Construction d’un modèle physique de joints de dilatation pour l’étude de la relation entre la température du béton et la perméabilité des joints

Abstract

Water infiltration through expansion joints is an important issue for tunnels. To maintain the structural competence of tunnels and extend their service life, the rapid and efficient resolution of water infiltration problems is of paramount importance. Several methods can be used to characterize infiltrations in a non-destructive way. Infrared thermography is one of these methods. However, at present, this method is mainly qualitative: it allows for the identification of infiltrations, but it does not allow for the measurement of flow rates or the classification of joints according to their damage. This project aims to simulate the thermal behaviour of expansion joints characterized by different permeabilities under different temperatures inside and outside the tunnel. A physical concrete model with four types of extruded polystyrene joints was constructed. The inside of the model represents the outside of the tunnel (extrados). The temperatures of the water inside the model, the water flowing out of the model, air, and concrete were measured with thermocouples. Infrared thermography was used to measure the concrete surface temperature. These temperature measurements were compared to infiltration rate measurements for each joint. The joint built with thin polystyrene sheets was the most permeable with an average leakage rate of 4.2 L/h. The joint with the waterstop strip was the tightest with an average leakage rate of 0.026 L/h. An average leakage rate of 3.0 L/h was recorded for the joint with a simple polystyrene sheet. The polystyrene joint sealed with silicone recorded a lower leakage rate with an average value of 1.4 L/h. The results show that each joint followed the same trends as a result of changes in the temperature of the infiltrated water. The concrete temperatures show that the most permeable joint always recorded the highest temperatures compared to the other joints with a minimum temperature of the concrete of 15,03°C recorded at a depth of 7 cm and at 10 cm from the joint for a water temperature inside the model of 12,9°C. The lowest temperatures were recorded for the joint with the waterstop with a minimum temperature of 14,17°C recorded at the same location and for the same water temperature. The measured concrete temperatures at a depth of 3 cm confirm the anomaly of the concrete surface temperature shown by thermographic imaging. Infrared thermographs show a clear link between the intensity of temperature anomalies and the flow rate measured for each joint. Changes in flow rate as a function of time can be correlated with the appearance and disappearance of temperature anomalies at the surface of the concrete and at the joint. The increasing difference between air and water temperatures in the model increases the contrast of the infrared thermography.

Date	15 Dec 2020
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	François Duhaime (Supervisor)