Experiments And Mechanical Model Study On Rock Creep Properties Under Multi-fields Environment

With the constantly emergence of the large rock mass engineering in our country, such as the Three Gorges Dam, Jinping Hydropower Station and subway tunnel, rock mass engineering's long-term stability has aroused more attention. Thus, the issue of rock creep mechanical properties under multiple fields becomes more and more severer. Carrying out the research on this issue has great theoretical significance to accurately predict and effectively control the long-term security and stability of rock mass engineering. On the basis of previous researches, this thesis adopts the combination method of indoor mechanical experiment, theoretical analysis and model exploitation, studies chemical corrosion, low temperature and seepage's influence law on rock creep mechanical properties. Based on the experiments results, establishing THB nonlinear creep model under low temperature, nonlinear improved H|M-CD creep model and seepage-creep coupling ZNS model under chemical corrosion environment, and realizing program exploitation by FLAC3D. Taking Dalian Metro and East Harbour's rock and soil subgrade as engineering background, adopting the theoretical model proposed by this thesis to compute and analyze numerical value. Detailed research contents are as follows:(1) This thesis sets forth from macroscopic-microcosmic and chemical injury perspectives, taking the slate in Dalian Metro as study object, to conduct corrosion experiments with different water chemical solutions (HCl, NaOH, NaCl). And discusses the slate's hydrochemistry corrosion mechanism, then comparatively analyzes slate's transformation, strength property and specimen's fracture morphology change law in different solutions. Based on the empirical formula of hydrochemical damage and longitudinal wave velocity, it introduces hydrochemical damage variate, and proceeds multi-fields coupling finite element program of rock elastic-plastic stress-chemical-damage (MCD) simulation validation; carries out the research on NaCl solution corrosion creep experiment to reveal slate specimens'corrosion properties with different immersion period; analyzes specimens' change laws and characteristics in every creep stage to summarize long term strength, creep rate, elasticity modulus' change law along with the immersion period. Finally, based on the experiment results, proposes five components nolinear viscoelastic plasticity creep model (H|M-CD Model) with consideration of chemical damage, and identifies model parameter with lstOpt optimization software.(2) In order to study rock creep properties in low temperature, improved a set of apparatus which can carry out a rock triaxial creep experiment in low temperature. Carrying out the research on hydrous rock-like material mechanical property experiment in low temperature(T<0?), contrasting and analyzing the rock-like specimen creep law with different temperature and moisture content, to reveal the mechanism of the rock-like specimen creep law effected by moisture condition in low temperature; introducing damage variable, and based on Burgers Model to establish THB (Thermo-hydro Burgers) creep damage constitutive model which is suitable with different moisture condition in low temperature, and matching damage variable and creep parameter by experiment datum. Based on the response regularity between resistivity and creep, invented a method of adopting resistivity to reflect every stage of rock triaxial creep in low temperature; carrying out frost-thaw cycle times and chemical corrosion coupling effect law experiment research, contrastively analyzes the surface microscopic images change law of quartz sandstone and quartzite before and after freez-thaw erosion, to reveal the rock creep mechanical properties change law in different conditions.(3) As to crack seepage issue, firstly carries out the ring to single fracture seepage experiment with self-made ring to the seepage coupling device, contrastively analyzes the seepage change law; And then, carries out research on slate transfixion crack corroded by hydrochemistry solutions (NaCl, HCl, NaOH) permeability experiment. By contrasting rock specimen SEM scan and the pH value of soak solutions, analyzing water-rock interaction influencing mechanism to stenopeic slate's micro structure, to list chemical reaction equation. Macroscopicly obtained stenopeic slate's permeability change law in corrosion environment, by stenopeic specimens' permeability experiment in different solutions with different immersion period. Based on experiment datum to establish a non-linear relationship between slate's permeability coefficient and immersion period in different solutions, and introducing fracture seepage calculation theory formula, and adopting FLAC3D fish language to code slate fracture chemistry-seepage-mechanical coupling calculation program to verify the experiment results.(4) Carrying out loading and unloading circulation disturbance seepage-creep coupling experiment, revealing seepage characteristic and creep law in creep process, analyzing the creep, permeability change law and seepage-creep coupling mechanism in rock loading and unloading process, obtained the development law of volumetric strain in the phases of pressure dense, crack propagation and crack coalescence, to summarize the relationship between permeability and volumetric strain. Introducing Zone State Index concept, estimating every creep stage's critical value by ZSI, establishing a relationship between ZSI and permeability, based on Nishihara Model, exploiting nonlinear creep-seepage coupling model ZNS (ZSI Nishihara Seepage). By contrast, numerical calculation results coincide with experiment results.(5) Based on seepage-creep coupling ZNS Model, to proceed numerical simulation for cross railway bridge's shield construction in section 202, Dalian Metro. Analyzing the ZSI value and change law of permeability coefficient when excavation face in different positions, realized the quantitative evaluation on rock mass damage degree and permeability coefficient real-time presents; with THB nonlinear creep model proposed above which is suitable for low temperature, to calculate the East Harbour rock and soil subgrade construction process in winter. Simulating the change law of subgrade's creep and sedimentation caused by applying gravel piles, calculating subgrade's creep and sedimentation in different temperatures and water conditions, and providing disposal methods to constructing in the frozen period.