Design Method for Geogrid-Reinforced Unpaved Roads. I. Development of Design Method

A theoretically based design method for the thickness of the base course of unpaved roads is developed in this paper, which considers distribution of stress, strength of base course material, interlock between geosynthetic and base course material, and geosynthetic stiffness in addition to the conditions considered in earlier methods: traffic volume, wheel loads, tire pressure, subgrade strength, rut depth, and influence of the presence of a reinforcing geosynthetic (geotextile or geogrid) on the failure mode of the unpaved road or area. In this method, the required base course thickness for a reinforced unpaved road is calculated using a unique equation, whereas more than one equation was needed with earlier methods. This design method was developed for geogrid-reinforced unpaved roads. However, it can be used for geotextile-reinforced unpaved roads and for unreinforced roads with appropriate values of relevant parameters. The calibration of this design method using data from field wheel load tests and laboratory cyclic plate loading tests on unreinforced and reinforced base courses is presented in the companion paper by the authors.     

Estimation of Axial Load Capacity for Bored Tapered Piles Using CPT Results in Sand

Tapered piles in comparison to cylindrical piles can be beneficial in terms of the load capacity. In this paper, estimation of the load capacity for tapered piles using cone penetration test (CPT) resistance was investigated. Fourteen calibration chamber load tests using different pile types and six CPTs were conducted under various soil conditions. From the calibration chamber test results, the total, base, and shaft load capacities were analyzed in terms of soil conditions and taper angle. To evaluate CPT-based load capacity of tapered piles, normalized base and shaft resistances were obtained from normalized unit load-settlement curves. Based on the normalized base and shaft resistances, design equations that can be used to evaluate the base and shaft resistances of tapered piles were proposed. The proposed method is valid for sands of medium to dense conditions, while it may result in unconservative predictions for loose sands. To check the accuracy of the proposed method, field load tests using both cylindrical and tapered piles were conducted and compared with the predictions using the proposed method. A simplified approach using an equivalent cylindrical pile was also investigated and compared.     

Calibration Assessment and Data Collection for Water Distribution Networks

Calibration of a water distribution network is intended to develop a model that mimics field conditions under a range of demand distributions. In this paper, a three-step calibration procedure is developed that considers the uncertainties in measurement and estimation and provides a measure of the quality of the calibration. The approach can also be used to identify preferable conditions for data collection. The procedure's steps are parameter estimation, calibration assessment, and data collection design. Parameter estimation considers input uncertainty and the resulting uncertainty in model parameters. Calibration assessment analyzes the propagation of the parameter errors on model predictions. The trace of the covariance matrix of the predictive heads is used to measure the model uncertainty. Based on this uncertainty and using a sensitivity-based heuristic analysis, data collection experiments can be designed for systemwide tests and critical pipe for individual pipe tests. An example system is analyzed to select calibration demand conditions.     

Estimation of Load Capacity of Pipe Piles in Sand Based on Cone Penetration Test Results

Pipe piles can be classified as either closed- or open-ended piles. In the present paper, the load capacity of both closed- and open-ended piles is related to cone penetration resistance qc through an experimental program using calibration chamber model pile load tests and field pile load tests. A total of 36 calibration chamber pile load tests and two full-scale field pile load tests were analyzed. All the test piles were instrumented for separate measurement of each component of pile load capacity. Based on the test results, the normalized base resistance qb/qc was obtained as a function of the relative density DR for closed-ended piles, and of both the relative density DR and the incremental filling ratio (IFR) for open-ended piles. A relationship between the IFR and the relative density DR is proposed as a function of the pile diameter and driving depth. The relationship between IFR and DR allows the estimation of IFR and thus of the pile load capacity of open-ended piles at the design stage, before pile driving operations.     

含31个元素铝基光谱标准样品的制备及定值结果

阐述了含31个元素铝基光谱标准样品的制备工艺、数据处理、定值结果等。研制出的标样经过生产试用达到设计指标,满足了国内外各大厂家在调整、校对先进光谱仪器时对标准样品的需求,为准确分析铝合金中各元素化学成分以及公司新产品的研发提供了技术支持和实物保障。其主要技术指标已达国际同类标样先进水平。     

Empirical Partitioning Leach Model for Solidified∕Stabilized Wastes

A model has been developed to describe dynamic leaching of metal contaminants from solidified wastes using data for calibration that are taken only from batch tests. The model describes the three major factors affecting leaching: (1) acid∕base reactions that determine the pH within the waste; (2) pH-dependent reactions that determine whether the contaminants are in mobile or immobile forms; and (3) diffusion that transports mobile contaminants from the waste. Acid∕base reactions and mobilization∕immobilization reactions of contaminants are described by empirical equations calibrated from batch equilibrium tests. Precipitation or sorption reactions are used to describe partitioning of contaminants among mobile and immobile forms. Fickian diffusion is used to describe transport of soluble compounds. Model predictions for observed diffusivities of copper, chromium, lead, and zinc agreed well with the experimental data obtained from dynamic leaching tests. Little difference was observed in model predictions when contaminant immobilization was assumed to be caused by precipitation or by sorption. Model simulations indicate that the assumption of an infinite bath may not apply to dynamic leach tests when contaminants are strongly immobilized.     

Model of Water Application under Pivot Sprinkler. II: Calibration and Results

A distributional semiempirical model for the simulation of spatial distribution of water application under center pivot sprinklers has been developed by the writers. This method describes the probability of water application for a sprinkler using a combination of beta functions. The calibration of this model has been undertaken using laboratory tests conducted in controlled conditions and then in windy conditions. The parameters calibrated are listed. The minimum number of tests needed for calibration has been estimated. The model used can be calibrated from one test in controlled conditions and three or four tests in windy conditions covering the range of usual wind speeds. Validation should be performed using at least two more infield tests. This simulation model of spatial water distribution under sprinklers of center pivot will thereafter be used to simulate the distribution of water under a typical pivot machine.     

Constriction-Based Retention Criterion for Granular Filter Design

The filter design criteria in practice are currently based on laboratory tests that were carried out on uniform base soil and filter materials. These criteria mostly involve specific particle size ratios, where the system of base soil and filter is represented by some characteristic particle sizes. Consequently, these criteria have limitations when applied to nonuniform materials. In filters, it is the constriction size rather than the particle size that affects filtration. In this paper, a mathematical procedure to determine the controlling constriction size is introduced, and subsequently, a constriction-based retention criterion for granular filters is presented. The model also incorporates the effect of nonuniformity of base soil in terms of its particle size distribution, considering the surface area of the particles. The proposed retention criterion is verified based on experimental data taken from past studies plus large-scale filtration tests carried out by the authors. The model successfully and distinctly demarcates the boundary between effective and ineffective filters in the case of cohensionless base soils.     

Audiometric bone conduction

Audiometric bone conduction test data are obtained with a unit that permits comparison with a recognized standard because the unit can be calibrated to operate within specified limits. Proper calibration of the unit is necessary if the equipment is to be accurate. Two procedures can be helpful in determining the need for calibration: the average loss method and the input voltage measurement method. Neither should supplant calibration, but each offers a means of checking the output of the unit. Confidence in auditory test data is increased when there is a high degree of consistency among the various tests; the availability of several different tests in the audiometric series can be used to an advantage then in a determination of consistency. An additional opportunity to ascertain the existence of consistency is present when tuning fork tests are employed as part of the total evaluation. The use of a masking stimulus in the nontest ear simultaneously with the presentation of the test tone to the test ear can be extremely useful in defining the type as well as the extent of the hearing loss. Presentation of the test tone and the masking stimulus in controlled discrete steps is the key to the interpretation of masking results.     

高炉渣控样的研制与应用

对高炉渣内控样成分变化的原因进行了分析,提出了补救措施及解决办法,为控样的长期使用提供了依据.     

Design aspects of calibration studies in nutrition, with analysis of missing data in linear measurement error models

Motivated by an example in nutritional epidemiology, we investigate some design and analysis aspects of linear measurement error models with missing surrogate data. The specific problem investigated consists of an initial large sample in which the response (a food frequency questionnaire, FFQ) is observed and then a smaller calibration study in which replicates of the error prone predictor are observed (food records or recalls, FR). The difference between our analysis and most of the measurement error model literature is that, in our study, the selection into the calibration study can depend on the value of the response. Rationale for this type of design is given. Two major problems are investigated. In the design of a calibration study, one has the option of larger sample sizes and fewer replicates or smaller sample sizes and more replicates. Somewhat surprisingly, neither strategy is uniformly preferable in cases of practical interest. The answers depend on the instrument used (recalls or records) and the parameters of interest. The second problem investigated is one of analysis. In the usual linear model with no missing data, method of moments estimates and normal-theory maximum likelihood estimates are approximately equivalent, with the former method in most use because it can be calculated easily and explicitly. Both estimates are valid without any distributional assumptions. In contrast, in the missing data problem under consideration, only the moments estimate is distribution-free, but the maximum likelihood estimate has at least 50% greater precision in practical situations when normality obtains. Implications for the design of nutritional calibration studies are discussed.     

Design and calibration of unicapillary pneumotachographs

This study presents a method for design and calibration of unicapillary pneumotachographs for small-animal experiments. The design, based on Poiseuille's law, defines a set of internal radius and length values that allows for laminar flow, measurable pressure differences, and minimal interference with animal's respiratory mechanics and gas exchange. A third-order polynomial calibration (Pol) of the pressure-flow relationship was employed and compared with linear calibration (Lin). Tests were done for conditions of ambient pressure (Pam) and positive pressure (Ppos) ventilation at different flow ranges. A physical model designed to match normal and low compliance in rats was used. At normal compliance, Pol provided lower errors than Lin for mixed (1-12 ml/s), mean (4-10 ml/s), and high (8-12 ml/s) flow rate calibrations for both Pam and Ppos inspiratory tests (P < 0.001 for all conditions) and expiratory tests (P < 0.001 for all conditions). At low compliance, they differed significantly with 8.6 +/- 4.1% underestimation when Lin at Pam was used in Ppos tests. Ppos calibration, preferably in combination with Pol, should be used in this case to minimize errors (Pol = 0.8 +/- 0.5%, Lin = 6.5 +/- 4.0%, P < 0.0005). Nonlinear calibration may be useful for improvement of flow and volume measurements in small animals during both Pam and Ppos ventilation.     

宝钢1580热轧精轧机辊缝零调研究

针对宝钢分公司1580热轧精轧机辊缝零调过程中出现的一些问题,比如轧制力偏差大、辊缝预埋不准确、零调过程受人为因素影响而无法确定统一标准等进行了研究,并提出了解决方案.通过对轧机的刚度实验,找出了轧制力和油柱值之间的线性关系,以此实验数据为基础,改进辊缝零调控制程序,实现了轧制力静偏差的自动调平,零调辊缝的自动预埋等目标.同时通过完善转车联锁条件,杜绝了零调过程中的人为误差.改进前后精轧机辊缝零调数据的对比表明,达到了改进的预期效果,解决了现场存在的实际问题.     

Load Testing of a Closed-Ended Pipe Pile Driven in Multilayered Soil

Piles are often driven in multilayered soil profiles. The accurate prediction of the ultimate bearing capacity of piles driven in mixed soil is more challenging than that of piles driven in either clay or sand because the mechanical behavior of these soils is better known. In order to study the behavior of closed-ended pipe piles driven into multilayered soil profiles, fully instrumented static and dynamic axial load tests were performed on three piles. One of these piles was tested dynamically and statically. A second pile served as reaction pile in the static load test and was tested dynamically. A third pile was tested dynamically. The base of each pile was embedded slightly in a very dense nonplastic silt layer overlying a clay layer. In this paper, results of these pile load tests are presented, and the lessons learned from the interpretation of the test data are discussed. A comparison is made of the ultimate base and limit shaft resistances measured in the pile load tests with corresponding values predicted from in situ test-based and soil property-based design methods.     

Bayesian Model Calibration Using Geotechnical Centrifuge Tests

The predicted performance using a geotechnical prediction model is expected to deviate from reality. A practical approach to assess the model error is through calibration with observed performances in physical model tests. In this paper, a Bayesian framework of model calibration using centrifuge modeling tests is proposed and the procedure of model calibration is illustrated. Two centrifuge tests conducted to investigate the performance of soil slopes under rainfall conditions are used to calibrate a coupled hydromechanical analysis model. It is found that for centrifuge tests with different levels of soil variability, the test with a smaller variability of soil properties is more efficient for model calibration. According to the concept of random field, a centrifuge model with a larger model size and accelerated to a lower acceleration is better for model calibration. When the discrepancy between the performance interpreted from the centrifuge model and the field performance is small, the improvement of the reliability estimation for a new slope is significant. However, when there is little information about the discrepancy, the reliability estimation cannot be significantly improved by the information from centrifuge modeling. The proposed procedure is shown to be able to quantify the calibration effects of centrifuge tests and may be used to achieve a more reliable calibration.     

Effect of Penetration Rate on Cone Penetration Resistance in Saturated Clayey Soils

In this paper, the effects of penetration rate on cone resistance in saturated clayey soils are investigated. Shear strength rate effects in clayey soils are related to two physical processes: the increase of shear strength with increasing rate of loading and the increase of shear strength as the process transitions from undrained to drained. Special focus is placed on this second effect. Cone penetration tests were performed at various penetration rates both in the field and in a calibration chamber, and the resulting data were analyzed. The field cone penetration tests were performed at two test sites with fairly homogeneous clayey silt and silty clay layers located below the groundwater table. Additionally, tests with both cone and flat-tip penetrometers in sand-clay mixtures were performed in a calibration chamber to investigate the change in drainage conditions from undrained to partially drained and from partially drained to fully drained. A series of flexible-wall permeameter tests were conducted in the laboratory for various clayey sand mixtures prepared at various mixing ratios in order to obtain values of the coefficient of consolidation, which is required to estimate the penetration rates below which penetration is drained and above which penetration is undrained. A correlation between cone resistance and drainage conditions was established based on the results of the calibration chamber and field penetration tests.     

Extrapolation for Future Maximum Load Statistics

The use of short-term load data to extrapolate or project remote future maximum load has been practiced in structural design code development and/or calibration. However, this approach has not been adequately evaluated or validated because of the absence of long-term data, which is important for the structures’ safety governed by these codes. In this paper, the application of such extrapolations to highway bridge design is studied by taking advantage of available long-term truck weight data obtained from the weigh-in-motion technique. A new extrapolation method is proposed from the understanding of the importance of the load probability distribution’s high tail. This approach significantly reduces the mathematical length of the extrapolation/projection and thus increases its reliability. Also presented in this paper are application examples. In addition, the extrapolation process proposed is evaluated with quantitative indexes. The application of a temporal extrapolation/projection can now be evaluated by using these indexes for its reliability and appropriateness.     

接触式板形仪通用动态测试标定平台的开发与应用

介绍了三种典型接触式板形测量仪的结构组成、测量原理及其校正装置,开发了一套通用板形仪动态模拟标定平台,并给出了使用步骤。实验结果表明,该平台稳定可靠,标定方法实用有效,并可对板形仪进行各种补偿算法测试。     

Evaluation of a Minimum Base Resistance for Driven Pipe Piles in Siliceous Sand

This paper provides a rational method for evaluating a realistic lower bound for the base resistance of pipe piles in siliceous sand. Separate expressions are developed to represent the response to load of the pile plug, the sand below the pile base, and the sand below the pile annulus. These expressions are combined to give the overall base response of a pipe pile. Predicted responses are compared with databases compiled on the ultimate capacities of pipe piles and with base pressure-displacement characteristics observed in static load tests. The estimations are shown to match observed base resistances of large diameter piles for which the coring mode of penetration during driving dominates.     

Determination of dimethindene in human tears by high-performance liquid chromatography

A high-performance liquid chromatographic method is described for the determination of dimethindene in human tears. The tear samples were diluted in a 0.01 M hydrochloric acid-n-propanol mixture to prevent the irreversible adsorption of dimethindene. The diluted samples were directly injected into the chromatographic system to avoid sample pretreatment. The validation data demonstrate that the method is specific, precise and accurate within the calibration range of 12 to 1000 ng/ml dimethindene free base.