基于CPTU土类指数的标贯值液化判别

Liquefaction assessment using standard penetration test value based on CPTU soil behavior type index

为提高可液化地基液化判别的准确性,依托宿新高速公路共振法加固可液化地基项目,对共振法处理后的液化地基进行CPTU试验和SPT试验.对CPTU试验得到的土类指数I_c和SPT试验得到的标贯值N_(63.5)进行处理分析.结果表明,饱和砂土和粉土的标贯值N_(63.5)是土类指数I_c的一次函数(N_(63.5)=-18.8I_c+52.0),即土类指数越大,土性越接近黏性,标贯值越小.基于N_(63.5)与I_c的拟合关系式提出一种新型液化判别方法,即根据标贯值参照《建筑抗震设计规范》进行饱和砂土和粉土地基的液化判别,其中标贯值根据I_c计算获得,I_c则通过CPTU试验获取.与规范中SPT判别法相比,该方法可以提供连续的标贯值参数,与基于CPT的周期阻力比法相比,该方法计算简单.

In order to increase the accuracy of liquefaction assessment on liquefiable foundation,the liquefiable foundation of the Suqian-Xinyi highway was treated by the resonant compaction method,and piezocone penetration test（ CPTU） and standard penetration test（ SPT） were carried out on the liquefiable foundation. The soil behavior type index（ Ic） obtained from CPTU and the standard penetration test index（ N（63.5）） obtained from SPT are analyzed. The results show that N（63.5） of saturated sands and silts is a linear function of Ic（ N（63.5） =-18. 8Ic ＋ 52. 0）. The larger the Ic,the smaller the N（63.5） will be,and the soil is more close to clay. Based on the fitting relationship between N（63.5） and Ic,a new liquefaction discrimination method is established. The liquefaction of saturated sands and silts foundation can be assessed by using N（63.5） based on the Code of Seismic Design of Building.N（63.5） is expressed by single Ic and Ic is acquired from CPTU. Compared with the SPT assessment method proposed in the code,this method can provide continuous standard penetration test value.Compared with the cyclic resistance ratio method based on cone penetration test,the calculation of the method is very simple.