Journal of Building Materials and Structures

Design and Construction Criteria of Twin Tunnel: Taking an Adverse Wind Condition Effects on Air Pollution Short Circuit at Tunnel Portals as a case

2020-03-30T20:41:08+00:00

This paper aims to study the influence of the tunnel portal designs, wind conditions and ventilation rate on the amount of air pollution short circuit from one tunnel tube to the other. These effects are investigated by Computational Fluid Dynamics (CFD) code used a Large Eddy Simulation (LES) method to control air quality inside the tunnel and reduced as far as possible a short circuited (flow Recirculation) flow level. A validation of CFD code to experimental data in 1:100 scale model of the road traffic tunnel tested in wind-tunnel showed that the CFD gave satisfactory prediction of the air pollution short circuit in the vicinity of tunnel portal. The predicted concentration of the gas tracer (CO₂) used as the safety criterion provide the useful information about a short circuit amount resulted for each structural variant of tunnel portals, such as a central dividing wall built as extensions from the end of road tunnel and offset tunnel portal entrance exit tested under different speed ratio of wind and ventilation. A detailed look at results is beyond the scope of analysis to determine optimal air pollution short circuit percentages. Finally, the perfect tunnel portals geometry can be suggested.

Comparative design procedures of stone columns for liquefaction stabilization

2020-04-03T15:33:06+00:00

Soil liquefaction is one of the most important and complex phenomena of soil dynamics. It is a loss of résistance of loose granular soils under a seismic shock.

The aim of this work is to study the improvement made on a liquefiable soil using a stone column solution by several methods namely observational, static and dynamic solutions. The site used for this application is located in a terminal port container in Algiers. The analysis was carried out using the test results of standard penetration and cone penetrometer tests completed during a site investigation.

A comparative study between the methods was carried out to determine the most suitable method. The results of the 3 methods showed that the sizing by taking into account the earthquake, the mesh of stone columns is denser. It was deduced that it is important to analyze by the dynamic method in seismic zones and by static or observational techniques in areas of no or low risk of liquefaction. Recommendation for further research was put forward to develop new tools in order to improve current design methods.

Valorization of calcined kaolinitic clay used in high performance mortar

2020-04-03T15:32:39+00:00

In this work, an experimental investigation was carried out to evaluate the potential of an industrial pozzolan, the metakaolin, on the behavior of mortar. The aim is to use metakaolin as a 10% partial replacement of cement. Its effect on the physico-mechanical properties of the mortar has been analyzed. The results show that the incorporation of metakaolin decreases the density of the dried mortar and increases that of the wet mortar but these remain lower than those of the control mortar. Moreover, thermal analysis ATD / ATG shows that in the heat flow curve appears two endothermic peaks which correspond to the loss of mass of the cement pastes. Heat flux of these pastes increases when metakaolin is used into the cement. In addition, metakaolin increases the compressive and flexural strengths of wet and dry mortars by approaching without exceeding those of the control mortar. The use of metakaolin as a cement substitution has shown its potential to be a pozzolanic material that can offer economic, environmental and technical benefits.