Farshad Astaraki

57195926806

Publications - 11

Investigation of Shear Strength Reduction Method in Slope Stability of Reinforced Slopes by Anchor and Nail

Seyed Mohammad Reza Imam Farshad Astaraki M. Movahedi Rad Jafar Chalabii Seyedsaber Hosseini

Publication Name: Buildings

Publication Date: 2024-02-01

Volume: 14

Issue: 2

Page Range: Unknown

Description:

Since the stability of slopes in infrastructures such as road and railroad embankments, excavations, and, in general, earthwork is important, analyzing the stability of these slopes has been one of the main focuses of geotechnical engineers. Although analyzing both reinforced and unreinforced slopes is needed, reinforced slopes require special attention as the reinforcement elements significantly affect the calculations. Hence, the current study’s aim is to find out the differences between obtained safety factors using the Limit Equilibrium Method (LEM) and Shear Strength Reduction Method (SSRM). For this purpose, first, the origin differences in terms of Safety Factor (SF) are theoretically determined according to basic formulas for the aforementioned techniques. Then, to verify the formula, several numerical modelings are carried out using in situ measured geotechnical data to better understand the differences in terms of safety factors. The results indicate that for the reinforced slope with an SF value of higher than 1, the SSRM provides a higher SF in comparison with the other techniques, and the origin of this difference is the definitions of the SF in the different methods.

Open Access: Yes

DOI: 10.3390/buildings14020432

Numerical Investigation of the Effect of Longitudinal Fiberglass Dowels on Tunnel Face Support in Layered Soils

Morteza Esmaeili Farshad Astaraki M. Movahedi Rad Jafar Chalabii Jafar Hosseini Manoujan

Publication Name: Infrastructures

Publication Date: 2023-10-01

Volume: 8

Issue: 10

Page Range: Unknown

Description:

Tunnel face extrusion rigidity is an important factor for solving stress–strain problems in loose ground conditions. In previous studies, the effect of horizontal and vertical soil layering on tunnel excavation face stability in the presence of longitudinal fiberglass dowels has not been studied. Therefore, in this study, the effect of fiberglass dowels on the stability of the tunnel face in layered soil has been investigated. In this matter, the best dowel arrangement for minimizing the excavation face extrusion in the case of two-layer soil (horizontal or vertical) has been focused on. For this purpose, firstly, a 3D numerical model was validated based on field data provided previously, and then a 3D numerical tunnel was developed in FLAC3D, adopting the Mohr–Coulomb failure criterion. In continuation, the effect of tunnel diameter, initial pressure ranging from 0.5 to 1.5 MPa, and different placement angles of fiberglass dowels ranging from 0 to 9 degrees, with respect to the tunnel longitudinal axes on the tunnel face extrusion, have been investigated. In the case of horizontal layering, the results showed that the maximum extrusion rate is significantly increased where the elasticity modulus of the soil is reduced. In addition, comparing the maximum extrusion in vertical and horizontal layering, it was found that its value in the horizontal mode is much higher than in the vertical. Additionally, the extrusion of the tunnel face has changed significantly due to an alteration in the initial stress. Finally, it was discovered that tunnel face extrusion is not significantly affected by altering the angle of the fiberglass dowels.

Open Access: Yes

DOI: 10.3390/infrastructures8100138

Slope stabilisation of railway embankments over loose subgrades using deep-mixed columns

Morteza Esmaeili Farshad Astaraki

Publication Name: Proceedings of the Institution of Civil Engineers Ground Improvement

Publication Date: 2022-12-01

Volume: 175

Issue: 4

Page Range: 247-260

Description:

An investigation was undertaken into the stability of railway embankment slopes over soft subgrades stabilised by deep-mixed columns (DMCs). Three 1:10 scale laboratory embankments were constructed over unreinforced and reinforced subgrade with DMCs in square and triangle patterns. The load-settlement responses of both embankments and columns were measured. The laboratory embankments were then mathematically modelled and the results were compared. After validation, a comprehensive parametric study was carried out to evaluate the factor of safety (FoS) of the embankment side slopes against sliding. Five embankment soil types from poor to high strength, three heights from 1.5 to 10 m and various DMC improvement area ratios from 0 to 65% were considered. The experimental outcomes indicated an increase of nearly 63% in the bearing capacity of both DMC-supported embankments compared with the unreinforced one. Regarding the parametric study, a minimum required FoS of 1.5 was observed for 1.5 m embankments of all soil types stabilised with a 60% improvement ratio. The greatest safety increase was associated with a 1.5 m height embankment with poor soil type, which showed a 36% increase.

Open Access: Yes

DOI: 10.1680/jgrim.20.00049

Ballast Stabilization with Polyurethane for Use in Desert Areas

Jabbar Ali Zakeri Morteza Esmaeili Farshad Astaraki M. Movahedi Rad Sina Ghahremani Reza Esfandiari Mehni Fateme Samimi

Publication Name: Periodica Polytechnica Civil Engineering

Publication Date: 2022-06-30

Volume: 66

Issue: 3

Page Range: 853-865

Description:

Sand dune accumulation in the railways passing through desert areas leads to ballast softening and settlement, which is one of the major challenges in the ballast maintenance operation. In this regard, ballast infilling with polyurethane could be mentioned as a novel solution that has been less attentional in previous studies. In this matter, in present study using a domestic cost-effective polyurethane, the ballast stabilization has been accomplished and the relevant shear strength parameters have been investigated via a series of large-scale direct shear tests. Since the utilized polyurethane has composed of two different components, in the first stage, the best weight ratios of components have been investigated via a series of compression tests. In this matter, the ratio of 1.5 units polyol to 1 unit isocyanate has been adopted as the best composition. Then, the resulting polyurethane was injected into the ballast to perform large-scale direct shear tests. According to the measurement results, the maximum shear stress, the internal friction angle, and the cohesion coefficient increased by 109%, 9.5%, and 162.5% with respect to the non-stabilized ballast (NSB), respectively. In addition, the dilation angle decreased by 66.4% with the injection of polyurethane into the ballast. Hence, the results indicate increased shear strength and lateral track resistance in the presence of polyurethane, which can prevent lateral deflection and improve track safety. In other words, the mentioned polyurethane has improved the shear parameters of the ballast more significantly than other polyurethanes and has shown its performance in increasing the bearing capacity.

Open Access: Yes

DOI: 10.3311/PPci.19968

Investigating Slope Stability of Geocell-Reinforced Railway Embankments

Morteza Esmaeili Farshad Astaraki M. Movahedi Rad Mohammad Reza Roozbini

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2022-01-01

Volume: 19

Issue: 6

Page Range: 197-212

Description:

The current paper aims to investigate stability of side’s slops of geocell-reinforced railway embankments. For this purpose, firstly a set of six 1:20 scaled models including a reference embankment and geocell-reinforced embankments was constructed in a loading chamber and their load-settlement behaviour was assessed. In the next stage, 3D FEM models of the embankments were developed and the relevant results were verified against the laboratory test outcomes. In continue, on the basis of verified models, the scaled up railway embankments were simulated and the real train loading applied to the models. In this matter, a wide-ranging parametric study was performed on the embankment soil properties ranged from poor (ST1) to high strength (ST5) materials, geocell elasticity modulus (E), number of geocell layers (N) and their vertical location in the embankment body (U) to achieve a minimum embankment sliding safety factor (SF) of 1.5. Outcomes indicate that geocell opening size, stiffness and the placement position play an important role where the concern is to stabilize the embankments' sides slopes. It was found that middle of the embankment was the best position of geocell layers. Elasticity modulus of 1400 MPa and opening size of 245*210 mm were also determined as the optimum for geocell layers.

Open Access: Yes

DOI: 10.12700/APH.19.6.2022.6.14

Modification of Concrete Railway Sleeper Mix Design, Using a Hybrid Application of Steel Fibers

Guoqing Jing Farshad Astaraki Mohammad Siahkouhi M. Movahedi Rad Sashka Uuganbayar Jun Wang

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2022-01-01

Volume: 19

Issue: 3

Page Range: 119-130

Description:

Concrete railway sleepers have been used for years without an update in production and design, to be compatible with demands for increasing train axle loads and speed. In the current research, concrete railway admixture is modified with consuming (0.5% straight-1.5% hooked), (1.5% straight-0.5% hooked) and (1% straight-1% hooked) steel fibers combinations. Three main mechanical experiments as compressive, flexural and splitting tensile strengths and fresh mortar “flowability” were performed. Results showed that the hybrid of 1% straight and 1% hooked steel fibers shows the optimal performance among other hybrid combinations. This hybrid admixture efficiently improves the compressive, flexural and splitting tensile strengths of the concrete railway sleeper mix design.

Open Access: Yes

DOI: DOI not available

Comparative Study of the Mechanical Behavior of Concrete Railway Sleeper Mix Design, using Waste Rubber and Glass Materials

Szabolcs Fischer Guoqing Jing Farshad Astaraki Mohammad Siahkouhi M. Movahedi Rad Chunchao Li

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2022-01-01

Volume: 19

Issue: 6

Page Range: 213-224

Description:

Waste rubber tires and glass powders, are hazardous materials for the environment. One of the methods to consume them, is their application in railway engineering projects. Rubber and glass materials, in this research, are provided from waste tires and glass bottles. Therefore, a modification is conducted to the concrete railway sleeper mix design, incorporated with waste rubber (R) and glass powder (GP). Three mechanical tests, including compressive, flexural and tensile splitting, have been studied on rubber and glass powder concrete specimens. Three different percentages of 5%, 10% and 15% by cement weight, for GP and by fine aggregate volume for R, are investigated herein. The results show that GP concrete has a better performance over the rubber concrete (RC), but lower than Ref. specimens. 5%GP as the best mix design, has compressive, flexural and tensile strengths of 45.4 MPa, 7.5 MPa and 5.82 MPa, respectively. Moreover, these strengths, for compressive and flexural, of 5%GP are about 24% and 6% lower than the Ref. strengths, respectively, while, tensile splitting strength is almost 14% higher than Ref. strength.

Open Access: Yes

DOI: DOI not available

Effects of Wheel Surface Defects on Ground Borne Vibration

Szabolcs Fischer Farshad Astaraki M. Movahedi Rad Milad Kazemian Milad Akbarivarmaziar Ahmad Mohammadi Doost

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2022-01-01

Volume: 19

Issue: 6

Page Range: 129-141

Description:

Wheel ground borne vibrations, may have a significant impact on human activity and on nearby buildings. In metropolitan cities, metro lines and their development may cause such vibrations. Despite many works and solutions for path and receiver, the excitation source could also have a great effect. Wheel and rail damages are the two sources of vibration which can increase the damage impact by a factor of 5x. Wheel damage would increase dynamic vertical force noticeably and an increase in ground-borne vibration is expected. In this study with the help of finite element modelling, wheel damage including wheel flat, spalling and wheel oval is studied for a slab track and results are discussed. The studied parameters are velocity and wheel damage and their effect on ground-borne vibrations are examined.

Open Access: Yes

DOI: DOI not available

Effect of Geocell, on the Mechanical Behavior of Railway Embankments, Using FE Modeling

Morteza Esmaeili Guoqing Jing Guixian Liu Farshad Astaraki M. Movahedi Rad Reza Esfandiari Mehni

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2022-01-01

Volume: 19

Issue: 6

Page Range: 63-80

Description:

In nature, the mechanical properties of soils, vary from region to region and in some areas, high-strength soil resources lack is a serious difficulty that geotechnical engineers may face where constructing earthworks such as railway and road embankments is required. Although a wide range of soil improvement techniques exists to improve such soils, the effect of geocell, as an effective solution, has not yet been investigated for railway embankments, hence, the present study aims to develop a three-dimensional (3D) Finite Element (FE) model, to fill the gap. To do this, first, six, 1/20 scaled-down railway embankments, including an unreinforced and 5 reinforced ones, were constructed in the lab and their load-settlement behavior, was assessed. Second, a 3D FE model was validated by experimental results and then, using a parametric study, the effect of geocell opening size and geocell layers number, were investigated on bearing capacity and settlement of the embankments, for five various types of soil ranging from poor soils (ST1), to high strength soils (ST5). The outcomes indicated, although adding geocell layers up to 15 layers, results in reducing the exerted stress in railway embankments by a maximum of near 50%, the crest settlement is not efficiently affected. Moreover, it was found that geocell’s opening size has a negligible effect on decreasing the embankment’s settlement, while it affects the bearing capacity significantly, up to a maximum of 50%.

Open Access: Yes

DOI: DOI not available

Laboratory Investigation on the Effect of Microsilica Additive on the Mechanical Behavior of Deep Soil Mixing Columns in Saline Dry Sand

Morteza Esmaeili Farshad Astaraki M. Movahedi Rad Hamed Yaghouti

Publication Name: Periodica Polytechnica Civil Engineering

Publication Date: 2021-11-02

Volume: 65

Issue: 4

Page Range: 1080-1091

Description:

Since loose and salty subgrades consider as problematic barriers while constructing new transportation infrastructures such as railway tracks and roads are required, the current study aims to find a solution to stabilize these kinds of subgrades using the deep soil mixing (DSM) technique and micro silica additive. In the present study a series of experimental DSM columns were executed in a salty sand-filled chamber utilizing a laboratory scale DSM apparatuses. In the first step, by adding three salt percentages of 5, 10 and 20 into the original sand, four different sandy subgrades with a relative density of 70% were prepared. Considering three percentages of 10, 15 and 20 for micro silica additive, the water-to-cement ratio of 1, salt percentages of 0, 5, 10 and 20 totally 150 sand-cement columns were constructed in the lab environment. In continuation, unconfined compression strength (UCS) and elasticity modulus of all capped DSM columns have been determined and interpreted using scanning electron microscope (SEM) images at three ages of 7,14 and 28 days. The results indicated that increasing the salinity of subgrade soil from 0 to 20% resulted in a falling UCS and Young module by 28 and 21% for 28-days specimens. Furthermore, as a solution, adding micro silica in cement-water grout up to 15% resulted in enhancing mechanical characteristics of the DSM columns. So that adding 15% microsilica caused a 21 and 42% increase in UCS and elasticity modulus of 28-days samples respectively, executed in subgrade with 20% salt.

Open Access: Yes

DOI: 10.3311/PPci.18126

Condition monitoring of vibration at weak parts of rail for ballasted railway tracks in Iran

Farshad Astaraki M. Movahedi Rad Ali Taheri Milad Kazemian

Publication Name: Journal of the Korean Society for Railway

Publication Date: 2021-06-01

Volume: 24

Issue: 6

Page Range: 544-551

Description:

Vibration monitoring has become important in railway tracks for many purposes. One of the most important purposes is to prevent exceeding limits of induced vibration to adjacent residential buildings. In the current study, to measure the level of vibration, a field investigation is carried at three critical positions including a curve, a fishplate and a deflected rail weld. The field study is an old ballasted railway track located at the critical /one of the entrance of Mashhad Railway station in Iran. In this regard, three distinct field tests are performed using accelerometer sensors and the obtained data arc analyzed and assessed. Besides this, vibrations at 5 and 10 m-distancc from the track arc also considered and rccordcd. As the main achievement, results show that induced vibration levels arc highly dependent on the condition of contact surface between wheel and rail

Open Access: Yes

DOI: 10.7782/JKSR.2021.24.6.544