Abstract: Due to high ground pressure and complex geological conditions of high stress soft-rock tunnel, the pre-determined support mode for high stress weak rock tunnel often fails to accord with the characteristics of wall rock deformation and destruction. The floor heave and roof instability in weak rock tunnels occur most ly due to the weak support at tunnel periphery and some local part. The support of weak rock tunnel is a technical challenge faced by the underground mining engineering and the floor heave is a major form of wall rock deformation and destruction. A larger number of practically measured data indicate that 50%~75% approaching amount of tunnel floor and roof is caused by floor heave. Serious floor heave in tunnels can bring a lot of maintenance work and maintenance workers' labor. The paper analyzes the weak support mechanism of high stress weak rock tunnel, expounds the causes for floor heave and roof instability, discusses the destruction characters and deformation law of weak rock tunnels, and puts forward some understanding and measures of support, providing new reference for the support structure design for weak rock tunnels.

Key words: High stress, Weak rock tunnel, Weak support, Elastic theory, Viscoelastic theory