The current study investigates the deformation and strength of Light-Weighted Soil (LWS) comprised of silt, Expanded Polystyrene (EPS) beads, cement, and water. The EPS bead sizes employed in this study are 4, 5, and 6mm in diameter with densities of 0.011, 0.009, and 0.006g/cm3 and cement concentrations of 10% and 15%. The effects of different EPS bead sizes and cement proportions on the mechanical properties (strength and deformation) of LWS are evaluated by Unconfined Compression Strength (UCS) tests. The findings show that the EPS bead sizes significantly impact the strength and deformations of the LWS. The smaller the EPS bead size, the higher the observed strength, but, on the other hand, bigger EPS bead sizes have lower strength and higher ductility. It was also revealed that the strength of LSW is entirely dependent on the cement concentration. High cement content in the LWS has more strength and brittleness, but it is more prone to deformation. The cost can be decreased by increasing the EPS bead size, and thus the prescription of mixed soil can be enhanced. The use of EPS beads with a diameter of 4-6mm is recommended in the construction process, especially in backfill for retaining walls. Each EPS bead size provides advantages in different context, depending on engineering applications and field conditions.

Numerical analysis for the safe rate determination of lowering of an embankment dam was performed in this study with the use of the finite element method. Coupled deformation and consolidation analysis were carried out for staged construction and drawdown of a 59m embankment dam for varying undrained shear strength of the clay core. The lowering of the reservoir was performed at different depths between two extreme scenarios, i.e. rapid lowering rate (1m/day) and slow lowering rate (0.1m/day). The reservoir of the dam was lowered to a depth from 10m to 55m in gradual increments. The results indicated that the safety of the dam was satisfactory when the reservoir was lowered at the quick rate for a depth of 10m, 20m, 30m respectively when the undrained shear strength of the clay core was taken as 20, 25 and 30kN/m². Regarding the case of slow drawdown rate of the reservoir, it was found that the reservoir could be lowered up to a depth of 55m at a rate of 0.1m/day when the undrained strength of clay core was 25kN/m². The stability of the dam was also found satisfactory even though the reservoir was lowered at a rate of 0.25m/day for a depth of 55m when the undrained shear strength of clay core was 30kN/m².

Tailings dam disasters are reported almost every year and are triggered by mechanisms, such as overtopping, piping, and others. The failures due to inadequate management cannot be neglected as well. These dams are constructed mostly in a step-by-step construction method that leads to a continuously changing state of vertical loads during construction and may lead to particle breakage and changes in strength. Therefore, a layer of tailings dam today may not be the same tomorrow during the construction phase. To study the effects of different loads on particle breakage and strength, direct shear tests were performed on remolded tailings samples that were separated into different particle sizes. The tests were performed using different normal stresses that ranged from 50 to 500 kPa. The results indicate that finer tailings exhibited slightly more shear resistance than that of coarser tailings irrespective of the deposition method. For normally deposited specimen, the dilatant and contractant behavior in vertical height was observed when the normal effective stress was less than 300 kPa and greater than 300 kPa, respectively. Under the vertical deposition method, the finer tailings showed contractant height behavior when subjected to a normal effective stress of 300 kPa. The friction angle and the cohesion of vertically deposited specimens were slightly higher and slightly lower, respectively, than that of normally deposited ones. The breakage of tailings particles was observed to be proportional to the particle size of the tailings.