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一、前言浙江滨海地区,诸河流中下游地段,广泛分布着厚约60余米的第四系冲洪积砂卵砾石地层,这些地区河床复盖层系由面层的松散砂砾石和下卧的含泥砂砾石或泥砾层组成:(一)松散砂砾石层的埋藏深度一般在地面以下十米左右,主要由卵砾石组成,其上部含泥量一般小于3％,土的不均匀系数很大,分选不好,结构松散,透水性强,渗透系数一般为100～300米/昼夜,最大可达500—1000米/昼夜左右。其下部的含泥量较上部
First, the preface Zhejiang Binhai area, the middle and lower reaches of rivers, widely distributed about 60 meters thick Quaternary alluvial sand pebble stratum, bed cover in these areas by the loose sand and gravel surface and the next Sandy gravel or muddy gravel composition: (a) loose sand gravel layer buried depth generally below the ground about 10 meters, mainly composed of pebbles, the upper mud content is generally less than 3%, the soil has a large non-uniform coefficient , Poor sorting, loose structure, strong water permeability, permeability coefficient is generally 100 ~ 300 m / day and night, up to 500-1000 m / day and night. Lower part of the clay content than the upper part