Evaluation of innovative sprayed-concrete-lined tunnelling

The front-shunt tunnel was the first tunnel of the Terminal 5 project at Heathrow to be constructed, and was the first section of sprayed-concrete-lined (SCL) tunnel to be constructed using the method known as LaserShell. This innovation represented a significant deviation from the methods previously used in SCL construction. Therefore it was subjected to a careful examination before and during construction using sophisticated 3D numerical modelling and monitoring during construction. The paper presents typical results from surface settlement levelling, inclinometers and extensometers, pressure cells and tunnel lining displacement measurements, and comments on the performance of the methods and instruments used. The paper then presents the methodology and typical results of the numerical modelling, and shows that the predictions of displacements and stresses compared well with the field measurements. In terms of the control of ground deformations and structural safety the tunnel performed well

Thermal conductivity of hemp concretes: Variation with formulation, density and water content

This study investigates the effect of formulation, density and water content on the thermal conductivity of hemp concretes. The investigations are based on experimental measurements and on self-consistent scheme modelling. The thermal conductivity of studied materials ranges from 90 to 160 mW/(m.K) at (23 degrees C; 50%HR). The impact of density on thermal conductivity is much more important than the impact of moisture content. It is shown that the thermal conductivity increases by about 54 % when the density increases by 2/3 while it increases by less than 15 % to 20 % from dry state to 90%RH

Overview of technologies for constructing the facilities at the Dniester pumped storage power station

Purpose. Perform an overview of the construction technologies and substantiate the effectiveness of the Ukrainian experience in building a pumped storage power station (PSPS) on the Dniester River in difficult engineering-geological conditions with the construction of large underground structures, including mine shafts and hydraulic engineering tunnels. Methods. In the work, the main technological methods have been studied and analysed of hydraulic engineering construction of complex large underground structures in the rocks with medium hardness according to M.M. Protodiakonov scale using a special method of a well lowering and a combined method of drilling and blasting operations during mine workings drivage, which is based on the slow and short-delay blasting. The anchors calculation, when driving the water sup-ply conduits, has been made from the condition of suspending the block of disturbed rock, the thickness of which was taken equal to the roof arch height according to M.M. Protodiakonov. The parameters of the sprayed plaster base concrete have also been calculated according to V.M. Mostkov theory. Findings. The analysis of the current state of research, theoretical positions and world practice of construction of PSPS has been made, which testifies the high potential of this type of energy facilities. The efficiency of the underground hydraulic engineering construction of the Dniester Station has been substantiated. The results are presented of a complex application of mining and construction methods, as well as processing equipment for the construction of horizontal and tailrace conduits, drainage adits and vertical mines for hydraulic units in difficult engineering and geological conditions. As a result of performed analytical studies, the combined method of constructing the anchor support of sprayed plaster base concrete, when driving the water supply conduits, which is the most rational for engineering and geological conditions of increased complexity, has been substantiated. Originality. The efficiency of the lowering well method in a thixotropic jacket when constructing in the soft soils has been determined under the conditions of building a PSPS on the Dniester River. The step-by-step combined method of constructing the anchor support of sprayed plaster base concrete, when driving the water supply conduits has been substantiated. Practical implications. The most rational ways of conducting a range of mining-construction works have been substantiated and implemented, allowing to construct a complex pumped storage facility with a capacity of over 2.0 million kilowatts, ensuring a significant increase in the power supply capacity of the West Ukraine region.Мета. Виконати огляд технологій спорудження й виявити ефективність українського досвіду будівництва гідроакумулюючої електростанції на р. Дністер у складних інженерно-геологічних умовах зі зведенням великих підземних об’єктів, включаючи шахтні стовбури та гідротехнічні тунелі. Методика. В роботі розглянуті та проаналізовані основні технологічні способи гідротехнічного будівництва складних великих підземних споруд у скальних породах середньої міцності за шкалою М.М. Протод’яконова із застосуванням спеціального способу опускного колодязя й комбінованого способу ведення буропідривних робіт при проходці гірничих виробок на основі уповільненого і короткоуповільненого підривання. Розрахунок анкерів при проходці водоводів виконувався з умови підвішування блоку порушеної породи, товщина якого приймалася рівною висоті склепіння обвалення за М.М. Протод’яконовим. Розрахунок параметрів набризгбетону проводився також за теорією В.М. Мосткова. Результати. Виконано аналіз сучасного стану досліджень, теоретичних положень і світової практики будівництва гідроакумулюючих станцій, що свідчить про високий потенціал даного виду енергетичних об’єктів. Обґрунтовано ефективність підземного гідротехнічного будівництва Дністровської станції. Представлені результати застосування комплексу гірничопрохідницьких і будівельних методів та технологічного обладнання для спорудження горизонтальних і відвідних водоводів, дренажних штолень та вертикальних шахт для гідроагрегатів у складних інженерно-геологічних умовах. В результаті виконаних аналітичних досліджень обґрунтова- ний комбінований метод створення анкерного набризгбетонного кріплення при проходці водоводів, що є най- більш раціональним для інженерно-геологічних умов підвищеної складності. Наукова новизна. Для умов будівництва гідроакумулюючої електростанції на р. Дністер визначено ефективність методу опускного колодязя в тиксотропної сорочці при будівництві в слабких ґрунтах. Обґрунтовано поетапний комбінований метод створення анкерного й набризгбетонного кріплення при проходці водоводів. Практична значимість. Обґрунтовано й впроваджено найбільш раціональні способи ведення комплексу гірничобудівельних робіт, що дозволяють здійснювати будівництво складного гідроакумулюючого об’єкта потужністю понад 2.0 млнкіловат, що забезпечує суттєве підвищення енергоозброєності західного регіону України.Цель. Выполнить обзор технологий сооружения и выявить эффективность украинского опыта строительства гидроаккумулирующей электростанции на р. Днестр в сложных инженерно-геологических условиях с воз- ведением крупных подземных объектов, включая шахтные стволы и гидротехнические тоннели. Методика. В работе рассмотрены и проанализированы основные технологические способы гидротехнического строительства сложных крупных подземных сооружений в скальных породах средней крепости по шкале М.М. Протодьяконова с применением специального способа опускного колодца и комбинированного способа ведения буровзрывных работ при проходке горных выработок на основе замедленного и короткозамедленного взрывания. Расчет анкеров при проходке водоводов выполнялся из условия подвешивания блока нарушенной породы, толщина которого принималась равной высоте свода обрушения по М.М. Протодьяконову. Расчет параметров набрызгбетона производился также по теории В.М. Мосткова. Результаты. Выполнен анализ современного состояния исследований, теоретических положений и мировой практики строительства гидроаккумулирующих станций, свидетельствующий о высоком потенциале данного вида энергетических объектов. Обоснована эффективность подземного гидротехнического строительства Днестровской станции. Представлены результаты применения комплекса горнопроходческих и строительных методов и технологического оборудования для сооружения горизонтальных и отводящих водоводов, дренажных штолен и вертикальных шахт для гидроагрегатов в сложных инженерно-геологических условиях. В результате выполненных аналитических исследований обоснован комбинированный метод создания анкерной набрызгбетонной крепи при проходке водоводов, являющийся наиболее рациональным для инженерно-геологических условий повышенной сложности. Научная новизна. Для условий строительства гидроаккумулирующей электростанции на р. Днестр определена эффективность метода опускного колодца в тиксотропной рубашке при строительстве в слабых грунтах. Обоснован поэтапный комбинированный метод создания анкерной и набрызгбетонной крепей при проходке водоводов. Практическая значимость. Обоснованы и внедрены наиболее рациональные способы ведения комплекса горностроительных работ, позволяющие осуществлять строительство сложного гидроаккумулирующего объекта мощностью более 2.0 млн киловатт и обеспечивающего существенное повышение энерговооруженности западного региона Украины.The authors express their gratitude to Viacheslav Korytskyi, Deputy Chief Engineer of the Tunnel Construction Department No.7, PJSC “Kyivmetrobud”, for advisory support and provided drawings

Early Detection of Near-Surface Void Defects in Concrete Pavement Using Drone Based Thermography and GPR Methods

The goal of this research is to evaluate the feasibility and the performance of using UAV-mounted infrared thermography (IRT) and ground penetration radar (GPR) to detect sub-surface voids caused by consolidation issues in concrete pavement. The motivation of the study is to identify the consolidation defects as early as the initial set of concrete to avoid having this problem in large pavement sections, which is costly and time consuming to repair. Using the two technologies in combination to detect subsurface voids in the concrete initial set stage is new and aims to take advantage of the strengths and minimize the limitations of each method. UAV-based IRT can cover large areas of the pavements in a short amount of time, while GPR can provide higher accuracy in locating the defects horizontally and vertically. Therefore, the combination of the two technologies can allow detection of small voids in large areas with improved confidence. In this project, both laboratory and field tests were conducted with both methods, and coring samples were used for validation of results. The results from multiple specimens and multiple experiments suggested that both technologies performed well in detecting the subsurface voids in the concrete pavement’s initial set stage. Despite some limitations discussed in the report, the outcomes of the project provided evidence that these technologies can be used separately or together on the field as efficient and economical quality control tools in concrete pavement construction

Maturity method to predict the evolution of the properties of sprayed concrete

The maturity method provides a simple approach for assessing the strength evolution of concrete. Although it is already used in the precast industry, no reported applications with sprayed concrete may be found in the literature. Such concrete presents singular characteristics due to the spraying process and, in some cases, due to the introduction of accelerators that modify the kinetics of cement hydration. Consequently, the traditional equations that relate the evolution of mechanical properties and the maturity index might not apply in this case. The objective of this study is to adapt the maturity method to sprayed concrete. An experimental program was conducted with 24 concrete mixes sprayed in laboratory and tested for the evolution of temperature and compressive strength. An alternative equation was proposed to relate the maturity index and the mechanical properties. Subsequently, finite element models were developed to generalize the maturity curves considering the local design parameters.Peer ReviewedPostprint (author's final draft

Heinz Isler: shells for two churches

This paper describes the concept, design and realisation of two churches where Heinz Isler (1926-2009) was responsible for the structural design and in one case also for the architectural concept. One example, the Heilig Geist Kirche (Holy Spirit Church) Lommiswil, near Solothurn, Switzerland (1967) includes, unusually for Isler, a “hypar” shell whilst the other, the “Steinkirche” of the Evangelische Kirchgemeinde in Cazis, Switzerland (1996), is derived directly from given natural forms

Durable, Cost-Effective Pavement Markings Phase I: Synthesis of Current Research, June 2001

Pavement marking technology is a continually evolving subject. There are numerous types of materials used in the field today, including (but not limited to) paint, epoxy, tape, and thermoplastic. Each material has its own set of unique characteristics related to durability, retro reflectivity, installation cost, and life-cycle cost. The Iowa Highway Research Board was interested in investigating the possibility of developing an ongoing program to evaluate the various products used in pavement marking. This potential program would maintain a database of performance and cost information to assist state and local agencies in determining which materials and placement methods are most appropriate for their use. The Center for Transportation Research and Education at Iowa State University has completed Phase I of this research: to identify the current practice and experiences from around the United States to recommend a further course of action for the State of Iowa. There has been a significant amount of research completed in the last several years. Research from Michigan, Pennsylvania, South Dakota, Ohio, and Alaska all had some common findings: white markings are more retro reflective than yellow markings; paint is by-and-large the least expensive material; paint tends to degrade faster than other materials; thermoplastic and tapes had higher retro reflective characteristics. Perhaps the most significant program going on in the area of pavement markings is the National Transportation Product Evaluation Program (NTPEP). This is an ongoing research program jointly conducted by the American Association of State Highway and Transportation Officials and its member states. Field and lab tests on numerous types of pavement marking materials are being conducted at sites representing four climatological areas. These results are published periodically for use by any jurisdiction interested in pavement marking materials performance.At this time, it is recommended that the State of Iowa not embark on a test deck evaluation program. Instead, close attention should be paid to the ongoing evaluations of the NTPEP program. Materials that fare well on the NTPEP test de cks should be considered for further field studies in Iowa

Briefing:Concrete – Innovations and practical applications

Concrete is a highly adaptable material and capable of considerable variation, development and innovation, as can be seen from the pages of journals such as the Proceedings of the Institution of Civil Engineers–Construction Materials. This briefing paper describes the 43rd Convention of the Institute of Concrete Technology, which took place on 26 March 2015. The event provided an opportunity for practitioners and researchers to meet and communicate, and to showcase the variety and diversity of current innovations, developments and applications in concrete and cement technology, including carbon-negative aggregate, polycarboxylate ether superplasticisers, waste wood in concrete, steel fibres, calcium aluminate cements, superabsorbent polymers and sprayed concrete tunnel linings