Field study on mechanism of hardness variation of bottom sediment of mud flat in lagoon

1.滩底硬度用直径为6cm圆板的锥形穿透仪测得的最大承载应力表示。最大承载应力为1.64kg/cm^2，最小承载应力为0.21kg/cm^2。承受压力随季节变化。将轴承应力变化的表现分为两类。砂质类型具有以下特点：底泥为砂质，切点靠近主流，靠近潮滩中心，底面高度较高。3 .砂质和泥质类型具有以下特征：底泥为砂质和泥质，基准点在主流外，靠近潮滩边缘，底面高度较低。在砂质类型中，承载应力较大，尤其是夏季，且变化较大。在砂质和泥质类型中，承载应力较小，特别是在夏季，其变化较小。暴露条件下的轴承应力大于水中条件。底部沉积物的性质呈垂直变化。在一种情况下，底栖动物对承载应力的影响很大，在另一种情况下，影响很小。

1.Hardness of bottom of tidal flat was expressed by muximum bearing stress measured by cone penetrometor which had 6cm diameter circular plate.2.Maximum bearing stress was 1.64kg/cm^2, and minimum bearing stress was 0.21kg/cm^2. and baering stress varied seasonally.3.Appearance of variation of bearing stress was classfied two categories. Sandy type had following character : bottom sediment was sandy, and mearing point was near mainflow, and it was near center of tidal flat, and height of bottom was high. Sandy and muddy type had following character that bottom sediment was sandy and muddy, and mearing point was out of mainflow, and it was near edge of tidal flat, and height of bottom was low.4.In sandy type, bearing stress was large, espetially in summer season and its variation was large. In sandy and muddy type, bearing stress was small, espetially in summer season and its variation was small.5.Bearing stress was larger in explosure conditions than in under water conditions.6.Properties of bottom sediments varied vertically.7.In one case, effect of benthos on bearing stress was large and in another case, it was small.