Probabilistic Seismic Stability Analysis of Reinforced Soil Retaining Structures in Partially Saturated Conditions
Publication: International Journal of Geomechanics
Volume 24, Issue 8
Abstract
The conventional design of reinforced soil retaining structures (RSRS) assumes a dry or fully saturated backfill in a deterministic approach, which may not reflect real-field conditions accurately. While there are ongoing efforts to integrate partially saturated conditions, there is a noticeable lack of emphasis on simplifying the design processes associated with these conditions. This constraint restricts their practical application, particularly in the context of probabilistic scenarios. This study employed the collocation-based stochastic response surface method to present a simple probabilistic method for the seismic stability analysis of reinforced soil retaining structures in partially saturated conditions. To improve accuracy, the horizontal slice is modified to include the effects of cohesion and suction stress in no-flow and infiltration conditions with the least number of assumptions. For practical applicability, the whole process is made efficient by using the nonlinear constrained sequential quadratic programming. To elaborate, a probabilistic parametric study is conducted on a typical reinforced soil structure with silty sand backfill, a recommended material for its construction. The randomness associated with each system, that is, soil, hydraulic parameters, and seismicity, is considered. The results emphasize the need to consider the probabilistic aspect while designing the reinforced soil structures, especially when dealing with partially saturated conditions. The research promotes the adoption of simplified probabilistic methods to encourage field engineers to re-evaluate designs that were originally calculated using deterministic methods.
Practical Applications
When designing the soil retaining structures, engineers usually assume the soil is either completely dry or completely wet. However, this may not match real-world conditions. While there are efforts to account for partially saturated conditions, the methods are often complicated. This makes it hard to use them in real-life situations, especially when considering the chance of earthquakes. This becomes more complicated when it comes to probabilistic design that involves considering uncertainties and variations in soil and environmental conditions. Even though engineers have been trying out new ways of predicting things in engineering, the industry is still a bit unsure about using these methods fully in their designs. This may render the structures prone to failure in case of an uncertain situation. This study uses a straightforward method to analyze the safety of soil retaining structures including the realistic scenarios of earthquake occurrences and uncertainty in soil and environmental conditions. The results encourage the incorporation of pragmatic scenarios for safe designing of soil retaining structures. The practical application of this study lies in the fact that a special emphasis has been laid to make the employed methodologies simple, accurate yet efficient so that field engineers can be encouraged to reassess their designs using the proposed practical probabilistic approach.
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Data Availability Statement
Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request including MATLAB code for determining the normalized required strength of reinforcement for a geosynthetic reinforced slope and MATLAB code to perform probabilistic analysis using the CBSRSM.
Acknowledgments
E. Agarwal acknowledges the financial support provided by the Royal Melbourne Institute of Technology (RMIT) University, Australia and CSIR-Central Building Research Institute (CBRI), India, during the period of this work.
Author contributions: Ekansh Agarwal: Methodology, Writing – Original draft preparation, Investigation, Software, Data curation, Validation; Anindya Pain: Methodology, Conceptualization, Writing – review & editing, Resources, Supervision; V. S. Ramakrishna Annapareddy: Methodology, Conceptualization, Writing – review & editing; Annan Zhou: Methodology, Conceptualization, Writing – review & editing, Resources, Supervision.
Notation
The following symbols are used in this paper:
- bi
- length of the slice base;
- cohesive force acting on slice base (kN/m2);
- fi
- arbitrary function (=1);
- Kn
- normalized total required tensile reinforcement strength;
- kh
- coefficient of horizontal seismic acceleration;
- ks
- saturated hydraulic conductivity;
- N
- number of reinforcements;
- NR
- total number of realizations;
- Nt
- normalized average value of reinforcement strength;
- n
- model fitting parameter (depicts the distribution of pore sizes);
- q
- vertical discharge;
- Tal
- total allowable reinforcement force (kN/m);
- Ti-max
- maximum force in the reinforcement layer (kN/m);
- Tj
- mobilized tension force in the reinforcement under consideration (N/m);
- ua
- pore air pressure;
- Yi+1
- vertical distance measured from the crest to the base of each slice (m);
- Yo
- location of ground water table (m);
- zr,j
- considered reinforcement layer’s distance from the slope crest (m);
- α
- model fitting parameter (kPa−1) (estimates the inverse of the air entry pressure);
- β
- inclination angle of wall with the horizontal (°);
- γ
- soil unit weight (kN/m3);
- γw
- unit weight of water;
- ϕ′
- soil internal friction angle (°);
- correlation coefficient;
- λm
- unknown scalar parameter;
- σs
- suction stress; and
- σt
- total stress.
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Information & Authors
Information
Published In
International Journal of Geomechanics
Volume 24 • Issue 8 • August 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: Jul 21, 2023
Accepted: Feb 13, 2024
Published online: Jun 10, 2024
Published in print: Aug 1, 2024
Discussion open until: Nov 10, 2024
ASCE Technical Topics:
- Design (by type)
- Engineering fundamentals
- Geomechanics
- Geotechnical engineering
- Mathematics
- Probability
- Retaining structures
- Saturated soils
- Soft soils
- Soil analysis
- Soil dynamics
- Soil mechanics
- Soil properties
- Soil stabilization
- Soil structures
- Soils (by type)
- Structural design
- Structural engineering
- Structure reinforcement
- Structures (by type)
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