This tutorial illustrates change in coupling of groundwater flow and thermal flow as a result of ground freezing. A tunnel is constructed with the use of freeze pipes. By first installing freeze pipes in the soil, the soil freezes and becomes watertight so that tunnel construction can take place. This method of construction requires a lot of energy for the cooling of the soil, so by being able to model the cooling behaviour while groundwater flow is present an optimal freezing system can be designed.
In this tutorial a tunnel with a radius of 3.0 m will be constructed in a 30 m deep soil layer. A groundwater flow from left to right is present, influencing the thermal behaviour of the soil. First the soil will be subjected to the low temperatures of the freeze pipes, and once the soil has frozen sufficiently, tunnel construction can take place. The latter is not included in this tutorial.
Because groundwater flow causes an asymmetric temperature distribution, the whole geometry needs to be modelled, where in previous examples only half of the geometry was sufficient.
Figure 1. Temperature distribution for a transient calculation
This exercise requires a PLAXIS 2D Ultimate license to access the Thermal features.
The attached *.p2dxlog file contains all the commands to generate the model. With a Bentley Geotechnical SELECT Entitlement [GSE] licence, you can use the commands runner to open the *.p2dxlog file and to execute all commands in one go, see also this instruction.
Scientific Manual PLAXIS 2D - Thermal and coupled THM analysis [Publications]
2D Thermal analysis of soil freezing with flowing water [Publications]
PLAXIS 2D Tutorial 17: Thermal expansion of a navigable lock [Tutorials]