Abstract: Current methods for groundwater level testing could not accurately reflect the actual variation of the groundwater level under vacuum pre-loading, and thus their limitations were comprehensively analyzed in this paper. A new testing method, namely closed piezometric testing method-laser testing method, was described in detail. Moreover, field tests were conducted to verify the rationality of the developed method. The results show that some restrictions are found in the existing closed piezometric testing method. On the one hand, the employed devices are very complex and challenging to install. On the other hand, experimental results are affected by many factors, which indicates that the results could not truly represent the ground level under vacuum pre-loading condition. However, the proposed new testing method has merits of easy, low-cost and intuitive results, owning to its principle of laser ranging. The field testing results show that during vacuum pre-loading, the groundwater level falls with the subsidence of ground foundation. In addition, the overall decline is slightly greater than the consolidation settlement of the foundation. Therefore, the new method can accurately reflect the actual variation of the groundwater level, and is useful to evaluate and analyse the effect of vacuum pre-loading.

Key words: vacuum preloading method, laser testing method, variation of groundwater level