Experimental Study On Bond Behavior Of Mortar-Rock Interface Of Anchorage System Under Different Loading Rates

Prestressed anchorage technology has been widely used in the construction of slope,foundation pit,tunnel and underground engineering for its advantages of economic safety,rapid construction,small disturbance to surrounding rock and so on.The failure of anchorage system is mainly the failure of the interfaces between anchor and mortar and the interfaces between mortar and surrounding rock.The research on the interface between anchor and mortar can draw lessons from the research results of the interface between steel and concrete.So a large number of experimental and theoretical studies have been carried out by researchers at home and abroad,and the related experimental methods and theoretical studies have been relatively mature.The bonding problem of the interface between mortar and the surrounding rock is relatively complex,and there is a lack of unified test standards.At present,there are few related research,and the study of the interface under different loading rates has not even been carried out.The bonding performance of the interfaces between mortar and rock in the rock anchorage system under different loading rates was preliminarily studied in this paper,and the main work is summarized as follows:(1)The bonding performance of the interfaces between mortar and rock in the rock anchorage system under different loading rates was preliminarily studied by push-out test,and the effects of loading rate,mortar water cement ratio,anchorage length and anchor diameter on the interfacial bonding performance were discussed respectively.The interfacial bond stress increases in the form of logarithmic function as the loading rate increases,but decreases with the increase of the length of the anchorage section or the diameter of the anchor solid.Compared with loading rate and water cement ratio,the influence of anchorage diameter on average bonding stress is more significant.(2)There is stick slip phenomenon on the interface between mortar and rock under high loading rate.The effect of loading rate on the sliding mode of the interface and the effect of loading rate on the viscoelastic stress drop are analyzed respectively.With the increase of loading rate,the sliding mode of anchorage interface changes from steady slip to stick slip,and the stress drop increases with the increase of loading rate.It is preliminarily determined that the critical strain rate of the interface sliding mode changes from stable slip to stick slip is 1.12×10-4s-1.(3)The relationship between shear dilatancy stress and loading rate and the relationship between stress drop and shear dilatancy stress is derived.Meanwhile,it is explained that how loading rates affects the interface slip mode and stress drop from the theoretical level.Furthermore,the failure and slip process of anchorage interface is explained from meso level according to the improved meso mechanical model of anchorage interface.(4)A mathematical model is established to describe the stick slip characteristics of the anchorage interface,meanwhile,the constitutive equation of the model is derived.And the accuracy of the model is verified by numerical simulation subsequently.