# Advanced Scanning Technology for Volume Change Measurement of Residual Soil
## 1 Introduction
The soil volume measurement is determined from the amount of liquid displaced by the specimen's volume following Archimedes' law. This method can provide a reasonable measurement of the irregular shape of the specimen. However, this technology is destructive when the specimen has large pores [25]. The wax particle may fill in the voids between solid particles, and it may weaken the bonding between each grain. In addition, the wax may not be in proper contact with the specimen, leading to an inaccurate volume measurement. The emergence of digital imaging technology contributes to the popular technique of volume change measurement of the specimen using a digital camera. [PERSON] et al. [26] proposed imaging technology to measure the volumetric strain of expansive soil using a digital camera. During the drying process, they photographed the top, sides, and bottom of the specimens. The restriction of this approach is the formation of cracks. It is difficult to obtain an accurate measurement of the depth of a crack using many photo combinations. [PERSON] and [PERSON] [27] and [PERSON] et al. [28] developed 3D scanning technology called \"Clodometer\". This technique required a reference object with known volume as a reference to measure specimen volume for each corresponding time. As a result, cumulative errors at the end of specimen volume measurement are quite large, resulting in an inaccurate volume change. Some researchers utilized the image correlation method, particle image velocity (PIV), to obtain the volume change in specimens based on the time-sequence displacement field [29; 30; 31]. This technique combines a 2D planar image from different directions. Therefore, PIV requires proper calibration of the digital camera prior to the test to avoid distortion due to the effect of the camera lens. The error can be quite significant if the calibration is not performed correctly, even though the image is taken from the same plane. This method is also not applicable for soil with the occurrence of cracks during the drying process. [PERSON] et al. [32] incorporated laser into photogrammetry to improve the accuracy of image scanning using the triangulation method for deformation monitoring. They observed that the error was only 1% during the image processing. The limitation of this technique is the assumption of specimen uniformity. In practice, obtaining a consistent soil surface is difficult, especially if the soil is classified as worn rock. [PERSON] and [PERSON] [33] proposed a novel method for improving the quality of photogrammetric post-processing images. The volume measurement error was roughly 0.4%. However, prior to testing, this procedure necessitates highly accurate calibration of the digital camera. Furthermore, the post-processing image requires transformation from 2D to 3D images, which may result in problems if not conducted correctly. Understanding the soil shrinkage curve is essential for geotechnical engineering implementation, as it directly influences the assessment of soil behavior under varying moisture conditions. Knowledge of this curve enables engineers to predict changes in soil volume, which can lead to issues such as settlement, heave, and instability in structures [34; 35; 36]. Accurate modeling of shrinkage behavior is crucial for designing foundations, slopes, and earth-retaining structures, as it informs the selection of appropriate materials and construction methods [11]. Furthermore, understanding the shrinkage characteristics of soil aids in evaluating the long-term performance and durability of geotechnical systems, ensuring that infrastructure can withstand environmental changes [37]. Incorporating the soil shrinkage curve into geotechnical assessments is therefore vital for enhancing project safety and effectiveness. The limitations of past methods for measurement of soil volume change are associated with the high-accuracy equipment which does not need complex and tedious calibration.