Dynamic response of shield cutting reinforced concrete pile foundation

The present study investigates the dynamic response characteristics during the shield cutting pile process. The dynamic response induced by shield cutting pile impact load was solved by combining numerical simulation and theoretical analysis with the background of the shield crossing group pile project of Nanjing Metro Line 10. Concurrently, vibration sensors were installed on the cutterhead to monitor the dynamic response of the shield cutting pile. The results of the study indicate that: (1) When the shield cuts the reinforced concrete pile foundation at a low speed of approximately 5 mm/s, the thrust and torque changes are small, and the thrust and torque show obvious hysteresis because the pile foundation is cylindrical and the cutting section increases slowly. The peak thrust and torque are about 1.3 times and 1.25 times the initial value. (2) As demonstrated by the simulation results, the rebar incision presents a compression-tension fracture under the action of multiple cuts by the cutter. Under the impact loading, multiple dynamic response waveforms appear at the cutterhead bearing position with peaks close to 0.6g. (3) The measured data show that under the impact load, the time domain curve of cutterhead vibration acceleration shows several consecutive peaks with an interval of about 0.1 s and an amplitude of 0.5g. The measured impact response waveform is highly consistent with the theoretical solution and they verify each other. The waveform can be used as a typical characteristic of continuous cutting of steel bars by multiple cutters. (4) During the whole pile cutting process, the acceleration response and peak value are significantly higher, and the maximum intensity is about twice as high as when cutting clay ground. After this, the response will undergo a rapid decline.