| Various rocks in Hokkaido were examined to establish a new judgment method for long-term stability of natural rock as subgrade in snowy cold region. Rocks were mainly collected from actual road construction site、 and rock type of them is sedimentary rock、 volcanic rock and pyroclastic rock. Sample number is twenty one. For the purpose、 saturated density、 water absorption、 P-wave velocity and unconfined compression strength of the specimen were measured after the repetition of freezing and thawing. Maximum cycle of freezing and thawing is 300、 and cycle number of 150 was adopted as a threshold for judging the long-term stability as subgrade from measurement result of actual subgrade rock which suffered freezing and thawing for several years. By comparing destruction cycles of each rock with measurement result for rock property、 the new judgment criteria can be evaluated as follows: 1. Saturated density is 2.2g/cm3 or more、 2. Water absorption ratio is 6% or less、 3. P-wave velocity is 3.0km/s or more、 and 4. Unconfined compression strength is 15MN/m2 or more. Rock which clears all of the criteria is judged to have long-term stability as subgrade in snowy cold region |
