Influence of Lateral Multistage Unloading Intensity on Mechanical Properties of Reconstituted Coastal Soils Containing Silty Particles

Abstract

The unclear understanding of the mechanical behavior of soil under unloading conditions is a significant reason for the frequent occurrence of accidents and difficulties in the deformation control of foundation pit engineering in coastal areas. This paper discusses the effect of multistage unloading intensity on the mechanical properties of reconstituted coastal soils containing silty particles through a series of laboratory tests, namely, the CU triaxial, bender-element, and permeability tests. Results indicate that, with an increase in unloading intensity, the shear strength and stiffness parameters decrease, while permeability slightly increases. The effect of unloading intensity on the mechanical properties of silt and mucky silty clay is more pronounced. Additional consideration should be given to the effect of a single excavation depth on the mechanical properties of fine-grained soil in foundation pit engineering in order to ensure the stability of the surrounding soil and the safety of adjacent structures.

Dynamic Characteristics of Reconstituted Silt Influenced by Axial Unloading Intensity and Fine Particle Content

“…However, the soil sample with 28.91% water content liquefies easily in the compaction process. The compaction curve was obtained, and the optimum water content and maximum dry density were 26% and 1.523 g/cm 3 , respectively. The dry density of the reconstituted silt under 22% water content was 1.497 g/cm 3 , which is close to the dry density of in-situ silt.…”

“…The compaction curve was obtained, and the optimum water content and maximum dry density were 26% and 1.523 g/cm 3 , respectively. The dry density of the reconstituted silt under 22% water content was 1.497 g/cm 3 , which is close to the dry density of in-situ silt. As a result, the de-aired water was added based on the controlled water content of 22%.…”

“…In each group, different dynamic stress was applied on the sample until the threshold dynamic stress amplitude was found. The static shear properties of the soil under unloading and reloading stress paths can be seen in reference [3].…”

“…The required weight of the silt and kaolin clay was calculated based on the parameters of the soil samples, including a dry density of 1.497 g/cm 3 , diameter of 39.1 mm, height of 79.8 mm, and fine particle content. However, the soil sample with 28.91% water content liquefies easily in the compaction process.…”

“…On the southeast coast of China, many metro lines cross the silt stratum with rich groundwater and complex geological conditions. In particular, the construction activities above the existing metro tunnels are increasing year by year due to the rapid development of the city [3]. Under the coupling effect of the above foundation pit excavation and the train vibration, the deformation and liquefaction of the silt surrounding existing shield tunnels must be studied.…”