Study on the reasonable width of coal pillar along the hollow roadway of extra-thick coal seam by leaving small coal pillar to cut the roof and unload the pressure

In order to quantitatively analyze the reasonable width of the coal pillar in the section where small coal pillar is cut to the top and unloaded along the empty tunnelling road, the roof fracture law along the empty tunnelling road was theoretically analyzed, and the conditions and characteristic parameters of the key block B were also analyzed, based on which the technical scheme of the cut to the top and unloaded was determined, and then the distribution of the lateral bearing pressure caused by mining, the deformation of the surrounding rocks of the roadway, and the stability of the coal pillar before and after the cut to the top were analyzed by numerical calculation, the results showed that under the condition of cut to the top width of 10 m, the deformation of the top and bottom plates and the two gangs was reduced by 32% and 41% compared with that before the cut to the top. The results show that: under the condition of 10 m width of coal pillar, the deformation of top and bottom plate and two gangs is reduced by 32.0% and 41.5% and the peak lateral bearing pressure is reduced by 29.4% compared with the condition before cutting the top, cutting the top can improve the stress environment of the coal pillar and the deformation of the surrounding rock of the roadway, and the comparison of the different widths of the coal pillar, the plastic damage area and the vertical stress curve are all in the logarithmic law, and the width of the coal pillar is the inflection point of the plastic damage area of the coal pillar, the plastic damage area of the coal pillar is the inflection point of the coal pillar, the plastic damage area of the coal pillar is the inflection point of the coal pillar. The inflection point is 49.2% of the plastic damage area of the coal pillar, and the peak vertical stress is 20.33 MPa, which shows that the 10 m width of the coal pillar can ensure the stability of the coal pillar under the condition of cutting the top and at the same time, the stress environment of the roadway surrounding rock and the deformation situation are greatly improved.