Patent EA-000555-B1 (EA)
Title: Undercut excavation with protection against seismic events or excessive ground movement
Inventor: GRYBA CHARLES M
IPC: E02D29/045
Filed: 1998-04-15
Abstract: 1. A method of excavation which comprises: (a) drilling holes of predetermined size and length in the ground; (b) placing at the bottom of said holes resilient elements capable of absorbing shock energy or excessive loads due to ground movement; (c) inserting concrete posts into said holes, said posts having their bottom ends resting on said resilient elements and having their top ends essentially flush with the ground, said posts being capable of supporting a concrete roof on said top ends; (d) pouring a concrete floor on said ground and on the top ends of said posts; and (e) excavating beneath said concrete floor which now serves as the concrete roof for the excavation, with said resilient elements providing protection against seismic events in the area of the excavation or against ground movement exceeding failure load of the concrete posts. 2. An undercut-and-fill mining method, which comprises: (a) cutting initial drifts in an underground mine to form rooms in a conventional manner with a sill at the upper end of an ore body, and recovering the mined material from said rooms; (b) drilling holes of a predetermined size and length in the sill of each room; (c) placing resilient elements at the bottom of said holes capable of absorbing shock energy or excessive loads due to ground movement; (d) inserting concrete posts in said holes to rest on said resilient elements with their bottom ends and having their top ends essentially flush with the sill of the rooms; (e) pouring a concrete floor in said rooms to be supported by the top ends of said posts; (f) back filling the rooms with a suitable fill; (g) once a complete lift has been so mined, repeating this mining procedure on a lower level where the concrete floors now serve as a roof supported by said posts and said resilient elements serve as protection against seismic events, such as rock bursts or against ground movement exceeding failure loads of the concrete posts; and (h) continuing mining in this manner from level to level until the desired ore body is mined, with the resilient elements under the posts of the lowermost level serving as protection against seismic events to which the mine may be exposed. 3. A method as claimed in Claim 2, in which additional posts are stood-up on top of the concrete posts inserted into holes drilled into the sill of each room under the concrete roof, so as to exert pressure and provide suitable load on said concrete posts and on the resilient elements on which they rest and thereby transmit protection against seismic events or excessive ground movement to the upper levels of the mine. 4. A method according to Claim 3, in which said additional posts are positioned adjacent to the posts supporting the concrete roof so as to facilitate tying them all together when pouring the concrete floor in the sill of the mined level and thereby providing a double-post mining system in which the posts at the lowermost level resting on the resilient elements provide protection against seismic events or excessive ground movement in the mine. 5. A yield post for an undercut excavation method, which is a post made of concrete and which has a resilient element capable of absorbing shock energy or excessive loads connected to the bottom end thereof.