Tula State University (Tula, Russia)

A. S. Sammal, Doctor of Engineering Sciences, Professor, assammal@mail.ru
P. M. Afanaskina, Assistant, Postgraduate Student
A. S. Kaplunov, Postg raduate Student
K. E. Zalesskiy, Candidate of Engineering Sciences, Associate Professor

A new analytical design method for tunnel linings constructed near an overlying layer of weakened rocks is proposed. The method implements a theoretical approach based on the rigorous solution of a corresponding plane problem in the theory of elasticity abo ut the stress-strain state of an infinite piecewise homogeneous medium modeling a rock massif, composed of two semi-infinite areas separated by a layer of finite thickness. All the considered areas are made of different materials and are in contact with each other along infinite straight boundaries, while the lower layer is weakened by a hole, the contour of which is reinforced by a circular ring that models the tunnel lining. The infinite three-layer medium and the ring are subjected to static loads caused by gravitational forces (rock's own weight pressure), residual pressures of groundwater flowing through permeable layers and linings, or internal pressure (when considering hydraulic tunnels in the discharge mode), and form a single deformable system, i.e., the continuity conditions of displacement vectors and total stresses are satisfied at the corresponding contact lines. In order to implement the method in practice, a computer software package has been developed that allows for the consideration of various geomechanical situations, both in solving scientific and research problems and in the design of various tunnel structures. As an illustration, specific results of the stress state computation of the underground structure are presented, which are compared with data obtained based on finite element modeling using the Russian software package CAE FIDESYS.

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