Browsing by Subject "Pavements"
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Item Bayesian estimation of finite mixture roughness model(2016-12) Serigos, Pedro A. (Pedro Antonio); Prozzi, Jorge Alberto; Zhang, Zhanmin; Gilbert, Robert B; Müller, Peter; Mikhail, MagdyHighway infrastructure systems provide a crucial service to society and constitute a major asset with a significant maintenance and rehabilitation cost, highway pavements comprising a major component of the total cost. The increasing need for greater capital investment, in the face of ever-decreasing federal funding to maintain highway infrastructure, highlights the importance of developing and implementing effective methods for managing pavement assets. A key for the success of pavement management is to accurately predict the future condition of the pavements in the network. This dissertation proposes a mixture of regression models to capture the systematic differences in pavement performance not explained by variables typically available in pavement management systems. This approach assumes that the heterogeneous pavement performance, which results from the combined effect of the several unobserved factors and interactions, is manifested through a finite number of latent groups. The estimation of the proposed model allows for defining the parameters of the group-specific models while clustering the observations into the latent groups. The insights provided by the model-based clustering of performance data can also be incorporated into the design of maintenance and rehabilitation strategies, as clustering of sections according to their deterioration rate allows for identifying pavements in the network with structural deficiencies and tailoring actions in response. The gain in model fit, along with the insights provided by the proposed methodology for the unsupervised model-based clustering of pavement performance was demonstrated using experimental data. In addition, the proposed mixture model was applied to develop a Bayesian pavement roughness model specified with variables from an existing pavement management system, plus climatic and preventive maintenance variables, and estimated using nationwide field data from the Long-Term Pavement Performance program. Lastly, the developed roughness mixture model was calibrated for Texas pavement conditions by combining both the nationwide data and data extracted from the processing and merging of various Texas Department of Transportation databases. The proposed methodology produces accurate predictions of the progression of roughness as well as robust estimates of the factor effects driving the deterioration of pavements, which, ultimately, lead to a more efficient management of highway assets.Item A Data Base for the U.S. Forest Service Pavement Management System(Council for Advanced Transportation Studies, 1981-05) Hernandez, Jorge E.; McCullough, B. Frank; Hudson, W. RonaldThis report is the first phase of a proposed three-phase project developing and implementing a database for the Pavement Design Management System (PDMS) which was developed by The University of Texas at Austin in cooperation with the U.S. Forest Service. PDMS may be used to design asphalt concrete, surface treatment, and aggregate surfaced pavement structures. Results from the implementation of PDMS in certain Forest Service design offices indicate good performance of PDMS regarding the asphalt concrete and surface treatment pavement designs. However, the implementation results also indicate that the models used in PDMS for the design of aggregate surfaced roads need to be improved. This is not surprising, since these models were not developed with data from Forest Service roads. The characteristics of the Forest Service road system make it truly unique in the world. Because of this, roadway structure design and management methodologies developed by other transportation agencies are not adequate for Forest Service needs. To improve these methodologies in PDMS, performance information on Forest Service roads must be collected and analyzed. Even a small improvement in the management of pavement structures system-wide will result in the saving of millions of dollars annually. Therefore, a data base is a necessary and valuable tool.Item Determination of potential vertical rise in expansive soils using centrifuge technology(2015-08) Snyder, Larson Mackenzie; Zornberg, Jorge G.; Cox, Brady RExpansive soils are a significant issue in Central Texas due to a high potential to shrink and swell which leads to cracking of roadways. A significant amount of research has been conducted on expansive soils, which has led to the development of direct and indirect methods to determine a soil’s swelling potential. The methods for direct measurement of the swell potential are typically both time consuming and expensive, which has led to the underutilization these methods. Indirect methods, which use index geotechnical properties to predict the swelling behavior of a soil, are empirically based correlations that are only approximations that don’t take into account variables such as the mineralogical composition of the soil and include the Texas Department of Transportation's (TxDOT) approach, Tex-124-E, which is based solely on Atterberg Limits and grain size distributions to determine the potential vertical rise of an expansive deposit beneath a pavement system. The purpose of this study is to develop an approach that both directly measures an expansive soil’s swelling potential using centrifuge technology (DMS-C) and determines a potential vertical rise (PVR) for use in site characterization. This study consists of eleven soils sampled from ten sites in Bexar, Atascosa, and Guadalupe Counties of the San Antonio TxDOT district to determine the PVR using the DMS-C and Tex-124-E approaches. Soil characterization tests were conducted including Atterberg Limits and compaction tests, as well as, over 300 specimens tested in the centrifuge testing program. The centrifuge testing program consisted of compacting samples into the double infiltration setup at initial conditions of 3% dry of optimum moisture content and 100% relative compaction and testing the samples at three separate artificial g-levels that correlate to three effective stresses to generate a swell-stress curve that was defined over a range of stresses typically found in the active zone. The results from the centrifuge tests for samples from each site are verified with the traditional free swell tests (ASTM D4546.) At each site, the swell-stress curve and stresses for the soil profile were used to determine the PVR for the DMS-C approach. From the results, seven of the sites received a high or severe degree of concern for potential damage to the pavement. Of these seven sites, six of the sites correlated to soils derived from the Navarro/Marlbrook Formation, which is a major geologic formation in both the San Antonio region as well as the rest of Central Texas east of the Balcones Fault zone. The same stresses, as well as, the liquid limit, plastic limit, and moisture content are used to predict the PVR with the traditional Tex-124-E approach. These results were analyzed and compared to the values to the PVR from the direct measurements taken in the DMS-C approach for each site. From the comparisons, the approximate prediction of PVR for Tex-124-E does not correlate to the direct measurements of swelling results to determine the DMS-C approach. Furthermore, the characterization the swell potential using the centrifuge for PVR calculation with the DMS-C approach was proven to be expeditious and can lead to a significant amount of savings by reducing maintenance and repair of damage. Thus, the DMS-C approach should be implemented into the protocol for the determination of potential vertical rise of expansive soils to more accurately determine whether a given location will be problematic.Item Evaluation of the curing time and other characteristics of prime coats applied to a granular base(2011-05) Mohan, Gouri; Stokoe, Kenneth H.; Yildirim, YetkinPrime coats have been in use for many decades to help protect the base before the subsequent application of bituminous surface treatments. Prime coat is an application of a low viscosity binder onto the base to help protect the base from moisture, to provide an adequate bond between the bituminous surface coating and the base, to strengthen the base near the surface by binding the fines, and to protect the base from detrimental effects of weather and light traffic until the surface can be constructed. For a prime coat to function efficiently it should penetrate sufficiently into the base and should be cured before the application of subsequent layers. Evaluation of the time required for curing of prime coats and how the curing time depends on various weather parameters has received a lack of attention. In view of this, the time taken for curing of different prime coats and the dependence of curing time on weather parameters was studied. The prime coats most commonly used in Texas were selected for this study, namely; MC-30, EC-30, CSS-1H, SS-1H and AEP. All testing was done in real conditions, that is, samples were prepared and exposed to actual weather conditions. Since each prime coat is chemically very different, they were analyzed separately to determine the minimum curing time. Curing time was calculated in three different weather conditions to understand how the weather affects curing time. Further, two different application methods were used to determine the effect of application method on the curing time. In addition to determining curing times, other important engineering properties of prime coats that determine the performance of prime coats such as strength, permeability and penetration were also studied. Strength and permeability tests were done on cured specimens and the effect of application method on these values was also determined. Strength values were measured using a pocket penetrometer and penetration was determined by using sand penetration tests. A unique ranking system list was developed using curing time, strength, penetration and permeability as the key factors to determine the prime coat which would serve all the intended functions effectively and efficiently.Item Field performance of geogrid reinforced low-volume pavements(2010-05) Joshi, Rutuparna Vidyadhar; Zornberg, Jorge G.; Prozzi, Jorge A.For the past three decades, geosynthetics have been recognized as materials that can significantly improve the performance of pavements on weak subgrade. Pavements exhibit non-linear elasto-plastic behavior. The addition of geosynthetics is undoubtedly beneficial. This being said, researchers have concentrated more on lower life cycle cost and high benefit-cost ratio whereas much less attention has been given to the complex behavior of the reinforced pavement system. Comprehension of the short-term and long-term field performance of reinforced pavements under continued traffic and cyclic environmental loading has remained unexplored. There is empirical evidence indicating quantitative benefits of reinforced versus unreinforced pavement structure. However, quantification of the relative benefits of different types of reinforcement like geogrids and geotextiles lacks information. Further, evaluation of the benefits and comparison of chemical stabilization in the form of lime treatment with mechanical stabilization in the form of reinforcement for pavements on soft soils has received lack of attention. In view of this, full-scale instrumented reinforced and lime treated pavement sections with different schemes were studied. Regular Falling Weight Deflectometer (FWD) testing was conducted in a Farm-to-Market Road, in Grimes County, Texas. Three different geosynthetic products were used for base reinforcement and lime treatment was used for subbase stabilization. Deflection measurements for 9 field trips in 3.5 years were evaluated. Modified deflection basin parameters (DBPs) were defined to typically identify layer properties and were used to measure the relative damage to the base, subbase and subgrade for different sections. A modified Base Damage Index (BDI) and a modified Base Curvature Index (BCI) were defined as a part of this study to capture the benefit of reinforced base and lime stabilized subbase respectively. The variation in the DBPs over three periods of wetting and drying along with explanation of the observed trends forms a part of this research. In addition, a number of condition surveys were performed, during 3 years, to visually identify distresses in various sections. A unique distress quantification technique was developed for measuring deterioration of the pavement sections in terms of the observed distresses and FWD measurements. With this, an index of pavement performance was developed. Thus, the FWD deflection data analyses complemented by visual observation, reveals important information on performance of different geosynthetics with the same base course. Analysis of the field performance of the multiple experimental sections throws light on the relative merits of base reinforcement against lime stabilization.Item Implication of Aggregates in the Frictional Performance of Seal Coat Overlays(International Center for Aggregates Research, 1988) International Center for Aggregates ResearchTo investigate the effect of aggregate type on pavement friction, researchers used Texas as a test model and constructed 59 seal coat test sections 1,000 feet (304 m) long in the four climatic regions of the state. The environmental characteristics of these four regions included: wet and no freeze; wet and freeze-thaw cycling; dry and no freeze; and dry and freeze-thaw cycling. Researchers used many of the aggregate types that are common to each region, and economically available, in the design mixture for each seal coat section.Item Integrating social equity into sustainable programming of road projects : a quantitative approach(2022-12-02) Kothari, Chirag; O'Brien, William J.; Jiao, Junfeng; Faust, Kasey; Zhang, ZhanminWith a growing emphasis on sustainable planning, highway agencies aim to develop sustainable highway programs incorporating the three sustainability components: economics, environment, and equity. Thus, highway agencies must incorporate multiple objectives while developing transportation programs. Moreover, limited funding and a rapidly aging highway infrastructure network further hinder maintaining the road network in a functional state while meeting sustainability goals. Literature has extensively explored ways to solve this resource allocation problem for preparing highway maintenance and rehabilitation (M&R) programs. However, these studies have mainly focused on economic and environmental objectives. The quantitative assessment and incorporation of social equity objectives are relatively new and limited. To better accommodate social equity goals, it is essential to assess the social equity level objectively. Moreover, exploring how social equity goals can be quantitatively incorporated into highway M&R programming is essential. Thus, this study aims to develop a framework to quantitatively assess and incorporate social equity goals in highway M&R programming. Firstly, the study proposes a quantitative approach to assess social equity in the road network. This is achieved by developing an assessment approach and exploring numerical measures to evaluate equity. Secondly, this study proposes a sustainable M&R resource allocation model that concurrently focuses on all three sustainability objectives. The multi-objective approach assists in exploring the relationships between the three fundamental pillars of sustainability. In addition to managing multiple objectives, the decision-makers must develop and implement transportation programs in a highly complex and dynamic fiscal environment. Hence, lastly, the study explores the performance of different social equity strategies (policies) to develop sustainable asset management plans in a fiscally constrained and dynamic environment. The formulations and measures proposed in this study expand the use of quantitative social equity metrics to assess needs and support decision-making. Additionally, the study encourages highway decision-makers to adopt a multi-objective approach to understand better the implications of their decisions on the economic, environmental, and social equity aspects. The case study findings indicate that the decision-makers can potentially adopt a suitable M&R treatment program that meets their social equity needs without significantly compromising on the economic or environmental objectives.Item On Bayesian estimation of spatial and dynamic count models using data augmentation techniques : application to road safety management(2015-08) Buddhavarapu, Prasad Naga Venkata Siva Rama; Prozzi, Jorge Alberto; Bhat, Chnadra R; Scott, James G; Carvalho, Carlos M; Smit, Andre FOver the past several years, roadway safety management has evolved into data-driven or evidence-based science. The corner stone of a data-driven roadway safety management is the knowledge about useful patterns in the complex crash data. Crash data is often difficult to model with several confounding factors and discrete target variables such as crash counts or crash severity. The major goal of this dissertation was to contribute to the methodological realm of roadway safety management. The research objectives are in two folds: 1) to develop state-of-the-art model specifications for modeling crash data, and 2) to develop a probabilistic model-based site ranking framework. This research addresses methodological issues in crash frequency modeling such as unobserved heterogeneity, spatial correlation, and temporal patterns. Two novel specifications were developed to address these methodological issues: 1) negative binomial spatial with random parameters (NBSRP) modeled as multi-variate normal finite mixture distribution; 2) negative binomial spatial model with dynamic parameters (NBSDP). The NBSRP with finite-mixture specification allows for identifying the underlying sub-groups of road segments, and for skewness and multi-modality in the underlying random parameter distribution. The NBSDP specification employs dynamic linear model (DLM) formulation of the discrete negative binomial count model by exploiting recently developed polya-gamma data-augmentation techniques. NBSDP model facilitates to investigate the evolution of the model parameters over the time and to make safety predictions for a future year. Both NBSRP and NBSDP models simultaneously accounts for potential spatial correlation of crash counts from neighboring road segments. Bayesian methods have been widely used for model building and recently gaining further popularity due to the availability of efficient algorithmic techniques for the parameter estimation. Computationally efficient Bayesian estimation frameworks that leverage recent advances in data augmentation techniques were developed in this research to estimate the proposed count specifications. Bayesian estimation methods also facilitate statistical inference on site ranks, thereby allowing for probabilistic ranking. A computationally efficient site ranking framework was developed incorporating the recent probabilistic ranking techniques towards the end of this dissertation. Overall, this dissertation demonstrates the feasibility of designing Bayesian modeling frameworks for probabilistic roadway safety management, which facilitate online learning. The research ideas presented in this dissertation may be extended to bigger networks to test the feasibility of developing a safety management framework that automatically learns from the latest crash data sources over the time.Item A Pavement Design and Management System for Forest Service Road : A Conceptual Study(Council for Advanced Transportation Studies, 1974-07) McGarragh, Thomas G.; Hudson, W. RonaldThe design of pavements for low-cost, low-volume roads is a complex procedure involving numerous variables. Because of the development of new information in the pavement field during the past decade, the complexity of the interaction of these design variables has become better understood and the need for a systematic approach to the problem of pavement design and management has become evident. This report is an attempt to apply this systematic approach to the design and management of low-volume Forest Service roads. The report summarizes the problem analysis efforts of the project staff, beginning with the identification of the problem through its recognition and definition. Using the FPS type of working Pavement Design System developed in Texas as a conceptual base, an extensive examination of the major subsystems that make up the majority of existing pavement management systems for "higher type" roads was conducted. In attempting to define these basic components for the proposed low-volume road system, it was found that interaction between the project research staff and Forest Service personnel was of great importance. This interaction was achieved in the form of an interagency "brainstorming session" and later an "importance rating" of the ideas presented at this meeting. The results of this interaction along with the research efforts of the project staff allowed for an initial definition of the major components in the proposed system. Where complete definition of these subsystems was not possible, relevant questions and ideas were formulated for consideration in their further development. Finally, an example conceptual pavement management system for low-volume roads that incorporates all the ideas and concepts developed during the past year's research is presented. It is concluded that the development of pavement management systems for low-volume Forest Service roads is indeed feasible and should be pursued in Phase II of the project. Recommendations for major areas of further research are also given.Item A Pavement Design and Management System for Forest Service Roads: A Working Model. Final Report, Phase II(Council for Advanced Transportation Studies, 1977-02) Roberts, Freddy L.; McCullough, B. Frank; Williamson, Hugh J.; Wallin, William R.This is the second phase of a three-phase effort to develop and implement a pavement design and management system for low-cost, low-volume roads, in particular, Forest Service roads. The specific object of this phase is to develop working pavement design and management models and other information needed for optimization and decision making. Using the results of the Phase I conceptual study and a pre-existing program, an initial computerized working pavement design and management model was developed. During this phase, through continual coordination with various Forest Service engineers, this initial model was constantly modified to better consider the Forest conditions, design requirements and operating procedures. The resulting model, LVR, which is now ready for implementation and trial usage by the Forest Service during Phase III of this project, will design pavement structures based on an equal-effectiveness criterion for bituminous surfaced, aggregate surfaced or surface treatment roads. Two roads are considered to have equal effectiveness if they provide the same quality of service for the same length of time. Bituminous surfaced pavements are designed using a single failure criterion which is based on the AASHTO method currently in use by the Forest Service.