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      Provisions on the use of the freezing method to drill vertical shafts

      Source: xe1x.com Author: admin Date: 2019-09-07 15:25 heat:
      When freezing shafts are drilled by the freezing method, the following requirements shall be observed:
      (1) The freezing depth should extend through the weathering zone to a stable bedrock of more than 10m. When the gushing water in the bedrock section is large, the freezing depth should be deepened.
      (2) The first frozen hole shall be cored in full to verify the reliability of the wellbore inspection hole data.
      (3) When drilling frozen holes, the direction and deflection of the borehole must be determined. The maximum interval between deflections must not exceed 30m, and the actual deflection plane position of the frozen hole must be plotted. When the deflection exceeds the stipulation, it must be corrected in time. When the freezing effect is affected by the deviation of the drilling hole, the hole must be repaired.
      (4) The hydrological observation hole shall be drilled in the wellbore, shall not deviate from the net section of the wellbore, and its depth shall not exceed the depth of the freezing section.
      (5) The frozen pipe shall be a seamless steel pipe, and shall be welded or threaded. After the frozen pipe is drilled into the hole, a pressure test shall be performed. When an abnormality is found, it must be handled in time.
      (6) After the freezing is started, the water level of the hydrological observation hole must be observed frequently. Only when the hydrological observation hole has water for 7 days and the water volume is normal, or the hydrological view of the water in advance,
      The borehole water pressure curve shows a significant inflection point and rises steadily for 7 days, and the trial excavation can be performed only after the frozen wall has been circled. During the freezing and excavation process, the brine temperature and flow, well temperature and displacement, and Well leakage and salt water leakage at working face. Inspection should have detailed records, and if abnormalities are found, they must be handled in time.
      (7) When the blasting operation is used in the freezing section of the excavation, antifreeze explosives must be used and special measures must be formulated. The blasting technical parameters should be specified in the operation regulations.
      (8) During the excavation and construction process, safety measures must be taken to prevent deformation of the frozen wall, chipping and pipe breakage.
      (9) The rooting wall socket shall be located in a stable and hard rock layer with less water.
      (10) When the freezing depth is less than 300m, the freezing can be stopped after the permanent borehole construction is completed; when the freezing depth is greater than 300m, the freezing time should be determined by the research, construction, freezing, excavation, and supervision unit based on the frozen temperature field observation data. (11) The wall structure of the frozen wellbore shall adopt double-layer or composite wellbore. After the completion of the freezing section of the wellbore, the filling and grouting between the walls shall be carried out in a timely manner. The temperature of the interlayer concrete between the walls shall not be lower than 4 ℃ during grouting And the frozen wall is still closed and can withstand external hydrostatic pressure.
      (12) The wall of the well in the alluvium section should not be reserved or post-bored.
      (13) When the freezing hole passes through the rock layer with the underground roadway and the chamber, the retarded slurry should be used to fill the annular space between the freezing hole wall and the freezing pipe.
      (14) After the freezing construction is completed, the frozen holes must be filled with cement mortar or concrete in time.
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