Midori ONO

Measurement of the Encroachment Special Quality of the Earth by a Model Experiment

Satoru OHTSUKA

Levee crevasse by the internal erosion and overtopping to slope collapse and river embankment is a serious disaster. The disaster prevention measures is essential. Among them, the cause of the accident to the embankment, is in the internal erosion of the ground 30% to 50%. Safety of civil engineering structures, such as the river embankment, attention has been paid to the slip of surface of slope and overflow. However, at present, disaster prevention measures of internal erosion is an issue of urgent need. Internal erosion, not information from the outside cannot be obtained. Therefore, early detection of internal erosion is difficult. Relationship of the erosion parameters and the ground characteristics of the ground is, the point of unexplained is often at present.
In the present study, in order to grasp the erosion characteristics in piping among the internal erosion, it was carried out model experiment called HET (Hole Erosion Test). The HET, not exact experimental procedure is defined. Not only that, the specimen creating and laboratory equipment, water head at the start of the test, at the end of the study, to be the same thing can be said. In the present study, the development of internal erosion of the measuring device, Establishment of test methods, the measured values were calculated with the erosion coefficient and shear stress.
Review the conventional laboratory methods, the flow rate and pressure difference, it was possible to calculate the critical shear stress and erosion rate. And expressions Wan & Fell, could be calculated by combining equations Lim. In the present study, it was possible to calculate the difference between eroded ease as a difference in magnitude of the value of the erosion factor. In the future, by installing a flow meter and a differential pressure gauge that matches the intensity of the test pies, thereby enabling more sophisticated experiments.

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