. Engineering and Contracting . General Arrangement of Earth Thrust Borer. thrust boring is begun by turning the gun up to a vertical of clay round the end. It is found that the clay locks theposition and dropping the pilot into it. The gun is then pins effectively, and that they never fall out. The with-turned down and clamped in position, and hydraulic pressure drawal of the extension pieces is easy, since their diameteris admitted behind the piston, pressing the pilot horizontally is a good deal less than that of the hole. The method gen-into the soil. The stroke being completed, the admiss


. Engineering and Contracting . General Arrangement of Earth Thrust Borer. thrust boring is begun by turning the gun up to a vertical of clay round the end. It is found that the clay locks theposition and dropping the pilot into it. The gun is then pins effectively, and that they never fall out. The with-turned down and clamped in position, and hydraulic pressure drawal of the extension pieces is easy, since their diameteris admitted behind the piston, pressing the pilot horizontally is a good deal less than that of the hole. The method gen-into the soil. The stroke being completed, the admission erally employed is to attach a rope to the last piece and carryvalve is closed and the exhaust valve opened—by one and it round a pulley. Two or three men on the surface canthe same lever—the gun is raised to the vertical and the then pull the whole chain of extension pieces back until thefirst extension piece pressed into it. The exhaust water is next .ioint is reached. The operation is repeated until thethus retirned


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