# Advanced Scanning Technology for Volume Change Measurement of Residual Soil
## 5 Testing on Residual Soil  
A Gel-Push (GP) method of data collection adopted from [PERSON] et al. [52] was applied to gather the undisturbed soil specimen across distinct sites, such as Tampines (with a 3-4 m depth) and Seletar Hill (3-4 m depth). The GP method is an innovative technique for collecting soil samples that involves using a specialized probe to insert a viscous gel into the soil at a desired depth. This gel encapsulates soil particles, minimizing disturbance and preserving the in situ properties of the sample. Once the probe is withdrawn, the gel, along with the collected soil, is extracted, allowing for easier transportation and analysis while maintaining the integrity of the sample. Figure 1 illustrates the landmarks of the soil specimens mentioned along Singapore's topographic map. Onward, with a test hole physically excavated toward a level ranging from 1.5 m, the earth has been bailed about a level between 1.5 and 3.0 m. The GP tester was again used throughout soil exploration for the collection of undisturbed samples of soil with high-quality. The GP tester also employs a polymer solution with a high concentration to lessen the resistance within the soil specimen and collecting pipe. Throughout the research lab, individual samples taken were once again manually compressed one by one from tester pipes. Following that, earth samples were cut to the necessary length and width for numerous scientific tests. After extrusion, the samples were subjected to index property tests to determine various index soil qualities. The tests were conducted according to the standards outlined in Table 1. The ASTM D6836-16 was used to perform laboratory tests to determine the drying SWCC [53]. The following equipment was used for measurements of SWCC in this  
Figure 7: Volume measurement of a solid soil specimen in Meshmixer. study: a Tempe Cell and 1 bar ceramic disk, a Pressure Plate and 5 bar ceramic disk, and a WP4C Dewpoint Potentiometer. The soil sample was cylindrical in shape with a height of 5 cm and a diameter of 5 cm. Prior to the SWCC test using Tempe cell, the one-bar ceramic disk was saturated in a desiccator with deaired distilled water. The soil specimen was then set into the Tempe cell. The specimen was saturated by applying de-aired distilled water from the top of the Tempe cell. The saturation process was ceased when the water content of the soil specimen reached its saturated value of at least 95%, which is the typical value adopted in practice for saturation of soil samples [53]. After the saturation stage, the weight of the saturated specimen and the Tempe cell was recorded. The air pressure system was connected from the top of the Tempe cell. Air pressure was then applied to the specified value to create respective matric suction in the soil specimen. Air would not flow through the porous ceramic disk when higher air pressure was introduced into the cell, as long as the air pressure did not exceed the air-entry value of the ceramic plate, and the ceramic plate was kept saturated. For this reason, the bottom of the Tempe cell was connected to a container filled with water to maintain the degree of saturation of the ceramic disk. Weighing the specimen at regular intervals was necessary to obtain sufficient data for the plot of the water volume change in the specimen at various matric suctions. The pressure plate consists of a pressure chamber that contains a saturated five-bar ceramic disk. The pressure plate was connected to a burette for measurement of water volume change and maintenance of degree of saturation of the ceramic disk. There must be a good contact between the soil specimen and the ceramic disk to ensure the water flow between the specimen and the ceramic disk is continuous. As with the Tempe cell test, the specimen was weighed at regular intervals. When equilibrium was reached, a higher pore-air pressure was then applied. The WP4C Dewpoint Potentiometer was utilized to measure the water potential of a soil specimen.