Mechanically Stabilized Earth (MSE) walls are a very common type of retaining structure in the recent world. Many countries use them to stabilize highway slopes and hill slopes or vulnerable soil masses. In this study, numerical analysis on the construction of an MSE wall located in Abilene, Texas, has been carried out. The backfill is reinforced with geogrids. Finite-Element Method (FEM) based software PLAXIS 2D is used for numerical modeling. The objective of the study is to analyze the effects of various geogrid parameters on the overall stability and performance of the wall. Two design parameters namely, the factor of safety and wall deflection were considered for the evaluation. The effects of geogrid spacing, length and strength, and friction angle of the backfill soil have been investigated on the performance of the MSE wall. It was observed that the factor of safety increased with the increase in strength and length of geogrids. A significant decrease in displacement was observed for an increase in geogrid length to wall height ratio from 0.5 to 0.7. Moreover, with the increment of vertical spacing of geogrid, the horizontal wall deflection decreased. Finally, three optimum design combinations are proposed which can be helpful for the engineers by providing them a suitable starting point for the design of an MSE wall.

Publication Link: https://ascelibrary.org/doi/10.1061/9780784484029.038

Open-ended pipe piles are often used for both land and offshore structure foundation because of their relatively low-driving resistance. During driving, soil enters into the open-ended displacement piles, which cause soil plugging. This paper investigates the plugging effect of open-ended piles jacked into sand. A series of tests were conducted in the laboratory on small scale model pipe piles installed in sand with different soil conditions. The effect of pile diameter and degree of saturation on plugging behavior was evaluated. The laboratory test results show that plug length generally increases as pile diameter increases. Furthermore, the plug length decreases with the increase in the value of matric suction. The tests were also conducted with three different types of sands: coarse, medium, and fine sand. The plug length ratio (PLR) was found higher in coarse sand and lower in fine sand. The jacking force for pile driving was evaluated from the model tests, which significantly depends on the plugged length as well as soil properties. The load settlement curve for the piles indicated that the ultimate load-carrying capacity for pipe piles under dry conditions is greater than saturated conditions.

Publication Link: https://ascelibrary.org/doi/10.1061/9780784484029.020

In this study an attempt is made to investigate the geo-environmental characteristics of a landslide disaster in the Chattogram Hill Tracts (CHT) region of Bangladesh. The hilly areas are composed of Tertiary and Quaternary sediments which have been folded, faulted, uplifted and, then deeply dissected by rivers and other water bodies. Extreme precipitation events have become more common due to climate change, which triggers more landslides in these areas. This paper presents a case study on the geotechnical investigation and numerical modeling of selected locations of Rangamati, where a devastating landslide took a toll of 152 lives and almost 223 million property damage in 2017. A field visit and soil sample collection followed by laboratory testing were conducted at the landslide-afflicted areas. The study has revealed that the soil type was an important factor behind landslide, while high precipitation, hill cutting, deforestation, and unplanned human settlements act as contributing factors behind the landslide disaster. Extensive analysis of geotechnical facts has been carried out, and an attempt is made to pinpoint the cause. A finite element modeling was conducted using PLAXIS 2D to investigate the failure mechanism. The numerical modeling results have suggested that most of the hill slopes were susceptible to failure after heavy rainfall. A conclusion is drawn that the landslides were triggered by incessant rainfall infiltrating into the subsoil, which led to a notable increase in its degree of saturation and a simultaneous reduction in suction and shear strength of the soil.

Publication Link: https://www.mdpi.com/2076-3263/11/8/337

Landslides and hill slope failures are very common in hilly areas of Bangladesh for several reasons including slope cutting, incessant rainfall, weathering, steep slope, etc. Hence, stabilizing hill slopes is essential. This paper presents a numerical study of stabilizing hill slopes using Recycled Plastic Pin (RPP) which is an environment-friendly and sustainable way to prevent shallow slope failures. It is produced from plastic waste and requires no maintenance which puts it ahead of other existing options of slope stabilization. For stability analysis, two slopes of height 10m and 15m each of an angle of 50⁰ have been considered to simulate the general slope characteristics of our country. Finite Element Model (FEM) analysis has been performed using PLAXIS 2D to simulate the bare slopes and the RPP installed slopes. In the case of bare slopes, the Factors of Safety (FoS) were below 1.3 which demonstrates their unstable nature. However, the Factor of Safety increased up to 1.7 by installing the RPP in slopes which validates the stabilization using RPP. Moreover, the relation between the vertical spacing of RPP and the Factor of Safety is also investigated. Hence, an optimum vertical spacing within 1-2 m is suggested at the end.

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Full Proceedings: ICACE 2020 Proceedings