PURPOSE: To presume the critical flow speed for erosion and the erosive speed using a simple method by preparing in advance a correlation diagram between the tensile destruction stress in soil, the critical flow speed for erosion, and the erosive speed, and putting the tensile destruction stress in the soil at any point in reference to the correlation diagram. ;CONSTITUTION: Using a shaping frame 4, a convex soil piece for measurement 8 is prepared from the soil at each point where measurement is to be made, and the tensile destruction force is measured by the use of a tensile testing device 2, and the obtained value is divided by the plane area so that the tensile destruction stress is determined. The tensile destruction stresses in the soil at different points, the critical flow speed for soil erosion at these points, and the soil erosive speeds with different water flow speeds are measured in advance, and the correlation diagram for them is prepared. Thereupon the critical flow speeds for soil erosion elsewhere than the measuring points are presumed simply and at a low cost without performing any measurement which involves a water feed.;COPYRIGHT: (C)1995,JPO
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