The Importance of deformation modulus on design of rocks with numerical modeling


AKSOY C. O. , UYAR AKSOY G. G. , YAMAN H. E.

GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES, vol.8, no.3, 2022 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 8 Issue: 3
  • Publication Date: 2022
  • Doi Number: 10.1007/s40948-022-00380-8
  • Journal Name: GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Keywords: Rock Mass, Intact Rock, Deformation Modulus, Deformation characteristic, Rock Structure, TIME-DEPENDENT BEHAVIOR, INTACT ROCKS, MASSES, DEFORMABILITY, STRESS, CREEP, TESTS

Abstract

The elasticity modulus of the rock material (E-i) is a parameter of these developed empirical formulas and is a constant value obtained from laboratory test. The rock material takes different E-i values under different stresses. The deformation modulus of rock mass (E-m) is the parameter used in the design of rock structures and reveals the deformation properties of the rock mass. This behavior is affected by rock mass characteristics such as discontinuities, discontinuities properties and groundwater conditions, as well as the properties of rock material, which is the smallest unit of rock masses. The strength and deformation behavior of the rock material directly affect the deformation characteristic of the rock masses. Determination of the E-m is done either by in-situ tests or estimates from empirical formulas developed by different researchers. The locations, where rock structures are built, can be different depths and different geological units. In this case, the amount of stress that the same rock structure is exposed at different depths will be different. Therefore, E-i will take different values under different stresses (depending on parameters such as depth, excavation-support geometry). When the E-i value, which varies depending on the depth, is used in the formulas developed by the researchers, different E-m values will be calculated against different E-i values. Currently, designs are made with the classical method. In the classical method, the E-i value obtained from the deformability test performed in the laboratory is used in empirical formulas and E-m is calculated. These E-i and E-m values are fixed values. However, the E-m value also changes depending on the stretch. In the new method proposed in this study, it is recommended to use the value of E-m, which varies according to the stress conditions. This new method includes a function based on time-stress-deformation-strength was developed to calculate the E-i value, which takes different values at different stresses. The E-i values that can be changed by this function are used in the empirical formulas used in calculating E-m. In the projects within the scope of the research, numerical modeling analyzes including the Em values obtained by this time-stress-deformation-strength dependent function and the Em values obtained by the classical method were performed and very important results were obtained.