Infrastructure construction on coastal areas such as ports, bridges and airports require ground improvements when marine soils contain soft ground which includes fine grains in general. Fine-grained soils consist of clastic or non-clastic grains. Based on the mineralogy of soils, compressibility of soils shows different behavior. Fine-grained clay mineral soils show plastic and time-dependent deformation due to consolidation during constructions while silty soils without clay minerals show low compressibility. However, biogenic soils such as diatomaceous earth are more compressible than other silty fine-grained soils. Although fine-grained soils with clastic minerals and biogenic minerals are classified as silt, the behavior of clastic soils are less compressible compared to biogenic soils which have inner pores. We conducted one-dimensional consolidation experiments to investigate compressibility of diatomaceous earth and non-plastic mineral fines such as silica silt. The coefficient of consolidation, and volumetric compressibility are estimated, and show that the trends of diatomaceous earth properties are different from other silty soil properties based on the consolidation tests. We found that particle breakage plays a crucial role in compressibility of diatomaceous soils. While the compressibility of diatomaceous soils is similar to clastic soils at low stress, the differences in compressional behavior between two soils are distinct at high stress. The diatomaceous earth shows time-dependent compressibility due to creep or secondary compression by particle breakage process. Thus, settlement analysis should include the impact of morphology and mineralogy of fine-grained soils.

Soil-rock mixtures are extensively used in geotechnical engineering applications, such as embankment construction, dam engineering, and slope reinforcement, where their compressive deformation characteristics play a crucial role in influencing the stability and settlement behavior of these structures. This study investigates how variations in rock content (W), effective stress (sigma v) and fine-grained soil properties (quartz sand and silty red clay) affect the one-dimensional compression behavior of soil-rock mixtures. Key compression parameters, including the compression index C c and the secondary compression index C a, were obtained and analyzed through one-dimensional consolidation tests to assess the deformation characteristics of these mixtures. Results show that under the same effective stress (sigma v), both the C c and C a exhibit different trends with W, depending on the properties of the fine-grained soil. Soil-rock mixtures with silty red clay demonstrate more pronounced secondary consolidation effects at low rock content, whereas mixtures with quartz sand display weaker secondary consolidation overall. The significantly lower C a /C c values in the quartz sand mixtures suggest that secondary settlement is much smaller in these mixtures compared to those containing silty red clay.

Ground settlement resulting from consolidation may lead to tilted buildings, cracks in the pavement, damage to underground utilities, etc. Therefore, it is crucial to understand the consolidation behaviors (including primary consolidation and secondary compression) of the soil of the subgrade. There is a large amount of soft clay deposited in Nanjing, located in the Yangtze River Basin. The consolidation behavior of Nanjing soft clay can significantly affect foundation design and the cost of construction. In this study, experimental measurements of the consolidation behavior of Nanjing soft clay were conducted, and parameters (such as pre-consolidation pressure, secondary consolidation index and secondary consolidation ratio) related to consolidation were assessed. The concept of simulated over-consolidation ratio (OCRs) was proposed, and the close relationship between primary consolidation and secondary compression settlement and the OCRs of Nanjing clay was investigated.

Computation of end-of-primary compression for clayey soils is an important step undertaken to meet the serviceability criteria of geotechnical engineering structures. But for soils that exhibit secondary compression behaviour, computing the end-of-secondary compression values is more significant. One of the prevailing methods suggested for its computation is the c(alpha) (coefficient of secondary compression) method. However, without sufficient data, interpretation of the end-of-secondary compressions could be challenging, if not erroneous. This paper presents the computation of the end-of-secondary compression for a set of five soils from India namely Red soil, Bombay marine clay, Kuttanad clay, Cochin marine clay and Peat by conducting long-term consolidation tests to the order of 10 days for each pressure increment. A non-linear creep function was used to determine the limiting creep condition of the soils. The curves obtained are more realistic compared to the c(alpha) concept which overestimates secondary compression settlements.