Monitoring vibro-tamper compaction by the analysis of ground-borne vibrations

摘要

This paper describes the use of an instrumented impact hammer test to study the dynamic response of a granular soil (Specification for Highway Works Type 1 fill material) and to monitor the performance of vibro-tamper compaction. A 3-D finite element model was adopted to predict the experimental results and separate the natural frequencies and their corresponding mode shapes. The effect of varying key material properties was also studied. An increase in the soil's modulus of elasticity resulted in higher natural frequencies. An impact hammer, fitted with a force transducer, was used to excite the soil. The response was measured by accelerometer and analysed in both time and frequency domains. The change in natural frequencies of the modes of soil vibration was observed after each pass of the vibro-tamper. A sudden increase in natural frequencies was observed after the first pass; this effect reduced with compaction. Shear wave velocities were used to calculate a low strain modulus of elasticity and a correlation was established with the modulus of elasticity derived from Clegg hammer impact values. The method has potential for exploitation: field trials at a larger scale are recommended.