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

1.潮滩底部硬度用直径为6 cm的圆板圆锥透视仪测得的最大支承应力来表示。2.最大支承应力为1.64 kg/cm~2，最小支承应力为0.21 kg/cm~2，贝氏应力随季节变化。砂质类型具有以下特征：底质为砂质，结合点靠近干流，靠近潮滩中心，底部高度较高。砂泥质类型具有底质为砂质泥质，米林点在干流外，靠近潮滩边缘，底部高度较低的特点。4.砂质类型中，承压应力大，尤其是在夏季，其变化较大。在砂泥质类型中，承载应力较小，尤其是在夏季，承载应力变化较小。5.开采条件下的承载应力大于水分条件下的承载应力。6.底泥性质垂直变化。7.底栖生物对承载应力的影响在一种情况下较大，而在另一种情况下影响较小。

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.