美国标准是怎样确定地基承载力的？

小弟现在正在做一个国外建筑的设计，但是地勘报告做了标准贯入度的实验 三轴有（无）排水的试验，给了很多试验数据，但是没有给土的承载力数值，他们的贯入度实验是这样描述的：The Standard Penetration Test (SPT) was carried out according the ASTM D
1586 (1974). The blow count of the SPT was observed for 6 successive drives of sampler spoon to a penetration each of 75mm. or to a maximum of 30 blows whichever happens first. The first two drives are considered as seating drive. The number of blows for the next 4 drives is considered as the Penetration Resistance (N). A value of 30 blows per 75mm. is considered as refusal. In case the N- value reaches 60 without achieving 300mm. penetration, the SPT was stopped to avoid damaging the SPT spoon and to
determine obstruction if any. In that case the number of blows and corresponding penetration in mm were recorded. The SPT N-Values are summarized in Table-2 and the detailed SPT results are shown in Appendix D, while borehole logs are presented in Appendix B.
然后给出的数据就是 孔一31/300 孔二 27/150这样的数据，就是说31锤打进300mm 27锤打进150mm这样的数据，那我究竟是怎样确定地基土的承载力呢？？
谢谢各位啊！！