| Rock-mass deterioration after repeated freezing and thawing was examined to establish a method of determining the long-term stability of rock masses as subgrade in cold、 snowy regions. The target rocks were sedimentary、 volcanic and pyroclastic rocks from different areas of Hokkaido、 north Japan. Freezing and thawing test was conducted repeatedly on these rocks、 and their engineering properties and frost heave conditions were subsequently measured and compared with field monitoring result. As a result、 the following new evaluation criteria were set by comparing the deterioration conditions of the specimens with those of actual rock-mass subgrade exposed to freezing and thawing action: 1. saturated density: 2.2 t/m3 or higher; 2. water absorption: 6.0% or lower; 3. P-wave velocity: 3.0 km/s or higher; and 4. unconfined compressive strength: 15 MN/m2 or higher. Rocks that satisfy all these criteria are considered to have long-term stability as rock-mass subgrade in cold、 snowy regions. |
