The Methodology for the Young Modulus Derivation for Rocks || Geotechnical Laboratory Test

The Methodology for the Young Modulus Derivation for Rocks and Its Value Young’s modulus (E) is one of the basic geomechanical parameters used in rock engineering in practice. It is determined based on a uniaxial compressive test (UCS). However, according to the International Society of Rock Mechanics, it can be calculated in three different ways: tangent, secant, and average modulus. The results from each method are significantly different. The UCS tests were carried out on 237 rock specimens with the slenderness ratio 2 of Carboniferous claystone, mudstones, and sandstones. The axial deformation was always measured automatically by the displacement measurement device (LVDT) built into the testing machine and connected to the hydraulic piston. Then Young’s modulus was calculated for each test by all three methods. The analysis of the results is presented in this paper to show the difference between all three moduli calculated for each specimen, and to recommend the best method of Young’s modulus determination. First, the typical range of the elastic linear deformability for the chosen rock types was determined as 25–75% of the peak strength at a confidence interval 95% for these sedimentary rocks. The modulus value distributions obtained from each calculation method were compared using statistical parameters: mean value, median, minimum, maximum, standard deviation, mean difference at confidence interval 95%, and non-uniformity coefficient. The proportions between the average-secant modulus (Eav/Esec) and average-tangent modulus (Eav/Etan) for the rock samples were estimated. For the studied rocks the obtained values were: 1.10–1.32% for Eav/Esec, 1.08–1.25% for Etan/Esec and 1.01–1.06 for Eav/Etan (for Etan with the range of 20–80% of peak strength). These values show low coherence between secant and average modulus (ca. 23% difference) and good consistency of average and tangent modulus. Based on the analysis, tangent Young’s modulus is recommended as the guiding one at the constant range of 30–70% of the ultimate stress. Secant Young’s modulus, as it comprises not only elastic strain but the pore compaction as well, should be named as modulus of deformability. This conclusion was further confirmed by the regression analysis between UCS and E. The highest regression coefficients and the lowest standard error of the regression was obtained for tangent Young’s modulus determination method. In addition, modulus ratio MR for claystones, mudstones and sandstones was studied and determined as 274, 232 and 223 respectively. #modules #test #rock Laboratory Test... 1. Triaxial UU Test-    • Triaxial UU Test | Unconsolidation Undrain...   2. Sieve Analysis Test-    • Sieve Analysis Test | Particle Size Distri...   3. Vane shear Test-    • Vane Shear Test | Shear Strength of Soil a...   4. Proctor Compaction Test-    • Proctor Compaction Test | Water Content Dr...   5. Atterberg Limit Tests-    • Atterberg Limit Tests | Casagrande Method ...   6. Plastic Limit Test-    • Plastic Limit Test | in English   7. Liquid Limit Test-    • Liquid Limit Test | Cone Penetration Metho...   8. Hydrometer Analysis-    • Hydrometer Analysis || Sedimentation Analy...   9. Direct shear test-    • Direct Shear Test | Shear Strength of Soil...   10. CBR Test of Soil-    • CBR Test of Soil || California Bearing Rat...   11. Permeability Test-    • Falling Head || Variable Head Permeability...   12. Rock- E-Modulus Test-    • The Methodology for the Young Modulus Deri...   Field Test... 1. PULL-OUT TEST-    • PULL-OUT TEST Procedure | Soil Nailling Pr...   2. PULL-OUT Test 2-    • PULL-OUT Test Method Of Grouted Rebar done...   3. Marsh Funnel Viscosity Test-    • Marsh Funnel Viscosity Test | Standard Tes...   4. Mud Balance Test-    • Mud Balance Test Procedure | Standard Test...   5. Making Concrete Test Cube-    • Making Concrete Test Cube | The Process Of...   6. SLUMP CONE TEST-    • SLUMP CONE TEST |Test for Workability of C...   7. DCM Pile Construction-    • DCM Pile Construction | Deep Cement Mixing...   8. MICROPILE REINFORCEMENT -    • MICROPILE REINFORCEMENT INSTALLATION | CIV...   9. CONCRETING OF MICROPILE-    • TECHNIQUE OF MICROPILE CONCRETING | CIVIL ...