强夯法在城市防洪工程地基加固中的应用研究

Application of dynamic compaction to foundation improvement of a flood-prevention dam in Yibin

对宜宾城市防洪工程中粉土地基强夯加固效果进行了检测,其结果表明:采用1 600 kN m夯击能,其有效加固深度大于6 m,地基土的干密度得到了明显增加,平均值从天然地基的1.48 g/cm3增加到强夯后的1.57 g/cm3,增幅达到6.1 %;粉土层的孔隙比平均值从0.852减小到0.724;地基土的压缩模量平均值从5.42 MPa提高到8.27 MPa;渗透系数算术平均值降低到天然地基的1/10以下,即从2.5×10-4 cm/s降低到3.5×10-6 cm/s;天然地基标准贯入击数有32.9 %小于5击,强夯以后,击数全部大于7击。粉土地基经过强夯处理,满足了防洪堤地基的承载力和渗透稳定要求,消除了7度地震液化势。

The testing results of dynamic compaction on a silty soil foundation of a flood-prevention dam in Yibin, Sichuan Province are introduced. The test data show that: the valid strengthened depth in the foundation is more than 6 meters at the compacting energy of 1 600 kN穖; the average dry density of the soils is increased from 1.48 g/cm3 to 1.57 g/cm3; the average void ratio is decreased from 0.852 at natural state to 0.724 after compaction; the average compression modulus is changed from 5.42 MPa to 8.27 MPa; the average permeability coefficient is decreased to the value of less than one-tenth of the natural state; the arithmetic average of permeability coefficients is reduced from 2.5×10-4cm/s to 3.5×10-6 cm/s; the N-values of SPT at natural state have 32.9 % less than 5 while all of them are more than 7 after compaction. The conclusion can be stated that the dynamic compaction method is suitable for the treatment of the silty soil foundation in the site of the foundation of flood control dam in Yibin. The ground can meet the requirement as the foundation of flood-prevention dam on capacity and seepage stability, as well as the liquefaction prevention at 7-degree earthquake.