A mixture of dredged soil and steelmaking slag solidifies owing to the pozzolanic reaction between the silica and alumina in the dredged soil and the calcium in the steelmaking slag. Previous studies have reported that, for the same steelmaking slag, the concentration of dissolved silica and the shear strength of a mixture of dredged soil and steelmaking slag increases as the content of amorphous silica in the clay increases. However, the relationship between factors that affect solidification strength, such as the ratio of amorphous silica content and the humic acid content, and the solidification strength of a mixture of clayey soil and steelmaking slag has not been clarified. In this study, focusing on the ratio of amorphous silica contents in clay, clays containing different ratios of amorphous silica content were prepared by mixing kaolin clay and metakaolin. The unconfined compressive strengths of the clay mixed with steelmaking slag were measured. For the same curing time and up to an amorphous silica content ratio of 15%, the strength increases with an increase in the ratio. In addition, the shear strength develops earlier for higher content ratios of amorphous silica. Compared with studies on dredged soils mixed with steelmaking slag, the amorphous silica content ratio of the clay in this study was higher than that of dredged soils. However, the shear strength in the dredged soil with amorphous silica from diatoms and minerals mixed with steelmaking slag developed earlier than that of the clay with amorphous silica from minerals mixed with steelmaking slag. The differences in the development of shear strength can be attributed to the difference of the amorphous silica from minerals or that from diatoms.

As a geotechnical backfill material, expanded polystyrene (EPS) composite soil has the advantages of low weight, high strength and easy in-site handling. EPS composite soil exhibits heterogeneity in mechanical behavior mainly due to the non-uniform distribution of EPS beads in the soil. In order to recognize the internal structural characteristics of EPS composite soil, this study applies the fully convolutional network (FCN) to identify each individual EPS bead on the cross-section planes of EPS composite soil samples. FCN is a powerful deep learning architecture that can make pixel-level classification of images. This paper introduces the structure of the FCN model, the data preparation and model training for the EPS bead identification task. The trained FCN model can satisfactorily identify EPS bead locations and in most cases give precise boundaries of EPS beads. However, for two adjacent EPS beads, the model may predict artificial overlap of the two EPS beads. Overall, the FCN model is capable of recognizing and assisting quantitative assessment of the internal structure of EPS composite soil.

In this study, triaxial compression tests were performed on wood chips mixed with steelmaking slag and blast furnace slag fine powder (BFSFP). To understand the manner in which the mechanical properties changed with the difference in the shape of the wood chips and the amount of BFSFP in the mixture, two types of wood chips (fibrous cocopeat and granular hinoki) were used. Consequently, it was found that the difference in the shape of the wood chips had different effects on the mechanical properties of the mixed material when the mixing ratio of BFSFP was low. Moreover, it was found that the shear strength of the slag containing a few percentage of wood chips was higher than that of the slag without wood chips.

Van der Waals interaction is one of the most important interactions between clay particles. Some complicated behavior of clay can be explained from the van der Waals interaction point of view. However, due to the complexity in the mathematical formulation, it is very difficult to analytically integrate the function. This study provides a method to numerically integrate the van der Waals force function. The numerical integration implementation and validation are introduced. The effects of geometric configuration of two clay plates on the van der Waals interaction are quantitatively discussed. The geometry variables include clay plate size, plate separation, plate inclination and the offset of two plates.

In this paper, the true triaxial drainage shear tests were carried out for the Tengger Desert Sand under different intermediate principal stress coefficients by the British GDS dynamic and static true triaxial test system. The influence of intermediate principal stress on the deformation and failure of Tengger Desert Sand and the evolution of deviatoric stress and volumetric strain with intermediate principal stress coefficient were studied. The following results were found. The intermediate principal stress had a great influence on the Tengger Desert Sand deformation. With the increase of the principal stress coefficient, deviatoric stress increases first and then remains approximately unchanged, volumetric strain increases.

Batch leaching tests with different liquid per solid ratios and contact times were conducted on tsunami deposit soil. The chemicals of concern are arsenic (As), boron (B), and sodium (Na). Two parameters were obtained from the tests, which are the partition coefficient (Kd) and the available mass of contaminants per unit mass of soil (MT). Here, the “available mass of contaminants” refers to the mass of contaminants that will take part in adsorption-desorption reaction, but not the total mass of contaminants which are present in the soil system. Using these two parameters, temporal concentration profiles based on the analytical solution of a one-dimensional advection-dispersion equation were plotted for different contact time, and compared with the results of column leaching tests, which were conducted separately using 10-cm long and 5-cm high columns. From the comparisons, multiple sets of two parameters at different contact times are needed to express the column test results for all three chemicals. To predict the column leaching behaviour from batch test with minimum numbers of contact times, two contact times, 6 and/or 24 hours can be selected.