Distribution and Evolution Characteristics of Macroscopic Stress Field in Gob-Side Entry Retaining by Roof Cutting

Abstract

Non-pillar mining technology plays an important role in sustainable exploitation of coal resources. Gob-side entry retaining by roof cutting (GERRC) is a new technique regarding a non-pillar mining method based on the “cutting cantilever beam theory”. In order to study the distribution and evolution characteristics of macroscopic stress field of surrounding rocks in GERRC, and find out differences from traditional pillar retained mining method (PRMM), some key issues about abutment pressure and stress concentration shell were analyzed by numerical simulations. Results show that: (1) distribution characteristics of lead abutment pressure for the two mining methods are basically the same during the primary mining stage; (2) during the secondary mining stage, peak stress in front of mining face of the two modes is close, while the abutment pressure can be transferred more evenly to coal and rock mass far away from goaf when using GERRC, and that is more likely to cause high stress concentration in the coal mass near the goaf when mining with PRMM; (3) for the PRMM, lateral abutment pressure will produce a higher stress concentration in section coal pillar and a high residual stress will be maintained in it when coal masses on both sides of the pillar are extracted; (4) adjacent goafs can be connected to form a wide range of pressure relief region when using GERRC, and shape of distribution of the maximum principal stress appears a semi-space ellipsoidal shell in three-dimensional space, and it is a single arch shape in the section perpendicularly to the mining direction, however, it looks like a “m” shape in that section when mining with PRMM because of the high stress concentration in the coal pillar.