Experimental bed active-layer survey with active RFID scour chains: Example of two braided rivers (the Drac and the Vénéon) in the French Alps

An innovative scour chains device composed of active UHF RFID tags is proposed to survey the bed active layer. This device is tested on three cross-sections deployed along two large Alpine braided rivers: the Drac and the Vénéon. A specific field deployment procedure is developed, using a technique of drilling with a tube and a jack-hammer. After each flood, the device allows recording presence/absence of active tags inside a scour chain column. This provides the maximum scouring depth of the bed at the position of the column, and the topographic resurvey of the channel provides the net fill depth. Results show that bed active layer can reach up to 1.43 m during high flow conditions and remains <0.1 m during low and moderate flows. The main advantage of this technology against traditional scour chains is the rapidity and easiness with which the scouring depth is obtained after a flow event, notably under conditions of massive net deposition after the flow. This technology is therefore particularly suitable for large braided rivers, where traditional scour chains necessitate too much field efforts for their relocation, and can be rapidly lost under deep active layers.

Post-construction settlement estimation and increased earthwork volumes calculation of high loess fill

In this study, the post-construction settlement (PCS) area distribution of high fill was analyzed based with reference to a case history of an airport runway crossing a deep gully reclaimed by a thick fill of loess. Earthwork volumes (EV) attributed to PCS was calculated based on in-situ tests. Results showed that the uneven PCS were related to fill depth, construction time, fill rate, integrated compaction degree, and boundary conditions. An empirical equation that considers the aforementioned influence factors was established to calculate the final PCS of high fill. The surface PCS of high fill and the EV can be estimated according to the proposed empirical equation and the original site topography using the three-dimensional finite element method.

Numerical Study of the Thermal Performance in Natural Draft Wet Cooling Tower with Different Fill Types

Based on the heat and mass transfer theory and characteristics of the FLUENT software, a three-dimensional numerical simulation platform composed by user defined functions had been developed to simulate the thermal performance in a natural draft wet cooling tower. This platform was used to study a typical hyperbolic natural draft wet cooling tower with different fill types. The variations of the flow and temperature field in the cooling tower caused by the two different methods of fill were investigated. It is found that the outlet water temperature will decrease due to the non-uniform fill depth. The non-uniform fill depth is beneficial to increasing the efficiency of the cooling tower.