Improved site investigation Acquisition of geotechnical rock mass parameters based on 3D computer vision

Acquisition and evaluation of geotechnical data are integrated parts of subsurface and surface construction works. Geotechnical data serve as input for decision making processes during all phases of projects, ranging from feasibility studies to construction and maintenance. The present system of data acquisition, specifically applied during underground construction works, has a number of constraints. Sampling bias may be caused by the “human factor” of individual capabilities, inaccessibility of the rock exposure and time limitations. In most cases data are irrecoverable when excavation proceeds or support has to be applied. Data processing and evaluation is time consuming so that input data for numerical calculations cannot be provided on a daily basis. To overcome the listed shortcomings a digital stereoscopic colour imaging system has been developed which enables the evaluation of a large number of geotechnical data by interactive two and three dimensional image analysis. Among others the data can be used for the innovative modelling of the rock mass structure, for the provision of geometrical input data for numerical simulations performed on site as well as for a descriptive visualisation of complex structural conditions. The developed hardware and software components have been tested in different environments and on different rock mass types to investigate their general suitability and effectiveness. It was found that digital stereoscopic imaging and image evaluation are suitable for a cpmprehensive and reproducible documentation of the structural inventory of rock surfaces, and are most effective for acquisition of geotechnical data.