IRANIAN JOURNAL OF SCIENCE AND TECHNOLOGY TRANSACTION B- ENGINEERING
Year:2007 | Volume:31 | Issue:B2|Papers Count:13

The variation of pore fluid properties in soil has a major effect on soil behaviour. This effect is a function of pore fluid properties and soil mineralogy. Such variation usually happens in the reservoirs of dams or in some geotechnical projects. The electro conductivity (EC) measurement is a simple method to monitor any variation in the pore fluid of soils. EC is the ability of a material to transmit (conduct) an electrical current. This paper focuses attention on the effect of soil-pore fluid interaction on the EC of clayey soils. A set of physico-chemical experiments are performed and the role of different factors including soil pH, soil mineralogy, soil: water ratio, cation and anion effects are investigated. The results of this study indicate that for soil that has a relatively low CEC, the anion type is an important factor, while the cation type does not noticeably affect the EC of the soil-solution. However, for such soil, an electrolyte property, i.e. its solubility, is much more effective than the CEC of the soil. In addition, it was observed that in the presence of neutral salts such as pore fluid, the pH of the soil-solution decreases causing an increase in the EC of the soil sample.

A multi-plane model for the post-liquefaction of the undrained behaviour of sand is presented. The model incorporates the critical/steady state concept that postulates the existence of a state where sand continuously deforms at a certain constant effective stress depending two main parameters of both initial bulk parameters (i.e. void ratio or relative density) and stress level (i.e. mean stress). The local instability of saturated sand within post-liquefaction is highly dependent on the residual inherent/induced anisotropy, bedding plane effects, and stress/strain path.Most of the models developed using stress/strain invariants are not capable of identifying the parameters depending on orientation such as fabric. This is mainly because stress/strain invariants are quantities similar to scalar quantities and not capable of carrying directional information with themselves. The constitutive equations of the model are derived within the context of the non-linear elastic behaviour of the whole medium and the plastic sliding of interfaces of predefined multi-planes.The proposed multi-plane based model is capable of predicting the behaviour of soils on the basis of plastic sliding mechanisms, elastic behaviour of particles and possibilities to see the micro-fabric effects as natural anisotropy as well as induced anisotropy in plasticity. The model is capable of predicting the behaviour of soil under different orientations of the bedding plane, and the history of strain progression during the application of any stress/strain paths. The influences of the rotation of the direction of principal stress and strain axes and induced anisotropy are included in a rational way without any additional hypotheses. The spatial strength distribution at a location as an approximation of the probable mobilized sliding mechanism is presented by an ellipsoid function built up on the bedding plane.

Each year, due to the uncontrolled exit of vehicles from the roadway and hitting roadside obstacles -especially rollovers on embankments-huge costs are imposed on communities. For the reduction of such costs, different safety improvement programs may be implemented; for example guard installations, embankment slope reduction and/or the roadside clear zone enhancement. But the real problem always is the scarcity of available resources and how to allocate such scarce resources among the proposed alternatives and programs. In this research work, by developing a specific approach, the optimized technique for the allocation of financial resources for safety improvement of roadside embankments is presented. Additionally, by developing special graphs, such facility is provided for planners and designers in different sections of road construction and maintenance to make optimum decisions either to install protective guards or to flatten roadside slopes. The results might also be beneficial for the correction and/or completion of the present related code of standards.

Post incident traffic management on a freeway network depends mainly on the decisions of traffic managers that surface from their individual exposure to similar conditions. This manual approach to tackle a dynamic scenario induces uncertainty, inconsistency and inefficient use of rescue resources. This paper suggests a decision support scheme known as Freeway Incident Analysis System, (FIAS). The novel idea presented here is the use of real time data from the Toll Collection System (TCS) and Vehicle Detection System (VDS). This data is conjugated with the historical data on a microscopic simulation platform to predict traffic flows in a post-incident scenario. The system employs Cellular Automata for the microscopic simulation of vehicle movement, and we also suggest two additional rules in the modified version of the conventional model. This has enabled us to model the dynamic flow parameters in a post incident scenario more realistically. The evaluation of FIAS indicates that it yields significantly accurate post incident information about traffic flows for the use of traffic managers.

The purpose of this research is to present an optimum model for route location considering access to all the main points of the roads, passing compulsory points and having the minimum total cost. It is assumed in this research that the involved areas are level or rolling. The major capability of such models is predicting protected areas in an optimal corridor route location. In this paper, after describing the fulfilled studies in the field of road alignment, two mathematical models for alignment in level areas are presented. In the first model the forbidden zones are not considered, but in the second model the forbidden zones are prevented from being passed through by modeling these zones in a circular shape. In this research the mathematical non-linear programming has been used for modeling.

This study tries to characterize national transportation modes to assess balancing and sustainability. Using a pioneer measure for sustainable development (SD), and based on the conformity of the growths of all sectors with transportation modes, the countries are comparatively studied. The proposed measure, elasticity, for each pair of variables indicates the extent to which the two variables have been changing consistently. Indeed the elasticity values are measures of" harmonic development" reflecting sustainability. The study database consisted of key aspects of transportation sustainability in the form of national variables including transportation, economic, social and environmental categories in the period 1980-1995. Having developed the elasticity of the social, environmental and economic variables with respect to those of modal transportation, composite modal sustainability indices were suggested. The composite indices were then integrated into a unique SD index utilizing the Data Envelopment Analysis (DEA), and Concordance Analysis (CA) techniques. For comparative appraisal, country ranking and grouping based on DEA scores, as well as CA results were developed. The sustainability appraisal showed interesting patterns within and between group similarities and differences. The study confirmed the significance of modal transportation balancing and sustainability challenges of the 21st century. The research focus is on its methodology. Thus, the data gathered from any other time period and geographical scope may be used for further analysis.

Debris flows caused by moraine-dam failure are common on the Qinghai-Tibet Plateau in China. Peak discharges of debris flows should be predicted to evaluate the risk to people and property in valleys below the moraine dams. On the basis of the critical wave method, we have reduced a new series of formulas about the peak discharge of debris flow, including the peak discharge (Qdmax) at the outlet of a failed moraine-dammed lake: m Qdmax= kqm or Qdmax= kQmax , and the maximal height of the flow below the dam (Hdmax): Hkh= hKH Hmax .The calculated peak discharge agrees well with the estimate based on the field data at Midui Gully, Tibet. The critical wave method may be applicable to moraine dams in other areas, including the entire Qinghai-Tibet Plateau region and the European Alps.

In seismic areas, ductility is an important factor in the design of high strength concrete (HSC) members under flexure. In order to investigate this, here in this study, eight HSC beams with different percentages of  r & r’ were cast and incrementally loaded under bending. During the test, the strain on the concrete middle faces, the tension and compression bars, and also the deflection at different points of the span length were measured up to failure. Based on the obtained results, the serviceability and ultimate behavior, and especially the ductility of the HCS members are more deeply reviewed. Also a comparison between theoretical and experimental results is reported here.

The European part of Turkey, the Thrace region, is of agricultural and industrial importance for the country and hence irrigational and industrial water demand drastically increases, whereas most of the rivers in the region have no flow in summer. Two gauged hydrological basins are studied in order to analyze the following stream flow characteristics of the region: Randomness, jump, trend, and best-fit probability distribution. Selected gauging stations are found with random annual stream flow data for a 40 year observation period (1961-2000). No jump is observed in the annual mean stream flow time series of the rivers; however, the presence of insignificant negative trends is indicated by the trend test. Results for the probability distribution goodness-of-fit test show gamma distribution to be the best fit distribution for the rivers.

The Revised Universal Soil Loss Equation (RUSLE) is used for predicting soil erosion. Rainfall erosivity (EI) in this equation is related to storm type, amount and intensity so it should be determined from rainfall characteristics. In the present research, data from 180 recording rain gauge stations throughout the I.R. of Iran were analyzed and single storm; daily, monthly and annual erosion indices were calculated and estimated by different simple models. For the single storm erosion index, the models EI=a Peb/D g and EI=pPeq were modified. Coefficients of these simple models were found to be elevation, longitude and latitude dependent. Therefore, multiple regression equations were used to estimate these coefficients based on the elevation, longitude and latitude of the stations. For the daily erosion index, a power function based on daily rainfall is presented. The values of coefficients for this equation were dependent on the elevation, longitude and latitude of stations and they are estimated by the given multiple regressions. For the monthly erosion index, a simple model based on the monthly maximum daily rainfall was proposed. The values of the coefficients for this equation were also determined by the given multiple regression equations. The coefficients of the Arnoldus model were modified for the study region to estimate the annual erosion index using monthly and annual rainfalls. The coefficients of this model are elevation, longitude and latitude dependent and are estimated by multiple regression equations. According to the simple model, for the monthly erosivity estimation with modified coefficients the annual iso-erosivity map was drawn for the study region. The range of annual erosivity for the study region was similar to those reported for a neighbor country (i.e., Iraq).

A force limiting device ideally possesses rigid-plastic force/shortening characteristics. When such a device is introduced in a compression member, and if the limit load of the device is set somewhat below the buckling load of the member, the member will behave in an elastic-plastic manner. The present paper outlines the non-liner behaviour of a novel multi-tubular, ductile compression member which exhibits an initial axial stiffness, followed by a steady load plateau and subsequent enhanced stiffness and strength, before the final failure. The multi-tubular member acts as an energy absorber and force redistributor. The theoretical cyclic response of the device, obtained using ABAQUS, is presented. For a comparison of the energy absorbing characteristics, two X braced frameworks have been considered, one with conventional tubular bracing, and one with the force limiting devices used for bracing. For relatively large horizontal displacements, the framework incorporating the force limiting devices exhibited greater ductility and energy absorbing characteristics than the conventionally braced framework.

The effect of the entrance geometry of a culvert on the discharge coefficient is studied. The experimental results of a sharp edge model, which is compared with Bodhaine's, are taken as the comparison base. The curved up edge model and the curved edge of a side walls model, was shown to be effective on increasing the discharge coefficient. In addition, the bottom slope, culvert length, and discharge variation have no effect on the coefficient of discharge for flow types 1, 2, and 3.