美标标准贯入试验及标贯值修正与应用

Introduction of SPT method in ASTM and correction and application of SPT

欧、美国家规范及工具书中,通常采用修正标贯N60换算黏性土指标,采用(N1)60换算砂土指标及进行液化判别。结合委内瑞拉某港口工程按照美标进行标贯试验的实例,对欧、美国家标准贯入试验方法及标贯值修正方法进行介绍,并对标贯修正中的一些影响因素进行分析。N60主要受锤的能量修正系数CE影响较大,在黏性土埋深超过10 m时,N60一般大于原始标贯值Nm。(N1)60在N60的基础上需进行深度修正,上部砂层时,(N1)60大于原始标贯值Nm;下部砂层时,(N1)60一般小于原始标贯值Nm。通过多种方法对比,对于标贯击数在15～50击,粗颗粒含量较少的超固结黏性土,采用N60值换算其不排水剪切强度Cu较可靠。

According to the standard and manual in the American and European countries, corrected SPT N60 is used to obtain the parameter for soil and （N1）6o is used to obtain the parameters and determine the liquefaction for sand. According to the port project in Venezuela, the SPT method according to ASTM and the corrected SPT method are introduced. The factors influencing the SPT correction are also analyzed. N60 is mainly influenced by energy correction factor CE. and when the soil locates more than 10 m, the N60 is usually more than the original value Nm. （N060 is corrected upon overburden factor CN based on N60, for the top layer sand, （N1）60 is usually more than the original value Nm and the lower layer （N06o is usually less than the original value Nm. Compared by several methods, the undrained shear strength Cu for a certain over-consolidated clay, with SPT values between 15 and 50 blows and with little coarse grains, can be derived by N60＂ which is confirmed to be reliable.