(1) General Provisions 1. When drilling by conventional method, the distance between the permanent support or temporary support of the vertical shaft to the working surface shall not exceed 2m; when using slipform construction or umbrella drilling, the distance shall not exceed 4m, but it must be Measures to prevent the help of the film were reported to the Chief Engineer of the Agency for approval. Permanent support, temporary support forms, section heights, etc. must be specified in the construction organization design or operating procedures.
2. The wellbore passes through the aquifer or fracture zone. The main safety requirements for pre-grouting on the ground or working surface are:
(1) The grouting depth should be greater than the total thickness of the grouted aquifer, and it should be 5~10m deep into the impervious rock layer or hard rock layer. When the design position of the bottom hole is in the grouted water-bearing rock stratum, the grouting depth should be greater than the well depth by 10m.
(2) Before the pre-grouting of the wellbore working face, above the grouted aquifer (including the section grouting), the grouting rock cap or concrete grouting pad must be set according to the design requirements. The structural form and thickness of the rock cap or the impeller should be determined according to the maximum grouting pressure, rock properties and working conditions. When the concrete stop pad is supported by the well wall, the strength of the well wall should be checked.
3. When using wellbore grouting to block water, the following regulations must be observed:
(1) When drilling, always check the amount of water in the hole and the amount of sand. When the amount of water inflow is large or the sand contains sand, it must stop drilling and grout in time; when drilling the water in the hole, the hole must be tightly sealed in time.
(2) When the wellbore is in the sand-sand layer, the depth of the grouting hole should be at least 200mm less than the thickness of the wellbore wall. When double-layer well wall support, the grouting hole should enter the outer wall 100mm. If it is necessary to carry out wall-breaking grouting, special measures need to be made and reported to the higher authorities for approval.
(3) The well wall must have the strength to withstand the maximum grouting pressure. Otherwise, do not grout.
(2) Freezing method sinking 1. When freezing the method, the geological inspection hole shall not be hit in the freezing wellbore. The hydrological observation borehole deflection shall not exceed the wellbore and the depth shall not exceed the lower aquifer of the frozen section.
2. Freeze the vertical shaft construction, the freezing depth should pass through the weathering zone and enter the stable bedrock for more than 10m. When the water in the bedrock section is large, the depth of freezing should be deepened.
3. When drilling the frozen section of the topsoil, blasting operations may be used, but safety technical measures must be established.
4. During the freezing and excavation process, it is necessary to check the salt water temperature and flow rate, the temperature and displacement of the well, and the leakage of salt water on the well and the working face. Recording is made and abnormalities must be dealt with in a timely manner.
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