Experimental Modal Analysis of Subgrade Based on Impact Excitation

In order to understand the levels of modal parameters such as modal frequency and modal damping of soil subgrade (treated with 4% slaked lime) during compaction, and find new quality evaluation parameters, reasonably evaluate the conventional vibration compaction technology, and optimize the vibration frequency (or serve intelligent compaction). The self-made modal tester and a portable falling weight deflectometer (PFWD) are used to test the modality and dynamic resilient modulus of soil subgrade under different compaction times. Levy method was used to identify parameters such as natural frequency, and the relationship between natural frequency and resilient modulus was analyzed. The results showed that there are three modes in the frequency range of interest in engineering for low-dose lime-improved soil subgrade, and the compaction technology adopted was obviously unreasonable. There was a significant relevance between the natural frequencies of each mode of the subgrade and the resilient modulus. This phenomenon indicates the reliability of the modal test and the accuracy of modal parameter identification, and indicates that the lower modal frequency can be used as a new parameter to reflect the subgrade compaction quality.