Based on the pull-out test on bolts in-situ

the test data are analyzed and the difference of shear stress distribution along the bolt is discovered between the usual simplified assumption and the actual condition. In usual analysis

the shear stress along the bolt is assumed even distribution

but the real result is negative exponential distribution under pull-out condition. Considering the working mechanism and damage process of cohesion strength

a theoretical model for the pull-out bolt is rebuilt. In this model

the interface shear strength and uncoupling length parameter can be easily deduced from the ultimate load measured from pull-out test. Furthermore

a numerical model including a friction-contact interface element which can simulate the complex mechanical properties of the interface is introduced; and the mechanical response of bolt under pull-out load is analyzed. Comparing the calculation result with the field test

the reliability and precision of the theoretical model and numerical analysis are verified.