Study On The Rock Creep Behaviors And Its Applications In Construction Control Of Underground Large Space Cavern

Creep is one of the most important mechanical properties to the study the rock rheology in rock mass material. In most cases, the deformation instability and failure of rock engineering is closely related to the rock creep behaviors, the practical engineering problem that caused by creep of rock has been widely concerned by many scholars at home and abroad, and achieved great progress, particularly in the that used by measured test data and then apply to the project forecast. But the creep theory, creep test instruments and the creep properties of engineering applications today is not very perfect, and construction of many major projects have still posed a serious challenge for study of rock creep, especially in rock rheological properties that under tension and compression and constitutive model still is the key study point and hot issue.In view of this, based on the well known research achievements this thesis will use a combination method including experimental research, theoretical analysis and numerical simulation. Based on uniaxial direct tensile creep test, uniaxial compression and triaxial compression creep tests; the non-linear theory was used to study the creep characteristics of the rock and established a non-linear tensile and compressive creep model. Results of creep mechanical properties were applied to the construction control of large underground arch cavern.In this dissertation, the main investigation work foruses on the following:①Designed and fabricated a rock direct tensile testing device, based on this device and rock materials serving compression machine, the uniaxial direct tension, uniaxial compression and triaxial compression short-term mechanical characteristics of red sandstone were studied, analysis of the law of rock deformation under direct tensile and compressive, discussed the yield strength under compression, compares uniaxial compression strength properties of two kinds of different measurement standard specimens, the short-term mechanical parameters of rocks under tension and compression has been obtained, finally, the mechanical short-term failure mechanism under corresponding mechanisms was analyzed.②The self-designed and developed rock hang weight type directly creep instrument and laboratory rock rheology automatic servo device were used to test the direct uniaxial tension, uniaxial compression and triaxial compression creep of red sandstone. The law of axial strain and lateral strain under direct uniaxial tension and the axial deformation of rocks under compression were studied. The creep rate under corresponding mechanism was also discussed. To better understand the mechanism of rock tensile and compressive creep, the creep was short-term, long-term and unloading creep behaviors of red sandstone were analysis, obtained t the long-term tensile strength.③Based on the rock tension and compression creep test results this dissertation compared with HK model and Burgers creep model and obtained that Burgers creep model can reflect rock creep characteristics which load is less than the long-term strength of rock (short-term creep compression is yield strength). And on the basis of the rock tension and compression accelerated creep results it was deduced two elements nonlinear visco-plastic constitutive mode that can be better reflect accelerated creep of rock, the model and the Burgers creep model series established a nonlinear visco-elastic plastic creep model. The creep behaviors of the nonlinear visco-elastic plastic creep mode in tension and compression stress was studied, and red sandstone under tension and compression creep test curve parameters were directly identified by MATLAB program which based on quasi-Newton algorithm (BFGS algorithm).④Based on Lagrangian finite difference theory this dissertation derived the finite difference form of nonlinear visco-elastic plastic creep the model which in tension and compression. The Mohr-Coulomb yield criterion was used to the establishment a complex non-linear visco-elastic plastic model in tension and compression, and combined with secondary development environment of FLAC3D the composite model was secondary developed. By tension and compression creep test and composite model to simulate experimental verified the correctness of the model secondary development. Later, comparison with monitoring results, the Cvisc model simulation calculate results and Mohr-Coulomb constitutive model calculate results of an engineering example, the applicability of the nonlinear visco-elastic plastic model was verified.⑤The composite tensile and compressive nonlinear visco-elastic plastic creep model is applied to construction control of the three-arch cavern of groundwater reservoir pumping stations that located in a certain place in Shenzhen, the stability of surrounding rock deformation during excavation and supporting structure deformation and carrying capability were analyzed. Finally, the long-term stability of rock engineering under complex stress state is predicted, which brings forward reasonable evaluation and suggestion for long-term stability and safety of rock engineering.