在三江平原地区进行水利建设,特别是沟渠土方开挖工程,施工难度比较大。三江平原属于沼泽地平原,从土质情况看,一般表层为沼泽土,下为2—17米的粘土层,再下为细中粗砂。粘土层中又分布厚度不等的灰黄或灰绿粉质粘土和粉砂土,以及密实坚硬的高粘土(通称铁盘层)。因此,在排水渠道工程施工中,最棘手的问题就是沼泽土层的开挖,再就是铁盘层的开挖。另外,三江平原的频繁降雨,也使这里有效施工期大大缩短,相对增加了施工的难度。在三 Construction of water conservancy projects in the Sanjiang Plain, especially for excavation of ditches and earthwork, will make construction more difficult. Sanjiang Plain belongs to the swamp plains, from the soil conditions, the general surface of the swamp soil, the next 2-17 meters of clay layer, and then the fine sand. Gray and silvery-brown silty clay and silty sand of varying thickness are also distributed in the clay layer, as well as dense, hard, high clay (commonly known as iron plate). Therefore, the most troublesome problem in the drainage channel construction is the excavation of the swamp soil layer, and then the excavation of the iron plate. In addition, the frequent rains in the Sanjiang Plain also greatly shortened the effective construction period here, which in turn increased the difficulty of construction. In three