Parametric Analysis of Slope Stability for River Embankment

This paper has aimed to investigate the slope stability for various conditions like embankment geometry, water level and soil property. The analysis has been performed by using the XSTABL program for di erent slope heights, slope angles and ood conditions with a xed soil cohesion value. Since the rapid drawdown is the worst case for a particular embankment therefore, the analysis has been further performed with di erent cohesion values. From this investigation it has been noticed that the increase of cohesion of soil can increase the stability to a great extent. All the analysises have been performed for twenty bore logs. It has been found that the underlying soil a ects the stability of slope as the failure surface intersects the soil of this region. It has been also observed that the loose, lique able sandy soil decreases the stability while the sti soil with su cient cohesion value stabilizes the slope of embankment.


Introduction
Slope stability becomes a major concern for civil engineers more precisely geotechnical engineers.
In geotechnical engineering dierent sections of river embankment are used to investigate slope stability, settlement and regulation measures [1].
Over the years, engineers put their eort to nd out the best, easy, reliable and simple solution for measuring slope stability based on dierent parameters. Nowadays, rivers are the beauty of the city. Most of the cities of the world are built around the river. Hence, Slope stability of river embankments becomes the issue of research for the engineers. Slope stability design of river embankment are generally controlled by dierent factors. The construction of river embankment is related to cost and safety [5]. For this reason, engineers conducted their studies to make slope stability analysis as simple and reliable as possible.
Many studies have been conducted by a number of researchers around the world considering dierent types of embankment. In the beginning of the 20th century the concept of discretizing a potential mass into slices was introduced.
Petterson (1955) investigated the slope stability of the Stigberg Quay in Gothenberg, Sweden in 1916 considering the slip surface to be circular where the sliding mass was divided into slices [2]. Janbu (1954) and Bishop (1955) made some advancement in this method [2]. Later Bishop 196 c 2020 Journal of Advanced Engineering and Computation (JAEC) VOLUME: 4 | ISSUE: 3 | 2020 | September (1955) proposed an analysis process that took into account inter-slice normal forces neglecting the inter-slice shear forces. Bishop's simplied method satises moment equilibrium while Janbu's Simplied method satises only horizontal force equilibrium [3]. In the design and analysis of river embankment rapid drawdown condition is considered to be a signicant phe- According to Terzaghi and Peck relation between SPT and cohesion of clays is given in equation (2) [9].
For silty clay with sandy soil the relationship of C and Φ with SPT value are given in equations (3) and (4) [10].
Where N is denoted as corrected SPT number and N > 13; Φ is measured in degree and C is in kPa.

XSTABL program
The slope stability analysis by the XSTABL program has to be followed by certain steps. The geometry of the slope (slope prole), soil data for both surface and subsurface have been provided.
To analyze the slope using these characteristic The prole geometry has been entered for the assumed surface and subsurface data. For example, the data for a slope of 6.10 meter height and 26.5 degree has been assigned as shown in

Findings
The slope stability has been analyzed for 20 bore   Figure 15 shows the change of Factor of safety for dierent water level condition (26.5 degree and 6.10 m height). It is observed that slope stability is highest when the river water gets higher during ood. However, the slope stability is lowest during rapid drawdown condition. This is because of the loss of stabilizing eect of water on the upstream and high pore water pressure within the embankment during rapid drawdown.

Slope stability for rapid drawdown condition at dierent cohesion value
It has been observed that stability of embankment slope is lowest at rapid drawdown condition with cohesion value 40 kPa. So, slope stability has been analyzed for previous heights and slopes with increased cohesion values 60 kPa, 80 kPa and 100 kPa. Figure 16 shows the factor of safety under rapid drawdown with variable cohesion value for a particular angle with dierent heights. Similarly Fig. 17

Recommendations
The following recommendation can be made for future study from the present research.
a. In this research, the analysis has been car-