3D FE Analyses of Buried Pipeline with Elbows Subjected to Lateral Loading

This study investigates the interaction between soil and pipeline in sand subjected to lateral ground displacements with emphasis on the peak force exerted to a bended elbow-pipe. A series of three-dimensional (3D) finite-element (FE) analyses were performed in both opening and closing modes of the elbow section for different initial pipe bending angles. To model the mechanical behavior of sands, two soil models were adopted: Mohr-Coulomb and Nor-Sand soil model. Investigations also included the effects of pipe embedment depth and soil density. Results show that the opening mode exhibits higher ultimate forces and greater localized deformations than the closing mode. Nondimensional charts that account for pipeline location, bending angle, and soil density are developed. Soil-spring pipeline analyses of an elbow-pipe were performed using modified F-δ soil-spring models based on the 3D FE results and were compared to the findings of conventional spring model analyses using the standard two-dimensional soil-spring model. Results show that the pipe strain does not change in the closing mode case. However, in the opening mode case, the pipe strain computed by the modified analysis is larger than that by the conventional analysis and the difference is more pronounced when the pipe stiffness is stiffer.     

Model for Quantifying the Impact of Change Orders on Project Cost for U.S. Roadwork Construction

Change orders are very common in almost every construction project nowadays, often resulting in increases of 5–10% in the contract price. Understanding the consequences of such trends, several studies have attempted to quantify the impact of change orders on the project cost. Most of the studies aimed at the quantification of the change orders were sponsored by contractors’ organizations, where statistical models used to quantify the impact of the change orders on the project cost were based on data supplied by the contractors; a situation that can lead to owner-contractor disagreements related to the quantification method used. In addition, most of the studies tackled commercial and electromechanical work, and very rare studies tackled the field of heavy construction; a field that suffers from change orders because of errors and omissions, scope of work changes, or changes because of unforeseen conditions. This study addresses the need for a statistical model to quantify the increase of the contract price due to change orders in heavy construction projects in Florida. The model is based on data collected from 16 Florida DOT projects with contract values that ranged between $10–$25 million, and that encountered an increase in the contract price from 0.01 to 15%. Eleven variables were analyzed to test their impact on the cost of the change orders. The study concluded that most significant variables that impact the value of the change order, which are (1) the timing of the change order and (2) when the reason for issuing the change order is unforeseen conditions. Two regression models are developed and validated as follows: (1) a model to quantify the percentage increase in the contract price due to the change orders that increase the contract price from 0.01 to 5% and (2) a model to quantify the percentage increase in the contract price due to the change orders that increase the contract price from 5 to 15%. Those models will provide the owner with a retrospective or forward pricing of the change orders, and hence, allow the owner to estimate and utilize contingency amounts.     

Condition Assessment of Buried Pipes Using Hierarchical Evidential Reasoning Model

Effective inspection and monitoring practices for the condition assessment of pipes ensure better decision(s) for repair or replacement before they fail. Pipe deterioration is a physical manifestation of the aging process in which many factors can contribute to structural failure. Various technologies/ techniques have been developed during the last few years to inspect/monitor piping systems, but how to intelligently interpret the collected data remains a challenge. In this paper, a new approach based on hierarchical evidential reasoning is proposed. This approach uses Dempster–Shafer (D-S) theory to make inferences for condition assessment of buried pipes. A hierarchical evidential reasoning model can help combine different distress indicators (bodies of evidence) at different hierarchical levels using D-S rule of combination. The proposed hierarchical evidential reasoning method is demonstrated with an example of condition assessment for a large diameter pipe. Information from multiple sources is fused to obtain a more reliable assessment of pipe deterioration.     

Uplift Mechanisms of Pipes Buried in Sand

Reliable design against upheaval buckling of offshore pipelines requires the uplift response to be predicted. This paper describes a model-scale investigation into the mechanisms by which uplift resistance is mobilized in silica sand, and illustrates how the observed mechanisms are captured in prediction models. A novel image-based deformation measurement technique has been used. The results show that peak uplift resistance is mobilized through the formation of an inverted trapezoidal block, bounded by a pair of distributed shear zones. The inclination of the shear zone is dependent on the soil density, and therefore dilatancy. After peak resistance, shear bands form and softening behavior is observed. At large pipe displacements, either a combination of a vertical sliding block mechanism and a flow-around mechanism near the pipe or a localized flow-around mechanism without surface heave is observed, depending on the soil density and particle size.     

Selection of Strategies for Winter Maintenance of Roads Based on Climatic Parameters

The aims of the presentation are to discuss the efficiency of the different methods for friction control of winter roads on the safety and accessibility due to climatic conditions, to show that the climate should be an important factor in selecting the strategies for winter maintenance and to establish climatic parameters that may be helpful in making those decisions. The analyses are based on Swedish data assembled by VTI on road accidents involving fatalities and severe injuries, road surface conditions and climate. The accident and the road condition recordings are compared to self-defined climatic parameters, which describe the severity, stability and instability of the winter climate in the regions investigated. The parameters are assumed to describe whether salting or sanding is favorable/unfavorable for friction control. The results of the analyses show that the effect of salting is substantial for improving accessibility. Generally the number of winter accidents resulting in fatalities and severe injuries is lower on the salted road network compared to the unsalted road network in the southern and central parts of Sweden. However, in the northern region, with very cold winters, the number of winter accidents is highest on the salted road network. The data also indicates that the highest accident numbers are found when the proportion of vehicle mileage on snow and ice in the winters varies within 30–40%. The paper recommends that salting should be avoided in areas and in periods when the frequency of road surface temperatures below ?8°C exceeds 20%. In such climates the warm-wetted sand method is probably more favorable for friction control. Warm-wetted sand is also favorable on roads with traffic less than average annual daily traffic 2,000 and in periods with stable winter conditions.     

Tunneling beneath Buried Pipes: View of Soil Strain and Its Effect on Pipeline Behavior

The paper examines the problem of tunneling beneath buried pipelines and the relationship between soil strains and pipeline bending behavior. Data are presented from centrifuge tests in which tunnel volume loss was induced in sand beneath pipelines of varying stiffness properties. The model tunnel and pipelines were all placed at a Perspex wall of the centrifuge strong box such that image-based deformation analyses could be performed. The method provided detailed data of subsurface soil and pipe displacements and illustrated the soil-pipe interaction mechanisms that occurred during tunnel volume loss, including the formation of a gap beneath the pipes. The relationship between tunnel volume loss, soil strain, and pipe bending behavior is illustrated. Experimental results of pipe bending moments are compared against predictions: (1) assuming the pipe simply follows greenfield displacements; (2) using an elastic continuum solution; and (3) using a new method in which an “out-of-plane” shear argument, due to soil-pipe interaction, is introduced into the elastic continuum solution. It is shown that the new method gives the best prediction of experimental pipe bending moments.     

Diffusion Wave Model for Simulating Storm-Water Runoff on Highway Pavement Surfaces at Superelevation Transition

On a curved section of highway, the cross slope of the road is often designed to be superelevated to balance the centrifugal force and gravity applied on vehicles. The accumulation of storm-water runoff (sheet flow) near superelevation transitions may significantly increase due to the extended flow path and converging flow lines. A two-dimensional finite-volume-based diffusion wave model is developed to simulate the sheet flow on these geometrically complex surfaces. Both Dirichlet- and Neumann-type boundary conditions are developed for open boundaries based on kinematic wave theory. Results show that the distribution of sheet flow is closely related to the cross slope, longitudinal slope, rainfall intensity, and the width of the road. The analysis of sheet flow characteristics on superelevation transition areas suggests that the optimal longitudinal slope in the range of 0.3–0.4% minimizes the depth of storm-water runoff on the road surface.     

Bayesian Belief Network Model for Decision Making in Highway Maintenance: Case Studies

This paper presents two case studies that were conducted to illustrate the functionality and application of a decision support system for predicting the influence of decisions made by state highway agencies regarding important work zone project variables such as work window, work zone length, lane closure strategy, and contract incentives on the cost, duration, quality, safety, and public satisfaction of a particular project under consideration. The first case study describes in detail the operation and function of the three major levels of the proposed framework using a completed project, whereas the second case study provides an opportunity for the application of the decision support system to a work zone project in the planning stages using the input of the actual decision maker for the project.     

Effects of Nonnormal Distributions on Highway Construction Acceptance Pay Factor Calculation

Percent within limits (PWL) is a commonly used quality control/quality assurance measure of highway pavement materials and construction, and it is a popular index for adjusting pay factors. However, PWL is based on the assumption of normal distribution of quality characteristics (e.g., concrete compressive strength and asphalt air voids). Skewness and kurtosis, which are common forms of statistical nonnormal distributions, can potentially bias the acceptance pay factor calculations. To examine this potential pay bias, simulations were performed to investigate the magnitude and the direction (overestimation or underestimation) of pay factor calculations. The study revealed that for both one-sided and two-sided specification limits, bias in pay factors not only did vary in magnitude but also reversed in direction over various ranges of PWL. These analyses showed that for a one-sided upper specification limit, on average, a positive skewness and kurtosis can underestimate the pay factor of an acceptable quality level population by 0.90%, and overestimates a rejectable quality level population by 3.8%. This leads to falsely penalizing acceptable products and rewarding bad products. The same was true for two-sided limits, which again varied based upon the percent of defective materials at the tails of the distribution. This is a very important issue because these biases in pay factors can easily upset the relative profit margins of the contractor. Furthermore, this may not be easily detectable without a detailed and sophisticated analysis as outlined in this paper. For multiple quality characteristics based pay factors, analyses showed that the combined magnitude of these biases was not linearly cumulative. Findings of the study indicate that bias in pay was higher for lots with fewer sublots and higher skewness and kurtosis.     

Effects of a Permeable Friction Course on Highway Runoff

This project documents the impact of a porous asphalt overlay on the quality and quantity of highway storm-water runoff. A permeable friction course, also known as open graded friction course, is a layer of porous asphalt approximately 50?mm thick, which is often applied on top of conventional asphalt or concrete highways to enhance safety and reduce noise. Storm-water runoff from a four-lane divided highway in the Austin, Texas area was monitored at two sites before and after the installation of a PFC. Observed concentrations of total suspended solids and pollutants associated with particulate material were much lower in the runoff from the PFC than that derived from the conventional asphalt surface. Concentration reductions were observed for total suspended solids, total lead, total copper, and total zinc at both monitoring locations. In addition to the above-mentioned constituents, concentrations of chemical oxygen demand and total Kjeldahl nitrogen were also lower in the runoff from the PFC at a site collecting paired samples from both pavement types. Concentrations of dissolved constituents were not significantly different and concentrations of polycyclic aromatic hydrocarbons were below the detection limit for both pavement types. The runoff coefficient for the PFC appears to be higher than for conventional pavements.     

Use of Supervisory Control and Data Acquisition for Damage Location of Water Delivery Systems

Urban water delivery systems can be damaged by earthquakes or severely cold weather. In either case, the damage cannot easily be detected and located, especially immediately after the event. In recent years, real-time damage estimation and diagnosis of buried pipelines attracted much attention of researchers focusing on establishing the relationship between damage ratio (breaks per unit length of pipe) and ground motion, taking the soil condition into consideration. Due to the uncertainty and complexity of the parameters that affect the pipe damage mechanism, it is not easy to estimate the degree of physical damage only with a few numbers of parameters. As an alternative, this paper develops a methodology to detect and locate the damage in a water delivery system by monitoring water pressure on-line at some selected positions in the water delivery systems. For the purpose of on-line monitoring, emerging supervisory control and data acquisition technology can be well used. A neural network-based inverse analysis method is constructed for detecting the extent and location of damage based on the variation of water pressure. The neural network is trained by using analytically simulated data from the water delivery system with one location of damage, and validated by using a set of data that have never been used in the training. It is found that the method provides a quick, effective, and practical way in which the damage sustained by a water delivery system can be detected and located.     

Contractor Performance Evaluation for the Best Value of Superpave Projects

The best-value (BV) procurement process uses other key factors as well as bid price in the evaluation and selection of the best-performing contractor for the job. Contract time, lane rental, warranty, and quality of delivered product are examples of the key factors that indicate the contractor-expected performance. Literature on best value shows a need for analyzing the past performance of the contractor in similar jobs as an indicator of his/her qualification trend. This paper addresses this issue and proposes a methodology to incorporate quality of delivered product in the BV procurement system of asphalt construction. The paper uses past quality control (QC) testing results and utilizes Monte Carlo simulation to estimate the probability that the contractor gets full payment as an indication of qualification trend. The QC data were obtained from the Nebraska Department of Roads for a number of Superpave pavement projects. The results show the possibility of assigning a quality score for the contractor based on the past performance. This paper contributes to the current practice of best value with a new approach of employing QC as part of the selection process.     

Effects of Recycled Materials on Long-Term Performance of Cold In-Place Recycled Asphalt Roads

With a limited maintenance budget and unprecedented construction cost increases, many owner/agencies in the United States are beginning to rehabilitate existing distressed pavements. Cold in-place recycling (CIR) provides an economical rehabilitation method and has been widely used in the past 20 years. However, recycled roads have experienced inconsistent performance and that has hindered the application of CIR. The objective of this paper is to study the cause and effect relationships between factors, such as traffic loading, support condition, and aged engineering properties of the CIR materials, and pavement performance. Twenty-four roads in Iowa were examined through field and lab tests. Statistical analyzes show that, within the range of data in this study, better performance was observed on CIR roads with lower CIR modulus value and/or higher air voids.     

Modeling the Effect of Subjective Factors on Productivity of Trenchless Technology Application to Buried Infrastructure Systems

Trenchless technology (TT) includes a large family of methods utilized for installing and rehabilitating underground utility systems with minimal surface disruption and destruction resulting from conventional excavation. Productivity of TT techniques is affected by a number of subjective factors that need to be evaluated. A productivity index (PI) model is developed in order to represent this subjective effect in refining productivity assessment. The analytic hierarchy process and fuzzy logic are used to develop the proposed PI model that relies on the actual performance of 12 subfactors under three main categories: management, environmental, and physical conditions. The developed PI model resulted in PI equal to 0.7323 and 0.7251 for microtunneling and horizontal directional drilling (HDD) projects, respectively. Multiattribute decision support system software is developed to determine the PI for a specific TT technique using Visual Basic. The PI model is tested, which shows reasonable results. This research is relevant to both industry practitioners and researchers. It provides practitioners with a model that justifies their productivity calculation by quantifying subjective factors effect, which will affect their schedule and cost estimation for trenchless projects. In addition, it provides researchers with the development methodology for the PI model.     

Measuring Soil Pressure on a Buried Model Structure for the Validation of Quantitative Frameworks

The paper presents the methodologies and results of an experimental study aimed at measuring the soil contact pressures which develop on a buried structure as it interacts with the surrounding soil under load. The study has been based on measurements made on model structures tested in a pressure chamber filled with a fine uniform sand. The buried model structure was a very rigid right cylinder designed such that it could be fitted with roofs of different thicknesses. The structure bottom and roof were instrumented with newly designed and constructed soil pressure cells based on the null response concept. The device is unaffected by the issues that affect the use of traditional soil pressure cells. The development of pressure on the structure was measured as uniform pressure was applied to the soil surface. The results illustrate the effect of roof stiffness on the development of pressure at the roof center. The midroof pressure was seen to increase with roof stiffness, however the development of pressure was also seen to be dependent upon the actual deflection. In the case of a flexible roof it was seen that the development of contact pressure is a nonlinear function of the pressure applied at the soil surface and is highly dependent upon stress history. In contrast, it was seen that pressure on a stiff roof develops as a linear function of pressure applied at the soil surface and is less dependent of stress history. The results of the model tests together with soil stiffness data supplied in the paper will be useful in the calibration and validation of numerical and analytical frameworks.     

Method of Up-Slope Mitigation Priority for Alishan Mountain Road in Taiwan

Rainfall-induced up-slope failure has been a major issue for the mountain road mitigation. To determine the mitigation priority of the roadside slopes, a model to evaluate the stability of the up-slopes is proposed in this paper. This model is developed using Bayesian classification theorem, historical rainfall and landslide data, and an artificial intelligence skill—Gaussian process. The parameters needed for this model include the up-slope features, catchment area, lithology, vegetation coverage, and rainfall data. Among these parameters, rainfall is considered to be the triggering factor of landslide in this study. In addition, each slope has also demonstrated a unique failure probability relationship with the 72-h accumulated rainfalls. Such a relationship is adopted to define a threshold rainfall factor which is used as an index to estimate the likelihood of landslide occurrence under a rainfall event. Using the threshold rainfall factor of each slope, a priority list is proposed for the mitigation of roadside up-slopes along the Alishan mountain road in Taiwan.     

Physical Modeling of Sheet Flow on Rough Impervious Surfaces

This paper presents results from an extensive experimental study of sheet flow on rough impervious surfaces that are used to represent highway pavement. Experiments were performed on three surfaces under no-rainfall and simulated rainfall conditions, and with slopes of 1, 2, and 3%. Measurements include flow depth and unit discharge. Turbulent boundary layer theory for a rough surface is used to describe the depth-discharge relationship, resulting in a model with a single parameter directly related to the surface roughness. Comparisons are made with Manning’s equation, and the variability of the Manning coefficient is assessed. Hydraulic effects of rainfall are generally found to be small compared to other factors.     

Effects of Road Salts on Heavy Metal Mobility in Two Eastern Washington Soils

Heavy metals deposited on road surfaces and transferred to roadside environments by rainfall and snowmelt runoff can have serious impacts on receiving ecosystems. Infiltration is an effective best management practice for controlling metal contamination in runoff, although metals retention within infiltration facilities depends on a number of factors, including metal species, soil characteristics, and influent water quality concentrations. In cold climates, deicing compounds have been shown to mobilize heavy metals putting receiving waters at risk. This study ascertains the effects of two widely used road salts (NaCl and MgCl2) on heavy metal mobility in two eastern Washington soils. Infiltration experiments were conducted using a basic soil, exhibiting a soil pH of 8.3, taken from a highway infiltration pond site in Spokane Washington and an acidic soil, exhibiting a soil pH of 5.9, taken from an infiltration pond site in Richland Washington. Three concentrations of each salt were percolated through both soils using continuous flow soil columns. Leachate samples were collected and analyzed for dissolved metals, organic matter, and pH. Experiments were also performed without salt and used as controls. Results indicate that metal mobilization can occur by a number of mechanisms including cation exchange, chloride complex formation, and colloid dispersion (release of organic matter and/or clay that can complex metal species). Sodium chloride resulted in the largest release of copper and lead via indirect mobilization of organic matter. The magnesium salt had less of an effect on lead and copper but had a much greater effect on the mobilization of cadmium. Releases of metals during or immediately following salt application produced concentrations that ranged from 50% to 1000% greater than the concentrations released from the control experiments.     

Laboratory Investigation of Performance and Impacts of Snow and Ice Control Chemicals for Winter Road Service

This work evaluated the performance attributes and impacts of several alternative deicers along with traditional chloride-based deicers. Four Strategic Highway Research Program tests were conducted to evaluate the ice melting, ice penetration, and ice undercutting capabilities of the deicers of interest, and also their impact to the freeze-thaw resistance of portland cement concrete. Three additional novel methods were utilized to assess the friction coefficient of deiced concrete surfaces, thermal properties of the deicers, and corrosion effects of deicers to metals. The laboratory data shed light on the complexity and challenges in evaluating various deicers. To facilitate scientifically sound decision-making, the writers propose a systematic approach to integrate the information available regarding various aspects of deicers, and to incorporate agency priorities, which is expected to aid agencies in selecting or formulating their snow and ice control chemicals.