Study On Time Effect Of Rock Mechanical Parameters And Unsteady Rheological Constitutive Model

ABSTRACT:Based on the researches achieved, a novel man-made rheological instruments was developed in this thesis, in which mudstone was used as subject investigated. The instantaneous strength property, uniaxial and triaxial rheological characteristics of rock was investigated systematically and comprehensively, and the weakening regularity was explored which the basic mechanical parameters, the deformation modulus (E), cohesion (C) and internal friction angle(φ), all degraded gradually with time and stress in the process of rock creep. Moreover, an unsteady rheological constitutive model was presented through introducing this weakening regularity into Bingham one-dimensional rheological model and P.Perzyna three-dimensional rheological model. At last, the secondary development of unsteady rheological constitutive model using ABAQUS software was realized successfully, and this model was verified to be correct by experimental data. The main works completed in this thesis were as followed:1. A novel man-made rheological instruments, namely five-Joint uniaxial rheological apparatus, was developed which can be used for rock rheological tests on the basis of analysis of merits and drawbacks of current rheological instrument. The five rheological experiments at deferent conditions could be carried simultaneously by using this new instrument, and automatic control and automatic data collection in the experiment could be implemented by computer.2. The instantaneous strength experiments of mudstone under four confining pressure condition:OMPa,5MPa, 10MPa and 15MPa were carried out, and the deformation and failure laws of mudstone were obtained. Thus, a new method was presented that long strength of rock could be determined by instantaneous strength test of rock. In addition, measuring principle of rock mechanics parameters using single specimen method was discussed and its data processing method was modified.3. Based on the analysis of creep damage threshold of rock, the creep process curves was explained through micro and macro mechanics. The uniaxial creep test of mudstone at eight stress levels was carried out, and then its creep characteristics were analyzed. The three time-point mechanics parameters were measured in the process of creep by single specimen method, thus the weakening regularity was obtained which the basic mechanical parameters all degraded gradually with time and stress.4. The creep deformation experiments were carried out at three different confining pressures of 5MPa, 10MPa and 15MPa. Thus, the weakening regularity of mudstone mechanical parameters of uniaxial conditions could be extended to triaxial condition, and was verified through creep destroyed strength of rock.5. Introducing weakening regularity of mudstone mechanical parameters into Bingham model, one-dimensional unsteady rheological model was established, and rationality of this model was verified by experimental data. Furthermore, one-dimensional Bingham model was extended to three-dimensional P.Perzyna model through using Drucker-Prager criterion, so the three-dimensional unsteady rheological model was established through introducing unsteady mechanical parameters.6. The secondary development of the three-dimensional P.Perzyna model using ABAQUS software was realized, and the rationality of this model was examined through experimental data.