强夯加固粉土地基试验研究

在某机场飞行区进行强夯加固浅层粉土地基的现场试验,对地表沉降、地下水位和孔隙水压力等进行了监测,并在试验后进行静力触探试验和标准贯入试验。结果表明:强夯处理后消除了地层6 m深度范围内粉土地基的液化,同时改善了该范围内土层的工程性质。强夯前需采取降水措施,可有效避免出现夯坑内积水和场地局部液化现象,强夯加固产生的超静孔隙水压力消散比较快。强夯施工间隔1 d后不同深度的超静孔隙水压消散比例都超过80%,间隔5 d后超静孔隙水压基本消散,点夯加满夯处理的加固效果整体上好于满夯,并且较小单击夯能和较多夯击次数的点夯施工工艺可以获得较好的加固效果,采用1 500 kN.m夯能点夯两遍和800 kN.m夯能满夯一遍的施工工艺较为合理。

FIELD EVALUATION OF DYNAMIC COMPACTION ON SILT FOUNDATION

An experimental study was made,which focused on the suitability and construction technique of eliminating silt liquefaction using dynamic compaction.During the trial program several items such as surface settlement and groundwater table and excess pore water pressure were monitored,and in-situ test such as standard penetration test(SPT) and cone penetration test(CPT) were carried out before and after compaction.The results showed that after dynamic compaction the liquefaction of silt up to 6 m was eliminated and the properties of the in-place soils were also improved.Dewatering process was needed before compaction to lower the water level of the site.The dissipation of excess pore water pressure after compaction was found quite fast,with 80 percent of excess pore water pressure dissipated after one day within different depth of the site and complete dissipation after 5 days.The results also showed that with less energy of single tamping combined with full tamping would come to better effect of improvement at this site,so the construction technique of 2 passes single tamping with 1 500 kN·m and one pass of full tamping with 800 kN·m was recommended.