基于高密度钻孔揭露的广州城区软土分布特征及震陷预测

Distribution Features of Soft Soil and the Prediction of Seismic Subsidencein Guangzhou Urban Area Based on High-Density Boreholes

摘要:

以面积达270 km²的广州城区为研究区，利用高密度分布的近12 000个钻孔，综合各行业规范对软土的定义，判别出广州城区的软土层，并详细分析其空间分布特征，结果为：研究区内近80%的面积其下伏地层有软土分布，软土层在广州城区埋藏较浅，其顶板埋深约6.0 m以浅，并呈现中部浅、南北两侧深的特点；另外，软土层在广州城区沉积厚度差异较大，厚度不足1.5~13.5 m者皆有分布，其中厚度大于3.0 m的地区占了研究区面积的32%，同时软土的厚度分布呈现出研究区南部、西部的厚度大，中部、北部的厚度小，河流岸边的厚度大，远离河流的厚度小的特点，并且呈现出两个沉积中心。结合上述结果，初步预测出研究区内近1/3的面积在强烈地震时可能产生软土震陷，软土震陷区主要集中在研究区的西部和南部。

Abstract:

This research was conducted in urban Guangzhou within an area of 270 km².About 12 000 high-density boreholes were used to investigate the soft soil in the region.The distribution features of the soft soil were analyzed in detail according to different standards.The results are summarized as follows:(1) Soft soil deposits shallower than 6 m are distributed in about 80% of the study area, and the soft soil underlying in the north and the south of the study area are both deeper than that in the middle.(2) The thickness of soft soil is rather different in urban Guangzhou, which extends from less than 1.5 m to 13.5 m.Furthermore, the soft soil in the south and the west of the study area is thicker than that in the middle and the north.The soft soil near the river is thicker than that far away from the river.(3) It is predicted that seismic subsidence of soft soil during earthquake is possible in about a third of the study area, mainly in the west and the south of the study area.