RESEARCH OF THE UNDERDRAIN EFFECT

十字板试验可从沉降量和滑移率两个方面进行测定，适用于完整的植物残体堆积较深的水田土壤的承载力测定。在砍伐稻株的时候，耕层就干了。土壤的抗剪力增加，因为土壤结构由植物残留物中的纤维组分重组，当它组成时。试验结果表明，在剪切阻力基本不变的情况下，粉质粘性土在割草阶段摩阻力分量最大。在两条暗渠之一连接成侧沟的方式下，土壤水分张力大部分处于干化趋势，特别是在8月连接的高温天，犁底层的干化程度大于耕层。它是基于水稻植株蒸腾作用的影响，因为在犁底层存在根群面积。

Vane test which can be measured from settlement and slip ratio is suitable for measuring bearing capacity of soil of paddy field where the plant remains of the intactness piles up deeply. In the time which cuts down the rice plant, plow layer dried. The shear resistance force of the soil increases, because the soil structure is reconstituted by fiber component in the plant remains, when it consists so. It was proven that the friction resistance component excelled for the mowing stage in the silty cohesive soil, though the shear resistance force was almost fixed. In the way which connected one of two underdrains in lateral drain, the soil water tension is largely in the drying tendency, and especially, there is largely the drying of the plowsole layer than the plow layer in the connected hot day in August. It is based on the effect of the transpiration from the rice plant, since there is the root group area in the plowsole layer.