Development of measurement system of aperture and tracer concentration distribution in a single fracture by optical visualization method

It is important to investigate fracture aperture distribution in order to study the influences of heterogeneous aperture distribution onto the fracture hydraulic and mass transport properties. There are any methods to measure fracture aperture distribution, such as an estimating method by measuring both fracture surface shape, a direct measuring method with cutting or grinding of rock sample at the direction perpendicular to the fracture, and nondestructive method such as CT. Each method has its own advantages and/or disadvantages, respectively. An optical method has an advantage that measurement resolution in high and tracer movement can be observed. We have developed aperture measurement and tracer movement measuring system by optical method, and have made transparent replica which model of artificial fracture, and measured aperture distribution and tracer concentration distribution. As a result, aperture distribution measured by this method was similar to the aperture distribution measured from fracture surface shape data, and average aperture measured from volume in a fracture was approximately equal to the value, measured by the optical method, and was able to confirm the effectiveness of aperture measurement. In addition, the optical method could acquire the tracer concentration distribution which was not disturbed by the influence of heterogeneous aperture distribution. (author)