| The problem of interface between soil and structure is widely existed in engineering problems.Along with a batch of high panel dams’ building in China’s southwest and northwest area,people pay more and more attention to the safety of the dams’ construction and operation.Due to the limitation of the test conditions,the interface study mainly focused on the interface tests of sand formerly,while few studies were about the interface between rockfill material and concrete panel.In this paper,the existing large-scale direct shear tester was improved,based on which the dynamic contact deformation characteristics between concrete panel and rockfill material are emphatically studied.The main content is as follows:(1)In the present,the measurement method and precision of the existing large-scale direct shear test instrument’s normal and shear displacements are not enough to meet the test requirements,thus a new control system was installed aiming at this problem.The measuring method of normal and shear displacement was redesigned and the data acquisition system was improved.New measurement method was more reasonable,and made the results of tests more reliable.(2)Friction is a key problem affecting the reliability of large direct shear test results,about which a lot of studies has been made at home and abroad,but it has not been well solved.To solve this problem,in the paper,on the one hand,the measure putting rubber sticks in the contact area between the panel and the shear box to reduce the friction was adopted on the basis of strengthening the lubrication of the slide.On the other hand,the tests of friction measuring were carried out in which the variation law between friction and normal pressure was studied.(3)A series of interface tests between coarse grained soil and concrete panel were carried out,including normal compression tests,monotone shear tests and dynamic modulus & damping ratio tests.The results of the monotonic shear tests showed that the relationship between shear stress peak and normal stress was consistent with Mohr-Coulomb strength criterion.With the increase of the shear displacement,the contact surface firstly showed shear shrinkage,then shear bulge,and the specimen generally showed a trend of shear shrinkage.With the increase of normal stress,the shear shrinkage of the initial segment is larger,while the subsequent shearing bulge is less.The results of the dynamic modulus & damping ratio tests showed that with the increase of amplitude of the shear displacement,the dynamic stiffness decreased,while the damping ratio tended to increase.In the same amplitude of shear displacement,with larger normal stress,the dynamic stiffness got larger while the damping ratio got smaller.The results of the analysis of deformation characteristics showed that With the increase of the cycles,the relation curve of normal displacement and shear displacement in each circle has been moved up,which means the specimen was gradually compressed,and showed a trend of shear shrinkage. |
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