Abstract：Through the analysis of effective factors on bolting stability in a soft coal body, the bolting mechanism was studied by numerical simulation, and the anchorage body formation conditions were analyzed in the soft coal body. The results show that the main causes for bolting failure in soft coal are bed separation, the slip between a resin-end anchorage body and a soft coal body, bolt shed and the failure of protecting surface component under the redistributing stress. After a single prestressed bolt is anchored in a soft coal body, bolt axial stress, additional stress and displacement fields increase with the increase of a prestressing force. Additional stress field ( anchorage body) regions is limited by a prestressing force, that is, additional stress fields ( anchorage body) in two free ends can produce a“some-more-no superposition”process with the increase of the prestressing force. Axial stress is uniform in a free segment, reducing gradually along the axial anchor segment. An integral anchorage body is formed in a superposition process of multiple-bolt additional stress fields. The first condition of a formation anchorage body is the characteristics of soft coal body strength, and controlled conditions are the bolt ( smaller) perstressing force matching soft coal body strength, the increase of bolt length and its density.

Keyword：soft coal body;bolting;anchorage body;failure characteristics;