Research On Shear Mechanism And Mechanics Characteristics Of The Interface Between Spoil Mixture And Concrete

Tunnel spoils have been widely and reasonably utilized in the construction of roadbeds,stations and other projects in difficult and dangerous mountainous areas.Inevitably,there will be a lot of interface problems between the spoil mixture and the concrete structure.And its shear mechanical properties are very important for the design,operation and maintenance of various geotechnical structures.Therefore,it is necessary to study the shear mechanical properties of the interface between the spoil mixture and concrete.Because of this,this paper studies the macro-shear mechanical properties,micro-shear mechanical properties and shear mechanism of the contact surface through laboratory tests and numerical simulations.Finally,a stress-strain prediction model considering the roughness of the interface is established through theoretical analysis.The main contents and research results are as follows:(1)Based on large-scale direct shear tests,the effects of gravel content,interface roughness and normal stress on the shear mechanical properties of the interface were studied.The conclusion shows that the roughness has a significant effect on the shear mechanical properties of the interface.And there is an optimal roughness to maximize the shear strength of the interface;The variation law of the shear strength of the interface with the increase of the stone content is greatly affected by the normal stress;The peak shear strength of the interface meets the Mohr-Coulomb strength criterion.(2)Based on the discrete element numerical simulation of the interface,I studied the mesoscopic shear failure mechanism of the interface.And the relationship between the mesoscopic parameters and the macroscopic shear characteristics is studied.The results show that the interface gradually develops from local failure to regional failure.The shear band of the smooth interface is not obvious,while the shear band of the rough interface is obvious,and the thickness is about 6～7d50.The fabric anisotropy and coordination number of the interface can better reflect the macroscopic shear mechanical properties of the interface.(3)Based on the results of laboratory tests and numerical simulations,combined with the theory of critical state soil mechanics,the state parameters of the interface are introduced into the hyperbolic model,and the relationship between the roughness and the critical state parameters is analyzed.A state-dependent hyperbolic model of the interface considering roughness is established.And the rationality of the model is verified by laboratory test data.