Damping ratio and dynamic shear modulus are fundamental parameters for assessing the seismic response of geotechnical structures such as retaining walls, dams, tunnels, foundations, landfill covers, and embankments. Numerous seismic wave sources can substantially impact the stability and integrity of geotechnical structures, influencing design choices and the implementation of alternative solutions. In this study, the damping ratio of sand mixed with small quantities of laponite was determined by an experimental set-up using bender elements meticulously constructed for this study. Comparative tests were conducted with pure sand (i.e., control test) and sand mixed with bentonite to evaluate the effects of two types of nanoparticles. The results revealed that the damping ratio (xi) of pure sand was approximately 7.48 %, which is generally compatible with values reported in the literature, taking into account the variations of sand and errors associated with laboratory equipment and electronic devices. Over time, the damping ratio of pure sand gradually decreased, reaching equilibrium at 0.99 % after 3-4 days of continuous shaking. The highest observed damping ratios for sand-laponite mixtures were 59 %, 69.7 %, and 98.6 % for sand+1 % laponite, sand+2 % laponite, and sand+3 % laponite, respectively. After reaching the peak, the damping ratio gradually decreased to equilibrium at 11 %, 16%, and 19.4%, respectively. The higher damping values for sand-laponite specimens reflect a viscous damping contribution from the presence of laponite at sand grain contacts, with higher laponite content resulting in increased damping. In comparison, the peak damping ratios for sand-bentonite mixtures were 21.9 %, 42.7 %, and 67.9 % for sand+1 %, +2 %, and +3 % bentonite, respectively. The findings highlight the potential of laponite to enhance the damping capacity of sands, which could be valuable for seismic design applications requiring improved energy dissipation.

Because of the inherent rheological property of transparent gel, laponite has been proposed for soil densification to withstand seismic events. Since the swelling behaviors of laponite could affect the soil-nanoparticle structure, one of the most important research topics is the swelling capacity of nanoparticles, particularly laponite. Hence, the objective of this study is to investigate the swelling properties of fresh laponite and sand treated with different contents of laponite. The swelling characteristics of compacted laponite hydrogel were investigated using a one-dimensional consolidation test setup. Results showed that the swelling strain of compacted laponite increased with time and as the concentration of laponite increased in specimens. The initial swelling of fresh laponite took around 4 weeks to attain equilibrium, while in the reswelling tests, laponite reached equilibrium within 60 h. The reswelling strain of laponite was higher than the initial swelling of fresh laponite, with a distinct reswelling behavior compared to other clay minerals. This swelling strain of laponite was found to be consistent with other clay minerals in which the swelling strain is caused by interlayer and double-layer forces. Scanning Electron Microscope images revealed that the structures of swollen laponite are continuous sheet-like irregular structures with pore size. Moreover, the swelling strain of the sand-laponite mixture with 3

The objectives of this study are to investigate the strength properties and permeability of soil specimens treated with microplastic at different concentrations and samples treated with both microplastic and plant roots. A clayey soil was treated with polyethylene terephthalate (PE-T) at a concentration range between 0.25 and 4

The objective of this paper is to investigate the dynamic stability of an elastic prismatic slender beam subject to axial parametric arbitrary loads by making use of a matrix method. Current research on the dynamic stability of structures are usually limited to harmonic loads, and the solution method is usually based on the Floquet’s theory. It is well known that loads on engineering structures are rarely harmonic, but arbitrary. These loads can be imposed on the structures by either human activities such as explosions and machine vibrations or natural phenomena such as earthquakes and hurricanes. This paper presents a method for the solution of second-order linear differential equations with periodic coefficients. In this approximation method, the elastic beam is considered as a continuous system with various simplifying assumptions under the sum of step functions, which is solved using a matrix method involving a set of chain of power of matrices. The governing dynamic equations of motion thus become a matrix or single differential equation being function of time only. The accuracy of the analysis is ensured by comparing the dynamic behaviour of an elastic beam obtained from this analysis with those obtained by other methods available in the previous studies of literature. Application examples are provided, and limitations of this approach are also discussed. The study provides an excellent theoretical knowledge to enhance the understanding of the dynamic stability of an elastic beam under axial arbitrary loads, which can be used to develop software and modify the relevant design codes.

In this study, mixing laponite with sand to reduce the development of pore water pressure in the fully saturated conditions has been studied to evaluate the strength properties of sand. The study investigated the effect of laponite concentration and resting time in a series of triaxial tests. The results show that even a little amount of laponite can significantly decrease the pore water pressure generation in the sand–laponite specimens due to the good rheological property of transparent gel. The results show that the decrease in the pore water pressure generated in specimens with increasing laponite contents [i.e., 0.5, 1, 1.5, and 2% (mass/mass)] was 17, 22.5, 25, and 27 kPa, respectively. It was also found that the modulus of elasticity of the sand–laponite specimens is almost double than that of the pure sand. In addition, changes in the friction angle and cohesion of the sand–laponite specimens with the four laponite concentrations were examined using direct shear box tests for three different temperatures. It was found that the effect of temperature was more prominent at the lower laponite contents as compared with the higher laponite contents. Microstructural imaging with scanning electron microscope was assessed in conjunction with the pore pressure generation mechanism. This study provides an elaborate explanation of the non-homogeneity of the sand–laponite mixture and novel insight into the improvement and modification of the sand strength properties in the presence of laponite under static loading.

Laponite nanoparticles have been proposed for soil densification to reduce the negative impacts of seismic hazards. However, the effects of laponite on the aquatic ecosystem are lacking. In this study, different concentrations (0.1, 0.2, 0.3, 0.4, and 0.5%) of laponite were used to investigate the growth and total chlorophyll content of microalgae: Chlorella sp. This study examined the potential toxic effects of laponite on the growth characteristics of freshwater green algae Chlorella sp. isolated from northern Ontario. The experiments were carried out in a 500-ml glass flask with 300 ml working volume and placed under white fluorescent lights for 16 h: 8 h day-night cultivation cycle in a constant orbital shaker. The results revealed that the lower concentration of laponite can enhance microalgae growth, while the higher laponite concentration had a growth inhibitory effect. The total chlorophyll content increased by 33% at 0.1% treatment group than that of the control group. Based on the SEM images, aggregation of microalgae was significantly noticeable at the lower concentration of laponite (0.1% treatment) whereas, in the higher laponite concentration (0.4 and 0.5% treatment), algal cells were embedded in laponite gel and also noticed some physical impairment.