Investigation of the slope behavior of saturated sands in drainage condition and over time–experimental and numerical study

Time-dependent behavior in soils causes mechanical, chemical, and geo-mechanical changes. This behavior in soils considers as a major challenge in geotechnical engineering, and yet need more attentions. The impact of time on geo-materials and their behavior such as rock and soils are undeniable. Based on researches previously performed on this issue, the importance of time-dependent behavior emerged. Creep (strain deformation under constant stress level), stress relaxation (stress deformation under constant strain level), and loading pace are among time-dependent special features, which are seen in experimental models. Creep divided in three categories: primary creep, in which rate of deformation reduced with time. This creep starts immediately after loading procedure. Secondary creep in which rate of deformation is constant. Finally, tertiary creep in which rate of deformation increased and at last material failed. In this research, the effect of time on the stability of the saturated sand has been investigated by building a small-scale experimental model and using finite element numerical method. Preparation of the sand slope was using sand downfall and the saturation process of the experimental models are carried out artificially with a flow rate of 1 liter per minute. Due to the friction angle of the sand, two physical models were created with slope angle of 35 degrees and 37 degrees. The results of physical modeling showed that drainage in sandy slopes, despite stability in non-drainage conditions, gradually increases the deformation in the slope so that over time it will cause failure in the slope. The results of physical modeling showed that in the first model, the maximum horizontal and vertical displacements are 10.5 and 9 cm, respectively. For the second model, these values ​​are 10.5 and 7 cm, in order. At the end of this research, statistical analyzes have been used to provide relationships for predicting vertical settlement in saturated sand slopes. Using numerical models with dimension analysis rules (make the dimensions 100 times in numerical models), in first model in order to reach 8.81 meter displacements, 3780 minutes of raining needed. While in second model, for reaching 7.20 meter displacement, 2280 minutes needed. Results indicate that by increasing cohesion, vertical displacement decrease. As friction angle increase, vertical displacement also decreases. While by increasing slope angle, vertical displacement increase. At the end of this study, statistical analysis has been used to provide relationships to predict the amount of vertical displacement in the slope crown, which is the maximum amount of displacement in the slope.