When tectonic pattern and characteristic of platy structure rock-mass met some conditions, its mechanical principle generally can be analyzed by board and shell theory. Based on the achievement, stress distribution in platy structure rock-mass was studied when length is much more than height of underground engineering in vertical stratified structure strata: According to reliability analysis principle of engineering structure, equation of stability probability analysis of upright stratified strata and its calculation methods was researched.
Structure and mechanical media of rock-mass are the most basic data in stability analysis and design of underground rock-mass engineering. In general, mechanical media can divided into continuous structure mechanical media, block- fragmental and platy[1988a] according to response of rock-mass mechanically on engineering construction. When engineering force was exerted on rock-mass, mechanical principle and deformation rule and failure mode of the former two mechanical media were researched adequately in some literatures [1988b],[1984], [1988]. Fragmental mechanical media can be translated into continuous media under some conditions. It can be regarded as a continuous media. Mechanical response of platy structure rock-mass on engineering construction differs from ordinary continuous media. A typical failure mode of surrounding rock of underground roadway in platy structure rock mass is shown in Fig.1. So far, mechanical principle of stability for them needs further research yet. The mechanical principle for typical platy structure media only is study in this paper because of limitation to length of it. Correspondingly, probability analysis method of stability for surrounding rock of underground roadway is probed Into.
There are differences between platy structure rock-mass and block. Block structure rock-mass is cut by various weak planes and alone rock mass is formed when uncover surfaces combine with weak planes. Weak planes and their combining mode dominate primary mechanical characters of block structure rock-mass. Disturbance of strata is basic reason that platy structure rock-mass is formed. Combining form of strata can be divided into interstratified bed, intercalated bed and inter bedded stratum. Majority of disturbance between strata is produced with slide of strata when strata are folded along a group of virgin joints in geological body. Detach of strata exist widespread in stratified rock. Disturbance of strata don't cut strata and majority of them is formed in weak inter bedded stratum which soft strata and hard strata jumbled. Thickness of the week inter bedded stratum generally is a few millimeters or centimeters or decades centimeters. Hard rock stratum is divided into approximately separate and thin rock board. The more weak inter bedded stratum in stratified rock mass is, the thinner thickness of rock board in hard rock mass divided by weak planes. Platy structure rock mass can be divided into integrated and fragmental[1988a]. According to some research achievements in literature[1988a], The following four rock mass have mechanical behaviors for platy structure rock mass[1988a]. 1) Ratio between length. 2)Joint surface in magmatic and metamorphic rock is developed into dislocation surface by means of structure stress in rock mass.
