| Most rock engineerings are not occur in a single geological environment, but in a more complex environment, such as:mechanical field (Mechanical, M), hydrological field (Hydrological, H), thermal field (Thermal, T) and chemical field (Chemical, C). The interaction between them constitutes the hot issues of international society for rock mechanics, namely "multi-field coupling problems of rock". The mechanical-hydrolo-gical-chemical (MHC) coupling problem of rock engineering under the action of load and water-rock has become important increasingly with the large-scale construction of rock engineering in China. In this paper, the numerical calculation method as the priority, the test means as the auxiliary, the elastoplastic damage and MHC coupling problem as the main research content, the program development as clue to research of implementation issues layer of progressive, the interaction between multi-field coupling, failure mechanism as the research target, Dalian subway tunnel engineering, Jilin FuSong tunnel engineering, Guiyang subway tunnel engineering as the background in order to reflect the significance and the value of research work.Based on the national natural science fund project (No.51079010:Research of Damage Mechanism and Model of Seabed Rock Excavation with the Mechanical-Hydrological Coupling) and the excellent doctor dissertation fund project of Dalian Maritime University (No.2013YB03:MHC and Damage Coupling Mechanism Test and the Model Research of Tunnel Surrounding Rock under the Action of Seawater), to carry out the research around "the rock elastoplastic damage and MHC coupling problem." Specific to divide it into5subproblems, rock ultrasonic damage, frost heaving force and permeability test, rock elastoplastic softening, damage model establishment and numerical algorithm, rock elastoplastic damage and MH coupling model and program implementation, rock elastoplastic damage and MHC coupling model and program implementation. At the same time, the parameter inversion problem is studied in order to accurately calculate and solve the bottleneck of parameters uncertain in complex model. Mainly in the following research work:(1) Compression process of rock with micro crack closure, initiation, extension and penetration, the macro performance deformation and failure process of rock. Acoustic wave velocity as the change law of damage, destruction in the process, using the change law to predict the stability of rock engineering structural has important significance. Testing acoustic wave velocity without stress state and stress state under the dry and saturated fractured schist and wave velocity vary with compressional strain response from the perspective of acoustic wave velocity. Full water wave characteristics of rock and the relationship between the change of wave speed and rock damage, fracture are analyzed. At the same time, fracture and damage of the full water schist are analyed, the tip of the radius of plastic zone of Drucker-Prager criterion is deduced. About fill water rock frost heaving force test device, the report of the ring seepage-stress coupling of rock permeability testing device is also rare. In order to study the frost heaving damage and the change rule of permeability of rock under the ring seepage-stress coupling, the corresponding test apparatus are developed. Different freezing and thawing temperature, moisture content of rock, frost heaving force under the conditions of different freeze-thaw cycles test are conducted using the saturated rock frost heaving force test device. Permeability tests are conducted under the conditions of different osmotic pressure and axial compression using the ring seepage-stress coupling device.(2) Set up elastoplastic damage and MHC coupling application framework of rock, each part of the program is developed separately adopting the idea of modularization, and then call each other according to certain rules, constitute an organic whole in this way which provide the numerical calculation method for multi-field coupling problems of rock. The corresponding solving program is compiled using C++language and using object-oriented programming method, based on fully implicit return mapping algorithm (Fully implicit return mapping algorithm) of von Mises constitutive model and Drucker Prager constitutive model as well as the corresponding to the Consistent tangent modulus (Consistent tangent modulus). It is the dominant mechanical basic parts program. Return mapping algorithm can avoid the drift phenomenon of the trial stress, and achieve the accurate solution of the constitutive equation on the condition of the quasi-static deformation, a quadratic convergence rate when using the Newton-Raphson iteration scheme, higher accuracy and stability. The results show that the superiority of the algorithm, and the correctness and the practicality of the program. The coupling procedure of the rock elastoplastic damage and MHC is embedded in differential evolution algorithm (Differential evolution algorithm, DE), then an intelligent back analysis program is developed. The computational efficiency and correctness of the relevant procedure is verification. It is applied in the practical engineering.(3) Softening and damage characteristics of rock have important influence on seepage field and chemical field. While researching the coupling problem of rock elastoplastic damage and MHC, rock softening and damage characteristics are studied firstly. Establish corresponding constitutive model and develop the solution program for it. Strain softening problem in geotechnical engineering and the difficult solution problem of the finite element numerical calculation due to the negative tangent stiffness of strain softening model are studied in this article. First of all, the elastoplastic strain softening constitutive model of rock is established based on the Drucker-Prager strength criteria. Then, consider the shortcomings of low efficiency of the arc-length method in judging stiffness matrix, Newton-Raphson scheme and arc-length method are combined to use in the iterative calculation of elastoplastic incremental finite element equations. Namely Newton-Raphson scheme is used before the structure reaches the limit load, and when the structure is close to the limit load turn to the arc-length method, so that the structure over the peak point ino the softening region until destruction. NR-AL method has the advantages of both in the iterative solution. Finally, a program of the built strain softening model and elastoplastic incremental finite element to solve the constitutive equation for the iterative process is compiled using C++language. The program is applied in numerical calculation, and the stress-strain curves of the idealied elastoplastic model, strain softening and strain hardening model based on the Drucker-Prager strength criteria are comparative analyzed. The research results show that the strain softening constitutive model can simulate the characteristics after the post-peak softening of rock material well, and it can reveal the features of the post-peak strain softening and failure mechanism. NR-AL method can solve the negative stiffness problem caused by strain softening and also overcome the shortcomings of low efficiency in judging stiffness matrix using the arc-length only.(4) In practical tunnel construction, the stress redistribution of underground rock is caused by tunnel excavation, which is usually made of microcrack of surrounding rock extension damage and accompanied the plastic flow deformation. In order to study the coupling effect of two kinds of failure mechanism which are the stiffness degradation caused by the damage and the flow caused by the plastic, from the perspective of elastoplastic mechanics and damage theory, the correction formula of effective stress is introduced to consider the role of the pore water pressure.The elastoplastic damage constitutive model is established based on the Drucker-Prager yield criterion.The most elastoplastic damage model involve in the problems of much parameters and not easy to determine. The damage parameters are given by back analysis method to solve the problem of damage model parameters are difficult to determine; The elastoplastic damage constitutive solver is compiled by adopting the method of object-oriented programming using C++language, and the experiment and numerical verification have carried on for two aspects of the established elastoplastic damage model and the program; Finally its application in Jilin FuSong tunnel project, the development and change of the plastic zone and the damage zone are simulated. The results show that the established elastoplastic damage constitutive model can describe the mechanical properties, plasticity and damage change trend of the rock well, and the practical engineering problems can be simulate by the program to give certain guidance to the site construction. The research of numerical computing problem involving coupled elastoplastic damage of the complex material not only need to select the appropriate constitutive model to forecast damage, but also need to be a robust and effective constitutive integration algorithm. The basic steps of seting up the elastoplastic damage constitutive model are expounded in the framework of thermodynamics and continuum mechanics. The finite element solving program of the constitutive is compiled using C++language in Visual6.0environment, which is based on Lemaitre’s isotropic hardening coupled elastoplastic damage constitutive model, the corresponding constitutive integration algorithm-fully implicit return mapping algorithm and the consistent tangent modulus. The constitutive equation is needed to solve a nonlinear scalar equation, and the form of the constitutive equation improving computational efficiency is simple relatively. The validity of the application program is demonstrated through a numerical example of a cylindrical notched bar. Enrich the constitutive model of dominant mechanical program in the elastoplastic damage and MHC coupling program of rock, provide ways and means for the study of damage and other problems of rock material.(5) It is more likely to cause the collapse of tunnel surrounding rock and water disasters under the action of the coupling effect of the groundwater seepage field, the stress field and the damage field. First of all, surrounding rock is regarded as the isotropic continuum material, and the elastoplastic damage constitutive model of rock is established based on the criterion of Drucker Prager. The fully implicit return mapping algorithm is adopted to achieve the numerical solution of elastoplastic damage constitutive equations. Secondly, according to the dynamic evolution formula of permeability coefficient in elastoplastic state based on the above research, the elasoplastic damage and MHC model of rock is established, and the coupling solving iterative method of many fields is presented. Back analysis program is compiled on the basis of the principle of differential evolution algorithm in order to solve the problem that elastoplastic damage model involves many parameters and not easy to determine, and the damage parameters are inversion; Finally, compile the corresponding coupling program of the elastoplastic damage and MHC and parameters inversion program using C++language respectively, the following calculations are conducted by using the program:①The calculation results of the displacement field and the stress field by the elastic model and the elastoplastic model are compared.②The pore water pressure and the seepage flow are calculated without considering the effect of mechanics.③The interaction rules of stress field, seepage field and damage field of tunnel surrounding rock are calculated using the coupling model. Results show that the macro failure of rock material can be more realistically reflect through the interaction of the stress, the seepage and the damage of the built coupling model. The calculation program which provides a method for the engineering construction affected by groundwater severely can simulate the coupling characteristics of groundwater seepage field, stress field and damage field. The stability of surrounding rock of the Dalian Maritime University subway test line over the river in the process of tunnel construction is calculated by the numerical program.(6) Research on MHC coupling proplem of rock is relatively small, it mostly revolves around test, and involving MHC coupling model of rock and relevant numerical program are relatively small. How to build a quantitative relationship and mathematical model considering the coupling effect of MHC of rock is still a urgently settled problem. Considering the coupling effect of stress field, seepage field and chemical field, MHC coupling damage variable is deduced according to the mechanical damage variable and the water chemical damage variable.①Given the dynamic evolution of the damage variable water chemistry empirical formula based on water chemistry damage between ultrasonic velocity from the results of experimental studies. The coupling damage variable is instead by the mechanical damage variable, and the numerical calculation is conducted by elastoplastic damage and MH coupling program. This coupling mode belongs to the unidirectional coupling mode, it can reflect the chemical field corresponds to the force field, seepage field only.②The water chemical damage variable is given in the form of porosity based on the calculation of chemical kinetics, and the elastoplastic damage and MHC coupling program of rock is developed combination the elastoplastic damage and MH coupling program and the water chemical dynamics software phreeqc. The coupling mode belongs to the relaxation coupling mode. The simulated calculation of the chemical corrosion problems is conducted. The results show that the deformation and the stress characteristics under the multi-field coupling condition can be analysis with this method to provide reference and basis for engineering. Finally, the tunnel of Guiyang Metro Line1under the Nanming river is simulated. |
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