中文摘要：

基于静压群桩模型试验，运用扫描电镜获取了压桩前后土样的微观结构照片，并运用图象处理技术提取了群桩沉桩前后不同位置处土体微观结构参数，通过对比分析认识到：沉桩前桩周土体结构疏松，孔隙形状不规则，群桩压入后桩群中土体孔隙明显减小，孔隙的方向性增强；群桩压入后，等效直径、平面孔隙率、孔隙周长在地表及一定深度内都有所减小；孔隙个数增多，有土体被挤密的现象，而且随着深度的增加这种挤密效果更加明显；压桩后土颗粒的圆度和形态比变大，颗粒在几何形态上向扁长方向发展，且孔隙定向性集中于一到两个方向。

英文摘要：

Based on model tests of the static pressed pile groups, the soil sample＇s microstructure pictures are acquired by the electronic scanning microscopy before and after pile driving. The parameters of the microstructure mechanism of soil are obtained by the image manipulation techniques. Through contrasting and analyzing, it is realized the structure of the soil is loose before pile driving, the figure of the pore is irregular, the size of pore in soil gets smaller after the pile group are driven, the directivity of pores gather. Equivalent diameter, the plane porosity and circumference of pores decrease from the ground surface to a certain depth below. The increasing number of pores results in the compacting phenomenon of the soil, and the compacting effect is more obvious along with the increase of the depth. After the pile being driven, the roundness and shape ratio of soil particles are enlarged, the geometry shape of particles develops to flat and long, and the directivity of the pore focus in one to two directions.