Application of Nanotechnology in Pavements, Geological Disasters, and Foundation Settlement Control Technology

Due to an increasing rate of traffic volume and truck loads in recent years, neat asphalt binders are often modified with expensive polymers for increased stiffness. Nanoclays, conversely, are relatively inexpensive and naturally abundant, and have favorable intrinsic properties (e.g., nanoscopic size and surface area). Although the stiffness of nanoclay-modified binder is reported to increase, its moisture resistance remains unknown. To this end, the current study investigated moisture resistance of a performance grade binder (PG 64-22OK) modified with different dosages of a selected nanoclay (Cloisite® 15A) through the surface free energy (SFE) technique. The state of dispersion of the nanoclay in the binder was examined using a scanning electron microscope (SEM) and small angle X-ray diffraction (SAXD) techniques. The cohesive energy of nanoclay-modified binder was found to be lower than that of the base binder. The adhesive energy between eight different aggregates (sandstone, gravel, granite, basalt, and limestone from four sources) and 2% nanoclay-modified binder in dry conditions decreased up to 22%. The adhesion energy in wet conditions reduced up to 24%. The compatibility ratio (CR) values of different aggregates with the nanoclay-modified binders show significant decrease in bond strength in cases of all aforementioned aggregates except granite.

Nanotechnology is the term used to cover the design, construction, and utilization of structures with at least one dimension measured in nanometers. Initially developed in the fields of physics and chemistry, nanotechnology has established itself as an inter-disciplinary science. However, for the technology to have practical effect the advancement of humanity, it needs to be applied in areas such as the engineering fields. This paper focuses specifically on current and potential developments in the field of pavement engineering where the unique properties of nanomaterials may be used for the betterment of this field, based on identified needs and challenges in pavement engineering. It is demonstrated that there are several areas where nanotechnology can complement pavement engineering, first, through the development of improved materials to be used in pavement constructions and second, through the use of characterization methods to improve the understanding of the materials. Examples of current and planned research in these areas are cited and discussed. Finally, current challenges in exploiting the unique properties of nanomaterials in pavement engineering are indicated and discussed.

A tack coat provides necessary bonding between pavement layers to ensure that they behave as a single system to withstand traffic and environmental stresses. Poor bonding at the interface lead to slippage failures. Even if the tack is applied correctly to the surface, the material is often picked up and contaminated by construction traffic. This study conducted a literature search to examine the major trends shaping the future and the trends' interrelationships with pavement engineering. It is believed that this will promote a framework for a research program that will address long-range strategic issues facing the pavement engineering community. Thus, transportation agencies will be better prepared to respond to new and emerging challenges. Many different transportation authorities reported the successes of utilizing trackless tacks. One of the emerging technologies on trackless tacks is utilizingnanotechnology to provide modification to the traditional tack through adding additive called nanomaterial. Although limited results are available, it appears thatnanotechnology has high potential to be used in trackless tacks.

This paper presents the research results of asphalt modification with a MWCNT/SBS nanocomposite, the preparation of nanocomposite asphalt mixes, some rheological properties of the modified asphalts, their microstructural characterization, and the dynamic evaluation of the asphalt mixes. The rheological properties of the modified asphalts were comparatively studied to choose the best composition to prepare the asphalt mixes. The microstructure of the SBS polymer nanocomposite and the nanocomposite modified asphalt were studied using a scanning electron microscope (SEM). A good dispersion of nanotubes was observed in the nanocomposite modified asphalt, as well as a progressive increase in the diameter of the nanotubes in the nanocomposites. From the experimental results, there is a positive influence of the nanotubes dispersion in the aging resistance of the modified asphalt. Asphalt mixes prepared with this new nanocomposite modified asphalt are not susceptible to moisture damage (tensile strength ratio = 97%), experienced 68% of the permanent deformation of the mixes prepared with plain SBS modified asphalt. The results further showed that the nanocomposite modified asphalt-binder can be used to prepare high modulus asphalt pavements with Pen 60/70 asphalt-binder.

With the development of expanding economies, waterway transportation has become the main transportation means in the process of international trade and domestic trade. When it comes to sustainable development, waterway transportation plays an important role in promoting the development of the national economy. Based on the sustainable development theory, its characteristics in China are analyzed in this paper. According to the characteristics of the economic development of developing countries, a comprehensive analysis of the sustainable development system was given. Some conditions of development of waterway transportation in recent years, especially 2013, were analyzed here. The evaluation criteria of sustainable development was put forward followed the general principles and special principles, respectively. Some mathematic methods were used here to carry out the synthesis evaluation. The conclusions can apply to quantitative analyses of the existing waterway transportation modes in China for sustainable development. Moreover, some policy recommendations are also given, which may have a role in guiding the development of waterway transportation in developing countries.

Derailment is one of the most hazardous occurrences affecting the safety of railroad cars that must be prevented. The potential threat of derailment could be especiallysignificant when length of tangent between vertical curves isn't long enough. Although the length of tangent between vertical curves could be relevant to railway safety, no research had been conducted to study its effect on derailment risk. The primary objective of this paper was to investigate the effect of tangent length between vertical curves on derailment. This study consisted of three major components: (1) review of 1999-2008 derailment reports in Iran, (2) a regression analysis, and (3) recommendation model for estimating the probability of derailment, based on the tangent length between vertical curves and the number of cars derailing. The most important finding from this research is the statistical significance of tangent length between vertical curves on railway safety. Analysis confirmed that the shorter length of tangent between vertical curves results in more cars being derailed.

The highway consists of roads that lack good management. Poor road management usually is the cause of government compensation cases due to vehicle accidents. To improve this, many cases were collected and studied to draw the following conclusions. First, this research divided the causes into six categories of factors that contribute to the damage of the roads: rock fall, bridge rupture, surface of road, gutters, trees beside the road, and traffic signs. Second, this research suggested 18 actions, divided into six categories as solutions. Because of limited budget, the government is limited in the actions it can take; however, this study uses the fuzzy analytic hierarchy process (AHP) method to prioritize these actions, taking into account technology, policy, economy, and 11 other subreferences. The main findings in reducing national compensation for provincial highway construction flaws show that the priority rankings for improving road defects are based on defuzzification value: (1) strengthen inspection procedures and standards, (2) remove weathered branches, (3) add warning signs, (4) design for earthquakes, (5) manage contractors, (6) improve gutter flow, and (7) inspect after big disasters. The contribution of this study is able to set up a model to evaluate the priority of actions under a budget limitation.

Dynamic compaction is an economical and effective method to improve foundation conditions. When widening the highway foundation, it is unclear whether the law of dynamic compaction vibration affects the original subgrade and structure, which restricts the use of dynamic compaction technology in the highway foundation-broaden project. By using free losslesss audio codec (FLAC) 3-D numerical calculation software, a dynamic compaction vibration finite difference model was built to analyze the dynamic compaction vibration propagation law of the roadside foundation in the subgrade and pavement structure. At the same time, the vibration acceleration of the key points and the rammer subsoil dynamic pressure value were made as double assessment indicators. The dynamic compaction vibration response of the subgrade and comprehensive evaluation of the foundation reinforcement effect with different parameters were obtained. Through the indoor model test, the reliability of the numerical analysis was verified. The tamping energy of 1500 KN m, drop height of 6 m (corresponding rammer weight of 25T) and rammer diameter of 1.5 m or 2 m are used in the test. The result showed that a good foundation reinforcement effect can be reached as well as the minimal vibration effects on the surrounding environment. Compared with flat terrain, the dynamic compaction vibration acceleration attenuation at embankment toe is more significant. For all, the pavement structure vibration accelerations tended to be a rapid decay. The medial maximum acceleration reached to 3.9m/s2. The compaction vibration's acceleration of road base and sub-base does not significantly change, which both are less than the surface layer.

One of the predominant distress failure modes in cement treated base (CTB) pavements currently in Zambia is reflective cracking that typically reflect through the bituminous or hot-mix asphalt (HMA) surfacing layer. CTB materials are generally prone to shrinkage cracking, and this is considered to be one of the primary sources of reflective cracking mechanism in CTB pavements. The perpetual and premature occurrence of this distress is an undesirable financial burden on the Zambian taxpayers in terms of the costly road maintenance and rehabilitation activities that ought to be minimized. This paper is a theoretical and analytical discourse on the causes of this distress and recommendations for mitigation measures based on studies by different researchers worldwide. Remedial measures such as proper materials selection, optimizing mix designs, following proper construction, compaction, and curing practices, providing stress relief layers in the pavement structure, and delaying the final surface paving to facilitate adequate curing, and micro-cracking have been reviewed and assessed for their potential applications to CTB pavements in Zambia. The paper then concludes with a recommendation of mitigation measures that are feasibility considered applicable to the Zambia CTB needs for subsequent implementation by the Road Development Agency.

The main objective of this paper was to study the dynamic performance of seals of the hydraulic steel sluice gate by experiments. Some modifications which involved of top, side, bottom, and rotation hinge of the water seal were done to seek and testify the reasonable shape and facilities. Then, the water sealing experiments with different conditions were performed. It is indicated that the preset compressive deformation of various water seals is changed along with the different water head. Moreover, the transformation law of the preset compressive deformation of different sealing parts under the reservoir water head was discovered.

Almost all aspects of geotechnical engineering are present in harbor works, namely foundation engineering, stability problems, above and under water, dredging, and the knowledge of sediments features, both geotechnical, key to define the type of dredger to use, and gradation and composition, since the chemical and organic contamination of those sediments define the final destination of the dredged material. But cliffs are also important, because often they overtop the harbor facilities and/or their accesses. One must also emphasize the presence of soft soils and the necessity of their improvement, related to structure and engineered fill foundations. Underwater embankments and their particular construction processes and quality control are also central. This paper presents the main geotechnical aspects of the Portuguese small harbors, detailing three major concerns: dredging, cliff stability and foundation of structures, and embankments on soft soils.

To intensify freezing local strata, a scheme of a reaming borehole filled with heat conductive material is proposed. The artificial freezing lab tests are conducted to freeze high-water-content sandy soil by covering heat conduction materials on the surface of freezing pipes. Meanwhile, the free lossless audio codec (FLAC) 3-D numerical simulation is respectively adopted to predict the temperature fields of two cases of the common freezing pipes and the freezing pipes covered with heat conductive materials. The differences of freezing effect are contrasted in detail. The results indicate that freezing pipes covered with heat conduction materials show very good freezing efficiency than that of common freezing pipes. After freezing 36 h, it can consume more cold energy by 30%, increase the thickness by 40%, and reduce the average temperature by 3.2°C of frozen wall. Local difficult-to-freeze strata accordingly can be frozen efficiently and excavated safely with the intensified freezing scheme.

A linear, multiple degrees of freedom (MDOF), lumped-mass model was used to simulate the linear propagation of longitudinal wave (P wave) during static phase change during carbon dioxide (CO₂) injection in a multilayered elastic media. The most critical modeling consideration is the multiphysical phase change at the oil producing layer, which is simplified into stiffness reduction in the model. Five cases were studied with the stiffness of oil bearing layer changes as 100%, 90%, 80%, 70% and 60% of its original stiffness.

The engineering, geological, and hydrogeological conditions of a tunnel project, which lies in a karst area, are extremely complex for kasrt and kasrt water bursting disasters. Using formation lithology, geological structure, terrain and ground feature, surface drainage, underground drainage,elevation of tunnel design, and other considereations as the main judgment factors, along with a comprehensive index method basied on hierarchical analysis for tunnel risk assessment of karst water geological disasters, and applying this to engineering practice, it is helpful to improve the prevention and management of karst water bursting disasters.

Using the RMT-150c rock mechanics test system, the triaxial compression tests for jointed soft rock were carried out under different confining pressures, and the compression mechanical properties of jointed soft rock were obtained. The results showed that the strength parameters, the elastic and deformation modulus of jointed sample are lower than that of an intact sample, which denotes joints affecting the strength and deformation properties of soft rock remarkably. Specifically, the sample peak strength with different jointed dip angles linearly increased with the confining pressure going up, and the sample peak strength with dip angle 60° is lowest. The sample elastic and deformation modulus with different jointed dip angles increased with the confining pressure going up, which makes it unlikely that the relationship is linear. Moreover, the sample shear failure angle with different jointed dip angles have a negative linear relation with the confining pressure.

This paper centers on the slab ballastless track widely used in China high-speed railway, using ABAQUS finite element software, establishes double-track high-speed railway vehicles-track-roadbed system secondary vertical coupling dynamic finite element model, and systematically analyzes the temporal-spatial distribution of subgrade bed vertical displacement in the situation that China Railways High-speed 3(CRH3) trains run in opposite directions. The result shows that when the distance of two trains running in opposite directions is more than 35 m, vertical displacement in the middle section of bedding is zero, which means that train load has no effect on the bed in the middle of longitudinal spacing. When the distance decreases from –20 m to –120 m, the vertical displacement decreases in oscillation type and gradually tends to zero finally. The vertical displacement peaks atthe center of a single line. There exists an inflection point where vertical displacement significantly decreases at 4.11 m away from centerline of double-track subgrade. Bedding bottom vertical displacement transverse distributions along the route tend to be more even and basin-shape. Within the scope of 7.2 m from the bedding surface, the increase of vertical displacement along the depth basically decays linearly. In the range of 7.2 m to deeper, the attenuation of vertical displacement is relatively slow.

The distribution of peat deposits can be found in many countries and peat-land constituents from 5-8% of earth land surface, where approximately 60% of the wetlands are peat. An increasing growth of the population leads to the necessity of peat-land utilization for development purposes. This article describes a laboratory study on the effect of different binders on the settlement of fibrous peat. The effect ofsodium silicate, ordinary Portland cement, and kaolinite on the settlement of peat is investigated through the Rowe Cell consolidation test. At the end of this study, it is shown by increasing sodium silicate (within 2.5%), cement, and kaolinite on treated peat, they are able to improve settlement of fibrous peat much more than conventional binders such as pure cement.

Railway engineering has rapidly evolved to accommodate higher speed and heavier transport loads in a timely fashion. This trend brings attention for railroad engineers to come up with an effective track structure design that minimizes frequent maintenance activities and prolongs service lives. In this study, the effectiveness of georeinforcement techniques for track substructure enhancement, such as cement treated subballast, asphalt subballast, and application of geosynthetics, is evaluated via a limited numerical analysis in terms of thickness design that related to material savings. For the evaluation of track substructure thickness design, a threshold stress approach is employed that gauges tie-ballast contact stress and vertical stress at the top of subgrade layer. It is envisioned that the application of geo-reinforcement for track substructure appears to be effective in improving the load-bearing capacity that results in reduced substructure thickness. Further studies need to be conducted to develop a logical mechanistic railroad design procedure to account for use of various types of reinforcement methods.

An experimental study on engineering characteristics of the thicker soft-soil composite foundation preloading was developed in the throat area of a high-speed railway station, which mainly includes variation of excess pore water pressure, settlement deformation, and pile-soil stress with time in different positions and depths. It can provide a theoretical basis for related engineering design and construction. Some consolidation characteristic laws of composite foundation were obtained: (1) Excess pore water pressure of composite foundation increases with the growth of load. After excess pore water pressure peak appears, it will disappear with time. The change of excess pore water pressure lags behind load. Excess pore water pressure obtained maximum value at the top of substratum, where additional stress is larger. With the growth of depth, excess pore water pressure decreases gradually in substratum; (2) Ground settlement and layered settlement have the same rule of 35 m pipe pile decreasing the settlement at the middle throat area of a railway station. The settlement obtained maximum value in the middle of the reinforced area with 25m CFG pile; (3) Pile stress, soil between piles stress, and pile-soil stress ratio have a decreasing trend from the center embankment to the edge. In the process of filling and preloading, stress transfers from soil to pile. Pile stress increases, and soil between piles stress gradually decreases.

The Terreiro do Trigo dockyard at the Jardim do Tabaco was filled to allow the construction of the new Santa Apolönia cruise terminal in Lisbon at the Tagus River right bank. A load transfer platform (LTP), founded over jet grouting columns, allowed the construction of a 4.2 m height hydraulic embankment, placed over a soft muddy alluvium layer (Cu lesser than 20 kPa) with about 20 m of average thickness. The existent dockyard peripheral centenary walls were previously refurbished and underpinned using micropiles and capped by reinforced concrete beams,to accommodate the new embankment earth pressures. The main design and execution criteria, including the quality control and quality assurance of the jet grouting columns are presented, as well as the main results of the adopted monitoring and survey plan. Finally, the technical and economic advantages of the adopted solutions, comparing with some more conventional ones, are presented.