Angela S. WoltersKathryn A. ZimmermanDavid L. HuftPaul A. Oien...
p.109-116页
查看更多>>摘要：On a daily basis, local road agencies in South Dakota face the challenge of how to maintain low-volume roads cost-effectively. Specifically, agencies are faced with the decision of determining when it is most economical to maintain, upgrade, or downgrade a road's existing surface. To assist decision makers with maintenance and rehabilitation decisions, the South Dakota Department of Transportation (SDDOT) initiated a study in 2002 to investigate surfacing criteria for low-volume roads. The overall objective of this research is to create a process that allows users to compare the costs associated with different types of roads to provide assistance in deciding which surface type (hot-mix asphalt, blotter, gravel, or stabilized gravel) is most economical under a specific set of circumstances. In addition to incorporating economic factors into the analysis, the process allows the user to consider other noneconomic factors that are more subjective and difficult to quantify. The process used during this study is flexible enough to allow users to consider any combination of agency costs incurred by the agency for maintaining its roads, user cost factors such as vehicle operating costs or crash potential, and noneconomic factors such as politics and housing densities. The methodology was created with agency cost and user cost models developed on the basis of specific road section information supplied by various local agencies in South Dakota, average daily traffic and crash occurrence information supplied by the SDDOT, information obtained through a literature search, and input from members of the project's technical panel.
查看更多>>摘要：Prime coat has a purpose in the pavement construction process, yet many times prime is misused or eliminated during the project. Although most of the time no harm appears to occur to the roadway, and thus this practice may be viewed as acceptable, technical guidance is warranted to ensure appropriate usage. The objective of this study was to produce a prime coat guide for Central Federal Lands Highway Division project development and field personnel to provide decision-making guidance. The study consisted of a literature search, which focused on handbooks and technical reports, and a review of agency construction specifications. A phone survey of state departments of transportation in the region was undertaken to provide information on current practice. Finally, a review of both the potential harmful and the positive environmental effects of the prime coat process, including the various bituminous products used, was undertaken. On the basis of the information collected, a guideline for project development and field personnel was developed. The guideline provides guidance on how to use, when to keep, and when to eliminate prime coats.
查看更多>>摘要：Major highways are designed to withstand heavy vehicles and high volumes of traffic year round. However, low-volume roads in seasonal frost areas are highly susceptible to damage from trafficking by heavy vehicles during spring thaw. Conventional practice is to place partial or full spring load restrictions on low-volume roads during spring thaw. This practice reduces road damage significantly. However, companies whose livelihood depends on trucking can suffer major economic losses as they await the removal of load restrictions. Using reduced tire pressure constitutes a less conventional technique that can reduce springtime damage. Reducing tire pressure generally appears to be less effective than reducing load. Nevertheless, it does appear that the load restriction window can be shortened in duration by implementing a reduction in tire pressure for a few weeks, starting toward the latter part of the standard spring load restriction period. With a mechanistic pavement design and evaluation model for seasonal frost areas, a critical combination of load and tire pressure reduction was developed; it contributes to optimizing the balance between minimizing springtime road damage and minimizing disruption to local economies caused by load restrictions. This analysis constitutes the first step in the development of simplified, general application guidelines for shortening the springtime load restriction window for a variety of pavement structures.
Nicolas FradetteGuy DorePascale PierreSerge Hebert...
p.137-147页
查看更多>>摘要：The functional service level of roads is quantified in terms of roughness. This parameter considers every road surface defect that causes passenger vehicle discomfort. Roughness is measured by a quality index, the international roughness index (IRI). Roughness gives an overall appreciation of road profile quality without, however, permitting a deeper analysis. The overall value of the IRI does not discriminate between the two main factors responsible for winter deterioration of roughness: the subgrade differential heave and crack heaving (winter tenting). Differential heave is the result of variability in frost susceptibility of subgrade. This phenomenon can be detected by isolating the long wavelengths produced at the road surface from the longitudinal profile. Crack heaving is a superficial phenomenon greatly influenced by the application of deicing salts. By isolating the short wavelengths from the profile, it is possible to highlight the influence of this phenomenon on deterioration. The goal of this research is to establish, with the use of a filtering technique of road profile, the contribution of these two main factors to winter deterioration of roughness on five road sections in the Quebec City, Canada, area. This study will then allow for the development of a tool to determine the dominant factor for longitudinal profile deterioration and therefore the use of the best technique to rehabilitate roads.
查看更多>>摘要：Environment is one of the essential factors that influence pavement material behavior and consequently its performance. The variation of climatic patterns from region to region, coupled with the variation of site-specific conditions across North America, makes it difficult to develop standard models to account for seasonal variation in material properties that apply for all regions. Consequently, the need to develop regional models becomes an essential requirement for most transportation departments. The enhanced integrated climatic model (EICM) was evaluated to determine its suitability in predicting subsurface temperature and moisture conditions within New Jersey sites. The validation of the model used environmental data collected through pavement instrumentation of a large-scale research study under the sponsorship of the New Jersey Department of Transportation. Site-specific data were input to the model, and the model output parameters were compared against field-measured values. The results of the validation for two of the instrumented sites are reported. Results of the study do not indicate a high correlation between field-measured values and EICM-predicted temperature and moisture profiles for the various pavement layers.
查看更多>>摘要：A new high-resolution temperature and strain sensor with fiber Bragg grating (FBG) technology was developed. The FBG sensor consists of a reference fiber grating and a grating pair scheme that could offer the potential of simultaneous measurement of strain and temperature for monitoring pavement structures. Experimental results showed that measurement errors of ±6 με and ±0.13℃ for strain and temperature could be achieved, respectively. Feasible applications of this sensor for monitoring pavement structures were investigated. The reliability and long-term stability tests for this sensor were examined by mounting it on the surface of two kinds of specimens, asphalt and concrete, and several temperature cycles with a designed working temperature range up to 110℃ were applied for at least 24 h. An electronic thermocouple and a long-period optical fiber grating (LPG) sensor with similar function were used to compare the performance. Small root-mean-squared temperature variations (better than 1℃) and excellent long-term stability (within 2%) were obtained. The maximum variations in temperature for 48 h were only 1.94% and 2.32% for asphalt and concrete specimens, respectively. Results indicated that although the performance of this FBG sensor was comparable with that of the conventional thermocouple, its long-term stability was four times better than its counterpart, the LPG sensor. This type of simple and low-cost fiber-optic sensor is expected to benefit the developments and applications of new paving materials, mix design procedures, or the enhancement of pavement management systems.
Jochen TeizerChangwan KimCarl T. HaasKatherine A. Liapi...
p.177-186页
查看更多>>摘要：Modeling transportation infrastructure assets in three dimensions (3D) is becoming increasingly necessary for good management. Condition assessment, maintenance, operations, and construction activities are exploiting 3D models for improved visualization, communications, and process control. Acquiring 3D models rapidly can improve safety and productivity and is becoming feasible through approaches based on sparse range point clouds; however, although this approach has contextual advantages, it is ultimately limited in speed. Emerging Flash laser detection and ranging (LADAR) technology is opening up the possibility of 3D modeling at rates better than 1 Hz (real time). A framework for 3D modeling is presented that includes the dimension of time. In particular, the performance of the Flash LADAR technology is examined, and potential applications are explored. Technologies such as Flash LADAR will play an important role in real-time modeling of infrastructure assets in the near future.
Siefko SlobBart van KnapenRobert HackKeith Turner...
p.187-194页
查看更多>>摘要：Three-dimensional (3D) laser scanning data can be used to characterize discontinuous rock masses in an unbiased, rapid, and accurate manner. With 3D laser scanning, it is now possible to measure rock faces whose access is restricted or rock slopes along highways or railway lines where working conditions are hazardous. The proposed method is less expensive than traditional manual survey and analysis methods. Laser scanning is a relatively new surveying technique that yields a so-called point cloud set of data; every single point represents a point in 3D space of the scanned rock surface. Because the density of the point cloud can be high (on the order of 5 mm to 1 cm), it allows for an accurate reconstruction of the original rock surface in the form of a 3D interpolated and meshed surface using different interpolation techniques. Through geometric analysis of this 3D mesh and plotting of the facet orientations in a polar plot, it is possible to observe clusters that represent different rock mass discontinuity sets. With fuzzy k-means clustering algorithms, individual discontinuity sets can be outlined automatically, and the mean orientations of these identified sets can be computed. Assuming a Fisher's distribution, the facet outliers can be removed subsequently. Finally, discontinuity set spacings can be calculated as well.
查看更多>>摘要：The effectiveness of catchment ditches along Ohio roadways was evaluated for 100 sites with the Oregon Rockfall Hazard Rating System (RHRS), the New York State Rock Slope Rating Procedure (RSRP), the Colorado Rockfall Simulation Program (CRSP), and the Oregon Rock-fall Catchment Area Design Guide. From the results of this evaluation, 48% of the ditches were ranked as adequate within an acceptable level of risk, 28% were ranked as marginally adequate, and 24% were ranked as inadequate. Although qualitative in nature, the ditch evaluation portion of the Oregon RHRS was found useful. None of the ditches evaluated met the Ritchie ditch depth criteria as used in RSRP. CRSP provided valuable information when the entire road cut was accessible for data collection. Because of slope height restrictions, the Oregon Rockfall Catchment Area Design Guide provided ditch evaluations for only 44% of the sites.
Navaratnarajah SasiharanBalasingam MuhunthanShanzhi ShuThomas C. Badger...
p.205-213页
查看更多>>摘要：Wire mesh and cable net slope protection have been in use for more than 50 years along North American highways to control rockfall on actively eroding slopes. The basic design of these systems is comparatively similar throughout North America. It consists of a top horizontal cable suspended by regularly spaced anchors, typically a perimeter or widely spaced grid of horizontal and vertical support cables, and double-twisted, hexagonal wire mesh laced to the support ropes. To date, the design of the slope protection systems has been based primarily on empirical methods, engineering judgment, and experience. Although these systems generally perform well, there is some consensus among geotechnical specialists that some elements in the system may be overdesigned or even unnecessary. In addition, system failures under a variety of loading conditions within the past few decades indicate that certain design elements may in fact be underdesigned for their desired application. Analytical and numerical models to evaluate the stability of slope protection systems are presented. The inclusion of interior horizontal support ropes in addition to the top horizontal rope does not reduce the stress within the mesh and accordingly provides no mechanical benefit. Results also show that the stresses on the vertical support rope are much smaller than the top horizontal support rope. Therefore, the vertical ropes do not need to be as strong as the top horizontal rope. Further, some useful design charts for the design of slope protection system are presented.
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