Adaptation and Correction of Dynamic Penetration Rod Length

In the geotechnical investigation of hydropower projects in western China, exploratory sampling and engineering property research are challenging on account of the thick overburden on the riverbed. The dynamic penetration test(DPT) has become the preferred method of in-situ tests for the river overburden layers in western China due to its simple operation and applicability for different soil types. The current standard only provides a correction method for the rod length within 20 m. For the problems of adaptation and correction of heavy and extra-heavy dynamic penetration rod length, there is always much controversy but rare research for a long time. To address this issue, a study is conducted, involving the following procedures. Firstly, combined with the field test and numerical simulation, the stress value of each monitoring point is obtained by monitoring the rod of field DPT. Then, LS-DYNA software is used for inverse analysis and relevant parameters are determinined. Lastly, different rod lengths of DPT, such as 25 m, 40 m, 60 m, 80 m and 120 m, are simulated, and the adaptation and correction of rod length are obtained. The research method and results can be used for reference in similar problems and other geotechnical investigation practices in areas with deep river overburden layers.