| Natural rock mass is a multi-crack body crisscrossed by geologic structure planes,and its strength characteristics and failure characteristics are controlled by these joint surfaces to some extent.Therefore,a study on shear behaviors of jointed rock masses is significant for evaluating rock mass instability.In this dissertation,taking natural joints as the research object,the factors affecting their morphological characteristics and shear behavior are studied with the help of reverse engineering technology such as 3D scanning technology and 3D printing technology.Based on these studies,the mechanism of joint anisotropy is explained,a new index for evaluating joint roughness considering multi-morphological characteristics is proposed,and a shear strength model considering joint wall strength combination is established.The main research work is as follows:(1)Quantitative analysis of the spacing effect and anisotropy of natural joints indicates that the statistical parameters of joint roughness show better stability in sampling interval ranges between 0.1?0.5mm and their deviation is less than 3%.Considering the burden of processing point cloud data,it is suggested that the sampling interval can be set to 0.5 mm when using a 3D scanner to measure joint surface topography characteristics.(2)With the help reverse engineering technology such as 3D scanning and 3D printing,a new method for preparing model containing natural joint morphology is proposed.This method can reduce the dispersion of the shear test and can permanently preserve the digital model of the original rock joint,which can achieve long-term continuous research on the same natural joint surface.(3)The shear behavior including dilatancy and shear strength of natural joints were affected by the compressive strengths of the upper and lower joint walls,and the new strength model considering different wall compressive strength combination types is proposed.This new model is complement of current JRC-JCS strength model.(4)Based on the point cloud model of natural joints,a method to quantify the shear failure volume is proposed.Furthermore,from the point of view of the failure characteristics of saperities on the joint surface,the mechanism of anisotropy of shear behaviorthe and the reason why normal stress weakens the joint anisotropy are investigated and analyzed.(5)A new index SRC for evaluating joint roughness is proposed based on some characteristic factors affecting the shear behavior.This new index can better measure the JRC value of the joint.Moreover,with the help of the index SRC,the classical JRC-JCS shear strength model can be extended from 2D joint surface to 3D joint surface,which can further improve the estimation accuracy of this model and enable this model to reflect the anisotropic characteristics of shear strength. |
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