强夯法加固岷江防洪堤粉土地基的效果检验

Effectiveness detection of dynamic compaction on silt foundations of a flood-prevention dyke at Yibin

对宜宾市岷江防洪堤工程粉土地基进行了强夯法加固现场试验,介绍了试验区强夯法的施工设计和现场检测与室内试验结果。强夯法加固地基现场检测结果表明,采用 1 600 kN·m 的夯击能使该粉土地基有效加固深度达到 8 m。 当夯点间距为 5 m,强夯 2 遍,满夯 1 遍后,现场检测和取土实验结果表明:由于强夯作用,粉土层的干密度明显增加,压缩性和渗透性降低。在天然地基中,32.2 %的标准贯入击数小于 5,强夯以后,标准贯入击数全部大于 7。粉土地基经过强夯处理后,满足了防洪堤地基对承载力和渗透性的要求,消除了Ⅶ度地震液化势。采用正三角形夯点布置区的加固效果明显优于正方形夯点布置区的加固效果。

The field detective results and the laboratory testing results are given for the silty soil foundation of the flood-prevention dyke in Yibin strengthened by dynamic compaction method. The field detective data of the strengthened foundation show that the valid strengthened depth is about 8 meters by the 1600kN·m compacted energy. The test site is compacted with 2 times of full compaction at the space of 5 meters and another low energy compaction at the space of 2 meters. The dry densities of the subsoils are increased and the compression and permeability are decreased through dynamic compaction. The standard penetration numbers are all more than 7 while there are 32.2% of the standard penetration numbers less than 5 for the natural subsoils. The subsoils can meet the need of the requirements in bearing capacity and settlements of the flood-prevention dyke after dynamic compaction. The liquefaction tendency at the 7 degrees of earthquake has been disappeared through the dynamic compaction. The equilateral triangle arrangement of the compacting points is better than the square arrangement of the compacting points through the dynamic penetration tests and standard penetration tests.