Innovative Materials and Design for Sustainable Transportation Infrastructure

This paper focuses on the improvement of thermal properties such as thermal conductivity, thermal diffusivity, and specific heat of asphalt mixtures using conductive fillers, and investigating the conduction performance by one-dimensional (1-D) simulation on pavements. Different asphalt mixtures used in this study was modified with milled carbon fiber, chopped carbon fiber, flake graphite powder and synthetic graphite powder individually. The conductivity properties of graphite and carbon fibers modified asphalt mixtures was measured and calculated to evaluate their conduction effects in order to obtain the appropriate kind and quantity of carbon fiber and graphite. The 1-D simulation was performed on a typical pavement design using finite difference method to comprehend the conduction performance taking place in pavement structure. Thermal testing and analysis results indicated that carbon fibers and graphite basically increase the thermal properties of asphalt mixtures. The simulation results presented the reliable heat conduction correlated with each conductive fillers.

The oxidation mechanism in polymer-modified bitumen tends to alter physical and chemical properties. In this study five anti-oxidants are evaluated to examine their potential to mitigate polymer-modified bitumen oxidation. Styrene copolymers and hindered phenol additives are evaluated at low, intermediate and high temperature using aging indices. The styrene copolymers were effective at high temperature while the hindered phenols were effective at low and intermediate temperature. Two blends of both additives were introduced to cover a wide spectrum of temperature. Frequency and temperature sweep testing suggested that the blend improved the recoverable imposed energy at wide range of temperature/frequency. The blends have also improved resistance to rutting and moisture susceptibility for the asphalt mixes.

In 1999, the Arkansas State Highway and Transportation Department (AHTD) began an ambitious program to rehabilitate over 300 miles of Interstate in 5 years. As part of this rehabilitation program, approximately 270 miles of deteriorated concrete pavement was rubblized and overlayed in an attempt to provide a sustainable alternative to traditional removal and replacement of the pavement structure. Many of the pavements constructed during this program are exhibiting a severe level of cracking. Most of these severely cracked asphalt pavements are located west of Conway on Interstate 40; while the rubblized pavements east of Little Rock on I-40 and I-30, which were constructed at virtually the same time, exhibit much less cracking. In this research, two interstate sections are compared. One section was evaluated as “good” condition and the second “poor” condition. A full forensic analysis included a review of the job diaries, rutting and cracking development over the life of the pavement, mix design, mixture testing from cores, and binder testing from cores. Several properties are currently being evaluated and discussed with AHTD in order to prevent future premature deterioration of the state highway network.

Engineering designs in cold regions should consider the influence of the frost heave of the ground. In such regions, the classification and evaluation of the frost susceptibility of rock mass is significant in the design of constructions. A calculation method for the frost heave ratio of rock is obtained by fitting the experiment data. The typical dilation of a saturated fracture is discussed, and the linear frost heave ratio of the fracture is provided. The frost heave ratios of different grades of rock masses are computed by simplifying the rock fracture morphology as “layered”. The frost susceptibility of rock mass is classified into non-frost susceptible, weakly susceptible, moderately susceptible, strongly susceptible, and very strongly susceptible according to frost heave ratio, based on the frost heaving classification of the soil. Rock masses are non-frost susceptible to weakly susceptible in deformation-based construction designs. In force-based designed constructions such as tunnels and caverns, grades I—III rock masses are non-frost susceptible to weakly susceptible, whereas grades IV—V rock masses are non-frost susceptible to very strongly susceptible. The frost susceptibility of rock mass can be evaluated according to the porosity of the rock, the grade of the rock mass, and the frost heave susceptibility of rock and fissure filler. The frost susceptibility of the surrounding rock in two cold-region tunnels are assessed, and the results provide references for anti-frost damage design of the tunnel.

The use of chemical deicers in cold regions has raised concerns over their potential negative effects on the performance and durability of concrete infrastructure. Extensive studies have been conducted in the laboratory setting, often in an accelerated manner, which reported the chemical and physical deterioration of concrete as a function of deicer type. Yet, little research has been published on how the deterioration of concrete bridge decks in the field environment is affected by their exposure to deicers, where the durability of concrete is also affected by temperature cycles and mechanical loadings. This work reports a comparative study of field cores taken from two select Nebraska concrete decks and from two select Utah concrete decks. The Nebraska decks had been exposed to mainly potassium acetate (KAc) deicers, whereas the Utah decks had been exposed to mainly sodium chloride (NaCl) deicers. The field cores were tested for their mechanical properties and transport properties. They were also subjected to staining tests to detect possible chloride penetration, carbonation, and aggregate silica reaction (ASR), and subjected to petrographic analysis to characterize their paste and air contents. The concrete cores from Nebraska exhibited more significant degradation, relative to those from Utah. Specifically, the exposure to KAc deicer led to significant reduction in mechanical properties (compressive strength, splitting tensile strength, and microhardness) and more signs of ASR. This case study sheds some light on this complex issue of concrete durability and raises the awareness over the risk of using KAc deicers on concrete structures and components.

Pervious concrete pavements are designed to allow rain water to percolate through the pavement voids and reduce runoff water and splashing. One of the problems of pervious pavements is clogging. This study evaluated pervious pavements cleaning methods and presents findings from a study conducted on a fourteen-year old pervious concrete parking lot. For this study, cores were taken from the existing pervious concrete parking lot, and the falling head test was performed on the samples: as cored, swept, and pressure washed. Sweeping removed little debris from the surface, but did significantly increase the infiltration. Pressure washing removed a relatively significant amount of debris from the samples, and also significantly increased the infiltration rates. The samples were then broken to determine remaining debris, since pressure washing did not completely remove all debris from the samples. The properties of the debris were compared to the lawn/garden soil around using sieve analysis, cohesion tests, and organics analysis. From The sieve analysis test, the debris was of a similar gradation to the garden soils; however, a presence of particles from the existing asphalt pavement was observed. A cohesion test revealed that cohesion in the removed debris was less than that of the garden soil around. An organics analysis indicated that organic matter in the debris was less than the organic matter in the garden soils. The study found out that pressure washing is more effective cleaning method on pervious pavements and the clogging materials are soils rather that organics matter.

Measurements of carbon emissions and sequestration are important in estimating the global warming potential of the built environment. Manufacturing of portland cement contributes to a portion of anthropogenic CO₂ emissions through the chemical process of calcination. CO₂ can also be sequestered from the air into concrete in the reverse process commonly called carbonation. Most research studies on carbonation typically focus on the exposed surfaces where the levels might be high. There is little information on the CO₂ which might be sequestered in the interior of pavements. Together, the near surface measurements and the interior levels will provide better information on carbon sequestration. Pavement samples that were from one to 85 years old were sliced and paste/mortar specimens were chipped from different depths. CO₂ sequestration was estimated using a thermo-gravimetric analysis (TGA) for the carbonate levels and X-ray fluorescence analysis (XRF) for elemental analysis. The results indicate that the amount of carbon sequestration in the interior of these pavements is in the early years of life around 10% of that released during calcinations increasing to 25% or more in arid climates. Interior carbon sequestration in humid climates might exceed 35% or more over several decades, but more information is needed to validate this.

This paper presents pervious concrete mixed with silica fume used to evaluate the role played by silica fume in enhancing the performance of the pervious concrete including compressive strength and freezing and thawing resistance. The purpose of this paper is to determine a set of promising pervious mixtures that can be used to withstand the cold climate of Flagstaff, AZ and can be adopted by agencies in Northern Arizona.

A research project was conducted to investigate the feasibility of replacing sulfate-resisting cement with locally available fly ash or slog to produce sulfate resistance concrete in northwestern China. This paper presents the durability results (sulfate resistance and impermeability) of the concrete made with varying contents of fly ash or slag. The sulfate resistance and impermeability properties of the sulfate resisting cement concrete (SRCC) were compared to those of ordinary portland cement concrete (OPCC). The test results show that SRCC had a better sulfate resistance than OPCC with the same mix proportions and the improvement in sulfate resistance ranged from 5% to 10%. Adding fly ash could enhance sulfate resistance of concrete, but not as good as adding S95 slag. Adding S75 slag adversely affected sulfate resistance of concrete. The impermeability test results show that fly ash could improve the impermeability of concrete, whereas S75 slag reduced impermeability.

Due to low precipitation and high evaporation, the soil and underground water in the vast northwest of China are rich in sulfates. In order to made durable concrete for pile foundation, it is required that either a special admixture (called “CM” admixture) or sulfate resistant cement (SRC) be added/used to improve the sulfate resistance of concrete. This study investigated the possibility of replacing CM admixture with local fly ash to make durable concrete piles. To achieve this goal, a series of laboratory tests were conducted to investigate the workability, mechanical and chemical properties, as well as the durability of concretes with different cementitious materials under sulfate attack. Based on the test results, the fly ash concrete had the lowest hydration heat and permeability while maintained good mechanical properties and workability. Additionally, use of fly ash provides a cost-effective and sustainable approach in concrete pile construction. Therefore, it is recommended that local fly ash be added in concrete piles in lieu of the CM admixture.

Under the complex environment of soils, rocks and underground water, the challenges in the repair and maintenance of urban metro structures confront engineers daily. The use of microcapsule-enabled self-healing cementitious composite has high potential as a new repair method for cracked concrete under complex service conditions. The benefit of using microcapsule-enabled self-healing cementitious composite will evidently provide extended durability, service life and security for the metro tunnels. In this study, the self-healing microcapsules enclosing epoxy resins as the adhesive agent are embedded in mortar to achieve the self-healing capability. The properties of healing agents are investigated. The microcapsules are observed by SEM (scanning electron microscope) to obtain the micrographs. The self-healing efficiency is assessed by mechanical restoration of the damaging specimens. The four-point bending test is used. The influence of the content of microcapsules and initial damage is investigated. The results demonstrate that the microcapsule-containing mortar can achieve the mechanical restorations depending on the content of microcapsules and initial damage. Some conclusions about the healing agents and the shell are drawn.

Microcapsule self-healing concrete as a new promising method to decrease the degradation of concretes and enhance the performance and prolong the service life of concretes has been viewed in the article. Abundant progress on many aspects of self-healing materials cooperating microcapsules indicates that the microcapsule self-healing concept is reasonable and the self-healing process truly occurs. The focus of this paper is to investigate the agent’s transportation in microcapsule self-healing concrete. Although little previous work has been made on the topic, two main conclusions can be obtained from the analysis of the previous work. Firstly, the agent’s transportation can be separated from other self-healing processes such as microcapsule cracking and curing reaction, which will provide a much simpler physical model when simulating the process of agent’s transportation. Secondly, microcapillary absorption is supported to be the prime driven force for the agent’s transportation in microcracks. Relative work on the capillary absorption in concrete and microchannel has been discussed to furtherly understand the movement and kinetic mechanism of the agent’s transportation in microcapsule self-healing concrete.

Berming is a common nationwide practice for pavement shoulder maintenance. Quality berming improves the capacity of pavement shoulders and prevents traffic accidents. Results of a nationwide survey show that there is a major desire to improve the safe and effective berm compaction. Emerging new equipment is being developed by Ohio DOT in-house and private industry that uses self-weight and vibratory plate to compact berm materials. An experimental study was conducted on four types of berm materials to evaluate the compaction effects using proctor or vibratory compaction. The effects of compaction energy level were evaluated by measuring the physical, mechanical and electrical properties. Particularly, NDTs were conducted to identify the best indicator on the quality of compaction. The experimental results indicate that vibratory compaction is effective for crushed limestone berm. The asphalt coating on RAPs might reduce the effectiveness of vibratory compaction. Natural soil berm is not well compacted by vibratory compaction. Heat treatment of RAPs up to 60°C did not significantly increase the material compaction or inter-particle adhesion. Wave speeds and Young’s modulus are found to be sensitive indicators for compaction energy levels. The electrical properties, which Ground Penetrating Radar is based on, are not sensitive to different compaction energies.

The media filter drain (MFD) or Ecology Embankment is a best management practice (BMP) approved to treat copper and zinc in highway runoff in many states. High levels of these metals may impact coldwater aquatic species in receiving waters. The MFD was originally based on a gradation of aggregate no longer readily available in Washington State and this research investigated substituting the original aggregate specification with a more widely available AASHTO Grading No. 8, which has slightly fewer fines. Results indicate that the MFD is effective at removing dissolved copper and zinc using the alternate aggregate specification in the MFD mix. Column experiments were used to show that the alternate MFD mix had a higher median removal rate than a suite of typical stormwater control BMPs for both dissolved zinc and copper, qualifying it as an enhanced treatment method. In addition, it was shown that the MFD mix design can be loaded with dissolved metals for at least 14 years with no loss in performance, even when subjected to larger storms. MFDs built with a wider range of aggregate gradations may be more economical in other regions based on standard aggregate gradations available.

Polymer geosynthetics exhibit obvious viscous behaviors related to the loading strain rate. A nonlinear three-component elasto-viscoplastic constitutive model is found relevant to simulate these rate-dependent load-strain behaviors of polymer geosynthetics under complex loading conditions, including variable loading rate, creep and stress relaxation. For the purpose of the wide use of this model, it is implemented into the finite element analysis software ABAQUS through its user material subroutine (UMAT) connector. The algorithm used for the numerical integration of the constitutive model is return mapping method and is presented in detail in this paper. Then FEM simulations are performed to validate that this model is very capable of simulating the viscous behaviors of geosynthetics under arbitrary loading conditions.

Two fundamental issues exist in the damage theory of geo-materials based on the concept of thermodynamics: existence or nonexistence of the dissipation potential, and whether the dissipation potential could be decoupled into a damage potential and a plastic one or not. Thermodynamics theory of elastoplastic damage assumes the existence of dissipation potential, but the presence of dissipation potential is conditional. Based on the dissipation inequality in accord with the second law of thermodynamics, the sufficient and necessary conditions are given for the existence of the dissipation potential separately in total and incremental forms firstly, and proved strictly in theory. With taking advantage of the basic mechanical properties of geo-materials, the nonexistence of the dissipative potential is verified. The sufficient and necessary conditions are also given and proved for the decoupling of the dissipation potential of geo-materials in total and incremental forms. Similarly, the non-decoupling of the dissipation potential has also been proved, which indicates the dissipation potential of geo-materials in total or incremental forms could not be decoupled into a dissipative potential for plasticity and that for damage respectively. The research results for the fundamental issues in the thermodynamics theory of damage will help establish and improve the theoretic basis of elastoplastic damage constitutive model for geo-materials.

To investigate unsaturated soil behavior during consolidation under K0 condition, a new undrained oedometer cell with matric suction measurement ability was developed based upon modifications on a conventional oedometer. A high-suction tensiometer was equipped to monitor matric suction variation during loading under undrained condition. Soil volume change during testing was recorded by a local displacement transducer. To validate the performance of this new oedometer cell, an undrained oedometer compression test was performed on an unsaturated soil specimen. Some preliminary results were obtained which included soil suction and volume variation during K0 loading. Test result indicated that the proposed system is very efficient and suitable to be utilized for unsaturated soil behaviors evaluation.

Sustainability of transportation infrastructure is influenced by how construction and geological materials respond to varying environmental conditions. A number of recent construction projects in Ohio have experienced significant sulfate induced heaving in cement stabilized soils. The involved mechanisms have been linked to the formation of ettringite as well as osmosis induced swelling. This paper presents a chemo-mechanical approach to better understand the expansive behavior of stabilized sulfate bearing soils. The interplay between different mechanisms is examined in numerical simulations based on recently reported experimental results. The simulation results show that ettringite formation and osmosis swelling can play comparable roles in the heaving process. The kinetics of osmosis is also explored and the modelling results are consistent with the experimental observations.

This paper is concerned with the mechanical properties of compacted silty clay subjected to freeze-thaw in cold regions. A series of unconsolidated-undrained triaxial compression experiments were conducted on compacted Harbin silty clay to investigate the effect of confining pressure, number of freeze-thaw cycle, initial compaction degree, and initial water content on the stress-strain relationship, failure strength and tangent modulus. The results show that the normalized failure strength and tangent modulus are stable after three freeze-thaw cycles, and increase with the increase in initial compaction degree and reduction in the initial water content. Finally, the modified parameters and six functions were proposed to consider effects of influence factors and were implemented into the empirical model of failure strength and tangent modulus. The validations show the calculated data get well agreement with experimental data.

Geotextiles have been widely used in soil structures such as road, embankment and reservoir as a drainage material. The aim of this paper is to give a comprehensive review of the characterization of geotextile hydraulic behavior in the past and present. The review includes the wetting and wicking theories, the hydraulic behavior characterization techniques, and the application of unsaturated soil mechanics in geotextile hydraulic behavior. Wetting and wicking are two coupled phenomena that drive the liquid to flow in geotextiles. Capillary pressure and permeability are two major parameters to characterize geotextile hydraulic behavior. The upward-horizontal-downward (UHD) characterization method can be used to quantify those parameters. However, the geotextile may not drain the water as originally expected under unsaturated conditions. Unsaturated soil theory provides as an effective tool to explain and evaluate the hydraulic behavior of geotextile in unsaturated condition. Unsaturated geotextiles not only can serve as drainage material (within transient stage), but also as capillary barrier (within boundary effect and residual stages).

Recently, a novel photogrammetry-based method has been developed for unsaturated soil deformation measurements during triaxial testing. This method provides a simple and cost effective alternative to the conventional double-wall cell method. In this study, a validation test on a saturated sand specimen was conducted to evaluate the accuracy of the newly developed photogrammetry-based method. A sensitivity analysis was also carried out on the impact of the system parameters (i.e., cell wall thickness, refractive indices of water and cell wall) on the overall measurement accuracy. The refractive index of water was found to have the most significant impact on overall measurement accuracy of the photogrammetry-based method.

Cylindrical shafts have been widely used in practice with prominent structural superiorities, primarily because of the spatial arching effects resulting from their circular retaining structures. The behaviors of cylindrical shafts were investigated via three-dimensional finite element analyses of two circular excavations for anchorage foundations in suspension bridge engineering. By comparing the FE-predicted results with the field measurements, the accuracy and reliability of the numerical models were verified. Additional calculations were also performed to study the influence factors of circular retaining structures. The following major findings were obtained: (1) The stresses in both the diaphragm walls and lining walls are relatively small, indicating that the arching effects of circular and double circular retaining structures are significant; (2) The main function of the lining walls is to enhance the rigidity of the diaphragm wall and to constrain its displacements, so the decrease in the lining wall thickness, the shape variation of the retaining structures and asymmetrical excavation make little difference to the structure stress. (3) The temperature change during circular or double circular excavation has a great influence on the stresses of the retaining structures.

The key to the project of lunar regolith sampling lies in the interactive mechanism between drilling implements and lunar regolith under special circumstances of lunar surface. Targeted at mechanical properties of CAS-1 lunar regolith simulant under low stress levels, the tri-axial test, direct shear test and compression test were carries out. Research findings show that: (1) Under low stress levels, when void ratio e ranges between 0.8 and 1.1, the value of cohesion c is 2.8~5.0 kPa and internal friction angle φ 39.84°~41.09°, and the compression curves show varying features of first upward concave and then downward concave; when e ranges between 0.9 and 1.1, initial compression modulus E₀ is 12.647~3.923 MPa, and the stress-strain curves consist of hardening and softening stages. During the softening stage, the decreasing rate is faster, and the stress ratio is concentratively distributed along the curves. (2) Under low stress levels, the smaller the value of e, the larger the peak deviator stress/stress ratio and the smaller the peak axial strain, but they all range between 2% and 5%. (3) The initial tangent slope α, peak stress ratio η_f and residual stress ratio η_r are all log-linear to the confining pressure P₀, but under low stress levels, α falls slowly, and the initial tangent modulus G_i(1/α) changes within a smaller range, whereas η_f and η_r fall faster.

This paper presents tunnel construction in caved karst strata base on the metro subway project between Maanshan Park station and Liantangnan station (Ma-Lian section) of Guangzhou metro line No. 9. The karst is highly developed with 98 karst caves along the tunnel route. The soil in the tunnel zone mainly consists of soft residual deposit, sand and slightly weathered limestone, which are unstable during construction. Complicated ground conditions were encountered during tunnel excavation, such as upper-soft-lower-hard ground, sand layer and caved karst. Geological risks including sink holes, water or stone ingress, and damage to constructed tunnels and the shield may occur during tunneling in the project of Ma-Lian section. Construction problems may be encountered during tunneling excavation, such as caved karst treatment and tunneling in complicated ground. Recommended solutions and modifications are proposed to solve the above problems.

The excavation of mountains due to the construction of infrastructures not only deteriorates the ecological environment but also causes severe secondary disasters, such as soil erosion, landslide, and debris flow. Therefore, the reinforcement and ecological protection of the high-steep slopes are important and attract more attentions from researchers. In this study, the bolted and seeded-geomat protection (BSGP) technology, which combines rock bolts with geomats which have seeding, was applied to stabilize an unstable high-steep slope. The erosion rate of the surface soil on the slope was analyzed based on the field-collected samples and laboratory test data. The influence of the slope angle, geomat type, vegetation type, and bolt spacing on the erosion rate under different rainfall intensities were investigated by orthogonal tests. The results indicate that the slope angle controlled the erosion rate of the slope and the geomat had more effects on the decrease of the erosion rate as compared with other variables.

Geosynthetics, factory-manufactured polymer materials, have been successfully used to solve many geotechnical problems in civil engineering. Two common applications are earth reinforcement and erosion control. Geosynthetics used for earth reinforcement include but are not limited to reinforced slopes, walls, embankments, and roads. Geosynthetics used for erosion control are mostly related to slopes, river channels and banks, and pond spillways. To enhance environmental sustainability, vegetation is often planted on the facing or surfaces of these earth structures. Under such a condition, geosynthetics mainly function as surficial soil stabilization while vegetation provides green appearance and erosion protection of earth surfaces. Geosynthetics and vegetation are often integrated to provide combined benefits. The interaction between geosynthetics and vegetation is important for the sustainability of the earth surfaces. This paper will provide a review of the current practice and research in the geosynthetic stabilization of vegetated earth surfaces for environmental sustainability in civil engineering with the emphases on geosynthetic-reinforced slopes and geosynthetic-reinforced unpaved shoulders.

Flexible joint is an important part of concrete immersed tunnel as it must be sufficiently flexible and resilient, as well as waterproof. The element tube at the joint is weakened in section to make space for joint construction. This weakened part, called extended shell, is a structural weak area, although it only transmits limited axial and vertical load between elements. This paper is based on an actual project, and investigates the structural performance of extended shell under external load, and its influence on adjacent tunnel structure. For the investigation, a model of tunnel segment at element end is established and analyzed with FEM software ANSYS. From the results, conclusions are drawn that the extended shell is structurally reliable, and does have a certain influence on the stress and deformation of adjacent tunnel structure, which is not considered yet by now. This should be paid more attention in further research and design.

The Quaternary deposits in coastal regions are multi-aquifer-aquitard system with characteristics of high compressibility, high sensitivity, and low shear strength. The metro tunnels have been widely constructed in coastal regions in recent years. The tunnel settles continuously since the metro tunnel operated. This paper gives a general introduction to influencing factors on the longitudinal deformation of metro tunnel in soft deposit in coastal regions of China: (i) regional land subsidence; (ii) shield tunnel construction; (iii) construction of nearby engineering, such as pit excavation, construction of pile, construction of bypass tunnels, etc; (iv) groundwater leakage; (v) dynamic loading of trains. Influence of land settlement, groundwater leakage and train loading is long-term and influence of tunnel construction and disturbance from the adjacent construction is short-term. Since all of these factors interact with each other, the longitudinal deformation of the tunnel is caused by the comprehensive action of the aforementioned factors.

Metro tunnels in the soft deposit often suffer from differential settlement during the long-term operation. The tunnel settlement will cause cracks of segments and opening of the joints, which may lead to groundwater penetration into the shield tunnels. Groundwater leakage may not only lead to degeneration of the infrastructures, but also it causes long-term reductions in pore pressures and associated consolidation settlement around tunnels. Serious groundwater leakage will cause tunnel settlement and accelerate groundwater leakage. In this paper, the analysis methods on the impact of groundwater leakage that adopted in the previous literatures, e.g. field monitoring, analytical method, and numerical simulations, are summarized. The advantages and disadvantages of these methods are also presented. At present, only a few field evidences that groundwater leakage cause reduction of pore water pressure and soil consolidation were obtained. The analytical methods often adopt two-dimensional model under the plane strain conditions with many hypothesis, which make it only applicable for qualitative analysis. Numerical simulation has been commonly conducted by assuming the permeability of the lining remains constant.

The existence of pressure arch of tunnel surrounding rock is while known in engineering. The idea that this pressure arch in surrounding rock is helpful to maintaining tunnel stability is accepted both in engineering and in research. In this paper, variations of surrounding rock stress are investigated by using PFC3D, a concept of dynamic pressure arch in the surrounding rock is proposed, and then the 3D dynamic pressure arch effect around the tunnel is analyzed. The 3D dynamic pressure arch effect will be helpful to judge tunnel stability, choose excavation method in tunneling, accurately determine the loosed load, economically design advancing reinforcement measures and rock bolts.

This paper presents an analytical mechanical model for tunnel boring machine (TBM) tunnel lining segmental joints exposed to fire. Based on the general flat joint model, the model was derived under the thermal effect induced by elevated temperature. A fitting function for describing the relationship among the ratio of concrete deformation, strain in the outer edge of compressive zone of joint and height of compressive zone is proposed using a result from a finite element method (FEM) analysis in which parameters were obtained by calibration against true scale model tests. The concept of temperature adjustment coefficient on joint section is proposed, which improves the calculation method of joint section temperature field. Influence of elevated temperature and axial force on the bending moment characteristic of a segmental joint was examined. The validation of this model was through the comparison with the results of fire tests. This model contributes to comprehending mechanics characteristics of shield TBM tunnel lining joint under high temperature and the design of the joint.

This paper takes the natural ventilated Donghu Tunnel as an example. The tunnel with vents on the roof is numerically simulated to investigate the characteristics in natural ventilation. Cases with different length and spacing of air vents are simulated. Based on the simulation results, history curves of ventilated air quantity in each vent are presented. What’s more, the maximum of exhaust and inlet air rate among all vents is presented. It’s shown that the efficiency of ventilation system increases with more air vents in each group and longer vents. The efficiency doesn’t change apparently while the spacing of vents is changing.

During the long-term service life of high-speed railway, increase of moisture in the subgrade will degrade the performance of the high-speed railway. Cracks on the surface of the subgrade are found in some existing high-speed railways and water will infiltrate into the subgrade through the cracks in rainy days. A numerical model using Geo-studio Seep/W is established to simulate moisture migration in the subgrade. Two cracks are set in the edges of the concrete base. The moisture migration in the subgrade within two years has been calculated. The results indicate that “saturation zone” occurs in the subgrade. The volumetric water content ranges from 10% to 27% in the surface layer and from 20% to 26% in the bottom layer, respectively. The seepage line reaches at the interface of bottom layer and subbase layer after 184 days and stays stable in the remaining 546 days. This is explained by the reason that water can only permeate into the subbase layer with an extremely low seepage velocity and then it accumulates at the bottom of subgrade bottom layer. And this accumulation area has a volumetric water content value of 28%, slightly higher than that in other areas of subgrade bottom layer in the final period.

Analytical design of surcharge preloading schemes on soft soils were performed using the deformation characteristics corresponding to several surcharge preloading tests. To ascertain the reliability of this technique, investigative data were collected during the construction of a passenger dedicated railway line in China to deduce the design specifications and control standards. This was done by establishing an unloading time equation based on regression curve fitting method of the measured data; given that different types of settlement deformation gives corresponding unloading time calculations. Specific methods for the calculation of surcharge preloading and unloading time point for passengers dedicated line in the railway sector were also examined. Finally, measured data from the Wuhan-Guangzhou passenger line surcharge preloaded embankment were used to verify the design validity and reliability. The predicted results matched with the settlement deformation trend and the post-construction settlement strictly meet with the control standards.

In this paper, numerical simulation with soil-water coupling finite element-finite difference (FE-FD) analysis is conducted to investigate the settlement and the excess pore water pressure (EPWP) of a piled-raft foundation for high-speed train (speed: 300km/h) due to cyclic train loading. To demonstrate the performance of this numerical simulation, the changes of the settlement and EPWP of Shanghai soils under train loading within one month was calculated and confirmed by monitoring data, which shows that the change of the settlement and EPWP can be simulated well on the whole. Based on the results obtained in this paper, it is possible for us to predict the long-term settlement and the changes of EPWP far longer time than one month using the proposed numerical method.

Remote monitoring and analysis system for high speed railway subgrade structure in mountainous areas is one of most effective method to ensure the safety operation, which as a strong practical significance. Diagnosis technology scheme for the monitoring of high speed railway subgrade health status in soft mountainous area was developed in this paper. To ensure the reliability of this technology, the use of a combination of intelligent sensor, fast data acquisition, signal processing and wireless communication technologies were adopted. This was done by establishing a point-line-surface, multi-level and multi-objective remote monitoring system for high speed railway subgrade. The monitoring parameters including dynamic soil pressure, settlement deformation, inclination and rainfall information are determined using data acquisition card. Data acquisition and wireless communication were obtained through an industrial computer and a 3G/GPRS technology. Client/server for the controlling of remote monitoring system was developed based on the Visual C++ network programming technology and the Access 2010 database platform. The server controlling software also analyze data for the provision of technical support for realizing the target of early warning forecast for high speed railway structure.

A full-scale chilled gas pipeline experiment was conducted in Fairbanks, Alaska to develop the design criteria for pipeline construction in arctic regions. The test pipeline had a length of 105 m and a diameter of 0.9 m. One-third of the pipeline was located in permafrost and the remaining was in non-permafrost. The monitoring data were collected from December 1999 to January 2005 including both freezing and thawing phases. In the transition zone between frozen and unfrozen soil, the foundation material experienced a vertical movement caused by differential frost heave. The test results indicated that the bending action was the main factor for the circumferential and longitudinal strain distribution in the pipeline. The circumferential strain ranged from about 100 to 500 during freezing. The maximum tensile and maximum compressive strains along the pipeline were approximately located at the edges of the transition zone.