With the increase of mining depth, the non-linear dynamic mechanical disasters, such as rock blasting, methane outburst, rheology, water outburst, etc., occur more and more. The rock mechanics problems caused by the deep mining engineering are focal problems of the field of the mining and rock mechanics field both in China and other countries. Focusing on special geological mechanical environment of deep engineering, the.conception system is put forward by deepening research into non-linear mechanical characters of deep engineering rock mass, which points out that the mechanical system of engineering rock mass in depth is non-linear mechanical system but not the linear mechanical system of that in shallow. Conventional theory, design method and technology are partially or entirely invalid. Using difficulty coefficient and hazard index as the evaluation indexes to evaluate the controlling condition of surrounding rock can synthetically reflect the mechanical characters and engineering characters of rock mass in deep engineering.
With the increase of energy demand and the intensity of exploitation, shallow resources reduce gradually, mines both in China and other countries all enter into deep exploitation in succession. Engineering calamity, such as rock burst in pit, gas explosion, sharp increase of mine pressure, large deformation of rock mass around tunnel, rheology, high ground temperature, etc., will increase due to the increase of the exploiting depth. It causes enormous threat to the security and efficiency of deep mining engineering, and the rock mechanics problems that caused by deep mining engineering become the focus of researchers both at home and abroad. However, there are a lot of Controversies in the concepts of "deep" and "deep engineering". To some extent, this impedes the development and exchange of theory and technical research In this field. To give a scientific definition for deep concept and its evaluation indexes is a primary task of promoting the basic theoretical research into the mechanics of deep rock mass, which lives in the special geomechanical environment of "three high and one disturbance".
To solve the rock mechanics problems caused by deep mining engineering, the experts abroad of mining engineering and rock engineering have put forward the concept of "deep" successively. It is commonly considered that the deep mining is a kind of mining with the emergence of some technologically difficult problems which would never meet during shallow mining. It is widely accepted by countries with history of deep mining that deep mining is a kind of mining when the depth of mining exceeds 600 m. But to some mining industry developed countries, such as South Africa and Canada etc., the "critical depth" is 800 m to 1000 m. In Germany, the critical depth exceeds 800 ~ 1000 m, and it is called ultra-deep mining when the depth exceeds 1200 m. In Japan, the critical depth is 600 m, but in UK and Poland, the critical depth is 750 m.
