Abstract
The present research work is concerned with the construction of road embankments on a specific soil called Sabkha in Algeria. This soil is not only soft and very humid during the flooding seasons but also has frequent small areas of very soft soil which we here call Locally Weak Zones (LWZ). LWZ is characterized by low strength and high compressibility. The paper presents the results of two-dimensional axisymmetric numerical analyze that were carried out using PLAXIS 2D 2017, for the modeling of an embankment supported by stone columns on Sabkha soil. The study focuses on the evaluation of the maximum bulging of the stone column and on the settlement of the embankment. It has been demonstrated that Ordinary Stone Columns (OSC) were ineffective due to excessive bulging (221.16 mm) caused by the lack of lateral pressure. On the other hand, the Encased Stone Columns (ESC) showed good behavior, namely a much reduced bulging (42.09 mm) and a reasonable settlement (0.962 m vs. 1.560 m for an OSC) so that it is possible to build safe very high embankments. The numerical analysis also shows that the length of the encasement should just be greater than the depth of the LWZ. Besides, an extensive parametric study was conducted to investigate the effects of the variations of embankment height, stiffness of geosynthetic, the depth of the locally weak zone, area replacement ratio (ARR), and the stone column friction angle, on the performance of the (ESC) - embankment composite in (LWZ). Some important guidelines for selecting the ideal encased stone column (ESC) to support embankments on over locally weak zone were established through this numerical study.
Highlights
Nowadays, structures such as dams, road embankments and storage tanks, frequently have many problems with irregular, excessive settlements or overall stability due to geological situation and weak soil
The numerical analyses were conducted to simulate the construction of embankment on ordinary stone column (OSC) and encased stone column (ESC), the behavior improvement is determined based on the decrease in stone column settlement and decrease in lateral deformation of the stone column with and without locally weak zone (Sabkha soil)
This research studies the behavior of embankments supported by encased stone columns in locally weak zones
Summary
Structures such as dams, road embankments and storage tanks, frequently have many problems with irregular, excessive settlements or overall stability due to geological situation and weak soil. No research till has taken into account the reinforcement of the soil of Sabkha by encased stone columns In this context, this research work is presented as a contribution in the form of a numerical modeling that studies the behavior of road embankments built on sabkha soil reinforced by encased stone columns and using a geotechnical data for (LWZ) from a real site in Algeria. An intense parametric study is carried out to determine the sensitivity of the targeted results (i.e. lateral deformation of the column and vertical settlement) with regard to the variation of the principal parameters, namely, the height of the embankment, the rigidity of the geosynthetic, the length of the envelope, the area replacement ratio (ARR), the thickness of the Sabkha layer, and the angle of friction of the granular material constituting the stone column. In this study, interesting solutions are suggested to solve the problems of Sabkha soil (LWZ), especially during the rainy seasons
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