(1) The longitudinal overlapping length between the two groups of pipe sheds shall not be less than 1.5m; I-steel arch or grid steel frame is often used for steel arch.<br>(2) The allowable error of verticality of steel arch frame shall be ± 2 °, and the allowable error of center line and elevation shall be ± 5cm.<br>(3) The drilling plane error shall not be more than 15cm, and the angle error shall not be more than 0.5 °. The steel pipe shall not intrude into the excavation contour.<br>(4) The front end of the first section of steel pipe shall be processed into a sharp cone shape to facilitate guide insertion. To make a hole, install a tube, from top to bottom.<br>(5) Long steel pipes shall be lengthened one by one with 4-6m pipe sections, driven into one section, and then connected to the next section. Thick wall pipe hoop shall be used as the connection head, full of screw thread, and the length of screw thread shall not be less than 15cm. To ensure the uniformity of stress, the steel pipe joint shall be staggered longitudinally.<br>(6) When the rigidity of the pipe shed needs to be increased, cement mortar can be injected into the installed steel pipe. Generally, a number of holes of 10-15mm shall be drilled alternately on the front section of the first section of the pipe to facilitate air exhaust and slurry discharge, or the gas outlet pipe shall be installed in the pipe, and the grouting can be stopped after the slurry is filled.<br>(7) In case of jamming or hole collapse during drilling, grouting shall be carried out before drilling. In some soil strata, steel pipes can be directly driven in.<br>
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