Plain language title:

Evaluation of lateral resistance of ballasted tracks considering dynamic load characteristics

What is it about?

We suggest a new test method to determine dynamic lateral resistance of sleeper. A pendulum loading test device (PLTD) is developed and assembled at laboratory. We subject a concrete sleeper to several impact loads utilising this apparatus in lab. The results are mainly functions of impact load, and compared with static outputs.

Why is it important?

This research opens a new window to the world of soil dynamics and track lateral resistance. Since the advent of high-speed trains, quasi-static analyses have been unable to predict the interaction between trains and tracks correctly. We have shown in this research that, contrary to their unique static lateral resistance, the dynamic lateral resistance of sleepers varies by load characteristics, and significantly diminishes in high-magnitude lateral impact loads. Therefore, we suggest others to use our methodologies instead of static ones.

Perspectives

This paper is my bachelors thesis. It literally took a toll on me - there were tons of hard-work, frustrations and all-nighters! It took us forever to publish it as a new idea, but finally we did it. I cannot express enough gratitude to those who helped me conclude my work. This research is the base of all other works I (will) have done in the field of dynamic lateral performance of ballasted tracks, and I do hope that it will be useful for others as well.

Plain language title:

Lateral interaction of concrete sleeper with ballast layer under various impact loads.

What is it about?

We subject a concrete sleeper to a number of lateral impact loads by a previously developed apparatus namely pendulum loading test device (PLTD) to understand the behavioural mechanisms existing between its three difference surfaces (base, sides and end) and their adjacent ballast layer under lateral impact loading conditions.

Why is it important?

High-speed trains era has arrived for a significant amount of time, and so should the designs and analyses. Quasi-static look at train-track interaction seems to have no meaning anymore. In this study, we present an impact factor for train lateral loads in terms of axle-load and speed up to 300 km/h, which is based on the dynamic friction coefficient between ballast layer and both base & sides of concrete sleeper. We also calculates dynamic lateral resistance for each contact surface of sleeper, leading to their contribution into providing the resistance required.

Perspectives

The most delightful week of my life (research-wise) was working on this paper! Revelations (to me) were very interesting and amusing.

This research is definitely extendable to many interesting topics, and I can't wait to see others benefit from it in their works.

Plain language title:

Comparing behaviour of concrete, wooden and steel railway sleepers under lateral impact loads.

What is it about?

We subjected three types of railway sleepers to lateral impact loads using a previously developed apparatus, pendulum loading test device (PLTD), in order to gain insight into their performance under such loading conditions. We also conducted static lateral push tests on them in a similar circumstance for comparison purposes.

Why is it important?

This paper presents an inclusive literature review on lateral resistance phenomenon, whether of a single sleeper, short panel or CWR track. We then compare sleeper-ballast interaction forces, sleeper inertial forces and lateral displacements as functions of lateral impact load among concrete, wooden and steel sleepers. Our findings revealed that wooden sleepers, in a certain domain of lateral impact load, provides higher dynamic lateral resistances compared to concrete sleepers. They also show that steel sleepers in their conventional form are of very low dynamic lateral resistance.

Perspectives

Writing this paper took a toll on me! It relates to lateral impact behaviour of sleepers, yet a reviewer mandated us to extend the literature review and include short panels and CWR tracks as well. It was for the best though I suppose! The laboratory workload was considerable, but nothing is better than having a nice and enthusiast colleague and a good supervisor. I hope that this effort will turn out to be useful for those interested on the topic of track lateral resistance because it is getting more serious day by day since the advent of high-speed trains.

Plain language title:

Behaviour of railway panels with limited number of sleepers subjected to lateral impact loads.

What is it about?

We subject two railway panels of five and seven sleepers to lateral impact loads by a previously developed apparatus called pendulum loading test device (PLTD) in the laboratory in order to find about their performance under such dynamic conditions and relevant dynamic parameters.

Why is it important?

Most methodologies assessing the lateral resistance of railway tracks are static in nature. We propose a comprehensive measurement test setup in order to capture the dynamic component of track lateral resistance under impact loading as well. Lateral displacements, panel-ballast interaction forces and lateral loading distribution patterns are attained in terms of various lateral impact loads. It is shown that dynamic and static lateral resistance of a railway short panel is basically the same, which partly eliminates the need to perform time-consuming lateral static tests on tracks.

Perspectives

I enjoyed every step taken for this publication; from testing and data gathering to data mining, analysing and interpretation - all were very new and interesting! Further work on this ground could be done, and we wish the project to be extended as much and soon as possible.

Plain language title:

Behaviour of mixture of railway ballast, rubbery materials and sand under repetitive loads.

What is it about?

We examine for the first time the behaviour of ballast, rubbery materials and sand altogether under cyclic loading. Considering parameters such as settlement, ballast breakage and damping ratio for our samples, we then select the best mixture, which is the one with 5% (by ballast weight) of rubbery materials.

Why is it important?

Ballasted railway tracks lose their mechanical properties significantly when attacked by sand. Their ballast layer gets more rigid and unable to attenuate train-induced vibrations effectively, resulting in necessity of premature tamping operation. Adding rubbery materials (or as we call them TDAs) could considerably revive stiffness and damping characteristics of ballasted tracks. Our findings indicate that by adopting this user-friendly and economical approach, instead of other costly measures (e.g. building sand barriers), this problem is resolved to a large extent.

Perspectives

I love this paper! I know this doesn't sound humble, yet I can't help but feel in this way! True reviewers always help manuscripts improve, and this is mostly the reason I love this paper - their suggestions were incredible in my opinion. Anyway, we hope this research endeavour will be found useful by scholars and practitioners interested in dynamic topics of railway geotechnics.

Plain language title:

Field tests and computer analyses to examine micropile group in foundation of transmission towers.

What is it about?

In this research, based upon compression & uplift experiments and subsequent calibration/verification in a computer software package, the behaviour of micropiled foundations is investigated in terms of each micropile and as a whole.

Why is it important?

Power transmission line towers, particularly those of high voltage, require foundations with high dimensions and volume of concreting, which makes these types of foundations relatively uneconomical and, more importantly, inconvenient in execution, especially in saturated soils. In order to solve the aforementioned challenge, utilising micropiles could go a long way to reduce foundation settlements. Research on compression behaviour of micropiled rafts are relatively abundant contrary to their uplift performance, which this research addresses as a gap in the literature.

Perspectives

I have not exaggerated if I'd say that the "response to reviewer comments" document of this paper was another paper itself! Working with my co-authors was definitely enjoyable - the discussions that we'd make to answer some questions would sometimes get hot and very interesting for us! Why this research should be of particular interest - especially for power industry - is the fact that (almost) only foundations of power transmission line towers undergo entire uplift due to the location of tower or under extreme wind loading conditions.

Plain language title:

Behaviour of mixture of railway ballast, rubbery materials, sand and water under repetitive loads.

What is it about?

Ballasted railway tracks in desert areas are the recipient of sand dunes and rainwater. This makes them very stiff and prone to premature degradation. We have shown in this research that how the efficacy of rubbery materials, which help ballasted tracks maintain their stiffness to some extent, can significantly diminish by rainwater based on a number of cyclic tests.

Why is it important?

We determine the critical moisture in which the efficacy of rubbery materials (or as we call them TDAs) is the least in terms of damping ratio, after which the stiffness escalates as well. This parameter has been calculated as 10% for the ballasted tracks completely contaminated - with fully fouled ballast layers, which gives an insight into designing drains in order to keep the water content in a reasonable range.

Perspectives

I am delighted to have been in association with the project that utilises tired derived aggregates (TDAs) as an approach for improving mechanical and dynamic characteristics of ballasted railway tracks under train-induced vibrations, and do hope that the idea behind using TDAs in this project really makes a difference for ballasted tracks in desert areas.