The Study on the movement of groundwater and acid-proof properties of civil engineering structure in the peat soil area.

本研究是在山形县Okitama平原东北部的Yashirogo低沼泽地区进行的。该地区占地约950公顷，泥炭矿床的最大深度约为9米。在沉积物的底部有一个约5.3公顷的生存湖。这个地区主要被用作水田，然而，今天由于农业的合理化，对干米的需求很大。然而，保护排水不良的水田和整理农田往往相互矛盾。为了探索一个可能的解决方案，本研究将检查以下六个点；1) Yashirogo低沼地地面沉降的实际情况，2)灌溉水回用对面积的影响，3)生存湖规模的过渡，4)道路质量的关系，6)泥炭沼地结构物的耐酸性能。以下是对结果的总结。1)基础过渡平均为70厘米。这种转变的主要原因是表面部分的消失。2)与北海道的情况相比，这种转变非常小。原因是这个地区在地理上是封闭的，灌溉水的再利用在里面进行。这种水资源管理有助于减缓生存湖面积的减少。3)道路压力使泥炭土固结。结果表明，水导率降低到通常水平的十分之一到十五分之一。4)指出的泥炭土重金属污染和水体污染情况并不严重。该地区结构的氧化也几乎无关紧要。这些结果强烈暗示了不良水田的改造和周边地区的开发可以同时实现。

This study has been done on the Yashirogo low moor area, which is located in the northeast of the Okitama plain in Yamagata prefecture. This area covers apporoximately 950 hectare, and the biggest depth of its peat deposits is apporoximately 9 meter. There is the apporoximately 5.3 hectare survival lake at the bottom of the deposits. This area has been mainly used as a paddy field, however, today there is a strong demand for a dry rice due to the rationalization of agriculture. Yet conservation of ill-drained paddy field and farm land consolidation often contradict each other.In order to explore a possible solution, this study will examine following six points ; 1) the actual condition of the land subsidence of the Yashirogo low moor area, 2) the influences of reuse of irrigation water upon the area, 3) the transition of the size of the survival lake, 4) the relationship between the road quality, 6) acid-proof properties of structures in the peat moor. The followings are the summary of the results.1) Avarage 70 centimeter of foundation transition is acknowledged. The main reason of this transition is the desappearance of the surface portion. 2) Compared to the case of Hokkaido, the transition is remarkablly small. The reason is because this area is geographically closed and reuse of irrigation water is going on within it. This water management contributes to slowing down the deminishment of the area of the survival lake. 3) The road pressure consolidates the peat soil. The consequence shows that hydraulic conductivity is reduced to from one tenth to one fifteenth of the usual level. 4) The heavy metal related pollution of peat soil and water pollution which have been pointed out turn out to be nothing serious. The oxidization of structures in the area hardly matters, either.These results give a strong implication that conversation of ill-drained paddy field and development of surrounding areas can be achieved simultaneously.