Analytical Approach to Predicting Temperature Fields in Multilayered Pavement Systems

An accurate and rapid estimation of the pavement temperature field is desired to better predict pavement responses and for pavement system design. In this paper, an innovative method to derive the theoretical solution of an axisymmetric temperature field in a multilayered pavement system is presented. The multilayered pavement system was modeled as a two-dimensional heat transfer problem. The temperature at any location (r,z) and any time t in an N-layer pavement system can be calculated by using the derived analytical solution. The Hankel integral transform with respect to the radial coordinate is utilized in the derivation of the solution. The interpolatory trigonometric polynomials based on discrete Fourier transform are used to fit the measured air temperatures and solar radiation intensities during a day, which are essential components in the boundary condition for the underlying heat transfer problem. A FORTRAN program was coded to implement this analytical solution. Measured field temperature results from a rigid pavement system demonstrate that the derived analytical solution generates reasonable temperature profiles in the concrete slab.     

Comparison of Models for Computing Drainage Discharge

The WAVE model describes the transport and transformations of matter and energy in the soil, crop, and vadose environment. A lateral field drainage subprogram was added to the WAVE model to simulate lateral subsurface drainage flow. The subsurface drainage is considered as the drainage provided by evenly spaced parallel drains with a free outlet: drain tubing or ditch. The rate of subsurface water movement into drain tubes or ditches depends on the hydraulic conductivity of the soil, drain or ditch spacing, hydraulic head in the drains, profile depth, and water table elevation. Hooghoudt's steady-state equation was selected for incorporation in the WAVE model. The subsurface drainage subprogram was calibrated and validated by comparison with the SWAP model (The Netherlands) and DRAINMOD (the United States) and partially by using 7 years of drain outflow data from an experimental field under fallow and cropped conditions. The comparative study revealed that the three models performed equally well and that the models were reliable and accurate tools for predicting the drainage flux as a function of rainfall-evapotranspiration and local conditions. The WAVE model, in comparison to the SWAP and DRAINMOD model, provided as good a prediction of the lateral subsurface drainage flow to drains. The statistical analysis between each model and observed data revealed that the three models were able to predict with sufficient accuracy the observed drainage discharge. The DRAINMOD model, however, has the advantage of giving a more accurate estimate of the discharge, resulting in a more precise modeling. The models were consistent in predicting water table levels, but they could not be verified against field data because of a lack of suitable measurements.     

Numerical Simulations of Efficiency of Curb-Opening Inlets

The geometry of highway pavement and drainage inlets, especially cross slope, longitudinal slope, and local depression and transition length, usually determine the highway surface drainage capacity. In this study, a three-dimensional computational fluid dynamics (CFD) software, FLOW-3D, is used to develop models simulating unsteady, free-surface, shallow flow through curb-opening inlets, thereby demonstrating that an advanced CFD model can be used as a virtual laboratory to evaluate performance (i.e., inlet efficiency) of curb-opening inlets with different geometry conditions. Predicted intercepted flow and inlet efficiency agree well with laboratory measurements. Flow simulations were extended to smaller cross slopes for which laboratory tests were not conducted but which can occur in a highway transition.     

Nonhomogeneous Spectral Element for Wave Motion in Multilayer Systems

This contribution deals with the use of the computationally efficient spectral element technique as a means of analyzing the dynamic behavior of axisymmetric multilayer systems consisting of homogenous and nonhomogeneous material layers and subjected to a stationary but transient force. Focus is placed on the mathematical formulation and numerical verification of a nonhomogeneous spectral element for soil material. The general solution of the wave equations and the boundary value problem are achieved by triple summation over fast Fourier, Fourier–Bessel, and Frobenius series. Practical utilization of the model is presented via a numerical example, which simulates a pavement structure subjected to the dynamic action of a falling weight deflectometer test as typically utilized for pavement structural evaluation.     

Pavement Life-Cycle Cost and Asphalt Binder Quality: Theoretical and Experimental Investigation

Quality control/quality assurance tests can be used to demonstrate that an as-constructed pavement has characteristics different from the contracted specifications of the as-designed pavement because the bitumen employed was of insufficient quality. Many different issues affect asphalt binder quality. Such problems can significantly increase the pavement life-cycle cost, which means that a pay adjustment (PA) is needed. Unfortunately, the quantitative analysis of this issue is very complex. The objectives of this study were to model the dependence of the pavement life-cycle cost on asphalt binder quality and to determine the quantitative relationship between bitumen viscosity and the PA for a given class of boundary conditions. In addition to modeling this problem theoretically, experiments and simulations were carried out through the use of the Mechanistic-Empirical Pavement Design Guide. We then derived the consequences of these effects on life-cycle cost by using a specific life-cycle cost model. Our results demonstrate that asphalt binder viscosity can strongly affect the expected pavement life and the PA, and thus needs to be taken into account in contract and construction management.     

Hydraulic Model for Sedimentation in Storm-Water Detention Basins

Treatment of storm-water runoff may be necessary before discharge to surface waters. In urban areas, space constraints limit selection of conventional treatment systems, and alternative systems are needed. This research program involves design and laboratory testing of a small footprint nonproprietary detention basin which consists of pipes and box culvert sections with a specialized inlet and outlet system. This system can be placed below grade near the roadway section as part of the conventional drainage system and does not require additional right-of-way. A mathematical model, based entirely on hydraulic principles, is developed to estimate particle removal efficiency of the rectangular detention basin for the treatment of storm-water runoff by extending ideal horizontal tank theory under the condition in which water level is varied. A physical model was built in 1/5 scale to measure particle removal performance and validates the conceptual model. Experiments were performed for steady inflow conditions with different inflow rates, durations, and suspended sediment concentrations. Measured time series outflow suspended sediment concentrations and particle removal efficiency compare well with calculated results from the conceptual model. The outflow particle-size distribution can also be estimated using the conceptual model.     

生活垃圾卫生填理场施工质量控制与实践

介绍了九江东郊生活垃圾填埋场填埋库区工程监理质量控制，其环节包括地下水导排系统、防渗膜铺设、填埋气体收集系统、渗滤液收集系统。并着重介绍HDPE土工膜施工过程工程监理实践。     

Calibrated Models of Deicing Agent Solids, Pavement Texture, and Specific Conductivity of Highway Runoff

Field data and existing theory suggest that pavement texture governs the seasonal persistence of deicing agent solids and the storm scale variability of the specific conductivity of highway runoff. We measured precipitation, runoff, and specific conductivity for 50 storms over four deicing seasons at a highway drainage system in southeastern Massachusetts. An average pavement texture of 2.44?mm was measured and 5.17×105?kg of calcium magnesium acetate, salt, and premix applications was reported as well. Catchments and a depression storage layer model the highway drainage system, which routes hyetographs and slowly dissolving deicing agent solids to storm scale hydrographs and specific conductivity pollutographs. We equate the average pavement texture to the depression storage layer depth, which receives applied deicing agent solids, controls their dissolution during a storm, and governs their seasonal scale persistence. The observed average pavement texture, precipitation, and deicing agent applications yield first flush (storm scale) specific conductivity values in the depression storage layer that range from a winter maximum of 15?mS/cm to summer values two orders of magnitude lower. The winter maximum, or seasonal scale first flush of specific conductivity, would be lower for rougher pavement due to slower dissolution. The rougher pavement would also induce stronger persistence of deicing agent solids throughout the year, so that appreciable storm scale first flushes would occur in the summer.     

Applying MODFLOW Model for Drainage Problem Solution: A Case Study from Jahir Irrigated Fields, Israel

High water table and soil salinization processes are common in irrigated fields in Israel. Subsurface drainage systems are a common technique to solve soil salinity problems. Subsurface drainage models can contribute to the efficiency of the drainage system as it can assist in the selection of the proper drainage system and its proper placement in the field. In this study we used the MODFLOW groundwater flow model to simulate groundwater levels in Jahir irrigated fields, the Jordan Valley, Israel. Using a three-layer groundwater flow model, the most efficient drainage system was found to be a combination of deep drains with relief wells and a pump placed in the area with soil salinity problem and upward hydraulic pressure. It was found that simulated drainage system can yield nearly 200,000?m3 of water per year. Given certain information, a spatially distributed groundwater flow model such as MODFLOW can provide more reliable information than different analytical solutions for planning of an effective subsurface drainage system.     

Process Modeling of Storm-Water Flow in a Bioretention Cell

A two-dimensional variable saturated flow model was developed to simulate subsurface flow in bioretention facilities employing the Richards’ equation. Variable hydrologic performances of bioretention are evaluated using the underdrain outflow hydrographs, outflow volumes for 10 storms with various duration and depth, and flow duration curves for 25 different storms. The effects of some important design parameters and elements are tested, including media type, surrounding soils, initial water content, ratio of drainage area to bioretention surface area, and ratio of cell length to width. Model results indicate that the outflow volume via underdrain is less than the inflow; the flow peak is significantly reduced and delayed. Underdrain outflow volume from loamy sand media (with larger Ks) is larger than that from sandy clay loam media. The saturated hydraulic conductivity, storage capacity, and exfiltration into surrounding soils contribute to the hydrologic performance of a bioretention cell. Initial media storage capacity is affected by the hydraulic properties of media soils, initial water content, and bioretention surface area. The exfiltration volume is determined by the surrounding soil type and exfiltration area, dominated by flow through the bottom of the media.     

Calculation of Inflow and Outflow in Phreatic Aquifers

Computer algebraic routines are applied for determination of the phreatic surface from standard boundary-value problems for ordinary differential equations. The method does not require iterative steps as other methods do and therefore may be readily used by engineers. The problem of seepage from (into) an unconfined semiinfinite aquifer into (from) an adjacent reservoir that has a sudden change of water level is revised. Comparisons with the Polubarinova-Kochina series expansion are done. Superelevation of the water table in a wetting regime compared to a drainage regime is quantified by the value of sorptivity (desorptivity). The absolute values of sorptivity and desorptivity diverge as the amplitude of the reservoir level change increases. A problem of a steady flow into (from) a constant head well from (into) an unconfined leaky aquifer is also examined. The water table elevation, well rate, and volume of the cone of depression (injection) are calculated.     

包钢热电厂CCPP循环水系统优化运行的研究

热电厂为包钢用排水大户,本研究目的是通过试验,了解热电厂CCPP(燃气蒸汽联合循环发电)用排水状况及循环水系统运行状态,根据试验研究提出切实可行的热电厂循环冷却水系统优化运行措施,降低热电厂循环水系统新水用量、排污水量,达到节水减排的目的。     

Adjoint Sensitivity Analysis for Shallow-Water Wave Control

An adjoint sensitivity method based on the shallow-water equations is developed for water wave control in river and estuarine systems. The method is used to compute the gradient of a user-defined objective function in the N-dimensional parameter space consisting of system control settings with just one solution of the basic problem and one solution of the associated adjoint problem. Characteristic equations are derived for the adjoint problem and a new formalism is proposed for the sensitivity of shallow-water flow to boundary changes in depth and discharge. New adjoint boundary conditions are developed for river and estuarine forecasting models with open-water inflow and outflow sections. This gives rise to new expressions for sensitivities at these sections. Characteristic analysis of the adjoint and basic problems shows that sensitivities propagate in the reverse time direction along the characteristic paths of the basic problem. The Riemann variables of the adjoint problem are shown to precisely describe the sensitivity of the objective function to changes in depth and discharge at system boundaries. The method is extended to two space dimensions by bicharacteristic analysis.     

Describing Near Surface, Transient Flow Processes in Unconfined Aquifers below Irrigated Lands: Model Application in the Western San Joaquin Valley, California

In order to rigorously examine near surface, field to field interactions between irrigation management regimes and a shallow fluctuating water table, an enhanced deforming finite element (DFE) model was recently developed. The enhanced DFE model, through a process of iteration within each time step, avoids making common assumptions regarding the changing geometry of an aquifer free surface. This paper demonstrates the usefulness and effectiveness of the model by employing it to an irrigated region in the western San Joaquin Valley, Calif., where shallow subsurface tile drains have been installed to control shallow water tables. By virtue of the problems created by the need to dispose off the drainage water, this region has been the focus of several important regional scale modeling exercises, which have evaluated the utility of management strategies, such as source control, groundwater pumping, and land retirement. By refining the focus of the analysis, the enhanced DFE model is found to be able to show that both sources control and managed pumping could be more effective drainage control strategies than predicted based on the results of regional models.     

Regional Salinity Modeling for Conjunctive Water Use Planning in Kheri Command

A one-dimensional water and solute transport UNSATCHEM model is calibrated and validated with a saline water use experiment for wheat and cotton crops. The model is further employed for regional scale salinity modeling with distributed data on soil, irrigation water supply, and its quality from six representative locations from the Kheri command of the Bhakra irrigation system. The wheat–cotton crop rotation, the main rotation in the command, is considered during long-term simulations. The CROPWAT model is used to determine the evapotranspiration requirements of different wheat and cotton crops, while soil water retention parameters are estimated by the RETC model. Atmospheric water and solute boundary conditions are assumed at the top boundary, while free drainage is considered for the lower boundary, as the watertable in the command is sufficiently deep. Simulated salinity and yield values are compared with observed values for regional validation of the model. Critical areas in the command are identified using regional scale modeling results, and applying irrigation water availability and root zone salinity criteria. Guidelines for sustainable conjunctive water use planning are for the Kheri command to get optimum agricultural production despite the use of saline water for irrigation under prevailing scenarios of water availability and its quality.     

Gradually Varied Flow Computation in Cyclic Looped Channel Networks

A novel and computationally efficient algorithm is presented to compute the water surface profiles in steady, gradually varied flows of open channel networks. This algorithm allows calculation of flow depths and discharges at all sections of a cyclic looped open channel network. The algorithm is based on the principles of (1) classifying the computations in an individual channel as an initial value problem or a boundary value problem; (2) determining the path for linking the solutions from individual channels; and (3) an iterative Newton–Raphson technique for obtaining the network solution, starting from initial assumptions for discharges in as few channels as possible. The proposed algorithm is computationally more efficient than the presently available direct method by orders of magnitude because it does not involve costly inversions of large matrices in its formulation. The application of this algorithm is illustrated through an example network.     

Power Series Approach to Holistic Sewer System Modeling

Fast and stable mathematical models for the computation of sewer system outflow are essential for real-time control of urban storm drainage systems. This paper presents a general method to design such models based on the reservoir approach. The unknown inflow-outflow function is developed into a power series. The a priori assumptions made for this are much weaker than the ones for the well-known linear models. The resulting models are nonlinear, but they subsume some of the linear models, depending on the selection of model parameters. Thus, a more general approach to validate the frequently made linearity postulation of the outflow process is provided. The new model is tested with some subcatchments of a larger urban storm drainage network.     

Simultaneous Prediction of Saturated Hydraulic Conductivity and Drainable Porosity Using the Inverse Problem Technique

The saturated hydraulic conductivity K and the effective porosity f are two important input parameters needed for lateral drain spacing design, as well as some other applications. The technical and economic justification, of most drainage projects, is mainly connected to these two parameters. The current design procedure is based upon calculation of the lateral spacing, using some average values of K and f within the drainage area. The objectives of this study were to introduce a new method for simultaneous estimation of K and f parameters using the inverse problem technique, and to evaluate five different unsteady drainage analytical models of the Boussinesq equation, suggested by different researchers for simultaneous prediction of the parameters. Consequently, five different analytical models for predicting water table profiles were solved, using the inverse problem technique. Each model was then evaluated. A physical drainage model of 2.2?m length, 0.3?m width, and 0.5?m height was established in the laboratory and carefully packed with a sandy loam soil. A perforated drainage pipe of 4.5?cm in diameter was installed at the bottom end of the model. Many piezometers were inserted in the soil for spatial and temporal water table monitoring. Different data sets from the experiments and literature were used for model calibration. The newly proposed approach that is based upon measuring water table profiles, at different times, was then evaluated with both constant and variable f. The predicted values of the proposed approach indicated reasonable agreement with the measured data. With variable effective porosity, the method was even more accurate to predict the water table profiles. Using the inverse problem technique, all the analytical models provided good agreement with the measured data. Among these, however, the Topp and Moody model predicted more accurate results than other models.     

A Study of Nonlinear Tire Contact Pressure Effects on HMA Rutting

The Indiana Department of Transportation/Purdue University accelerated pavement testing (APT) facility has been utilized in a number of studies of hot mix asphalt (HMA) rutting performance. The benefit of using APT is that rutting performance can be established in a few days of testing. Finite element (FE) models have been developed for relating APT to in‐service pavement performance. Factors addressed in the models include pavement geometry, boundary conditions, materials, loads, test conditions, and construction variables. Determining the effects of these factors provides a means for better interpreting APT test results and HMA rutting performance. A detailed analysis using 3D and 2D FE has been made of tire/pavement contact pressure effects on rutting. The analyses include tread pattern and constant and varying contact pressure. A creep model is used to represent the HMA time‐dependent material behavior. Based on test data, the material constants in the creep model were back calculated. Results of the FE studies show that the creep model can successfully characterize pavement material behavior through a reasonable approximation of loading and other factors.     

Coexisting conical bipolar and equatorial outflows from a high-mass protostar

The BN/KL region in the Orion molecular cloud is an archetype for the study of the formation of stars much more massive than the Sun. This region contains luminous young stars and protostars but, like most star-forming regions, is difficult to study in detail because of the obscuring effects of dust and gas. Our basic expectations are shaped to some extent by the present theoretical picture of star formation, the cornerstone of which is that protostars accrete gas from rotating equatorial disks and shed angular momentum by ejecting gas in bipolar outflows. The main source of the outflow in the BN/KL region may be an object known as radio source I, which is commonly believed to be surrounded by a rotating disk of molecular material. Here we report high-resolution observations of silicon monoxide (SiO) and water maser emission from the gas surrounding source I. We show that within 60 AU of the source (about the size of the Solar System), the region is dominated by a conical bipolar outflow, rather than the expected disk. A slower outflow, close to the equatorial plane of the protostellar system, extends to radii of 1,000 AU.