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[tunnel early bus] tunnel construction safety distance requires the distance between the invert arch and the face of the tunnel face: 1
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The level of inverting arch is less than 90m from the face of the first, second and third level surrounding rocks; the level of inverting arch from the face of the 2 and the fourth grade is not greater than 50m; the 3, fifth, and sixth surrounding rock inverting distance is not more than 40m
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The distance between secondary lining and tunnel face: 1
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The distance between secondary lining and tunnel face in grade I and II surrounding rock section should not be more than 200m; 2
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The distance between secondary lining and tunnel face in grade III surrounding rock section should not be more than 120m; 3
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The distance between secondary lining and tunnel face in grade IV and above surrounding rock section should not be more than 90m or design requirements
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2
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According to JJ [2010] No
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352 and TJS [2010] No
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120, the distance between the sealing position of grade 1, IV, V and VI surrounding rock and the working face shall not be more than 35m
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2
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Grade IV surrounding rock of secondary lining shall not be greater than 90m, and grade V and VI surrounding rock shall not be greater than 70m
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To sum up, the following regulations should be adopted in the current tunnel construction: the distance between the invert and the tunnel face: 1
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The distance between the invert and the tunnel face in grade I, II and III surrounding rock section should not be greater than 90m; 2
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The distance between the invert and the tunnel face in grade IV, V and VI surrounding rock section should not be greater than 35m; the distance between the secondary lining and the tunnel face: 1
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The distance between the secondary lining and the tunnel face in grade I and II surrounding rock section should not be greater than 90m The distance between the secondary lining and the working face of grade 2 and grade III surrounding rock should not be greater than 200m; the distance between the secondary lining and the working face of grade 3 and grade IV surrounding rock should not be greater than 90m or as specified in the design
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4
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The distance between the secondary lining and the tunnel face in the surrounding rock section of V and VI should not be greater than 70m or as specified in the design
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Ministry of Railways document notice on further defining relevant technical regulations on design and construction of railway tunnel in weak surrounding rock and unfavorable geology all railway bureaus, investment companies and railway companies (preparatory group): in order to further strengthen the technical measures for design and construction of railway tunnel in weak surrounding rock and unfavorable geology and ensure the safety of railway tunnel construction in weak surrounding rock and unfavorable geology, this paper aims at In view of the outstanding problems existing in the construction, the following technical regulations are put forward for the design and construction of railway tunnel in weak surrounding rock and unfavorable geology
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Please implement them carefully
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In case of any contradiction between the previous relevant regulations and norms, these Regulations shall prevail
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The principle of “early in and late out” should be strictly implemented at the tunnel portal
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The design of advanced support and slope protection at portal section shall be strengthened, and the tunnel portal section with shallow buried depth shall adopt open cut or half light and half dark method
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2
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The tunnel portal slope engineering should be excavated and supported step by step from top to bottom, and the reinforcement, protection, waterproof and drainage engineering of portal slope should be completed in time
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3
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The construction of main tunnel can be started only after the advance support of tunnel portal is completed according to the design
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A closed structure shall be formed at the entrance section in time, and long bench construction is strictly prohibited
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2
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Advanced geological prediction 4
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For the weak surrounding rock and unfavorable geological tunnel with high risk and extremely high risk in the construction drawing stage, the main unit responsible for the advanced geological prediction is the design unit, and the advanced geological prediction work is organized and implemented by the design unit
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The main responsible unit of other tunnel advanced geological prediction is the construction unit, and the advanced geological prediction is implemented by professional personnel of the construction unit
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5
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For karst and water rich fractured fault tunnels, the comprehensive method of horizontal drilling should be adopted in advance geological prediction
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6
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For tunnels with weak surrounding rock and unfavorable geological conditions, the design unit shall carry out special advance geological prediction design, collect and analyze the prediction data in time, improve the design scheme and guide the construction
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3
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Tunnel excavation 7
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Controlled blasting or non blasting method shall be adopted for the construction and excavation of surrounding rock sections of grade IV, V and VI, shallow buried tunnels, under buildings and adjacent existing lines in accordance with the safety regulations for blasting
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8
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When the bench method is used in the construction of the weak surrounding rock tunnel at grade IV, V and VI, the following requirements shall be met: (1) the excavation and support footage of each cycle of the upper bench, grade V and VI surrounding rock shall not be greater than the spacing of one steel frame, and grade IV surrounding rock shall not be greater than the spacing of two steel frames
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(2) the excavation and support footage of each cycle of side wall shall not be more than 2 pieces
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(3) before the excavation of invert, the steel frame foot lock anchor must be completed, and the excavation footage per cycle shall not be more than 3m
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(4) After the tunnel excavation, the initial support should be constructed in time and closed into a ring
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The distance between the closed position of grade IV, V and VI surrounding rock and the face should not be more than 35m
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4
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Initial support 9
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When the double track tunnel with grade IV and V surrounding rock is constructed by bench method, it is necessary to set foot locking anchor (pipe) and other measures to control the displacement of arch (wall) foot
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When the double track tunnel with grade V surrounding rock is constructed by bench method, the transverse temporary support or temporary invert shall be set, the temporary support shall be made of section steel, and 1 place shall be set for every 2 longitudinal beams
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10
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The initial support steel frame shall be factory manufactured, and must be inspected and trial assembled before leaving the factory
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When the grid steel arch is used, the octagonal grid arch should be used
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11
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Wet shotcreting process shall be adopted for shotcreting, which can be designed separately under special geological conditions
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5
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Monitoring and measurement 12
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The tunnel monitoring and measurement shall establish the hierarchical management, information feedback and reporting system according to the current technical specification for railway tunnel monitoring and measurement (tb10121-2007)
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13
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Tunnel monitoring and measurement should be included in the site construction organization as a key process
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Full time monitoring and measurement personnel must be set up and trained before taking up their posts
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Third party monitoring should be carried out for urban railway tunnels that may have serious impact on surrounding buildings
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14
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The measurement section spacing of tunnel vault subsidence and clearance change: grade IV surrounding rock shall not be greater than 10m, grade V surrounding rock shall not be greater than 5m
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15
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The monitoring network must be set up on the surface of the tunnel at the section where the tunnel is shallow buried and under the buildings
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16
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When the vault subsides, the horizontal convergence rate reaches 5 mm / D or the cumulative displacement reaches 100 mm, the excavation shall be suspended, the causes shall be analyzed in time and the treatment measures shall be taken
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Stamp“
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