Yüksek hızlı trenlerin ürettiği titreşimlerin azaltılması için önerilen bir dalga bariyer modelinin yerinde ölçümlerle etkinliğinin araştırılması
Investigation of the effectiveness of a proposed wave barrier model for reducing vibrations generated by high-speed trains through in-situ measurements
Yazar: BERNA İSTEGÜN
Danışman: PROF. DR. ERKAN ÇELEBİ
Sakarya Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı
Derece: Doktora, 2024
Konu: İnşaat Mühendisliği = Civil Engineering

Özet:
Demiryolu trafiğinin oluşturduğu titreşimleri etkili ve ekonomik bir biçimde azaltmak için kullanılan açık hendek yaklaşımı ilgili literatürde kendisine hatırı sayılır bir yer bulmuş olmasına karşın, derin ve desteksiz hendek uygulamaları özellikle yerleşim bölgelerinde mühendislik pratiği açısından uygun değildir. Öte yandan katı dalga bariyerlerinin kullanımı ise titreşimleri etkin bir şekilde azaltma beklentisini karşılayamamaktadır. Açık hendeklerin araştırma konusu edildiği çalışmalarda, gerçekleştirilen saha ölçümleri gerek zayıf zemin koşulları gerekse dinamik yük kaynağı bakımından değerlendirildiğinde dar bir kapsama sahiptir. Bu tez çalışması, Türkiye'nin en yüksek hızda seyreden İstanbul-Ankara tren güzergahı yakınında ve oldukça zayıf bir zemin üzerine inşa edilmiş özel bir test binasının demiryolu trafiği kaynaklı titreşimlerden pasif izolasyon yöntemi ile korunmasına odaklanmaktadır. Bu bağlamda, dinamik yük kaynağı ve korunacak yapı arasına konuşlandırılan ve özel olarak üretilmiş düşük empedanslı prefabrike paneller ile desteklenen ince cidarlı dikdörtgen bir açık hendek uygulamasının çevresel titreşimleri yalıtım performansı tam ölçekli saha çalışmalarıyla incelenmiştir. Alüvyon zemin koşulları dikkate alındığında zemini bir istinat duvarı gibi destekleme fikri özellikle derin hendek uygulamalarında bir zorunluluk olarak öne çıkmaktadır. Ancak bununla birlikte dalga mekaniği göz önünde bulundurulduğunda ilerleyen ve zemin dışında bir ortam ile karşılaşan dalga genliklerinin büyümemesi de bir başka önemli konudur. Bu sebeple çalışma kapsamında kullanılan gaz beton panellerin gerek zeminde stabilite problemini ortadan kaldırması gerekse düşük yoğunluklu olmalarından ötürü titreşimin karakteristiğini büyük ölçüde değiştirmemesi ince cidarlı açık hendek uygulamasının titreşim yalıtım performansı konusunda beklentileri karşılamasını sağlamıştır. Bariyerin tasarımında kullanılan yenilikçi malzemenin yanı sıra içerisinde kullanılan odun talaşı, genleştirilmiş cam kürecik ve strafor köpük gibi farklı özelliklerdeki geri dönüştürebilir atık dolgu malzemelerin titreşim yalıtımına katkısını araştırmak çalışmanın katma değerini artırmıştır. Bu doktora tezi kapsamında, tam ölçekli olarak inşa edilen farklı bariyer tiplerinin gerçek dinamik yük kaynağının yakınında test edilmesine ek olarak PLAXIS 3D yazılımı aracılığıyla deney sahasının sayısal modeli oluşturulmuş ve yalıtım performansı saha verileriyle örtüşecek, gaz beton cidarlı açık hendek tipi bariyeri temsil eden bir sonlu eleman modeli geliştirilmiştir. Doğrulanan nümerik modelin geometrik özelliklerinin dalga enerjisinin soğurulma kapasitesine etkisini sayısal bir model aracılığıyla inceleyebilmek için birtakım parametrik araştırmalar yapılarak ince cidarlı gaz beton panellerle desteklenmiş hendek tipi ideal bir dalga bariyer modeli önerilmiştir.

Abstract:
High-speed transportation systems integrated with railway lines offer comfortable and safe travel and have the advantage of being less affected by traffic density and climatic conditions in residential areas than highways. Economic growth, urban expansion and the need for passenger and freight transfer links between different regions make high-speed trains an important part of modern transportation systems. Significant investments have been made in Turkey in railway infrastructure suitable for high-speed trains, which provide considerable time savings compared to traditional rail transportation and are a more environmentally friendly alternative to road transportation when environmental sustainability impacts are taken into consideration. In Turkey, high-speed trains, which can travel at a speed of 250 km/h, not only create vitality in sectors such as trade and tourism, but also have a strategic importance in terms of reducing road traffic and increasing road safety. However, vibrations from rail traffic have been a growing concern, particularly in densely populated and industrially developed modern urban communities. This concern is based on issues such as the disturbance of comfort, failure of sensitive electronic equipment used in industrial areas, and shortened operational life of structural elements.
In today's world of transportation-geotechnical-structural engineering, the planning of transportation systems and the reduction of these vibrations is critical, as continuous train movements bring potential problems especially in residential and industrial areas built on weak ground deposits. The dynamic effects caused by the continuous increase in traffic loads and travel speeds of railway transportation systems with the developing technology are propagated to the environment through Rayleigh-Love surface waves and body waves. The ability of body waves to penetrate deep into the ground can damage the structural integrity of building foundations, but Rayleigh surface waves generally carry a significant portion of the vibration energy from rail traffic. Surface waves traveling through the Earth's outer layer are more pronounced in soft ground, but their amplitude and frequency are modulated by ground properties. 
Considering the alluvial soil conditions where the shear wave propagation velocity is quite low, the vibrations generated by trains that repeatedly pass through these regions have disturbing and uncomfortable effects for the residents of the region, but also pose a risk to the functionality and longevity of equipment such as medical devices and production machines sensitive to dynamic forces, so successful mitigation of these effects is an important research topic in modern and developing societies. In this context, investigation of railroad induced vibration problems in terms of wave propagation in alluvial soil under full-scale field conditions and development of effective vibration mitigation strategies constitute the main backbone of this study.
Although the open trench approach to effectively and economically attenuate vibrations generated by rail traffic has found a considerable place in the relevant literature, deep and unsupported trench applications, especially in residential areas, are not suitable for engineering practice. On the other hand, the use of solid wave barriers does not fulfill the expectation of successfully reducing vibrations. In studies where open trenches have been investigated, the field measurements carried out have a relatively narrow scope in terms of both poor soil conditions and dynamic load source.
The goal of this study is to investigate in detail the impact of high-speed trains on regions characterized by soft ground and the structures built in these regions, and to investigate the vibration energy absorption capacity of various types of wave barriers designed to reduce these environmental vibrations with full-scale experimental studies.
The research aims to answer questions such as what the characteristics and magnitude of vibrations caused by high-speed trains in soft ground areas are, how these vibrations affect the comfort level of building occupants located close to railway lines, and whether low-budget and environmentally friendly strategies can be developed to reduce the negative effects of environmental vibrations on sensitive equipment and human welfare. Pamukova district, which is an industrial and residential area characterized by very weak ground near the Istanbul-Ankara train line, one of the highest speed train routes in Turkey, was selected as the test site. In this region, a series of train passages were recorded using five accelerometers for three different trips on seven different dates. Considering that each vibration record was analyzed in three axes, a total of 945 acceleration, velocity and displacement records were evaluated within the scope of this study. In addition, a single-storey reinforced concrete structure was built in the area and the effects of environmental vibrations on the structure were also investigated. In order to protect this structure from dynamic forces that pose social and economic risks, the effectiveness of the passive isolation method was examined by using an innovativley-designed wave barrier, which was placed near the structure. Although it is known from the literature that open trench type wave isolation systems generally perform at the highest level, the difficulty of deep trench applications, especially in weak soils, is also an issue to be considered. This concern has led to the search for a material that does not greatly reduce the vibration energy absorption capacity of the open trench while also eliminating the stability problem in deep excavations, and the idea of using low density aerated concrete panels for this purpose was born. 
In addition to the rectangular open trench application where the aerated concrete panels are designed to act as an inner wall, the research also investigated whether the use of recyclable waste materials inside the barrier can make an additional contribution to vibration isolation. In two of the seven field measurements, measurements were taken in natural field conditions representing the barrier-free condition, and in the remaining five measurements, hollow barrier, Styrofoam foam barrier, wood chip barrier, water-filled barrier and glass bead barrier were tested respectively.  The surface vibration motions recorded from accelerometers placed on the free ground in front of and behind the barrier were evaluated with two different evaluation criteria, VRMS and Lv, in order to reveal the effectiveness of the filling material used in the trench-type passive wave barrier model placed in front of a test building near the high-speed railroad route. These criteria were utilized in order to compare the barriers in a more understandable way in terms of their effect on human perception and the operation of sensitive devices, as well as their ability to absorb vibration energy. 
Furthermore, based on the field data, a ground model of the measured Pamukova region was constructed using PLAXIS 3D software and then a series of numerical and parametric analyses were performed by including an open trench type wave barrier with aerated concrete panels in the model. In summary, this thesis is a comprehensive research that combines experimental, numerical and parametric approaches to determine the amplitude and frequency characteristics of the dynamic effects of railway traffic on the free ground surface and structurally and to propose an effective vibration mitigation method. By evaluating the measurement results obtained from full-scale field experiments, different types of trench-type passive wave barrier models have been developed that stand out for their high vibration isolation performance, aerated concrete walls and recyclable waste material used in the internal filling. The aim is for these models to be utilized for the first time in engineering practice, especially for structures facing significant ground vibrations near railways.