| With the growing of China’s economic strength, represented by rail and road infrastructure construction gradually advancing to district.Due to the limitation of topography, the high mountain of traffic engineering tunnels, construction difficulty bigger, in the surrounding rock stability in tunnel construction is a key issue in the engineering design. XuYong is located in the sichuan region to large railway tunnel in construction process of remote village, layered cataclastic structure constraints in instability of surrounding rock, landslides, the early failure of engineering problems, these problems with high frequency, large scope, characteristics of the serious, the He Tao wan tunnel engineering construction and safety operation of the project presents a massive risks. Therefore, the analysis in this type of structure characteristics of surrounding rock in tunnel excavation surrounding rock stability, and explore the tunnel excavation of disaster prevention countermeasures in this kind of rock mass, has important engineering significance and practical value.The author on the basis of a large number of field investigation, find out the walnut bay tunnel engineering geological conditions, Syria’s big railway was layered rock mass were analyzed and summarized in this paper in the deformation and failure of the main forms and the lining structure show the damage at the beginning of the phenomenon.The main engineering geological problems of the tunnel for walnut bay, by geophysical methods to detect deformation section constraints and encryption track and field test, affects the stability of surrounding rock are quantitative research.Conclusion simulated by the state of damage mechanics and the tunnel cross-section failure process, describe the damage evolution process of surrounding rock is analyzed.In combination with FLAC3 D numerical simulation technology, analyzed the supporting effect of 4 kinds of supporting methods, to simulate the various measures to control of the surrounding rock deformation.The main research results obtained were as follows:(1) Through the constraints of walnut bay tunnel tracking survey, statistics of all kinds of the structure of the development scale and features, put forward according to the characteristics of structural plane walnut bay tunnel project classification scheme.In general can be divided into four, five subgroups.On the basis of walnut bay structure surface classification scheme, combined with the instability of surrounding rock is happening with the structural plane statistical rule, found that large landslides, large deformation and Ⅲ, Ⅳ2 structural plane development happens to have stronger affinity.Accordingly the walnut bay tunnel surrounding rock dynamic classification.(2) More layer of Syria’s large railway tunnel rock mass deformation and failure phenomena of the statistics and induction, the summary of layered rock mass destruction form and lining structure in the early damage phenomenon, found the main factors which influence the stability of layered rock mass are: the uniaxial compressive strength, axis and controlling combination relation of the structure and structure plane obliquity, groundwater.(3) In walnut bay tunnel surrounding rock classification based on the factors and the stability of surrounding rock in the supplementary considering structural plane Angle of axis and controlling and the controlling factors, structural plane Angle level on the stability of surrounding rock.(4) Combined with geologic and engineering characteristics of surrounding rock of tunnel, with a prediction of the stability of surrounding rock of the tunnel, to determine the possible large deformation of high-risk period.Results showed that the DK41+174~DK41+203 for underground disasters incidence paragraphs.Construction process, using encryption advance geological survey and the forecast technology to potentially risky period on the stability criterion of surrounding rock, and geological conditions are verified through the excavation and anticipation.The excavation instability occurs after a certain scale.(5) On the basis of the experiment was carried out on the instability of surrounding rock failure mechanism analysis, summarizes three major damage mechanisms: gravity, compressive stress, tensile stress centralization.Using state to simulate the failure process tunnel, analysis the damage evolution of the deformation within the period of the process: the gravity collapse, plastic extrusion, sliding pressure cracking, tensile fracture morphology.And found that the gravity collapsing destruction process is relatively independent, mainly because of blasting causes the table of the relaxation;Plastic extrusion and sliding pressure induced cracking stage almost occurred at the same time, the tensile fracture morphology and lead to an arch department.The sliding pressure caused by cracking of the sidewall and believe, destruction of the whole damage process is controlled.(6) using FLAC3 D to simulate analysis without supporting under the condition of deformation and deformation characteristics, then the current under the support of level IV type I(only anchor systems), and after the change of surrounding rock grade Ⅳ Ⅱtype(arch anchor rod and anchor) system in advance under the support of tunnel excavation is analyzed by the response characteristics of surrounding rock, found that have advancing support measures of the surrounding rock convergence effect is better.Based on the geotechnical control deformation analysis method(ADECO- RS), combined with the actual geological conditions, design different advance ductule and anchoring advancing core soil forepole means, combining Ⅳlevel Ⅰtype simulated analysis of surrounding rock deformation of supporting measures.The geological conditions of the excavation support simulation, found to advance on the right side of the wall rock pre-reinforcement of surrounding rock can be effectively reduced by means of the value of convergence and convergence value;Constraints on it in front of the core of soil can also obtain the smaller surrounding rock pre-reinforcement convergence value, showed that poor rock mass excavation, the rock and its control core soil deformation of tunnel surrounding rock is particularly important. |
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