Integrated Emergency Construction and Engineering Response to 2013 Colorado Storm Damage

Union Pacific Railroad’s Moffat Tunnel Subdivision, west of Denver, Colorado, was significantly impacted by an approximately 500 to 1,000 year storm event that occurred between September 9, 2013 and September 13, 2013. As a result of this historic event, washouts, earth slides, and debris flows severely impacted track infrastructure by eroding track embankments, destabilizing surrounding native slopes, and overwhelming stormwater infrastructure. Emergency response activities performed to restore track operations at Milepost (MP) 25.65 and MP 22.86 required the integration of civil, hydraulic, environmental and geotechnical engineering disciplines into emergency response and construction management efforts. Additionally, support from UPRR’s Real Estate Division was required when addressing private ownership and site access issues. The following text summarizes how coordinated efforts between various groups worked together in a pressure setting to restore rail service. The most significant damage occurred at MP 25.65 in a mountainous slot canyon between two tunnels accessible only by rail and consisted of a washout, approximately 200 feet (61 m) in length with a depth of 100 feet (30 m). MP 22.86 experienced slides on both sides of the track resulting in an unstable and near vertical track embankment which required significant fill and rock armoring. In addition to the embankment failures at MP 22.86, flood flows scoured around the underlying creek culvert, further threatening the geotechnical stability of the track embankment. The storm event highlighted the vulnerability of fill sections, where original construction used trestles. The repair plan engineered for MP 25.65 was developed to restore the lost embankment fill to near pre-flood conditions while limiting environmental impacts in order to minimize regulatory permitting requirements. Fill replacement performed during the initial emergency response was completed within 22 days, notwithstanding site remoteness and difficult access. Repair of the embankment required the placement of approximately 90,000 cubic yards (68,800 cubic meters) of fill and installation of four 48-inch (122-cm) culverts. Repair of embankment sloughing and scour damage at MP 22.86 was accomplished without the need for environmental permits by working from above the ordinary high water mark, using a “one track in – one track out” approach while restoring infrastructure to pre-flood conditions. A new headwall to address flow around the culvert inlet received expedited permit authorization from the U.S. Army Corps of Engineers by limiting the construction footprint through implementation of best management practices and minimizing placement of fill below the ordinary high water mark. Service interruptions, such as those at MP 22.86 and MP 25.65, require sound engineering practices that can be quickly and efficiently implemented during emergency response situations that often occur in less than ideal working environments. Track outages not only impact the efficiency of a railroad’s operating network, but also impact interstate and global commerce as transportation of goods are hindered. The need to have a team of experienced engineering and construction professionals responding to natural disasters was demonstrated by this storm event.

Air Entrainment and the Fabrication of Concrete Railroad Ties

Handling and vibration can affect the air content of prestressed concrete railroad ties. The amount and variation in vibration experienced in concrete railroad ties were investigated to determine the concrete fabrication conditions typically used. Two methods of fabrication were investigated by measuring the concrete properties and vibration exposure during placement at two concrete tie manufacturing plants. In addition to measuring the vibration distribution in concrete railroad ties, a pair of ties were selected for hardened-air void analyses to determine any variation of air content in relation to the height of the ties. The vibration results indicate the existence of constructive and destructive wave-interferences in tie cavities. These interferences may contribute to large variations in the vibration acceleration throughout the length, depth, and width of concrete crossties during fabrication. This may account for the air-loss across the depth of the ties.

Model Track Studies by Ground Penetrating Radar (GPR) on Ballast With Different Fouling and Geotechnical Properties

In recent years there has been an increase in the knowledge of, and need for, non-invasive monitoring of ballast in order to identify the problematic sections of track and decrease the maintenance cost. Various technologies such as Ground Penetrating Radar (GPR) are becoming accepted for investigating the condition of ballast. However since these techniques were not originally developed for engineering applications, their applicability in ballast evaluations can be sometimes uncertain. Continued empirical studies and condition specific calibrations are needed to demonstrate repeatable and quantifiable results. In this study large-scale track models with trapezoidal section area were constructed at the University of Massachusetts to investigate the effects of breakdown fouling, and the effects of changing geotechnical properties on GPR traces. This paper presents the design and construction of large scale track models, and methods used for GPR data collection. GPR data are presented in this paper that demonstrate sensitivity to the track model properties and variables. In particular, the experiments are being used to evaluate changes in GPR data with changing geotechnical properties of the ballast such as density, water content, grain size distribution (GSD), and fouling percentage.

Analysis of Instabilities in Railway Vehicles Employing Operational Modal Analysis

The application of Operational Modal Analysis (OMA) in the railway sector opens a broad field of opportunities. The validation of the numerical model employed in the design phase is usually performed employing data obtained in static tests. The drawback is that some suspension parameters, such as dampers, only have an influence in the dynamic behavior and not in the static behavior. Because of that, the use of the mode shapes identified from track measurements in combination with the static tests leads to a more accurate validation of the numerical model. Apart from that, most passenger comfort and dynamic problems are associated to slightly damped modes. A correct identification of the modal parameters can be used as a continuous design improvement tool to improve the comfort and dynamic characteristics of future designs. Another valuable application of OMA techniques is the identification of the mode shapes corresponding to instabilities, due to the safety impact that they have. In railway vehicles, instabilities are associated to mode shapes that present a damping rate which decreases with the increase of the running speed. Above a certain speed value, the excitation coming from track cannot be damped by the vehicle and it reaches an unstable condition. This unstable condition leads to high acceleration levels experienced by the passengers and high interaction forces between the wheel and the rail that may lead to safety hazards. The speed above which the vehicle is unstable is known as critical speed, and has to be greater than the maximum speed of the vehicle with a reasonable safety margin. The use of OMA techniques allows identifying the mode shape that causes the instability. This paper presents the application of OMA techniques to measurements performed on a passenger vehicle, in which the speed was increased until the vehicle was unstable. The mode shape that caused the instability was identified as well as its corresponding natural frequency and damping rate.

Automatic Detection of Corrugation: Preliminary Results in the Dutch Network Using Axle Box Acceleration Measurements

Short pitch corrugation is commonly seen in all kinds of tracks. There is not yet a conclusive explanation in the literature for its initiation and growth mechanisms. In this paper, we use an axle box acceleration (ABA) measurement system to detect corrugation. ABA can be easily implemented in operational trains, providing direct and reliable health monitoring of the track. We have extended a detection algorithm for rail surface local short wavelength defects to also detect short pitch corrugation, which is a continuous defect over the track. A 3D transient FE wheel-track model is employed to find theoretical signature tunes of the wheel-track system response when passing over a short pitch corrugation. Numerical simulations agree with ABA measurement obtained in the Dutch rail network. Based on the signature tune identified, an automatic detection algorithm is developed. Preliminary results with the algorithm are discussed. Field observations show a good potential of the detection algorithm to be used by inframanagers, to detect and monitor corrugation.

Effect of Concrete Release Strength on the Development Length and Flexural Capacity of Members Made With Different Prestressing Wires Commonly Used in Pretensioned Concrete Railroad Ties

A study was conducted to determine the effect of concrete release strength on the development length and flexural capacity of members utilizing five different 5.32-mm-diameter prestressing wires that are commonly used in the manufacture of prestressed concrete railroad ties worldwide. These included two chevron-indented wires with different indent depths, one spiral-indented wire, one dot-indented wire, and one smooth wire (with no surface indentation). A consistent concrete mixture was used for the manufacture of all test specimens, and the different release strengths were obtained by allowing the specimens to cure for different amounts of time prior to de-tensioning. Each prismatic specimen (prism) had a 3.5″ (88.9 mm) × 3.5″ (88.9 mm) square cross section with four wires arranged symmetrically. The prisms were identical except for the wire type and the compressive strength at the time of de-tensioning. All four wires were each initially tensioned to 7000 pounds (31.14 KN) and then de-tensioned gradually when the concrete compressive strength reached 3500 (24.13 MPa), 4500 (31.03 MPa) and 6000 (41.37 MPa) psi. Precise de-tensioning strengths were ensured by testing 4-in.-diameter (101.6 mm) × 8-in.-long (203.2 mm) compression strength cylinders that were temperature match-cured. The prisms were loaded in 3-point-bending to determine the ultimate bond characteristics of each reinforcement type for the different concrete release strengths. A loading rate of 300 lb/min (1334 N/min) was applied at mid-span and the maximum sustained moment was calculated for each test. Two 69-in.-long (175.26 cm) prisms, each having different concrete release strength, were tested with each of the 5 wire types. These prisms were tested at both ends, with a different embedment length assessed at each end. Thus, for each wire type and concrete release strength evaluated, a total of 4 tests were conducted for a total of 60 tests (5 wire types × 3 release strengths × 4 tested embedment lengths). Test results indicate that the concrete compressive strength at de-tensioning can have a direct impact on the ultimate flexural capacity of the members, and this has significant design implications for pretensioned concrete railroad ties. Results are discussed and recommendations made.

Simulation of Longitudinal Train Dynamics: Case Studies Using the Train Energy and Dynamics Simulator (TEDS)

Longitudinal dynamics influence several measures of train performance, including schedules and energy efficiency, stopping distances, run-in/run-out forces, etc. Therefore, an effective set of tools for studying longitudinal dynamics is essential to improving the safety and performance of train operations. Train Energy and Dynamics Simulator (TEDS) is a state-of-the-art software program designed and developed by the Federal Railroad Administration (FRA), for studying and simulating train safety and performance, and can be used for modeling train performance under a wide variety of equipment, track, and operating configurations [1]. Several case studies and real-world applications of TEDS, including the investigation of multiple train make-up and train handling related derailments, a study of train stopping distances, evaluations of the safety benefits of Electronically Controlled Pneumatic (ECP) brakes, Distributed Power operations, and a study of alternate train handling methodologies are described in this paper. These studies demonstrate the effectiveness of using the appropriate simulation tools to quantify and enhance a better understanding of train dynamics, and the resultant safety benefits.

VoLTE Performance in Railway Scenarios

GSM-Railways (GSM-R) is the current standard for railway voice and data communication. GSM-R provides railway specific voice services, such as Railway Emergency Call (REC). GSM-R provides also the European Train Control System (ETCS), which offers in-cab signaling and Automatic Train Protection (ATP). Despite these features and services, GSM-R has various major shortcomings. Therefore, alternative technologies are considered to replace GSM-R and become the next generation railway mobile communication network. 3GPP Long Term Evolution (LTE) is a likely candidate for GSM-R replacement. LTE is more efficient, flexible and offers much higher capacity, which allows the railway network to provide new communication-based applications for railways. Most of the research on LTE in railways has been focused on data-based railway applications (ETCS signaling and other). Nevertheless, voice communication is still a crucial service for railways. Regardless of its advantages, LTE can only become a railway communication technology if it provides voice communication fulfilling railway requirements. This paper presents how Voice over LTE (VoLTE) can be used to build railway communication services. Examples of Railway Emergency Call and One-to-One Call are provided. Service performance, in terms of call setup times and voice transmission quality, is analyzed in simulation scenarios modelling two railway scenarios in Denmark.

I-Girders Method Used to Support Existing Railway Operations During Highway Underpass Construction

In metropolitan areas, when a highway underpass project is being planned to go beneath an existing railway corridor, there are a number of concerns that could have an impact on the project. For example, will the underpass construction impact the existing railway operations? How to maintain the construction safety in both rail and highway operations? This paper brings construction technology using I-girder systems to provide a solution for highway underpass projects constructing beneath the existing rail corridors. The I-girder systems have been proved as a reliable method for highway underpass construction without the interruption of railway operations. This type of I-girder systems has been widely used in several countries as a temporary “bridge” structure in support of dynamic rail movements during underpass construction. Depending on the spans of underpass structures, a contractor can decide the number of I-girder units to be assembled and installed on site. This paper describes the construction procedures of the I-girder systems installation and daily inspection processes. A case study is used to demonstrate the applicability of I-girder systems in ensuring underpass construction smoothly while maintaining existing railway operations in a safety manner. During the construction of underpass, the contractor encountered geotechnical issues that had a severe impact on the construction safety and the integrity of foundation. This paper further discusses strategies that were used to mitigate the potential building collapses and foundation failures. It is concluded the method of I-girder systems is capable of supporting railway dynamic movements during highway underpass construction.

Structural Behavior of Rail Fastening System Used for Recycled Plastic Composite Crossties

Currently, the railroad industry is leaning towards alternative solutions to hardwood timber for crossties applications. This trend is part of an effort to increase train speeds beyond the wooden crossties capacity and minimize the negative environmental effects associated with them. Among the available alternatives are recycled plastic composite crossties. Their sustainably, environmental benefits, durability performance and ease of installation or one to one replacement of timber crossties render them an attractive and competitive solution. Several research programs have studied this material in the past. However, additional research is required to fully understand the behavior of these materials. This study aims to investigate the performance of fastening system used for recycled High Density Polyethylene crossties. The study encompasses comprehensive experimental investigations and analytical finite element modeling. The testing program evaluated each of the fastening system components using static test methods recommended by the AREMA manual. These tests addressed the spike pullout and lateral restraint for both screw and cut spikes as well as the fastening system uplift behavior. Moreover cyclic testing was also conducted on the full system to study the interactions of the fastening system components with the plastic composite crosstie. Finite element models were constructed and calibrated using the experimental data in order to extrapolate on the experimental results and predict different scenarios. The results observed in this study showed great promise highlighting the potential of these material if properly optimized and engineered.