Method of controlling long term safety of underground entry system by regulating formation of stress envelopes

Abstract

Abstract The long term safety of underground rooms excavated in weak ground media which are subjected to large overburden and lateral earth pressures is regulated by controlling the formation of stress envelopes embracing an entry system. Within the entry system the rooms to be protected are placed parallel to the relief openings which are specifically designed to fail. An entry system designed with a predetermined safety period up to infinity is used for making extensive underground excavations safe and economical by supporting the overburden with an orderly development of stress envelopes. In order to create an entry system with a protected room or rooms, two relief openings are first excavated for the purpose of forming primary stress envelopes around the individual relief openings, then one or more protected rooms are excavated between the relief openings in such a manner that the primary envelopes are quickly transformed into a single secondary stress envelope which embraces the entire group of relief openings and protected rooms. A stress relieved zone is thereby created inside the secondary envelope which acts as a stable lining, forming a tubular shield against rock deterioration at the inside boundary of the stress envelope. The envelope supports the overburden and lateral earth pressures. Besides the protection of underground rooms, the stress envelopes may be utilized to control deformation and subsidence of the ground over a mined-out area by creating large protective stress envelopes in the main body of the overburden formation in the same manner as for the protection of underground rooms.

Inventors

• 👤 Shosei Serata

Bibliographic Details