A full-scale experimental study of sub-slab pressure fields induced by underground perforated pipes as a soil depressurisation technique in radon mitigation

Abstract

Sub-slab depressurisation systems have proven to effectively mitigate radon entry. A poor understanding of the fluid physics underlying the technique has been shown to lower the success rate substantially. This article describes a study of pressure fields in a sub-slab gravel 2 bed induced by a soil depressurisation system consisting of perforated pipes run under the slab at a depth of 75 cm. The advantage of the approach is that pipes can be laid from outside the building to be protected. The study was conducted on a large-scale experimental facility where the variations in morphology and scope of pressure fields with different pipe combinations could be monitored and characterised. The findings showed that pressure was uniform across the entire area in the gravel bed, whereas the sensors buried in natural soil showed pressure to depend on distance from the source. Pressure transfer to the sub-slab plane was also observed to vary depending on the active pipe. Air-flow resistance studies in the layers of soil lying between the pipes and the gravel delivered different results for each pipe. That finding would appear to be related to the presence of preferential pathways in some parts of the soil. Total pressure when several pipes were activated was observed to be practically the same as the sum of the pressures transferred by each when working separately. The correlation between extraction fan power and pressure generated was also analysed. These and other factors are discussed and analysed from a perspective of the understanding of such highly effective techniques.

Modelo CFD con validación de campo para el estudio de los alcances de efectividad de técnicas de mitigación de radón por despresurización = CFD model with field validation for the study of the effectiveness of radon mitigation techniques by depressurisation

“…Two of them are directly supported on the ground and two of them are built on a gravel surface. The details of the performance are described in (Frutos et al, 2020). As a guideline for the simulation, measurements of soil permeability of 4±2 10-12 m 2 on average were taken under another slab with similar general characteristics, although the soil has a very heterogeneous composition.…”

Definition and Sensitivity Analysis of a CFD Model for the Study of Radon Entry and Accumulation in Buildings

“…The integration of parameters and equations can be done through mathematical modeling [12] [8]. The use of finite element analysis software, such as COMSOL Multiphysics, facilitates the work of integrating equations and parameters and generates detailed studies [13] [14]. The information obtained can be applied directly to the problem to be treated or used to develop simplified models that adapt to the data available for each building.…”