Experimental and numerical investigation of selective artificial ground freezing with air insulation

2017

Mr Aurelien Nie-Rouquette ( - McGill University), Mr Mahmoud Alzoubi ( - McGill University), Mr Agus Sasmito ( - McGill University)

Artificial ground freezing (AGF) is an energy intensive technique used to strengthen saturated porous rock masses and render them impermeable. When freezing is only required at specific depths, an air insulation casing can be installed to create a passive freezing zone and thus reduce energy losses. A lack of radial support to ensure concentricity can cause inner and outer pipe walls to touch and thus bypass/short-circuit the air insulation. To quantify the importance of such phenomena, an experimental artificial ground freezing rig equipped with air-insulation bayonet tube is developed at McGill University. Several operating parameters were evaluated with regard to freezing efficiency. A mathematical model and numerical simulation to mimic our experiment is also developed and validated. It is further employed to evaluate the effect pipe short-circuit at the air insulation, and compare it with that of perfectly installed air insulation. The results indicate the short-circuit significantly reduces the effectiveness of the insulation by up to 90%.