16:35 〜 16:55
[DE-06] Continuous high-speed resistivity tomography experiment for ground improvement monitoring
Chemical grouting is used as a countermeasure against liquefaction in loose sandy ground. Generally, check boring and dynamic cone penetration tests are used to evaluate the performance of the improved ground. Recently, resistivity tomography technique has been conducted before and after the soil improvement because resistivity of the ground changes significantly due to grout.
However, to visualize and manage the ground improvement process, it is not enough to conduct measurements before and after the improvement, real time monitoring is required as much as possible. In this study, continuous high-speed 2-D resistivity tomography was conducted using a small-scale model and its performance was evaluated.
The laboratory test was performed using a PVC tank with a diameter of 600 mm and a height of 400 mm. For the model preparation, two borehole electrodes (16 electrodes with 2cm separation) for resistivity tomography were installed vertically in a PVC tank, and Iide silica sand No.7 was filled. In addition, two pipes for chemical grouting were also installed to create the improved body in the PVC tank at predetermined positions.The Syscal Pro system was used for the measurement and 270 data with dipole-dipole array could be measured in 40 seconds. Continuous high-speed measurement was conducted during the ground improvement, and the total number of measurements was over 300.
Time-series data of inline and crossline potential data were evaluated, typical resistivity change times were extracted. Then, two-dimensional inversions of the typical time were conducted. Compared the inversion results, resistivity change was confirmed due to grout injection, and the process of ground improvement could be visualized by continuous measurement.
However, to visualize and manage the ground improvement process, it is not enough to conduct measurements before and after the improvement, real time monitoring is required as much as possible. In this study, continuous high-speed 2-D resistivity tomography was conducted using a small-scale model and its performance was evaluated.
The laboratory test was performed using a PVC tank with a diameter of 600 mm and a height of 400 mm. For the model preparation, two borehole electrodes (16 electrodes with 2cm separation) for resistivity tomography were installed vertically in a PVC tank, and Iide silica sand No.7 was filled. In addition, two pipes for chemical grouting were also installed to create the improved body in the PVC tank at predetermined positions.The Syscal Pro system was used for the measurement and 270 data with dipole-dipole array could be measured in 40 seconds. Continuous high-speed measurement was conducted during the ground improvement, and the total number of measurements was over 300.
Time-series data of inline and crossline potential data were evaluated, typical resistivity change times were extracted. Then, two-dimensional inversions of the typical time were conducted. Compared the inversion results, resistivity change was confirmed due to grout injection, and the process of ground improvement could be visualized by continuous measurement.
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