TY - THES

T1 - Detection and quantification of blast-induced cracks in small scale bench blasting

AU - Navarro Miguel, Juan

N1 - embargoed until null

PY - 2015

Y1 - 2015

N2 - In order to understand how the cracks are generated in the surrounding rock during a bench blast, it is important to classify and quantify them. This thesis is developing a 3D model of the cracks generated in small scale blasting tests. By a visualization of the internal crack network it becomes possible to describe how and where the cracks are created. To obtain the 3D model, the blasted specimen is cut into several slices. Then dye-penetrant is applied to the cut surfaces and the crack trace patterns are photographed. Each slice represents a vertical or horizontal cut through the specimen. These trace patterns are then used to create digital 3D models in AutoCAD. From the AutoCAD models trace, angles and lengths can be measured and trace connections between the different levels drawn. Crack families can be identified based on angles, lengths and origin and characteristics in terms of crack density and intersection densities e.g. can be determined. The proposed crack quantification method and the results obtained with it will be combined with the fragmentation and surface roughness results in other projects where model scale blasting was used to verify how crack development from previous blast influences rock fragmentation in subsequent blasts. Results show that if blocks are blasted with different delay time between rows and holes, the longer the delay time, the higher the number of cracks, the more homogenous the distribution of radial cracks around the borehole and the greater damage in the block. In addition, an influence on the number of cracks has been shown, if different delay times are used only in the first row.

AB - In order to understand how the cracks are generated in the surrounding rock during a bench blast, it is important to classify and quantify them. This thesis is developing a 3D model of the cracks generated in small scale blasting tests. By a visualization of the internal crack network it becomes possible to describe how and where the cracks are created. To obtain the 3D model, the blasted specimen is cut into several slices. Then dye-penetrant is applied to the cut surfaces and the crack trace patterns are photographed. Each slice represents a vertical or horizontal cut through the specimen. These trace patterns are then used to create digital 3D models in AutoCAD. From the AutoCAD models trace, angles and lengths can be measured and trace connections between the different levels drawn. Crack families can be identified based on angles, lengths and origin and characteristics in terms of crack density and intersection densities e.g. can be determined. The proposed crack quantification method and the results obtained with it will be combined with the fragmentation and surface roughness results in other projects where model scale blasting was used to verify how crack development from previous blast influences rock fragmentation in subsequent blasts. Results show that if blocks are blasted with different delay time between rows and holes, the longer the delay time, the higher the number of cracks, the more homogenous the distribution of radial cracks around the borehole and the greater damage in the block. In addition, an influence on the number of cracks has been shown, if different delay times are used only in the first row.

KW - Crack detection

KW - 3D Model

KW - Riss

KW - 3D Modell

M3 - Master's Thesis

ER -