The load variations of each anchor in coal stratum are recorded with load cells for more than two years. The instantaneous losses of load that occurred during the lock-out operation have been measured. The load changes versus time after lock-out are analyzed. The comparison between measured deformations and calculated displacements at the heads of the anchors is discussed. The gray model

GM (1

1)

of load loss is established. The trend of variation is researched. Results show that the gray model has a higher precision. This study is of referential value to construction and design for other similar projects.