Abstract
Bearing capacity, on the surface and subsurface horizon, is a factor deciding the trafficability of bulldozers, tractors, combines and other such heavy equipment. By statistical analysis, the author investigated the relationship between the bearing capacity and the soft grounds of alluvial areas in the Kanto plain, the Tsugaru plain, and the Sarobetsu plain. In this paper, the bearing capacity is calculated from the average of the results that are measured at each point, 0 to 50cm. deep, by cone penetro-meter. Asa result of his investigations, the author comes to the following conclusions: 1) The bearing capacity is different for alluvial fan areas, natural levee areas, and delta areas in the Kanto and the Tsugaru alluvial plains. 2) Except alluvial fan areas, the standard deviation is from 13 to 15 in both the Kanto and the Tsugaru alluvial plains with a normal frequency distribution at each area. 3) Except of surface soils, the bearing capacity shows the same change for every area made up of silt, clay and peat. 4) The plowpan (Sukidoko) horizon, lying under the Ap horizon, causes the difference in bearing capacity between natural levee areas and delta areas. 5) Where land is made up of silt and clay, the standard deviation is the same, so the relationship between the number of survey points for bearing capacity survey and the allowable errors to the sample mean can be accurately delimited (the Y-N Curve, Fig. 4) .
