Similar Materials Developed And Mechanical Reliability Study On Model Rock Structural Plane

Shear strength is the key index of stability analysis and strengthening design of rock joints, and laboratory direct shear test is a basic method to determine the shear strength. However, the rock compressive strength and joint roughness coefficient (JRC) both have the scale effect, when the shear strength scale effect is analyzed by using similarity ratio; it is common to neglect the scale effect of rock strength and JRC while the scales change. Then, it is hard to evaluate the similarity with different scales. Therefore, in order to eliminate the effect to shear strength scale effect by mechanical parameter of samples, the samples of structural planes with the same geometric feature and main mechanical parameter as the prototype are research for this work. According to the analysis, some main original works are made.Firstly, based on shear strength mechanism of rock joints and the selection principles and requirements of similar materials, a new type of similar material with the mixture of high-strength cement, silica fume, superplasticizer, standard sand and water was developed. A large number of physical and mechanical tests were analyzed by use of samples made from the new similar materials. The result shows that the compressive strength and elastic modulus of similar materials are close to the mechanical feature of original rock and similar materials can cover low and medium-intensive rock types through adjusting the content of different materials.Secondly, based on the making particularity of rock structural plane in different scales, sample modes in series scales with perfect match to upper wall and bottom wall were developed, and the making process of model sample was designed. Through this, the natural rock structural plane can be used repeatedly, which will increase the using efficiency, reduce the sample cost and trial cycle; what’s more, the different scales of structural plane model making on the same natural rock structural plane are achieved. In the second part of the work, the similar evaluation results of surface morphology shows:the model sample made by inverse controlling technology is capable of duplicating the same surface morphology of rock structural plane and highly match between upper wall and bottom wall model samples, which is suitable for the demand of making model samples in different scales.Finally, the direct shear testing apparatus of multi-scale rock joint(MSJ-DST) are developed, which provides the condiction for the direct shear testing that can be made on the same direct shear testing apparatus for multi-scale rock joints.According to the direct shear test, the surface wear degree, roughness ccefficient attenuation law and failure mode of original rock structural plane and simulation structural plane agree well and the difference between the test results and theoretical values is same.