Stability study of CRREL permafrost tunnel

Underground excavated openings in permafrost can have significant ground stability problems if the thermal regime of the area is disturbed. Other factors influencing ground stability besides temperature variation include dimensions of the excavation, thickness of the overburden, and geometry of the opening. This paper summarizes the results of a research project conducted at the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) permafrost tunnel. The relationships between the ground temperature, the roof span dimensions, and the vertical convergence rate of the CRREL tunnel correlates with a combined exponential and logarithmic model. The continuous deformation of the tunnel is primarily temperature dependent. In addition to the effect of temperature, the opening width also exhibits a strong influence on tunnel deformation. The span length gradually achieved a constant effect upon tunnel deformation as the opening width increased. The overburden thickness also exhibits an influence on convergence rate.