软岩强度较低，结构松散，难以加工成标准试件测其单轴抗压强度，为解决这一工程实践难题，引入了日本的一种通过测试软岩针贯入指标间接推算其抗压强度的试验仪器——针贯入仪。首先简要地介绍了针贯入试验的仪器装置、操作过程、注意事项以及数据处理方法，然后运用该仪器在现场和室内分别对不同软岩进行强度测试。统计分析测试结果表明，测试数据离散性大小与岩性均一程度、结构面分布情况密切相关。最后，选取了一组软岩岩样进行针贯入和点荷载对比试验，计算得出两种试验结果相差不大。因此，采用针贯入仪测试软岩强度是合理可行的，可在软岩工程中推广使用。

How to get the uniaxial compressive strength value of soft rocks is always a problem in engineering because of their low strength, loose structure and difficult processing. Needle penetrometer invented by Japanese, can be used to calculate compressive strength of soft rocks indirectly by testing its needle penetration index (NPI). The paper introduces experimental instrument, operating procedures, announcements and data processing methods of needle penetration test(NPT). Then the strengths of different soft rocks are tested by needle penetrometer in situ and laboratory. According to statistical analysis of test results, the discreteness of sampled value is closely related to rock uniformity and structural discontinuous surface. Finally, contrast methods of NPT and point load test on a set of soft rock samples. It turns out that the results based on these two methods are similar. Therefore, NPT is reasonable and feasible in soft rock strength test and it can be popularized and applied to the soft rock engineering in China.