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The 21st century, water conservancy and hydropower construction, often require the excavation of underground tunnel, where the stability of the surrounding rock has a very important significance. The engineering examples Jinping hydropower diversion tunnel of about 17km, excavation diameter of 13m and a maximum depth of 2525m, to stress value of 70MPa, the external water pressure greater than 10 MPa, with a large depth of hole lines long, the hole large diameter and on high ground stress, high external water pressure characteristics. In addition, four diversion tunnel of Jinping Hydropower Station adjacent to the construction of the drilling and blasting method long caving, auxiliary hole # 1 and # diversion tunnel TBM construction, one into the hole, a circular cross section; 2 and # 4 # diversion tunnel construction method, using drill and blast excavation in two steps, the cross section of four heart round horseshoe. The diversion tunnel span, on-site measurements, observation difficult, especially the TBM construction excavation fast, supporting rapid follow-up. In Jinping hydropower tunnel design and construction phases, an accurate assessment of tunnel surrounding rock stability economically and reasonably for rock support reinforcement design, fast and safe construction and diversion tunnel safe operation indispensable condition, in this complex. geological conditions, the stability of the diversion tunnel of Jinping long deep problems are more prominent. Therefore, the for Jinping diversion tunnel excavation process as much as possible to consider various factors affecting the tunnel surrounding rock stability is very important. Jinping hydropower tunnel surrounding rock stability In this paper, a common geological processes mechanisms, rock classification and numerical simulation of the three methods. Detailed description of the engineering geological conditions of the diversion tunnel line area; failure characteristics of surrounding rock deformation followed by diversion tunnel surrounding rock conditions and different construction methods for statistical analysis, for different construction conditions of the subsequent chapters of the thesis diversion tunnel surrounding rock stability provide a reference; again by geological processes mechanisms for analysis, from theory to analyze the stability of surrounding rock in the diversion tunnel excavation process; followed by the use of the Jinping existing rock classification (JPF) system, diversion tunnel construction conditions open burrow paragraph applicability analysis, to explore the different construction methods lead to the stability of surrounding rock where the differences; Finally, the numerical simulation analysis method under the conditions of different construction of diversion tunnel surrounding rock stability study, summed up the construction process on the stability of surrounding rock of impact. In summary, this article by geological processes mechanisms, rock classification and numerical simulation of the three methods, the diversion tunnel of Jinping Hydropower Station construction conditions surrounding rock stability analysis, the following conclusions: First, The geological process mechanism analysis showed that in the project area to stress, diversion tunnel excavation, the maximum principal stress direction south side of the spandrel to the north side of the arch of the foot, the minimum principal stress is perpendicular to the south side of the north side of the spandrel The arch of the foot. Therefore, on the north side of the spandrel compressive stress concentration at the south side of the spandrel tensile stress concentration, leading to severe deformation and failure, but different manifestations, including the north side of the spandrel prone to rock burst, the stress collapse of the high-stress destruction the south spandrel prone to collapse, off the block and general destruction, and the scene surrounding rock deformation and failure characteristics match the statistical results. Second, the applicability analysis shows that has Jinping rock classification system (JPF) in different construction conditions of the diversion tunnel, the JPF surrounding rock classification system in the diversion tunnel of 2 #, 4 # 1 #, 3 # diversion tunnel drilling and blasting higher rate of matching segments Kai-dig method, more than 80%; 1 #, 3 # Diversion Tunnel TBM open burrow segment, lower rate of matching, up to 70%. Different lithology, depth segment JPF surrounding rock classification system in TBM construction hole section of drill and blast construction hole section of the anastomosis is low, and which classification of the JPHC system results with the actual surrounding rock classification consistent with the highest rate of system, followed JPQ, system somewhat less JPRMR. Existing JPF rock classification system suitable for drilling and blasting method Tunnel Construction in TBM construction tunnel applicability poor, need to be further amended perfect. Finally, numerical simulation results show that the depth and the surrounding rock classification under the same conditions, diversion tunnel face excavation and step-by-step excavation of surrounding rock stress, displacement and plastic zone distribution, have the same law, that stress concentration and distribution of plastic zone are mainly in the north side of spandrel and south side of the arch of the foot displacement distribution in the south side of the spandrel and the north side of the arch of the foot. But the degree of stress concentration, the range of displacement and plastic zone difference, diversion tunnel with # 2 and # 4, # 1 and # 3 diversion tunnel excavation of rock stress concentration is higher, displacement and plastic zone wider range. In addition, the full-face excavation of diversion tunnel and step-by-step excavation process, ahead of the face are the maximum principal stress appear the vaults and bottom arch parts of stress concentration, the minimum principal stress is reduced and gradually increases from the outside to the inside. 1 times the hole diameter range of the tunnel face, the supporting role of the working face control stress concentration, after 2 times the hole diameter, wall rock within the maximum and minimum principal stress distribution no longer changes, indicating that the disappearance of spatial effects, end of the stress release, close to the convergence of surrounding rock deformation; burial depth under the same conditions, the surrounding rock of tunnel excavation after Class III increases, the distribution range has been expanded to surrounding rock stress concentration than the Class II; surrounding rock classification under the same conditions, with the stress concentration increase with depth, stress level increased, resulting in the surrounding rock has become increasingly serious, expanding the scope of distribution; the different excavation led to the excavation face different spatial effects, # 2 and # 4 diversion tunnel up and down bench excavation, and finally the crown of sinking displacement ratio # 1 and # 3 section of the diversion tunnel excavation large. In summary, the step-by-step excavation is conducive to the stability of the surrounding rock.
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