Mining College, MISIS, Moscow, Russia:
Yu. A. Alyushin, Professor, Doctor of Engineering Science
A. V. Korchak, Head of a Department, Professor, Doctor of Engineering Sciences, e-mail: kafedrasp@gmail.com
M. N. Shuplik, Professor, Doctor of Engineering Sciences

In civil underground construction, tunneling machines often intersect unstable heavily moist soil. Smooth operation of tunneling machines requires artificial pre-freezing of soil in this case. The freezing technology actually in use includes drilling of a vertical hole usually 138 mm in diameter (more seldom—159 mm) and placement of a freezing pipe 114 mm in diameter in the hole when drilling reaches an assigned depth. Drilling of host holes and assembly of freezing pipes in them takes 45–50% of the total work of soil freezing and is very expensive. The authors put forward a patented design of a freezing pipe made as a hollow pipe with a nose-piece and welded worn fin, which allows driving the pipe in soil by forced revolving. In this case, drilling of host hole is avoided, firm contact is created between the pipe and soil, and power consumption of freezing is reduced. The mathematical model of the forced driving of the freezing pipe in soil is constructred, and the values of axial force and drive torque are calculated as functions of the pipe design parameters and physico-mechanical properties of soil. The theoretical relations obtained using the models were checked and refined in the course of the commercial experimental testing of the new freezing pipe design. As a result, the working ability and high economic efficiency of the freezing pipe were proved.

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