Abstract: The roadway surrounding rock often produces single or multiple bed separation due to deformation incoordination. Based on the mechanism of bolt pullout force during the relative movement to the strata, an elastic-plastic mechanics model of additional stress occurred by bed separation was established. The influence of bolt loading caused by bed separation in elastic state was firstly discussed. The interface of anchorage body will enter elastic-plastic stage under further expansion of bed separation. The sliding ranges on both sides of the bed separation were determined through the two-stage linear function shear slide model. Loading process of the anchorage body under the bed separation function was divided into four general stages, which included elastic stage, one side elastic-plastic stage, two sides elastic-plastic stage, one side sliding further with one side sliding all stage, and both sides sliding all stage. The axial force distribution during bed separation was verified by experimental results. The results show that calculated value has good agreement with the measured value. The bolt stress distribution caused by the multiple bed separation was summarized according to the superposition principle. The multiple peak curves of stress distribution were proved. Finally, the parameter analysis of bed separation value location was made through an example. The influence of bed separation on bolt loading should be considered in future anchorage design.

Key words: single bed separation, multiple bed separation, bolt, elastic-plastic mechanical model, force characteristics