INSPECTION METHOD FOR GROUTING EFFECT IN TREATING LARGE COMPLICATED CAVITIES DUE TO MINING

Complicated cavities with wide distribution, multi-layers, variable thicknesses and depths as well as the complex surrounding lithology, result in difficulties on their grouting effect test. Therefore, there is no reliable testing system at present. Based on cavities grouting practice, the resistivity of the slurry stones is tested and the apparent resistivity range of 93～130 m has a great difference quantity from cavities and surrounding rocks. Cavities are tested by sounding method and electromagnetic wave CT before and after grouting, showing that: after grouting, in shallow range of 0～30m, the apparent resistivity generally is reduced and becomes relatively uniform and stable; low resistivity abnormity in deep range is mitigated with expanded uniform range; electromagnetic wave absorption coefficient increased by about 25% in 40～70m range. Core drilling indicates that, grouting slurry stone is visible in most boreholes, and 10 detecting holes' grouting volume is not more than 15% of the adjacent four holes grouting average. The above test results show that: the cavities have lower electromagnetic wave absorption coefficient, which rises after grouting; cavities above the water table have high resistivity, which come down after grouting, and cavities below the water table have totally reverse attribute. Before and after grouting the cavities have great difference on the properties, showing the grouting quality is very good and there is a good correspondence between the results of several detection methods. The result indicates that, by comparing with drilling results and detection-hole grouting data, geophysical method of overall electrical sounding detection and partial detailed electromagnetic wave CT,can effectively detect complicated cavities grouting effect. The achievement can be drawn on in other similar cavities.