Ground improvement by Dynamic Compaction (DC) is a commonly used method for the densification of in-situ sandy soil to a large depth. After pounding, a crater on the ground is formed, and surface heaved. To evaluate the effectiveness of pounding, the volume change of crater and ground heave before and after pounding needs to be measured. Traditionally, the volume of dynamic compaction induced crater and ground heave is measured by means of level surveying and ruler measurement. However, since ground heave around the crater and the shape of the crater itself are irregular, it is not only difficult but also time-consuming to accurately measure the volume of crater and ground heave. This study proposes a method that adopts the image processing (photogrammetry) technology to accurately measure the crater volume and the ground heave around it. A commercial software, which is initially used for the drone, is used here to generate point cloud of the crater and its surrounding area using the images captured with a video camera or smartphone. The accuracy of this method was calibrated with a known volume box in the laboratory first before it was used in a field trial test. The study will present and discuss the operation procedure and image processing of this method. The crater volume measured from the photogrammetry method is compared with that measured from the traditional measuring method. It is found that the volume of DC crater can be better approximated by cone shape crater than by truncated cone shape crater, which is commonly used in the DC industry and can seriously overestimate the actual volume of DC craters.

Ground improvement by Dynamic Compaction (DC) is a commonly used method for the densification of in-situ sandy soil to a large depth. After pounding, a crater on the ground is formed, and surface heaved. To evaluate the effectiveness of pounding, the volume change of crater and ground heave before and after pounding needs to be measured. Traditionally, the volume of dynamic compaction induced crater and ground heave is measured by means of level surveying and ruler measurement. However, since ground heave around the crater and the shape of the crater itself are irregular, it is not only difficult but also time-consuming to accurately measure the volume of crater and ground heave. This study proposes a method that adopts the image processing (photogrammetry) technology to accurately measure the crater volume and the ground heave around it. A commercial software, which is initially used for the drone, is used here to generate point cloud of the crater and its surrounding area using the images captured with a video camera or smartphone. The accuracy of this method was calibrated with a known volume box in the laboratory first before it was used in a field trial test. The study will present and discuss the operation procedure and image processing of this method. The crater volume measured from the photogrammetry method is compared with that measured from the traditional measuring method. It is found that the volume of DC crater can be better approximated by cone shape crater than by truncated cone shape crater, which is commonly used in the DC industry and can seriously overestimate the actual volume of DC craters.

1. Chow, Y. K., Yong, D. M., Yong, K. Y. and Lee, S. L. (1992). “Dynamic Compaction Analysis”, Journal of Geotechnical Engineering, ASCE, 118(8), pp. 1141.
2. Gouw, T. L. (2018). “Proposed Design Guideline of Dynamic Compaction for Practicing Engineers”, Geotechnical Engineering Journal of SEAGS &AGSSEA, Vol. 49 (2), pp. 32-40.
3. Kumar, S. and Puri, V. K. (2001). “Soil Improvement Using Heavy Tamping – A Case History”, ISET Journal of Earthquake Technology, Vol. 38 (2-4), pp. 123-133.
4. Li, L., Zhang, X., Chen, G. and Lytton, R. (2016). “Measuring Unsaturated Soil Deformations during Triaxial Testing Using a Photogrammetry-Based Method”, Canadian Geotechnical Journal, NRC Research Press, 53, pp. 476.
5. Pix4D SA. (2017). Pix4Dmapper 4.1 User Manual, Switzerland, pp. 11-46.
6. Simpson, L. A., Jang, S. T., Ronan, C. E. and Splitter, L. M. (2008). “Liquefaction Potential Mitigation using Rapid Impact Compaction”, Geotechnical Earthquake Engineering and Soil Dynamics IV, ASCE, pp. 5.
7. Sužiedelytė-Visockienė, J., Bagdžiūnaitė, R., Malys, N., and Maliene, V. (2015). “Close-Range Photogrammetry Enables Documentation of Environment-Induced Deformation of Architectural Heritage”, Environmental Engineering and Management Journal, 6, pp. 1371-1381.
8. Tang, I. E. (2016). “Effect of Dynamic Replacement on the Engineering Properties of Coal Ash Pond”, Master’s Thesis, NTUST, Taipei, Taiwan
9. http://support.pix4d.com/hc/en-us