Application of the needle penetration test to a calcarenite, Maastricht, the Netherlands

In this paper, first, the needle penetrometer test is briefly presented and experience gained, mainly in Japan and Turkey, with a model manufactured in Japan is reviewed. Second, the needle penetrometer test is used successfully to distinguish qualitatively carbonate sands from very weak and weak calcarenites in borehole cores recovered for cut-and-cover tunnel projects in Maastricht. Third, the relation between UCS and needle penetration resistance (NPR) for the Maastrichtian limestones is further analyzed. Needle penetration tests are conducted with the help of a loading frame. Results suggest that there is a statistically significant relationship between the UCS and NPR, that leaves however to high predictive uncertainty. During testing, very high compressive and shear stresses develop under the needle and stresses normal to the needle shaft increase. Microscopic observations show the extent of grain crushing and compaction ahead and around the needle. Nevertheless, resistance to needle penetration and UCS values are somehow related. The needle penetrometer is recommended as an index test rather than a way to determine accurately the UCS of the Maastrichtian limestones.

► Very high compressive and shear stresses develop under the needle.
► Grain crushing and compaction take place ahead of the needle tip and around the needle shaft.
► However, resistance to needle penetration and UCS values are related.
► The Needle penetration test is recommended as an index strength test.
► It has been used successfully to distinguish carbonate sands from very weak and weak calcarenites.