Considering the problems of lacking sealing theory

poor effect and high cost of sealing material and unreasonable sealing length for hydraulic fracturing drilling sealing in mine

mechanical models of sealed drilling for hydraulic fracturing were established. Relationships between the maximum bearing capacity of sealing material and sealing material property

sealing length were obtained. The reasonable sealing lengths of hydraulic fracturing under the sealed conditions

drainage conditions and constructional conditions were analyzed; and the field experiments were conducted. The results show that sealing material property and sealing length are the main factors influencing the maximum bearing capacity of sealing material. The maximum bearing capacity of sealing material increases with the increase of the strength of sealing material

the elasticity modulus and the sealing length. However

when the sealing length reaches a certain value

the maximum bearing capacity of sealing material verges to a constant value along with the increase of the sealing length. Taking Chongqing Songzao mine area as an example

the reasonable sealing length of crossing boreholes for hydraulic fracturing is considered to be 10 m; and the reasonable sealing length of coal seam boreholes for hydraulic fracturing is considered to be 13 m. The results of field experiment and the theoretical analysis are virtually consistent.