Special Issue on Sustainable Civil Infrastructures: Innovative Technologies and Materials

Recent developments of innovative technologies and materials have offered many exciting opportunities for engineers to design and build more sustainable civil infrastructures. Innovation may come in the form of, e.g., better material performance, lower production costs, improved construction and monitoring techniques, reduced health, and environmental impacts. The use of new materials or technologies in an infrastructure project requires a rethink of the existing design philosophy and construction processes. Collaboration between all parties involved (owner, design consultant, contractor, and local authority) is also necessary. Pilot field, laboratory, or numerical studies are often, though not always, undertaken to evaluate the performance of the new technique prior to full-scale applications.

This special issue covers a wide range of contemporary issues in the field of geotechnical, pavement, and bridge engineering. The aim of the special issue is to share ideas, knowledge, and experience on the recent developments of innovative materials and technologies for sustainable civil infrastructures. This special issue includes 12 papers that have been subject to the same rigorous peer review process as regular articles in this Journal.

There is one paper in this special issue on the sustainable development of bridge infrastructures. Mehrabi discusses advances in evaluation, health monitoring, and rehabilitation of cable-stayed bridges. In addition, the author presents a unified approach for in-service evaluation and cable replacement design of cable-stayed bridges. The author introduces its first application to the Luling Bridge in Louisiana. The cable replacement design accommodates an extraordinary construction sequence to address constraints on space and traffic flow. Temporary cables minimize stress variation and allow for the live load without restriction. The new cable system allows individual strand installation and tensioning, and is expected to facilitate future inspections and replacement. The bridge evaluation process and cable replacement design is unique and successful, which is useful for sustainable development of all cable-stayed bridges.

There are three papers in this special issue that discuss the use of innovative techniques to reduce the risk of damage to key infrastructure. The first paper by Huang et al. discusses the use of a global positioning system (GPS) to monitor the Shuping landslide in the Three Gorges Reservoir in China. More than 10 years of ground surface movement data are presented. The triggering factors for surface movement are correlated with fluctuations of reservoir water levels and rainfall records. This important case history shows that long-term and near-real-time monitoring is invaluable for the understanding of landslide movements and their hydrological triggers. On a similar note, in the second paper, Yang discusses the use of remote sensing techniques (satellite images and aerial photos) to determine the probability of road interruption due to landslides for different rainfall return periods. Rainfall-induced landslides are common in Taiwan and often result in road closures. Yang develops a validated landslide prediction model using logistic regression for a rural township in Taiwan. The study area is mainly hilly and mountainous and covers five main roads and 13 villages. The model provides the local authority a useful means to prioritize road maintenance works and to select emergency evacuation routes with lower probabilities of landslide occurrence. High-speed railway (HSR) bridges are important infrastructure in many countries. To ensure their safe operations during the construction of new underpass bridges, in the third paper He et al. describe a risk assessment method and an automated early warning system and their application for a project in Tianjin City, China, where a new bridge was constructed to cross the Beijing-Tianjin Intercity Railway. During construction of the underpass structure, settlement and deformation of the HSR bridges were closely monitored and compared with the predetermined threshold values. This successful case history demonstrates the importance of risk control for the protection of existing key infrastructure.

There are three papers in this special issue that discuss different aspects of innovative pavement materials and management. The first paper, by Wang et al., develops a fast treatment of winter distresses by using a 1-cm-thick prefabricated rollable pavement based on a textile-reinforced concrete. They find that this innovative prefabricated rollable pavement has high mechanical resistance and positive texture characteristics. With this technique, winter distresses can be repaired and the roadway can be opened for traffic within only a few hours. This technique has the potential to prolong roadway life and enhance sustainability. In the second paper, Steyn et al. investigate the required properties of foamed concrete for possible implementation as an alternative to engineered material arresting system on airports. As part of the investigation, plate load tests, unconfined compressive strength tests, stiffness tests, and density evaluations are carried out on the foamed concrete, using a range of plate sizes that represent different contact areas of tires for vehicles entering an arrestor bed. They find that foamed concrete can be used as an arresting material because the compressive strength and energy absorption of foamed concrete met the requirements. Foamed concrete with densities of 600 and $800\mathrm{kg}/{\mathrm{m}}^3$ allow for more settlement, while the stress-deformation relationship is very similar to that of material currently used in arrestor beds. The third paper, by Chang and Lin, explores the building information modeling to be used in Taiwan as a basis for developing the concept of road information modeling (RIM) for underground pipeline management. Residents in urban areas rely on a complex and dense network of underground pipelines. Underground infrastructure presents unique challenges for pavement engineers because usable underground space is limited and is not easily accessible or observed. Chang and Lin examine frameworks and strategies for the promotion of RIM from policy, legal, technical, implementation, and application viewpoints. Without a clear understanding of the existing underground pipelines, errors such as the mistaken excavation of gas or oil pipelines are more likely to happen, thus creating a threat to public safety. An implementable example of RIM map data is developed. Overall, the study makes a significant contribution to underground pipeline management that can be used as a basis for improving the effectiveness of road maintenance and management.

The following two papers deal with the impact of soil properties on road construction. Red clay is widely distributed across China and is commonly used as a subgrade material in road construction. However, this material is difficult to compact due to the high natural moisture content and also the high shrink-swell potential. The paper by Yuan et al. compares the physical and chemical properties of red clay from different regions of China. The effect of different compaction methods on the moisture content of the soil is also investigated by a series of laboratory and field tests. Based on the results, recommendations are given on the field compaction method and the optimum moisture range when red clay is used as subgrade. Motivated by the abundance of soft soil resulting from dredging activities in South Korea, in the next paper Vo and Park explore the use of lightweight treated soil as a potential subbase material in road construction. Specimens of lightweight treated soil were prepared by mixing dredged soil, cement, air foam, and water at predetermined proportions. The specimens are tested for their stress-strain behavior and durability after freeze-thaw cycles (FTCs). From the results, it is found that the strength of the lightweight treated soil increased with increasing cement content but decreased with increasing air-foam content or the number of FTCs. The effect of different mix design is further evaluated by observing the cracking (top-down and bottom-up) and rutting in a pavement structure with a 10-year service life. The results show that if prepared properly, lightweight treated soil can offer many desirable characteristics and could be used as a sustainable pavement material.

There is one paper in this special issue that relates to the sustainable development of underground infrastructures. Wang et al. present a case history of rehabilitation of underwater shield tunnel using a method called the sleeve method. The original tunnel was damaged due to an inrush of water and silt caused by an unexpected methane eruption during construction. The process and technologies for this sleeve rehabilitation method are explained in this paper. A finite-element approach is also used to simulate the repair procedure and to analyze the risks in the construction phases to ensure the safety of the tunnel.

There is also one paper on the sustainable development of earth-retaining structures. Liu et al. use the system failure probability approach to assess the main failure modes of a soil-nailed retaining structure. Analyses Are carried out for the East Public Square of Jinan high-speed railway station in China. The probability of each failure mode is calculated by considering various random variables of a soil-nailed wall. A numerical simulation is also carried out to analyze the stability of excavation during each construction stage. The factors of safety are computed by using the strength-reduction method. Field measurements confirm the reliability of the numerical analyses and satisfactory performance of the earth-retaining system.

There is one paper on the sustainable development of asphalt pavements. Jaskula and Judycki present experimental investigation of the detrimental effects of water and frost on asphalt pavements. It includes laboratory testing of fatigue life of asphalt concrete that was subjected to action of water and frost and field testing of damages caused by water and frost on existing asphalt pavements. Laboratory simulation of water and frost action is based on the original AASHTO T283 method (AASHTO 2010) and its modification. The original method was modified in such a way that instead of a single freeze-thaw cycle, 50 and 150 cycles were applied. Fatigue life is measured in the indirect tensile fatigue test in the Nottingham Asphalt Tester (NAT) apparatus. The asphalt concrete specimens are prepared in laboratory. Some specimens contained a liquid adhesive agent, namely, fatty amine, and others did not. The detrimental effect of water and frost is clearly identified. Also, the results of field condition survey of existing pavements and the results of laboratory tests on water and frost resistance of samples cored from the these pavements are also presented.

The papers in this themed issue all show that the use of innovative technologies and materials are key to the development and maintenance of civil infrastructure. We thank the authors who have contributed to this issue and the reviewers that have worked diligently to upkeep the quality of the papers presented here.