Sato Aiko

Measuring tensile range of undisturbed soil

Fukumoto Yutaka

Cracks in the ground can pose significant issues from both geotechnical and environmental perspectives. For example, the development of cracks can facilitate water infiltration, which may reduce the safety of structures and lead to the leaching of contaminants from waste cover materials. These cracks are often caused by tensile stresses acting on the soil, making it crucial to understand the soil's tensile strength. Previous studies have faced challenges, such as the need for specialized molds and the inability to conduct tests on undisturbed soils. This study aims to measure the tensile strength of undisturbed soil using a newly proposed method that applies va
In addition to testing undisturbed soil, tensile tests were also conducted on reconstituted samples. Compression tests were carried out on both undisturbed and reconstituted soils for comparison. Undisturbed soil samples, with a diameter of approximately 70mm and a height of about 100mm, were reshaped using a wire saw to a diameter of 50mm and a height of 80mm. It was essential to avoid voids during reshaping, as small stones could affect the tensile test. For the reconstituted soil, undisturbed soil was dried, sieved through a 425µm sieve, and compacted in seven layers, with 25 tamping cycles per layer, to create specimens of the same dimensions.
The study found that tensile tests could be performed on various soil types, including silty, clayey, and sandy soils, using the proposed vacuum pressure method. However, careful attention must be paid to the vacuum pressure settings. If the vacuum pressure exceeds the specimen’s tensile strength, failure occurs before the load is applied, while too low a pressure leads to stagnation near the tensile strength. Differences in the behavior of various soil types were observed; for example, clayey soil exhibited larger strain at peak and a slower decrease in strength compared to other soil types. Reconstituted soils showed lower tensile strength and smaller peak strain than undisturbed soils. Future research will focus on optimizing vacuum pressure settings, reconstitution methods, and comparing tensile and compressive strengths under varying conditions.