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Welcome to pay attention to the top, and also welcome you The official account of water tunnel is: the tunnel construction quality is getting higher and higher
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The research on tunnel construction is also more and more thorough
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The water leakage of the tunnel is the key and difficult point in the design and construction
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Once the water leakage occurs, the tunnel will directly affect the quality and safety of the main structure of the tunnel
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Here are seven measures to prevent tunnel leakage and ensure tunnel construction quality and safety
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1、 Smooth blasting scheme is adopted to ensure the smooth excavation surface, which is the foundation of no seepage and leakage of the tunnel
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If smooth blasting is not done well, it is easy to bring: ① it is difficult to backfill the arch, and once it is not dense, it is easy to form water pocket; ② the rock surface is uneven, and it is difficult to level the shotcrete; ③ it is difficult to lay waterproof board
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Therefore, in the construction, the smooth blasting process requirements are strictly followed
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2、 In order to ensure the quality of grouting waterproofing, achieve the effect of water sealing, basically realize the wireless flow in the grouting section, and initially form the water sealing ring outside the initial support, the grouting design shall be strictly followed, and the principle of “prevention first, combination of prevention and drainage, and comprehensive treatment” shall be implemented To create conditions for safe excavation and tunnel waterproofing
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3、 Strictly control the small pipe grouting
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When using the short bench method, strictly implement the construction principle of “pipe exceeding the front, strict grouting, short excavation, strong support, quick closure and frequent measurement”, and seriously do a good job in the initial support, especially the backfill grouting behind the initial support, so as to ensure the wireless flow of leakage water, otherwise, punch holes at the serious leakage water and add grouting under the pipe until it meets the requirements
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The work must be carried out in parallel, in sections, in one section and in the first inspection, otherwise, the secondary lining will not be allowed
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(1) before construction, according to the engineering geological and hydrogeological conditions, grouting shall be carried out after passing the test
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(2) according to the scope of pre grouting, geological conditions and groundwater conditions, in order to ensure the effect of grouting reinforcement and water shutoff, reasonable grouting parameters and slurry ratio are selected
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(3) in the process of grouting, the grouting pressure shall be strictly controlled to prevent structural deformation and grouting
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(4) after grouting, radial drilling method is used to check, analyze and judge the grouting effect
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4、 Hold the key of shotcrete Waterproofing (1) wet shotcrete technology is adopted
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(2) shotcrete adopts the method of re shotcreting
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The cover of the first shotcreting is set up, the grid is erected, and the re shotcreting is carried out after the net is hung, and the identification reinforcement for detecting the thickness of shotcrete is embedded to check the thickness of shotcrete
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(3) 28 days before shotcrete construction, the site layout, machines and tools, and mix proportion data shall be submitted to the supervisor for approval before implementation
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(4) allowable deviation of raw material weighing (by weight): cement, accelerator ± 2%, sand ± 3%
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(5) mixing time: the shotcrete is fed by a forced mixer, and the mixing time shall not be less than 2min
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(6) the transportation and storage time shall not exceed 2 hours when the accelerator is not added, and shall not exceed 20 minutes when the accelerator is added
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The mixture shall be used as soon as it is mixed
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(7) sampling test shall be conducted according to the specification requirements
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After the completion of shotcrete, the tunnel is basically dry
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In some places where there is seepage, one is that the pipe can be inserted for supplementary grouting, and the other is that the larger seepage can be inserted to connect with the drainage blind pipe and lead to the side ditch for drainage
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5、 Control the construction quality of waterproof layer (1) the construction of waterproof layer must be carried out by professional team
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(2) the base surface must be treated well
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(3) the construction technology of no nail laying and double weld welding must be adopted
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(4) ensure the quality of construction joints of waterproof layer
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(5) strengthen the protection measures of finished waterproof layer
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In strict accordance with the structural waterproof design requirements, the longitudinal and circumferential soft permeable pipes are set first, and then the waterproof board is laid
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In the process of construction, the quality of sealing and welding should be guaranteed to avoid the holes caused by trauma
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Before the waterproof board is laid, the reinforcement head and anchor head on the shotcrete surface shall be cut off first, and then the hand-held grinder shall be used for grinding
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The uneven parts shall be chiseled and sprayed to make the concrete surface smooth, and the local water seepage shall be treated
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(6) the waterproof board shall be laid in circular direction, and the welding process shall be closely coordinated with the fixing process
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Generally, the waterproof board shall be welded first and then fixed
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(7) the lap width of the waterproof board is 10 cm, and the welding width is not less than 2 cm
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The missed welding and false welding shall be repaired
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If there is scorch and welding through, the same waterproof board welding paste shall be used for covering or according to the instructions of the supervision engineer
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(8) glue heat welding shall be adopted for fixing the waterproof board
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The waterproof layer between the glue pad and the glue pad shall not be tight, and the board surface shall be closely adhered to the shotcrete
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(9) the distance between the waterproof board section and the excavation face shall not be less than the safety distance required by blasting, and the waterproof layer shall not be damaged when the secondary lining is poured with concrete
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(10) before pouring concrete into the secondary lining, the tightness of the slab surface and the bottom layer shall be checked, the quality of the lap welds shall be checked, the quality inspection records shall be filled in, and the construction can be continued only after the approval of the supervision engineer
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6、 Strictly control the waterproof of secondary lining concrete
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In the process of pouring and curing, the water cement ratio of secondary lining concrete must not be changed, which will lead to shrinkage cracks and reduce its waterproof performance
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(1) the performance of cement used for waterproof concrete must meet the requirements of the specification; expired or damp caking cement shall not be used, and different kinds or grades of cement shall not be mixed; and (2) except for the technical indexes of sand and stone used for waterproof concrete, the mud content of sand shall not be greater than 3%, and the mud content shall not be greater than 1%; the maximum particle size of stone shall not be greater than 40mm, and the mud content shall not be greater than 1% No more than 1%, and the content of mud block shall not be more than 0.5%
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(3) the water used for waterproof concrete shall be clean water without harmful materials; the admixtures added to improve the impermeability of concrete must have quality certification documents and product technical data
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(4) the concrete must be poured and vibrated in layers, the thickness of each layer shall not exceed 300-400mm, the pouring time interval between two adjacent layers shall not exceed 2h, the self falling height of concrete shall not exceed 2m, and the tumbling barrel or chute shall be used when exceeding
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(5) the concrete pouring must be continuous
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The construction needs to leave the construction joint
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The admixture added for the impermeability of the designed concrete must be obtained
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The quality certificate and product technical data must be provided
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(6) the concrete must be poured and vibrated in layers, the thickness of each layer shall not exceed 300-400mm, the pouring time interval between two adjacent layers shall not exceed 2h, the self falling height of concrete shall not exceed 2m, and the tumbling barrel or chute shall be used when exceeding
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(7) the concrete pouring must be continuous
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If the construction needs to leave the construction joint, the design approval must be obtained and the supervisor’s approval must be obtained
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The allowable interval time is shown in the table below; the frequency, amplitude, vibration speed and other parameters of the vibrator selected for tamping depend on the slump of concrete and the particle size of aggregate
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(8) the whole ring pouring construction is adopted in the pouring construction
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When the concrete is poured to the junction of the wall and arch, the interval is about 1 hour, so as to make the side wall concrete compact
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When the arch ring is capped, it shall be tamped in time with the pouring of the arch ring
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(9) during vibration, the vibrator shall not contact the waterproof layer and formwork, and the moving distance each time shall not be greater than half of the action radius of the vibrator
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(10) strictly control the formwork removal time, and it is strictly forbidden to remove the formwork before the concrete strength fails to meet the specification requirements
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(11) strengthen the maintenance of concrete.
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