Variations in strength and creep life of six Japanese rocks

1. Introduction

2. Theory 

  2.1 Review

  2.2 Relationship between strength and creep life

3. Examination based on previous experiments

  3.1 Uniaxial test in dry and wet conditions

  3.2 Compressional and tensile strength

  3.3 Triaxial strength

4. Discussion 

  4.1 Time dependency in creep and strength

  4.2 Effect of environment on variability in strength

  4.3 Numerical model for strength variability

5. Conclusion


Keywords: creep life, strength, time-dependent failure, variation of strength, triaxial test, tensile test


In this paper, variations in strength and creep life are investigated for rocks under various conditions: dry and wet, uniaxial and triaxial, and compressional and tensile. A number of parameters are introduced for this purpose, to assess time-dependent failure under constant and monotonic loading using these common parameters, i.e. the parameter of time dependency , coefficient of creep life and coefficient of strength . explains the rate dependency of strength or stress level dependency of creep life. and are related to each other. Variations in have been evaluated using the data of previous rigorous experiments. It is confirmed here that , and variations in determined by creep tests are in most cases identical to those determined using strength tests. Variation in in wet conditions is almost the same as that in dry conditions, however variation in tension increases more than in compression. Under confining pressure, variation in is reduced for Neogene sedimentary rocks, and does not appear to change for igneous rock and welded tuff.