岩盤の破壊基準と長期強度

1.はじめに

2.過去の研究

3.時間依存性を考えた破壊基準と長期強度

 3.1 三城目安山岩の載荷速度依存性

 3.2 載荷速度依存性を考えた破壊基準

 3.3 クーロンの破壊基準と長期強度

4.地圧測定結果と長期強度

5.考察およびまとめ

参考文献

キーワード:岩石,破壊基準,長期強度,岩盤内構造物,地圧


Failure Criterion and Long-Term Strength of Rock

Abstract

At first, study on loading-rate dependency of strength was briefly summarized. It is well known that uniaxial (unconfined) compression strength increases with loading rate. Though only limited data are available, some authors reported that confined strength increases with loading rate. Also, tensile strength obtained by uniaxial tension, indirect tension and bending tests increases with loading rate.

Based on the summarized experimental results, a failure criterion in which loading-rate dependency of strength is considered was proposed; high criterion for high loading rate and low criterion for low loading rate. As an extreme case, long-term strength or failure criterion at extremely low loading rate can be obtained. The simplest form of the long-term strength is σ=a・σ where σ are major and minor principal stresses, and constant 'a' varies from 2 to 6 depending on rock.

For validation of the proposed failure criterion, rock stresses were plotted on σ vs.σ diagram. It was found that all data except one were plotted under the line σ=4σ. It is reasonable to consider that, in relatively stable rock mass, rock stress is maintained at a certain value or condition lower than a long-term strength. If so, this result supports the validity of the proposed failure criterion.

KEY WORDS: Rock, Failure Criterion, Long-Term Strength, Underground Structures, Rock Stress