| Because earth core materials of rockfill dams are very sensitive to their water content, an earth core zone cannot be constructed in rainy and cold days. Therefore, construction of core zone is the critical path of the construction process of rockfill dams. As a result, to reduce construction cost and to shorten construction period of rockfill dams, it is necessary to speed up the construction of earth core zone. Then, we should investigate the probability of compaction thickness of earth core zone to be thicker and earth core width to be narrower. However, at present, earth core width is decided empirically, appropriate core width should be designed based on evaluation of the safety against hydraulic fracturing as well as sliding. Hydraulic fracturing of core materials for rockfill dams has not been studied comprehensively.In this study, banking and seepage analyses were carried out with various combinations of the core and the filter widths in order to evaluate safety of earth core zone, which has the function of imperviousness of dam body, based on hydraulic fracturing. For the safety evaluation of earth core zone, we used the results of hydraulic fracturing tests for earth core materials. As a result, a smaller safety evaluation based on hydraulic fracturing enough to cause a steep the gradient the core and the filter, if the same cross section of the core, to increase the safety evaluation based on hydraulic fracturing is more loosely to form a gradient on the upstream side of the core. Based on the laboratory tests of hydraulic fracturing of core materials for rockfill dams and the safety evaluation against hydraulic fracturing of earth core using banking and seepage analyses, we finally proposed rational design method of earth core width. |
