Enhanced Criterion for Base Soil Retention in Embankment Dam Filters

In effective filters, potentially erodible base particles are transported to the filter and retained to form a stable self-filtration layer. At any given time, the mass proportion of the filter and the base materials in this layer depends on the initial porosity of the filter and the subsequent porosity of the self-filtration layer. In this paper, an analytical procedure is given to obtain the particle size distribution (PSD) of the self-filtration layer by combining the PSDs of the filter and the base soil modified by Dc95, where 95% of filter constrictions are finer than the size denoted by Dc95. The assessment of internal stability of the PSD of the self-filtration layer forms a rational model to successfully identify the effective filters from their ineffective counterparts. The proposed model is verified by large-scale laboratory tests carried out by the writers in addition to other published data. The model performance is acceptable in relation to various base and filter materials, and provides an alternative and rigorous design approach by eliminating most limitations of the conventional particle based criteria (e.g., D15/d85 ratio).     

Karl Terzaghi: From Theory to Practice in Geotechnical Filter Design

In a period of just over 10 years, Karl Terzaghi proved the idea of a weighted filter in simple laboratory tests while on faculty at the American Robert College in Turkey, patented the concept, developed empirical rules for the grain size distribution of filter through specialist consulting advice on relatively small weirs in Europe, and firmly established those rules as a basis for engineering practice on the Bou-Hanifia Dam in North Africa. The Terzaghi filter criteria are commonly attributed to experience gained on that latter project. However, an evaluation of unpublished letter reports, contract documents, and correspondence suggests the evolution of those criteria for soil retention and permeability occurred during his earlier collaboration with the Austrian consulting company of J. Pfletschinger & Co. This new insight appears to be confirmed by the uncovering of a draft patent claim, prepared in the name of Josef Pfletschinger, which sets out the precise details of those filter criteria and whose existence was acknowledged in contract documents for Bou-Hanifia.     

General Strength Criterion for Geomaterials

This note presents the results of a study on the variation of the strength of geomaterials. A general isotropic strength criterion is proposed which unifies the peak strength and critical state (or steady state) strength into one strength criterion. The proposed criterion describes the strength of a geomaterial in terms of its current stress state, its current voids ratio, and the bonding of its constituents. The proposed criterion has been applied to sand, clay, cemented sand and rocks. Based on comparisons presented between theoretical simulations and experimental data, it is seen that the proposed criterion describes successfully the isotropic strength of all these materials for general stress conditions.     

贵溪冶炼厂防腐工程的设计与施工

冶炼厂的防腐工程施工和设计同样重要,本文针对我厂实际情况从设计与施工出发探讨各区域及建筑物各部位防腐做法的成功与不足之处,以供参考.     

Three-Dimensional Hoek-Brown Strength Criterion for Rocks

A great number of rock strength criteria have been proposed over the past decades. Of these different strength criteria, the Hoek-Brown strength criterion has been used most widely, because: (1) it has been developed specifically for rock materials and rock masses; (2) its input parameters can be determined from routine unconfined compression tests, mineralogical examination, and discontinuity characterization; and (3) it has been applied for over 20?years by practitioners in rock engineering, and has been applied successfully to a wide range of intact and fractured rock types. The Hoek-Brown strength criterion, however, does not take account of the influence of the intermediate principal stress, although much evidence has been accumulating to indicate that the intermediate principal stress does influence the rock strength in many instances. In this paper, a three-dimensional (3D) version of the Hoek-Brown strength criterion has been proposed. The original Hoek-Brown strength criterion is just a two-dimensional (2D) version of the proposed 3D strength criterion. The 3D strength criterion not only inherits the advantages of the original Hoek-Brown strength criterion, but can take account of the influence of the intermediate principal stress. Polyaxial or true triaxial compression test data of intact rocks and jointed rock masses has been collected from the published literature and used to validate the proposed 3D Hoek-Brown strength criterion. Predictions of the proposed 3D Hoek-Brown strength criterion are in good agreement with the test data for a range of different rock types. The proposed 3D Hoek-Brown strength criterion is also compared with a simplified 3D Hoek-Brown strength criterion proposed by Pan and Hudson. The Pan-Hudson criterion cannot be considered a true 3D version of the Hoek-Brown criterion, because it does not reduce to the form of the original Hoek-Brown criterion at either triaxial or biaxial state. The Pan-Hudson criterion underpredicts the strength at the triaxial state, but overpredicts the strength at the biaxial state.     

新型过滤机的研究设计

本文审视了各类过滤机设备的现状后，介绍了新型过滤机的研究设计概况，对其性能及特点作了分析，阐明其应用的灵活性和多功能性，指出该机可替代目前所用的各类过滤机，它的广泛推广应用将会带来显著的经济效益、环境效益和综合社会效益。     

Nonlinear Unified Strength Criterion for Concrete under Three-Dimensional Stress States

This paper shows that the mechanical behavior of concrete materials can be described by a nonlinear unified strength criterion which requires four independent parameters for model calibration. The criterion covers all the area from spatially mobilized plane curve in the lower bound to Mises circle in the upper bound on the deviatoric plane, with an exponential curve on the meridian plane in principal stress space. Four material parameters in the strength criterion have their clear physical meanings and their determination approaches are also given. Four sets of true triaxial experimental results are compared with the modeling results of the proposed criterion. It shows that the proposed criterion is capable to capture the characteristics of yielding and failure and reasonably calculate the multiaxis strength of concrete materials.     

Three-Dimensional Multiscale Bifurcation Analysis of Granular Media

This paper deals with Hill’s bifurcation criterion, which is very well suited to describe various failure modes in granular media. The first part of this paper is dedicated to the analytical and numerical investigation of this criterion by considering phenomenological constitutive relations: the incrementally piece-wise linear and nonlinear relations proposed by Darve. The 3D bifurcation domain and 3D cones of unstable directions are given for these two relations. A similar analysis is performed with a micromechanical model in the second part of the article. Finally, a qualitative comparison of the results obtained with these two different approaches leads us to some key conclusions about this material instability criterion, which is studied for the first time for general 3D conditions, by considering these nonconventional constitutive relations.     

Simple Single-Surface Failure Criterion for Concrete

This technical note presents a new single-surface failure criterion for concrete that is derived using an approach developed for geologic materials. The main advantage of the proposed failure criterion is its simplicity and ease of implementation into nonlinear finite-element programs compared to existing criteria based on tension and compression meridians and a third function defining the deviatoric trace between meridians. The new failure criterion is able to closely describe concrete strength under general three-dimensional stress states and it gives improved predictions of concrete strength under plane stress conditions compared to existing single function models. A method for deriving the strength parameters is presented so that practitioners may consider adapting the function for materials such as high-strength or steel fiber-reinforced concrete. The work summarized herein is considered novel practical information that should be of use to practitioners wanting to implement simple phenomenological models for concrete in their finite element codes.     

Energy Capacity Criterion for the Design of Columns against Collapse

Current practice in buckling design is based on the ultimate strength of a member such that excessive lateral deflections do not occur. This ultimate strength is often dictated by empirically derived formulae which correspond to postulated element imperfections including residual stresses. In this paper, the postbuckling behavior of columns is considered, and the limit state is considered to be total collapse. The load versus end displacement relationship is derived for a simplified elastic–perfectly plastic column model. Using this curve, the energy absorbed and released in going from one load/deflection state to another can be easily quantified. With this, the energy absorption capacity of an already loaded column is considered to be the critical performance metric. This “energy capacity criterion” is then used to develop alternative design curves for different levels of energy absorption capacity.     

Use of Impedance Probe for Estimation of Porosity Changes in Saturated Granular Filters under Cyclic Loading: Calibration and Application

Gravimetric and volumetric sampling techniques are reliable for the measurement of porosity in fully saturated granular filters. However, both methods require a significant effort to gather and prepare samples, are time intensive to process, and do not capture real-time changes. Portable impedance probes serve as a valuable alternative to these destructive and laborious sampling methods. These probes measure the dielectric properties of the soil-water mixtures from which the porosity of filters may be inferred. This study demonstrates that generalized calibrations can result in large errors for porosity estimation when using diverse and small-scale filter types. By comparing with gravimetric and volumetric based porosity measurements for saturated granular filter porosity, impedance probes with filter-specific calibration offer the reliability and confidence owing to its reduced error in a quick, nondestructive fashion. This paper also presents the results of a laboratory investigation using an impedance probe to monitor real-time changes in the porosity of saturated granular filters subjected to cyclic train loading.     

热轧厂35kV右母线滤波装置优化

热轧厂在轧制难度大的产品时，引进的３５ｋＶ右母线滤波装置经常过流跳闸，并影响主变压器跳闸。通过现场测试，对过流跳闸原因进行综合分析，确定了设备优化改造对策。经１年多时间的实践考核证明改造是成功的。     

Engineering, Design and Construction of Lunar Bases

How do we begin to expand our civilization to the Moon? What are the technical issues that infrastructural engineers, in particular, must address? This paper has the goal of introducing this fascinating area of structural mechanics, design, and construction. Published work of the past several decades about lunar bases is summarized. Additional emphasis is placed on issues related to regolith mechanics and robotic construction. Although many hundreds of papers have been written on these subjects, and only a few tens of these have been referred to here, it is believed that a representative view has been created. This summary includes environmental issues, a classification of structural types being considered for the Moon, and some possible usage of in situ resources for lunar construction. An appendix provides, in tabular form, an overview of structural types and their lunar applications and technology drivers.     

Framework of Success Criteria for Design/Build Projects

Success has always been the ultimate goal of every activity, and a construction project is no exception. Due to the ambiguous definition of project success and the different perceptions of participants toward this concept, it may be difficult to tell whether a project is successful as there is a lack of consensus. Time, cost, and quality have long been the success criteria used to evaluate the performance of a construction project. However, such a list has been criticized as not being comprehensive. Even studies of the project success of a particular construction method, such as the design/build procurement system, are lacking in most previous research considering construction projects in general. This paper sets out to establish criteria for project success for a design/build project in construction, first by identifying relevant measures of project success for a construction project in past studies, with particular emphasis on design/build projects, and then by establishing a comprehensive assessment framework for project success for design/build projects. The significant impacts on the construction field of study, in terms of educational value and practical use, are also presented. With little research in the project success of design/build projects, the writers suggest a research focus for the study.     

Failure Criterion for Structural Masonry based on Critical Plane Approach

The paper presents a macroscopic failure criterion for structural masonry. This criterion is derived within the framework of the critical plane approach. First, a general discussion is provided examining the performance of this framework in the context of classical linear as well as nonlinear criteria. Subsequently, a bilinear form of failure criterion for structural masonry is proposed incorporating a set of distribution functions for describing the spatial variation of material properties. Extensive numerical study is performed examining the behavior in biaxial compression–tension and compression–compression regimes for different orientations of the sample relative to the loading direction. The results are compared with the available experimental data.     

Identifying a Design Management Package to Support Concurrent Design in Building Wafer Fabrication Facilities

Concurrent design is commonly used in building a semiconductor wafer fabrication facilities to shorten projects. Current practice in managing a design schedule involves preset milestones that represent percentages of completion. Such a simple control scheme does not provide sufficient information to support concurrent design. This study presents an analytical model that applies a cluster identification algorithm to separate the work of designing a multisystem project into management packages that support concurrent design. Tasks within a package have strong informational dependency relationships on each other, and are not suited for concurrent design. Tasks of different packages have weak dependency relationships on each other, and are suited for concurrent design. Tendering design work based on these packages may reduce the number of design interfaces between participating design firms. Possible application of the model includes the management of design schedule, design contract tendering, and design information flow.     

Achieving Lean Design Process: Improvement Methodology

An improvement methodology is proposed for the design process in construction projects. Based on concepts and principles of lean production, the methodology considers the design process as a set of three different models—conversion, flow, and value. Four stages are necessary to produce improvements and changes—(1) diagnosis/evaluation; (2) changes implementation; (3) control; and (4) standardization. The methodology suggests the application of seven tools in accordance to specific needs (detected and desired) on five potential areas of improvement—client, administration, project, resources, and information. Results of an application included an increase of 31% in the share of value adding activities, 44% reduction of unit errors in the products, up to 58% decrease of waiting times in the process, and an expansion of the utilization in the cycle times. In this manner, not only did the efficiency and effectiveness of internal engineering products improve, but also the whole project, by improving one of the main suppliers of construction.     

Apparatus for Streaming Potential Measurements on Granular Filter Media

This paper is intended to provide the necessary information to construct and properly operate a simple streaming potential apparatus capable of measuring the zeta potential of granular media. Through an understanding of the principles of the technique, such a device can readily be used in the study of a variety of granular materials including unstable and dynamic surfaces, as shown for surface coatings and even biofilm growth. The simplified mathematical theory of the streaming potential is herein explained, as well as operational factors and the general reasons for nonreproducible measurements such as electrode maintenance, electrode polarization, nonzero rest potentials, and sample equilibration. This specific apparatus design is intended for use with granular materials and has intentionally been developed in a simplistic fashion to encourage wider usage of the technique. The overall precision of this instrument was ±10% based on a 95% confidence interval. In addition, the accuracy of the device was found to be very good based on comparisons with literature values.     

Empirical Comparison of Design/Build and Design/Bid/Build Project Delivery Methods

This study compares the performance of design/bid/build and design/build to see if one project delivery method is superior in regards to time and cost. Similar military buildings were used to identify two samples of projects delivered with each of the two delivery methods. These projects provide a meaningful comparison because they include buildings of the same typology (i.e., U.S. Navy Bachelor Enlisted Quarters) delivered using similar design models. Project duration, project duration per bed, project time growth, cost growth and cost per bed were statistically compared. Upon completion of the analysis, the hypothesis that design/build projects are superior to design/bid/build projects in regards to time and cost was tested. Design/build projects were proven superior in performance in almost every measure. Other findings, including recommendations to practitioners and researchers, will be provided as well.     

Behavior of Field-Scale Biotrickling Filter under Nonsteady State Conditions

The performance of a field-scale biotrickling filter was investigated for the treatment of styrene vapors released from a bathtub manufacturing process. The two-stage biotrickling filter was operated in series with an average gas flow rate of 350 m3?h?1 corresponding to an overall empty bed gas contact time of 84 s. Daily average values of styrene removal efficiency varied from 40 to 90% with inlet concentrations ranging between 0.4 and 1.7 g?m?3. System performance was not significantly affected by changes in temperature and was moderately susceptible to 3-day starvation or complete system shutdown. After 7 months of styrene treatment, toluene contaminated air was fed to the system and experiments were performed in which styrene and toluene were fed alternately at 3-h intervals. While styrene elimination remained unchanged over the cycles, the elimination capacity of toluene increased with the number of cycles, indicating some adaptation of the process culture to the new contaminant. Overall, the results suggest that biotrickling filters for air pollution control can be successful even under greatly varying operating conditions.