similar performance at the microscopic pore water through peak after crushing rock fractures or fissures seepage.In a comparative analysis of four core samples penetration-strain and stress-permeability characteristics of the coupling relationship, explores the soft rock and hard rock in the whole stress-strain process exhibit different permeability of internal differences, for soft rock, the stress reaches a peak before the rock strength, permeability with increasing load gradually increases;while hard rock before reaching the peak strength of rock permeability changes are not obvious, but soft and hard rock penetration peak rates tend to lag behind the rock intensity peak.At the same time, for different variation of the permeability of the rock there are differences, arranged in order of the four largest rock permeability rock is mudstone (1.681 × 10-4 Darcy) minimum, followed by siltstone (1.564 × 10-4 Darcy) and limestone (2.306 × 10-4 Darcy), coarse sand (3.342 × 10-4 Darcy) maximum penetration.The results indicate that the permeability of the shale smallest, is the best floor strata impermeable rock.Combining these four rock samples permeability test results analysis, peak flow mostly rocky peak stress in the rock after the strain softening stage where the rock has been demonstrated macro fissures, water inrush from floor strata is confined water through rock stresses, therefore, time to peak stress of rocks formed macroscopic crack before-seepage characteristics and laws, is an important theoretical basis for analysis and judgment floor water inrush conditions.