Stability Of Embankment Slopes: Study Of The Contribution Of Reinforcement Geotextiles To Reducing Deformation

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Stability Of Embankment Slopes: Study Of The Contribution Of Reinforcement Geotextiles To Reducing Deformation

https://doi.org/10.21203/rs.3.rs-4883297/v1

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Analysis of the deformations that emerge within embankments is of vital importance in ensuring the durability of structures and anticipating any potential risks. The aim of this study is to assess the deformations and stability of an embankment slope using PLAXIS version 8.2 finite element simulation software. A slope model was built, taking into account the appropriate geotechnical parameters, in order to calculate deformations, displacements and safety coefficients, firstly for an unreinforced case and then for a model enhanced by geotextile layers. For the unreinforced slope, the total extreme displacement is 0.63 m, the shear deformation is 42.04% and the safety coefficient is 1.007. As for the reinforced slope, the total extreme displacement is 0.2 m, the shear deformation is 5.61% and the safety coefficient is 1.619. The results showed a significant reduction in total displacements in the case of the reinforced slope compared with the unreinforced slope. In addition, the safety coefficient increased considerably for the reinforced slope. Volumetric vertical deformations were reduced by more than 25%, while shear deformations were reduced by more than seven times. The results obtained particularly highlighted the significant advantages of geotextile reinforcement in terms of reducing deformations and displacements, and confirmed the improvement in the safety coefficient of the slopes.

Physical sciences/Engineering

Physical sciences/Mathematics and computing

Slope stability is a crucial issue in civil engineering, as slope failures can cause significant damage to downstream infrastructure and property. Slope stability analysis is an essential parameter in the design of road embankments, which the designer must take into account to ensure a stable and safe construction. The slope stability is always considered to be crucial as the slightest slope failure can be destructive in terms of monetary losses and harm to human lives [1]. Slope stability assessment is essential for safe and sustainable development widely applied in mining, civil, and environmental engineering projects around the world [2].

Given the serious consequences that the phenomena of instability can have, it is necessary to carry out extensive

studies on the technical condition of the slopes and the factors that can release slide. The large number of factors involved in such phenomena makes it difficult to accurately determine the stability reserve or to predict the time when the risk of slide occurs [3],[4],[5],[6].

Slope stability analysis involves assessing various factors such as soil composition, slope inclination, hydrological conditions and applied loads. Engineers must use geotechnical models and simulation tools to predict the possible behaviour of slopes under different conditions. This analysis enables the design of appropriate solutions, such as effective drainage systems, geotechnical reinforcements or slope modifications, to prevent failure and ensure durable construction. In Fact, numerous of studies had been exist since the manuscript of the earliest technique of analysis by Fellenius (1936) that were either related to slope stability or involved slope stability assessment issues [7].

In addition, several sources confirm the importance for engineers to have slope stability analysis tools. For example, (Slopes, 2014),[8] highlight that slope stability analyses are a key element in ensuring the safety of people and infrastructure. Similarly, [9],[10] indicate that slope stability analysis tools are essential for assessing the risk of ground movement and designing appropriate protective measures.[11] used anchored slope stability method, and an accurate evaluation method with a simple operation is proposed.

[12] used the analytical method combined with the numerical method to analyse a road embankment, his study reveals linearity between the embankment safety coefficient and the cohesion of the backfill material. In addition, [13] concluded that the incorporation of geotextile layers can improve the stability of road embankments by exerting stresses on the material.

forces that unbalance slope stability. To improve the understanding of embankment stability, studies have been carried out, such as the analysis of embankment stability by the finite element method [14],[15] (Zhang et al., 2021), research on slope stability in geotechnical engineering and a GIS-based study for landslide susceptibility mapping [16]. have been interested in analysing slope stability in a number of ways because it is a subject that represents a serious threat to infrastructures, which can compromise their durability and generate potential risks, as explained by authors [17],[18],[19]. Civil engineering disciplines are of crucial importance today in the context of the new construction challenges we are facing. In order to provide comprehensive solutions for the analysis of slopes in geotechnical engineering, the assessment of deformations can be of particular importance, as it will help to understand geotechnical behaviour and ensure their durability. Deformations in these structures can have harmful consequences for their stability and operation, so it is crucial to be able to assess them. Engineers need to take these deformations into account when designing structures to ensure their safety and durability.

Thanks to technological advances, numerical models have become essential tools for studying the behaviour of reinforced slopes and analysing their deformations[20],[21]. In particular, calculation methods based on finite elements and finite differences have gained in popularity, as they allow complex parameters to be taken into account and provide more accurate results.

This is the background to our study, which aims to analyse the deformations of embankment slopes reinforced with geotextiles. Our aim is to assess the effectiveness of this reinforcement in terms of reducing deformations, displacements and improving the safety coefficient. By understanding the behaviour of these embankments in detail, we will be able to propose appropriate technical solutions to ensure their long-term stability.

The main objective of this study is to analyse in depth the effects of reinforcement on the deformations, displacements and safety coefficients of an embankment slope. More specifically, our aim is to contribute to the understanding of the behaviour of embankment slopes reinforced with geotextiles. To do this, our analysis focuses on results related to deformations observed in reinforced embankment slopes, with less emphasis on the characteristics of the geotextiles themselves. By better understanding the effects of reinforcement on the overall behaviour of the embankment, we aim to provide valuable information for the design and implementation of future reinforced embankment structures, thereby helping to improve their stability and durability.

To conduct the study, the PLAXIS 2D version 8.2 finite element program will be used, as in studies [22], [23], [24] for numerical evaluation. This program will be used to insert a number of geotechnical data, which will be used to create a model using the modelling functions. Analyses will then be carried out to evaluate the various indicators. The results from PLAXIS 2D version 8.2 are the result of finite element calculations.

Presentation of the case

The Fig. 1 presents the geometry of our study

The data relating to the geometry of the slope are as follows:

a foundation layer 3 m thick;

an initial fill 5 m high with a slope of 65° to the horizontal;

a second fill 5 m high with a slope of 55° to the horizontal;

a 10 kPa surcharge uniformly distributed over 12 m at the top of the first slope

The water table is static and located 1 m from the bottom of the first embankment.

The geotechnical characteristics are summarized in the Table 1 below

Table 1

Geotechnical data
Type	Density γ (kN/m³)	Saturated density γsat (kN/m³)	Cohesion C (kPa)	Internal angle of friction φ (°)	Young's modulus E (kPa)	Poisson's ratio ν
Foundation	17	20	12	22	3000	0,33
Backfill soil 1	18	21	8	30	4500	0,33
Backfill soil 2	16	19	5	30	4000	0,33

When using PLAXIS for geotechnical reinforcement with geotextiles, the only essential property required is axial elastic stiffness, known as EA, which is expressed in units of force per linear metre [25]. This value, generally supplied by the manufacturer, can be determined from graphs showing elongation as a function of the force applied in the longitudinal direction. For our study, we will use an axial elastic stiffness value equal to 10×10^5 kN/m.

Unreinforced embankment

The Fig. 2 present the deformed shape of the geometry

The identification of zones of maximum deformation by visualising the zones undergoing the greatest changes on this deformed mesh makes it possible to pinpoint weak points or zones of stress concentration in the embankment. The application of the surcharge on the first embankment generates significant changes in the structure of the slope, which may indicate a sensitive response to the additional load.

The Fig. 3 shows the total displacement of the geometry

The total displacements, represented by the absolute cumulative displacements |u|, are calculated by taking into account the horizontal (x) and vertical (y) displacements at each node. The results obtained show that displacements are observed on both slopes studied, but they are greater on the slope subject to an applied surcharge. This difference in total displacements between the two slopes can be attributed to the impact of the surcharge on the stability and strength of the soil.The Fig. 4 presents the shear deformations of the model .

It can be seen that a failure mechanism develops. This type of deformation is linked to the sliding of layers relative to each other along shear surfaces. The Fig. 5 shows the resuslt of volumetric vertical deformations .

Reinforced embankment

It can be seen that the reinforced areas show relatively little deformation compared with other parts of the slope. However, significant deformation is visible at the upper slope, despite its reinforcement. This can be explained by the effect of the overload exerted on the unreinforced part of the embankment below.The Figs. 6,7,8 illustrate respectively the deformed mesh ,total dsiplacemnts and shear deformations .

The results obtained after reinforcing the embankment with geotextiles testify to the effectiveness of this technique, as demonstrated by the extremely insignificant total shear deformations observed. Close observation reveals that the toes of both slopes of the embankment no longer show any trace of deformation or failure mechanism, clearly highlighting a very significant reduction in shear deformation throughout the reinforced zone. These observations provide strong evidence of the effectiveness of the reinforcement and protection against shear deformation in the reinforced zone of the embankment. The Fig. 9 shows the results of volumetric vertical deformations (reinforced slope).

The results of the analyses are presented in Table 2, including extreme total displacements (in metres), total shear displacements (in metres) and total volumetric displacements (in metres).

Table 2

Results table
Indicators	Unreinforced embankment	Reinforced embankment
Extreme total displacement (m)	637.77.\(\:{10}^{-3}\)	198.85.\(\:{10}^{-3}\)
Total shear displacement (m)	42.04	5.61
Total volumetric displacement (m)	11.69	3

The Fig. 10 shows the comparison of total trips

The data collected enabled a direct comparison to be made between the displacements observed in the unreinforced slope and those in the slope reinforced with geotextiles. The unreinforced slope had an extreme total displacement of 637.77 \(\:{10}^{-3}\)m, while the geotextile-reinforced slope recorded a total displacement of only 198.85. \(\:{10}^{-3}\)m. This significant contrast is highlighted by the calculation of the ratio of total displacements between the two configurations, revealing a ratio of 0.312. This ratio suggests that displacements in the reinforced embankment are around three times less than in the unreinforced embankment. This result is a crucial indicator of the effectiveness of the reinforcement, convincingly demonstrating the ability of geotextiles to significantly reduce displacements in the embankment. This analysis thus reinforces confidence in the use of geotextiles as an effective method of improving slope stability and performance in a variety of geotechnical applications. The Fig. 11 shows the comprison of the shrear strains between reinforce slope and non-reinforce. The Fig. 11 shows the comparison of total shear strains

Calculation of the ratio of shear deformations between the unreinforced slope and the geotextile-reinforced slope revealed a ratio of 0.133. This indicates that the reinforced embankment has shear strains approximately 7.5 times lower than the unreinforced embankment. In addition, the absolute difference between the shear strains showed a significant reduction of 36.43%, indicating a significant improvement in the slope's resistance to shear forces as a result of the geotextile reinforcement. With regard to volumetric deformations, the results showed values of 11.69% for the unreinforced slope and 3% for the reinforced slope, representing a reduction of more than 25%. These results confirm the effectiveness of the reinforcement in reducing shear deformation and volumetric deformation of the slope.

In addition, the areas with the most significant deformations in the slope include the foot of both slopes as well as the stress concentration zones[26]-[30]. These areas undergo significant deformation due to the high stresses present. On the other hand, the upper parts of the two slopes show less pronounced deformations due to the lower stresses applied there. However, when a reinforcement is installed, an improvement in the stability of the foot of the slope is observed. These observations highlight the importance of reinforcement in reducing deformation and improving stability in the most critical areas of the slope.

Displacement and deformation results were carefully examined for both reinforced and unreinforced embankments. These analyses revealed a significant improvement in the displacements and deformations in the reinforced embankments compared with the unreinforced embankments. An in-depth analysis was carried out on the consolidation calculation approach used in PLAXIS version 8.2, highlighting its crucial role in understanding the long-term behaviour of reinforced slopes, taking into account soil consolidation processes. Unlike a simple plastic approach, the consolidation calculation approach has enabled the slow deformation, stress transfer and consolidation phenomena that occur in slopes over time to be captured more accurately. This level of detail is essential for an accurate assessment of the performance and stability of reinforced embankments in various geotechnical contexts.

Competing Interests:

The authors declare no competing interests.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Author Contribution

All authors reviewed the manuscript

Data Availability

Data from this study is available and can be provided upon reasonable request. You can contact [email protected] and [email protected] for further details.

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No competing interests reported.

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Stability Of Embankment Slopes: Study Of The Contribution Of Reinforcement Geotextiles To Reducing Deformation

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Abstract

Figures

Introduction

Materials and methods

Presentation of the case

Results and discussion

Unreinforced embankment

Reinforced embankment

Conclusion

Declarations

Publisher's note

Author Contribution

Data Availability

References

Additional Declarations

Status:

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