广东汕头韩江三角洲第四系沉积规律及其工程地质特征评价

THE EVALUATION OF SEDIMENTARY REGULARITY OFQUATERNARY SYSTEM OF HANJIANG DELTA AND ITS ENGINEERING PROPERTY IN SHANTOU,GUANGDONG

韩江三角洲第四系是以河流搬运为主而形成的三角洲相沉积物。部分地带缺失底积层沉积物；前积层中具有３个大旋回沉积韵律，每个旋回从下往上颗粒由细变粗，具典型的“海退序列”。三角洲的形成晚期为海边洼地或沼泽地，形成一套厚为２０～２５ｍ的以淤泥为主的软粘土层。因此，区内表层或浅部不存在良好的建筑物基础持力层。较好的建筑物基础持力层均分布于前积层３个旋回顶部的砂层，埋深顶面分别为－２０～－２５ｍ、－３０～－３５ｍ、－４０～－４５ｍ；在近海边一带，花岗岩埋深较浅，为－４５～－５５ｍ，是建筑物基础的良好持力层。

The Quaternary system in Hanjiang delta is formed by delta sedimentation which is mainly controlled by river trasportation.The bottomset beds in the delta are underdeveloped,but the foreset beds possess a sedimentary rhythm with three major cycles.Each cycle has typical“retrogression sequence”and its grainsize increases upwards.The delta has been finally evolved into coastal pots or morass,forming a set of 20m to 25m thick and soft clay beds composed of muck.Accordingly,there are not effective bearing strata for construction foundation on the ground or shallow underground in this area.The effective bearing strata occur in sand layers on the top of the foreset beds with three cycles.The contours of top surfaces of sand layers are-20～-25m,-30～-35m and -40～-45m respectively.The contour of burried granite,which is an effective bearing stratum for construction foundation,is-45～-55m.