Rashad Alsirawan

57951728200

Publications - 11

Compressibility of expansive soil mixed with sand and its correlation to index properties

Rashad Alsirawan Ammar N. Alnmr Mounzer Omran Alzawi R. P. Ray

Publication Name: Heliyon

Publication Date: 2024-08-15

Volume: 10

Issue: 15

Page Range: Unknown

Description:

Prior research has primarily focused on Atterberg limits, void ratios, and/or water content, often disregarding the impact of coarse material percentage in the soil, which significantly affects compressibility behavior. This paper examines the effects of sand content, initial degree of saturation, and initial dry unit weight on the compressibility behavior of expansive soils. Ninty-six oedometer tests were performed in order to accurately predict the compressibility behavior of expansive soils. The previous studies have attempted to correlate compressibility with different index properties separately, but no single study has taken into consideration all properties influencing compressibility behavior, especially for expansive soils. The findings show that compressibility is greatly influenced by the sand content, initial degree of saturation, and initial dry unit weight. Increasing the initial dry unit weight specifically lowers the compression index and permeability while raising the recompression index for the same percentage of added sand. Moreover, since swelling reduces with increasing initial saturation, raising the saturation degree also lowers the permeability, recompression index, and compression index. The results indicate that a sand content of more than 30 % is recommended for achieving desired properties in expansive clayey soil. This is a result of sand taking the dominant role in the soil mixture, which lowers soil suction and improves soil properties by reducing swelling, permeability, and compressibility. Symbolic regression equations were created to predict the compression and recompression indices, outperforming previous models in accurately predicting the compressibility behavior of expansive soils, considering the percentage of sand. The validation of these equations demonstrates their predictive capabilities.

Open Access: Yes

DOI: 10.1016/j.heliyon.2024.e35711

Numerical Study of the Effect of the Shape and Area of Shallow Foundations on the Bearing Capacity of Sandy Soils

Rashad Alsirawan Ammar N. Alnmr

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2024-01-01

Volume: 21

Issue: 1

Page Range: 103-120

Description:

The settlement and bearing capacity of shallow foundation models with different shapes and areas on cohesionless subsoil under the applied vertical load are presented in this study. Different shapes of foundations with rectangular, square, strip, plus horizontal cross-sectional shapes are numerically studied after the validation on the laboratory model has been conducted and the constitutive soil model that simulates the behaviour of sandy soil has been chosen. The result of the validation showed that the HS model is the most suitable for the simulation of stress-deformation behaviour of sand. The effect of the shape and area are clearly visible and greatly affects the bearing capacity of the soil. The study generally compared Vesic's, Hansen's and German’s bearing capacity equations and showed that Vesic's and Hansen's bearing capacity equations are best suited to the bearing capacity computed from numerical analysis by Plaxis3D. Finally, as a development of Hansen's bearing capacity equation, a new equation of plus shape foundation bearing capacity has been determined.

Open Access: Yes

DOI: 10.12700/APH.21.1.2024.1.7

Dynamic Analysis of Geosynthetic-reinforced Pile-supported Embankment for a High-Speed Rail

Edina Koch Rashad Alsirawan

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2024-01-01

Volume: 21

Issue: 1

Page Range: 31-50

Description:

Geosynthetic-Reinforced-Pile-Supported (GRPS) embankments are a trustworthy option ideal to support the railways over soft soils. They are widely used for the time-bound infrastructure projects. The majority of earlier research concentrated on the analysis of the GRPS embankments under static loads while the studies on the behavior of these constructions under dynamic loads are scarce. The fundamental purpose of this study has been to better comprehend the dynamic behavior of GRPS embankments in terms of stresses and settlements distribution via 3D modeling employing the finite element method (FEM). The advanced constitutive model of Hardening soil with small-strain stiffness was utilized to simulate the behavior of the soils under dynamic loads and the train load was modeled according to the recommendations of LM71 Eurocode. The results indicate to the contribution of the piles and geosynthetic reinforcement in the decrease of the settlements. The behavior of settlements and stresses under static and dynamic loads is similar. The load efficiency of the piles decreases during the passage of the train remarkably. The train speed affects obviously on the behavior of the GRPS embankment.

Open Access: Yes

DOI: 10.12700/APH.21.1.2024.1.3

Experimental and Numerical Investigation of Geosynthetic-Reinforced Pile-Supported Embankments for Loose Sandy Soils

Edina Koch Rashad Alsirawan Ammar N. Alnmr

Publication Name: Buildings

Publication Date: 2023-09-01

Volume: 13

Issue: 9

Page Range: Unknown

Description:

This research focuses on advancing the geosynthetic-reinforced pile-supported embankment technology over loose sandy soil. A small-scale laboratory model supported by floating piles and a geotextile layer was constructed, and a numerical model was validated against laboratory measurements. This study aims to achieve a more uniform distribution of the load over all piles of the system via a parametric study that analyzes the influence of embankment fill material, horizontal reinforcement scenarios, pile cap shape, and pile type. The results demonstrate that using embankment fill with high cohesion and internal friction properties leads to a significant reduction of 46% and 37% in maximum settlements, respectively, and similarly, results in a noteworthy reduction of 48% and 50% in differential settlements. The incorporation of two geotextile layers contributes to a reduction of up to 30% in maximum settlement. The utilization of plus-shaped caps in small areas, with an area equal to three times the cross-sectional area of the pile, has been substantiated as the preeminent approach for the reduction of settlements. Piles with caps also present better behavior regarding differential settlements compared to longer piles and piles with bigger diameters under the same volume condition.

Open Access: Yes

DOI: 10.3390/buildings13092179

Two-Dimensional Numerical Analysis for TBM Tunneling-Induced Structure Settlement: A Proposed Modeling Method and Parametric Study

Rashad Alsirawan Ammar N. Alnmr Ashraf Sheble

Publication Name: Infrastructures

Publication Date: 2023-05-01

Volume: 8

Issue: 5

Page Range: Unknown

Description:

The construction of tunnels in densely populated urban areas poses a significant challenge in terms of anticipating the settlement that may result from tunnel excavation. This paper presents a new and more realistic modeling method for tunnel excavation using a Tunnel Boring Machine (TBM). This method is compared with other reference modeling methods using a validated model of a subsurface tunnel excavated by a TBM with a slurry shield. A parametric study is conducted to investigate the impact of key parameters, including structure width, foundation depth, eccentricity, load on the structure, overburden depth, and tunnel diameter, on tunnel–soil–structure interaction and the resulting structure settlements. The results reveal that the tunnel diameter, eccentricity, and overburden depth have a significant impact on structure settlements, with values of 22.5%, 17%, and 7.1%, respectively. Finally, the paper proposes an equation for predicting the maximum settlement of a structure, considering the critical parameters. The validity of the equation is evaluated by comparing its results with the outputs from various case studies, including a newly validated model, two real-life case studies, and centrifuge tests. The results indicate a high level of consistency between the calculated and measured settlements.

Open Access: Yes

DOI: 10.3390/infrastructures8050088

Proposed Method for the Design of Geosynthetic-Reinforced Pile-Supported (GRPS) Embankments

Edina Koch Rashad Alsirawan Ammar N. Alnmr

Publication Name: Sustainability Switzerland

Publication Date: 2023-04-01

Volume: 15

Issue: 7

Page Range: Unknown

Description:

Soft soils with unfavorable properties can be improved using various ground-improvement methods. Among these methods, geosynthetic-reinforced pile-supported (GRPS) embankments are considered a reliable option for challenging ground conditions and time-bound projects. Nevertheless, the intricate load transfer mechanism of the GRPS embankment presents challenges due to the multiple interactions among its components. To overcome the limitations of current design methods that do not fully account for all interactions, a simplified design method has been developed for GRPS embankments. This method uses numerical analysis to predict pile load efficiency and geosynthetic tension. In this study, a validated model of the GRPS embankment, which incorporates certain simplifications for design purposes, was adopted. Based on this simplified model, a database of load efficiency and geosynthetic tension was collected to derive the design equations. The design method employed six parameters, namely, pile cap width, pile spacing, embankment height, oedometric modulus of the subsoil, geosynthetic stiffness, and embankment fill unit weight. The design process utilized Plaxis 3D and Curve Expert software. The results showed reasonable agreement between the findings of the proposed design method and the field measurements of eight case studies.

Open Access: Yes

DOI: 10.3390/su15076196

Dynamic behavior of gravity segmental retaining walls

Rashad Alsirawan Ammar N. Alnmr

Publication Name: Pollack Periodica

Publication Date: 2023-03-07

Volume: 18

Issue: 1

Page Range: 94-99

Description:

This work aims to highlight gravity segmental retaining walls with their varied advantages. The paper investigates the dynamic behavior analysis of segmental retaining walls. The stability analysis is conducted on the basis of a pseudo-static Mononobe-Okabe theory that provides safety factors against sliding and overturning failure. The results demonstrate that the crucial safety factor of internal stability is the safety factor against overturning. Moreover, the positive wall inclination angle contributes to an improvement in the stability of the segmental retaining walls and the effect of the vertical seismic coefficient on the stability can be disregarding. Finally, a new equation is proposed for the elementary design of the segmental retaining walls.

Open Access: Yes

DOI: 10.1556/606.2022.00722

A State-of-the-Art Review and Numerical Study of Reinforced Expansive Soil with Granular Anchor Piles and Helical Piles

Rashad Alsirawan Ammar N. Alnmr R. P. Ray

Publication Name: Sustainability Switzerland

Publication Date: 2023-02-01

Volume: 15

Issue: 3

Page Range: Unknown

Description:

Expansive soils exist in many countries worldwide, and their characteristics make them exceedingly difficult to engineer. Due to its significant swelling and shrinkage characteristics, expansive soil defies many of the stabilization solutions available to engineers. Differential heave or settlement occurs when expansive soil swells or shrinks, causing severe damage to foundations, buildings, roadways, and retaining structures. In such soils, it is necessary to construct a foundation that avoids the adverse effects of settlement. As a result, building the structure’s foundations on expansive soil necessitates special consideration. Helical piles provide resistance to uplift in light structures. However, they may not fully stabilize foundations in expansive soils. A granular anchor pile is another anchor technique that may provide the necessary resistance to uplift in expansive soils using simpler methods. This review and numerical study investigate the fundamental foundation treatments for expansive soils and the behavior of granular anchors and helical piles. Results indicate that granular anchor piles performed better than helical piles for uplift and settlement performance. For heave performance, the granular anchor and helical piles perform nearly identically. Both achieve heave reductions greater than 90% when L/H > 1.5 and D = 0.6 m.

Open Access: Yes

DOI: 10.3390/su15032802

The finite element modeling of rigid inclusion-supported embankment

Edina Koch Rashad Alsirawan

Publication Name: Pollack Periodica

Publication Date: 2022-01-01

Volume: 17

Issue: 2

Page Range: 86-91

Description:

The design of supported embankments on soft soil is a common challenge for civil engineers. This article aims to evaluate the performance of three advanced constitutive models for predicting the behavior of soft soils, i.e., hardening soil, hardening soil model with small-strain stiffness, and soft soil creep. A case study of a rigid inclusion-supported embankment is used for this purpose. Plaxis 3D program was adopted to predict the settlements in subsoil layers and vertical stresses in the load transfer platform. Comparison between field measurements and result of Plaxis 3D modeling was performed. Results demonstrate that soft soil creep model yields predictions in a good agreement with the field measurements, while hardening soil small strain model gives slightly worst predictions.

Open Access: Yes

DOI: 10.1556/606.2021.00504

Analysis of Embankment Supported by Rigid Inclusions Using Plaxis 3D

Rashad Alsirawan

Publication Name: Acta Technica Jaurinensis

Publication Date: 2021-11-24

Volume: 14

Issue: 4

Page Range: 455-476

Description:

A rigid inclusion-supported embankment is used to overcome the problems of soft soils. This system is considered complex due to the various interactions between its elements, namely the embankment body, load transfer platform, geogrid layers, piles, and soft soils. The load transfer mechanism is based on the phenomenon of soil arching, the tension in the geogrid layers, support of the soft soils, and friction between piles and soft soil. In this paper, the first part highlights the behaviour of a rigid inclusion-supported embankment validated by field measurements, and the contribution of rigid inclusions technology to the reduction of settlement and creep settlement. In addition, the effect of geogrid in improving the load efficiency and reducing the settlements is presented. In the second part, a comparison is made between many analytical design methods and a three-dimensional finite element analysis method. The results show the inconsistencies between the analytical methods in calculating the load efficiency and the tension in the geogrid.

Open Access: Yes

DOI: 10.14513/actatechjaur.00615

Review of geosynthetic-reinforced pile-supported (GRPS) embankments-parametric study and design methods

Rashad Alsirawan

Publication Name: Acta Technica Jaurinensis

Publication Date: 2021-02-24

Volume: 14

Issue: 1

Page Range: 36-59

Description:

Embankment construction on soft soil may result in excessive settlement, loss of bearing capacity, or sliding instability. However, geosynthetic-reinforced pile-supported (GRPS) embankments offer an effective technique to overcome the problems resulting from soft foundations soils. This paper presents a review of the most important parameters affecting the behaviour of GRPS embankments as well as design methods that estimate tensile forces in the geosynthetic layers and load efficiency. Results highlight the importance of using GRPS embankments, but also reveal the inconsistencies between design methods. Finally, general conclusions about the design and construction of GRPS systems are presented.

Open Access: Yes

DOI: 10.14513/actatechjaur.00566