A Study On Rapid Extraction Of Information Of Rock Joint Based On Digital Image Processing Technology

Rock masses naturally have several kinds of discontinuities, including the most common one, rock joint. The joints in rock mass is the crucial factor of rock stability and permeability. Therfore, to obtain geometric properties of joints in rock mass, such as orientation, aperture, and consistence etc, becomes a crucial impotant step in the process of rock mass analysis.The traditional method for extracting geometric properties of joints on exposure of the rock mass is manual measuring with the help of measuring tools. Obviously, it is time-consuming, low effcient and sensitive to the external environment. By contrast, digital close photogrammetry can be more efficient in extraction of joints information.After reffering the current literatures, this paper uses digital close range photogrammetry to acquire joints information from exposure of the rock mass, focusing on rapid extracting joints information on exposure of the rock mass. This study is carried out in Jinshandian Iron Mine, The content of research in this paper is mainly divided into three steps: image acquisition, geometric correction and image analysis statistical.For image acquisition, based on the existing ways about method of digital image acquisition, a digital camera is used to collect digital image for exposure on the rock mass. By consideraing the research objectives in this paper and field conditions, a suitable method, two-dimensional normal projection method is selected as the image acquisition method.In terms of geometric correction for digital image, a new geometric correction method in processing close range digital photograph is proposed. The correction method covers four main points, determing of control points on the exposure of the rock mass, converting the coordinate value on the exposure of rock mass into the plane coordinate value which correspond with digital image space, mathematically solving the transformation matrix, geometrically correcting and resampling the digital photograph. Detailes for the correction method are presented in the process of geometrically correcting the digital photograph taken from the outcrop of a rock mass in Jinshandian. From the illustrative example, it has been found that the geometric correction method is effective in processing close range digital photograph.In respect of image analysis, by consideraing the complexity of the digital image from the exposure of rock mass, a semi-automated extraction and statistical method is proposed. The method includes image digitization, semi-automated detection and recognition for edge of joints edge, extracting edge coordinate values and redrawing binary image relation with joints, computing statistical data for joints parameters. MATLAB software is used in this process, and finally obtaining the statistical data for rock joints from the exposure on the rock mass. Detailes for the semi-automated extraction and statistical method are presented in the process of processing the same digital photograph taken from the outcrop of a rock mass in Jinshandian. It has been found that the method is fast and effective.