No abstract

No abstract

Distributed temperature sensing (DTS) can be used to monitor the production process of diaphragm walls. DTS is able to differentiate between already present or fresh bentonite suspensions during refreshing of the bentonite slurry in the trench. During concrete casting, DTS is able to differentiate between the bentonite suspension and concrete. As a result, the continuity of the casting process and the arrival of good grade concrete at crucial locations in the trench can be monitored. Tests conducted on laboratory models provided reference information for interpretation of field data. Field experiences have shown the benefits of DTS tests and the predictive value of the reference measurements. Results are compared with crosshole sonic logging measurements at the same location.Key words: distributed temperature sensing (DTS), diaphragm wall, joint, quality control.Résumé : Des capteurs de température distribués (CTD) peuvent être utilisés pour surveiller le processus de production de parois moulées. CTD est capable de faire la différence entre des suspensions de bentonite déjà présentes et des nouvelles lors de l'actualisation de la suspension de bentonite dans la tranchée est en course. Au cours de la coulée du béton, CTD est capable de faire la différence entre la suspension de bentonite et de béton. En conséquence, la continuité du processus de coulée et l'arrivée de béton de bonne qualité à des endroits cruciaux dans la tranchée peuvent être surveillés. Les essais effectués sur des modèles de laboratoire ont fourni des informations de référence pour l'interprétation des données sur le terrain. Des expériences de terrain ont montré les avantages des essais CTD et la valeur prédictive des mesures de référence. Les résultats sont comparés avec les mesures d'auscultation sonique au même endroit.Mots-clés : capteurs de température distribués (CTD), paroi moulée, joint, contrôle de qualité.

Summary Spilled petroleum products spread laterally in the capillary transition zone above the water table. Ground penetrating radar (GPR) is a technique that can potentially delineate the air/water capillary transition zone (CTZ), because a varying water content strongly influences the reflected signal through its effect on the electrical properties. The vertical water distribution is determined on the pore scale by the grain size distribution and on the reservoir scale, mainly, by the permeability distribution. We present the integral equations for the reflected signal from a inhomogeneous slab with a depth-dependent dielectric constant and electrical conductivity. The numerical solution of the equations allows us to compute the signal reflected from different sand profiles. The results show that the reflected signal is strongly influenced by both the grain size distribution and the variation in permeability. A strong frequency dependence is also observed. We present a two-dimensional GPR profile measured in the field that shows a clear effect of the CTZ on the reflection of the radar signal. All these results are considered of importance for the interpretation of GPR data involving the capillary transition zone.

No abstract