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目前在岩土工程勘察中进行标准贯入试验(SPT)应用更多的是φ50钻杆,这与规范规定的φ42钻杆有所不同。在山西孝义某工程用两种直径的钻杆进行了标贯试验结果对比,统计分析了钻杆直径对标贯击数N值的影响。对比结果表明,钻杆直径对标贯试验击数N值有一定的影响,在不同的试验深度和地层中对标贯击数N值影响结果也有所不同。在0~30 m范围内,φ42钻杆与φ50钻杆测得标贯击数N值的平均值比值在0.85~0.87之间,30~40 m范围内φ42钻杆与φ50钻杆测得标贯击数N值的平均值比值为1.09。在粉质黏土和粉土中φ50钻杆所测得标贯击数N值大于φ42钻杆,在密实砂土中,两种钻杆所测得标贯击数N值较为接近。
At present, the standard penetration test (SPT) in geotechnical investigation is more applied to the φ50 drill pipe, which is different from the φ42 drill pipe specified in the code. Shanxi Xiaoyi a project with two diameters of drill pipe standard test results were compared, the statistical analysis of the diameter of the drill pipe on the standard number of shots N value. The comparison results show that the diameter of the drill pipe has a certain influence on the number of N of the standard test, and the results of the test on the number of standard runs N are also different in different test depths and strata. In the range of 0 ~ 30 m, the average ratio of the values of standard penetration hits between φ42 and φ50 was between 0.85 and 0.87. The measured values of φ42 and φ50 were between 30 and 40 m The average value of coherency N is 1.09. In the silty clay and silt φ50 drill pipe measured the number of standard penetration number N greater than φ42 drill pipe, in dense sand, the two drill pipe measured the number of standard penetration hit N values are closer.