| The demand for the underground caverns is increasing by the persistent national economy increase in recent years. A great deal of engineering is being built or planed. The underground engineering is in the ascendant. For western water-power engineering only, quite a number of large-scale water-power engineering and storage plants has been built and designed. Most of them use large or ultra-large underground caverns as hydraulic architectures and mostly are immerged. The western bears the most strong modern lithosphere movement. The geologic environment is very complicated. Because of the landform and physiognomy such as alp and canyon, there always is high geostress filed. There will be fracture phenomena in constructing under the condition. A series of high side wall were found splitting cracks and standing out by the scale. This phenomenon has attracted the expert's attention. But the mechanism and anchorage effect has not been gone deep into analyze and research. The theory analysis, numerical simulation and experiment validation were combined in this thesis. The splitting failure mechanism and anchorage effect are systematically studied from both microcosmic and macroscopic aspect. Combine the theory analysis with engineering practice tightly. The main results discussed in this thesis are as follows:(1) Based on fracture mechanics, the characteristics and failure criterions of wall rock cracks including initiation, propagation, and coalescence are analyzed systematically under different conditions. The coalescence mechanism and extremum distribution of cracks are researched. The coalescence mode and mechanism among cracks are revealed in theory. Finally, take the compressed crack propagation analysis as an example, simulate the whole process that the cracks in rock develop into splitting cracks.(2) To realize the basic process of fracture analysis in ansys. The fore treatment program of crack propagation simulation is compiled by parameterization method of apdl. The calculation and analysis is automatic. Ansys is well for simulating the structures which contain cracks and bugs. When the parameters are suitable, the propagation of cracks can be simulated well in ansys. The different phases of crack propagation are simulated. To compare with the results by theory, perfect the formation process and mechanism of splitting cracks.(3) According to the results of experiments, the failure process of rock under uniaxial and triaxial compression is analyzed. The characteristics of energy dissipation and release in the process are revealed. Via the similar experiments in lab, the fracture energy of bolted rock mass is studied. In order to analyze the degree of released energy quantitatively, the ratio of energy release is computed based on the acquaintance to the failure phenomenon which the crack propagation give priority to the energy release. This method is applied into Pubugou power station excavation. Both the curves of elastic energy change in different positions and the contour chart of elastic energy density are received. The relationship between energy and crack propagation can be analyzed straightly.(4) In order to consider the interaction among cracks, adopt the sliding model of multi-cracks to simulate the splitting failure of rock in axial compress. According to the energy balance principle in the process of crack propagation, the splitting criterions under both linear elastic and small range yield are set up. Both of them are put into the excavation of Langyashan pumped storage power station. The distribution charts of splitting failure range are obtained. The splitting failure degree in different positions can be grasped and judged by quantificational concepts and intuitionistic images. The method offer more scientific and rational criterion to evaluate the splitting failure of underground engineering in high geostress.(5) When the underground caverns of brittle wall rock that locate in high geostress are being excavated, the longitudinal splitting cracks always present and lead to brittle craze. The splitting cracks will evolve into large parallel splitting crack groups. It can be treated as thin plate. According to G.R.Kirchoff thin plate theory, test the applicability of thin plate. The stress and displacement are resolved by elastic thin plate at the condition of basic hypothesis and geostress. The resolution calculation of critical stress and displacement are settled in theory based on energy method. Set Pubugou power station as engineering background. The criterion is programmed into fish language and the splitting failure range is confirmed. The critical stress and displacement are calculated by the resolution formula in the splitting failure range.(6) The reinforcement of bolts and shotcrete supporting to rock mass can control the cracks propagation well. Adopt both theory analysis and simulation method to study the mechanism of controlling the propagation. Firstly, from the theory aspect analyze the influence of shotcrete and bolts on stress intensity factor based on fracture mechanism theory. The best fixed angle of bolts is calculated. Then use ansys to simulate the crack arrest function of bolt to crack. Analyze the influence of different factors on stress intensity factor.(7) The splitting failure criterion of bolted rock mass is set up depending on energy balance principle including the work by external force, dissipation energy by bolts, plastic energy, elastic strain energy and dissipation energy by cracks propagation. The criterion is also applied into the excavation analysis of Houziyan water power station. The splitting failure range of surrounding rock is calculated, separately considering three separations, three excavation sequences and anchorage. And compare with the plastic range. The results show that the plastic range can not be treated as the only index which evaluates the excavation sequence and caverns layout scheme. The splitting failure may reflect more characters of geostress distribution sometimes and can give more reference opinions to optimization of excavation schemes. |
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