Experimental studies on the weatherability of the capivara dam basalts,rio paranapanema,brazil

The weatherability of the basalts in the Capivara Dam site, Rio Paranapanema, São Paulo State, Brazil, has been studied by means of saturation-drying tests. A great number of samples have disaggre — gated intensively with production of fines. The behavior of these rocks is related to their petrography, especially to their content in expansive clay minerals. These studies were performed in order to obtain data for the utilization of this material as rock fill, including ripraps.     

Prediction of the effectiveness of rolling dynamic compaction using artificial neural networks and cone penetration test data

Rolling Dynamic Compaction(RDC),which is a ground improvement technique involving non-circular modules drawn behind a tractor,has provided the construction industry with an improved ground compaction capability,especially with respect to a greater influence depth and a higher speed of compaction,resulting in increased productivity. However,to date,there is no reliable method to predict the effectiveness of RDC in a range of ground conditions. This paper presents a new and unique predictive tool developed by means of artificial neural networks(ANNs) that permits a priori prediction of density improvement resulting from a range of ground improvement projects that employed 4-sided RDC modules;commercially known as"impact rollers". The strong coefficient of correlation(i.e. R0.86) and the parametric behavior achieved in this study indicate that the model is successful in providing reliable predictions of the effectiveness of RDC in various ground conditions.     

Tunnel fire and life safety within the world road association (PIARC)

This paper presents the global activities of the World Road Association (PIARC) in the area of fire and life safety in road tunnels. It traces the organizational structure in the form of technical committees, its publications, current activities and concludes with a summary as to the position of the organization with regard to fire and life safety in tunnels.     

Finite element three-dimensional elastic-plastic creep analysis

This paper presents a continued development of computationally efficient finite element methods for accurately predicting the isothermal three-dimensional elastic-plastic creep responses of thick and thin shell structures subjected to mechanical and thermal loads. This work is applicable to a wide range of engineering structures and most recently has been used in the elastic-plastic creep analyses of high-temperature nuclear reactor components and rotating turbine blades.Previous work in this area for elastic-plastic analysis has been demonstrated by Levy et al. In that reference, use of a variable number of stress points within an element to describe elastic-plastic behaviour was demonstrated. These ideas have been extended for combined plasticity and creep behaviour. Thus, within an element, the order of the allowable total kinematic strain distribution is dependent on the number of element nodes (assumed displacement distribution), and the order of the allowable plastic strain distribution (and hence the elastic-plastic boundaries) and/or creep strain distribution is dependent on the number and location of the stress points used to numerically integrate the inelastic effects. This allows for an accurate representation of the elastic-plastic creep behaviour within an element. This higher inelastic representation results in the use of a minimum number of degrees of freedom for a given nonlinear analysis, which is particularly important for combined creep and plasticity behaviour and for cyclic loading, where computer times can be prohibitive.The basic numerical solution procedure for the elastic-plastic creep analysis is an incremental predictor-corrector iterative scheme combined with the ‘initial strain’ approach. Attention has been given to the time step increment strategy for combined plasticity and creep as this governs efficiency and accuracy.The methods have been implemented into the three-dimensional solid element module (HEX) of the Grumman PLANS finite element program.Sample problems are used to demonstrate and investigate the accuracy and efficiency of these methods. Sample problems include combined plasticity and creep analysis of a simple rod under time varying load, stress-relaxation of a simple rod, thermal stress-relaxation of a plate subjected to a temperature variation across the width, and creep analysis of an internally loaded thick-walled pressure vessel.     

Separation of physical loading from photosynthesis/respiration processes in rivers by mass balance

Diurnal variations in physical and chemical concentrations, including nutrients, are observed in river ecosystems. Understanding these cycles and separating the effects of physical loading (from point and non-point sources) and biogeochemical processes are necessary for water management and the TMDL process. A chloride mass balance approach is used to separate the relative influences of physical loading and biogeochemical processes in the Bow River through Calgary, Canada, which has a significant influence on the river water chemistry. Sampling campaigns were conducted in December 2005, when minimal photosynthesis and respiration occur, and in July 2006, when river discharge is high and some photosynthesis and respiration activity is present. Samples in each campaign were collected at point source input and output along the river reach through the city every hour for a 24-hour period, allowing for time of travel. The two wastewater treatment facilities within the city contributed the majority of physical mass loading to the river, with temporal variations in effluent discharge, chloride, and nutrient concentrations. Wastewater effluent chloride to nutrient (as well as other parameter relationships) concentrations also varied diurnally. An hourly chloride mass balance was achieved, within 0.5% (average, S.D.=4.4) for December and 7.7% (average, S.D.=4.2) for July, between estimated cumulative sum values from all inputs and measured values at the river output downgradient of the city, allowing for the investigation of other parameter conservativeness. Some slight diurnal variations associated with photosynthesis and respiration were observed even with limited productivity in the river. Nitrate mass fluxes appeared to be most strongly influenced by photosynthesis and respiration processes, with phosphate being less influenced. Ammonia mass fluxes appeared to be most strongly influenced by wastewater effluent loading. Physical loading can mask or enhance biogeochemical diurnal fluctuations, creating errors in river process interpretations. Chloride was a useful tracer in the mass balance to distinguish between and assist in separating physical loading and biogeochemical processes in the river.     

Interaction of bacteriophage R17 and reovirus type III with the clay mineral allophane

A study has been made of the adsorption of bacteriophage R17 and reovirus type 3 by the amorphous aluminosilicate clay mineral allophane. In agreement with previous studies of virus adsorption to other minerals such as montmorillonite and aluminium hydroxide, the principal factors influencing adsorption were found to be mixing time, pH and the concentrations and isoelectric points of both the virus and the absorbent. However, allophane was found to be a much better adsorbent for reovirus and R17 over the pH range 5–7, the natural pH range of many fresh waters.By using highly purified radioactive reovirus it was possible to follow both the distribution of radioactive virus in a clay suspension and the specific infectivity of the virus. This study revealed that when adsorbed virus was eluted by neutral phosphate solutions it retained its physical integrity but was of a lower specific infectivity.     

A steady-state model for the rotating biological disc reactor

A steady-state model for substrate removal in a rotating biological disc reactor is presented. The model considers the consumption of substrate by micro-organisms in the biofilm attached to the rotating disc, and mass transfer from the attached liquid film to the biofilm. A mass balance on substrate over the liquid in the trough provides an expression for effluent substrate in terms of the microbial kinetic constants, the geometry of the system and the operating conditions. In order to simplify the solution of the equations in the model, first order kinetics are assumed for the rate of microbial growth and substrate utilization. This simplified model can be solved, for example, by using a programmable calculator. The model predicts that the fractional removal of substrate per stage is strongly dependent on the hydraulic loading rate per unit disc area but independent of feed substrate concentration. It predicts constant removal independent of disc size provided the hydraulic loading per unit area is kept constant. The rotational speed has only a slight predicted effect on the rate of substrate removal. The predictions of the model are compared with published data from the literature for both domestic wastewater and some industrial wastes. Trends observed in the field are predicted qualitatively by the model.     

Betons a hautes performances,a granulats artificiels actifs

High strength concretes, in particular at early ages (more than 40 MPa at 3 days and up to 80 MPa at 7 days), are obtained by replacement of certain granular size ranges of sand or gravel by cement-active artificial aggregates in a given concrete composition elaborated with a local supply of aggregates and cement. The strengthening of the paste-aggregate bond by chemical reactions between the artificial aggregates and the cement also involves an improvement of other concrete performances and not only of mechanical strengths. The cracking ability is decreased, the wear strength is higher, and water permeability is low or even nil for certain compositions. The laboratory results are confirmed by tests on the site and show the possibility of achieving high strength concretes without any particular selection of cement and natural aggregates.