T. G. MURTHY, D. LOUKIDIS, J. A. H. CARRARO, M. PREZZI and R. SALGADO (2007).Ge´otechnique 57, No. 3, 273–288E. Jua´rez-Badillo, Graduate School of Engineering, NationalUniversity of MexicoAfter reading this interesting paper the discusser wastempted to apply the theoretical equations given by theprinciple of natural proportionality to the experimental datacontained in this paper and to gain additional experience onthe common natural parameters corresponding to the un-drained monotonic response of clean and silty sands. Figs 18to 20 show the theoretical equations: pre-peak inverted func-tion Y

Undrained monotonic response of clean and silty sands

The particle breakage of porous and angular calcareous sand (CS) at the high-stress level is essential on compression feature but less quantified. In this research, a series of compression experiments and laser particle size analyzer tests were conducted under different ending pressures considering relative compaction and fine-grained soil (FS) content to investigate compression behavior and particle breakage of CS. The results indicate that the rebound curves are almost horizontal with a rebound index are between 0.0021 and 0.0054, and the FS content (smaller than 10%) has a little impact on resilience behavior. The irreversible plastic deformation is the main part of compression deformation. Besides, there exist two pressure thresholds of 400 kPa and 100 kPa corresponding to void ratio change trend when FS contents are smaller than 10% and reach 10%, respectively. Moreover, with FS contents increase from 0 to 10%, the moving distance of grading curves to the right becomes shorter gradually which suggests that the quantities of particle crushability decrease. FS can relieve stress concentration among CS that leading to less particle crushability. The combination of these factors including FS content, relative compaction, and axial loading has a complex effect on the relative crushability ratio. Both FS content and relative compaction can restrain particle crushability while axial loading could promote particle crushing. In addition, the relative crushability ratio has a negative linear relation with FS content and relative compaction. But, the relation between particle crushability ratios with axial loading can be described as a logarithmic function well. However, when relative compaction increases to a certain degree of 0.7, the influence of pressure on the relative crushability ratio is weakened. Similarly, the effect of relative compaction on the void ratio is weakened when the FS content is increased. Furthermore, there is a good negative linear correlation between the void ratio and relative crushability ratio.

One-dimensional compression feature and particle crushability behavior of dry calcareous sand considering fine-grained soil content and relative compaction

Cyclic undrained triaxial and torsional shear strength of sands for different sample preparation methods

Effect of non-plastic fines on the anisotropic small strain stiffness of a calcareous sand

In many large‐scale land reclamation projects, vacuum preloading combined with a prefabricated vertical drain (PVD) system has been utilized successfully to improve the slurry with extremely high water content. However, in the use of PVD systems for soft soil with high fine contents, a dense “soil column” forms around the drainage board, which dramatically impedes the drainage and compromises the improvement level. To understand the soil column formation mechanism, coupled computational fluid dynamics‐discrete element method (CFD‐DEM) and scale‐up strategy were employed in this work to study microsized soil particle movements. The results showed that the soil particles driven by the fluid gradually clogged the PVD board filter and then piled up. Under vacuum preloading, seepage occurred in the soil column, causing vacuum pressure loss and reducing the drainage velocity. As the permeability of the micron‐sized soil column is exponentially related to the particle size, the drainage velocity through the soil column with high fine content was low. With the development of the soil column, the drainage velocity decreased, slowing the subsequent soil column development, and changing the packing structure of the soil column. In addition, the vacuum pressure, opening size of the drainage board filter, and cohesion among soil particles influenced the soil column formation. The effects of these aspects are discussed in this work to provide ideas for improving the drainage efficiencies of PVD systems.

Studying the soil column formation in soft soil improved by vacuum preloading via coupled scale‐up CFD‐DEM simulations

This study examines the effect of the initial fabric on the coefficient of the lateral earth pressure at rest K-0, the undrained monotonic loading strength and the liquefaction resistance of a calcareous sand from a reclamation land in Persian Gulf. K(0)consolidation, undrained compression and extension and cyclic undrained loading triaxial tests are performed on laboratory samples reconstituted by air and water pluviation, dry and moist tamping and dry funnel deposition methods. Test results show that the air pluviation and moist tamping samples own the highest and the lowest K(0)respectively. All the samples at medium loose and medium dense states show strain hardening when subjected to undrained monotonic loading. The air pluviation samples are more contractive than the other samples at the phase transformation points and the moist tamping samples exhibit an over-consolidated behavior. In the cyclic loading tests, the air pluviation and the moist tamping samples exhibit the lowest and the highest liquefaction resistance. It is shown that the evaluation and comparison of the cyclic undrained strength of various sands should take the sample preparation method into consideration scrupulously. The test results also indicate that although the mechanical property of soil sample is influenced by the fabric differences induced by sample preparation method, other factors such as homogeneity and stress history should not be neglected.

Investigation on the mechanical properties of a calcareous sand: the role of the initial fabric

The main method for the determination of consolidation parameters in Flanders (Belgium) is still the incremental loading test (IL test). This method can take up to several weeks for some typical Flemish overconsolidated (OC) clays. In theory, the same relationship between settlement and vertical stress can be obtained by performing a constant rate of strain test (CRS test). The main advantages of a CRS test are that the data is continuous and that the test can often be completed considerably faster than an IL test. In this paper, results of both IL and CRS tests on two undisturbed stiff OC clay samples of the same geological formation (Maldegem formation deposited during the Paleogene period) were compared. CRS tests were performed based on ASTM D4186, but constant stress stages were controlled using effective vertical stress instead of total vertical stress as most important adjustment to the standard. In addition, special attention was paid to the development of initial swell pressure and selecting an appropriate rate of strain for this clay with a very high plasticity. Similar values for compressibility and hydraulic conductivity were found using both IL and CRS test results. As the duration of a CRS test on this clay with low hydraulic conductivity can also take up to a few weeks, the time saving aspect of the test was found to be limited for the stiff OC clay tested. The uncertainty in estimating the pre-consolidation pressure and swell pressure was smaller using the continuous CRS test results.

/pdf/one-dimensional-consolidation-of-overconsolidated-clay-using-j9eu4d8wl2.pdf

Joren Andries

Papers

Investigation on the mechanical properties of a calcareous sand: the role of the initial fabric

One-dimensional consolidation of overconsolidated clay using Constant Rate of Strain testing