Deformation And Damage Law And Its Nonlinear Characteristics Of Rock Under Cyclic Load

The deformation and damage of rock in the complex loading path and loading history is one of the most difficult study points on rock mechanics. Cyclic load is the most common and the simplest mechanical phenomenon, and it is related with its monotone loading manner closely. So, the study of rock under the cyclic load can be regared as'important breakthrough jaws'of rock mechanical study in the complex loading path and loading history. This paper chooses sandstone and limestone that are common in Chongqing as study objects, mainly with sandstone, by using MTS815 Rock Mechanics Test System, 16CHs SAMOS? System and the specified loading equipment of the CT machine to do the experimental research on the deformation and damage properties, acoustic emission characteristics and CT micro-damage evolution in the process of rock damage and failure under monotonous load and cyclic load, meanwhile the paper is combined with damage mechanics and the nonlinear theory to do a hepful research. The main research work and results are as follow:1) Four phases law of rock damage failure under cyclic load have been proposed, and are proved and further explained by AE experiment, CT experiment, catastrophe theory, fractal theory;2) Experiment of this paper shows: There is obvious Felicity effect on process of rock failure under low cyclic load, the rate of Felicity is decreased in general, and the rate of Felicity has obvious characteristics of stage. The study on this paper also shows: on process of rock damage failure under cyclic load, there is no impact on the evolution trend of the rate of Felicity as long as the threshold(minimum) of obvious AE fall in a reasonable range;3) In order to study the AE Characteristics of rock during the process of unloading, this paper puts forward the concept of AE unload rate.whether AE unload rate of the axial stress or the axial strain confirm the phases character of rock damage failure under cyclic load;4) Rock types, structure and uniformity are all the main influence factors of AE location experiment. The results of Chongqing fine sandstone AE location experiment show that AE sources distribute in the central of sample, there is no obvious band and cluster grouping phenomenon on the two sides of sample, and no AE-location"blank areas"in the middle of sample. For such rock, the spatial distribution of micro-fracture is no apparent instructions significance to the spatial position of main rupture;5) By using the specified loading equipment of the CT machine from State Key Laboratory of Frozen Soil Engineering of the Chinese Academy of Sciences to do the multilevel cyclic load experimental research study, this paper observed the transformation process of rock sample damage evolution,and obtained CT number and density evolution on process of rock damage and failure under cyclic load;6) It puts forward the concept of damage mutation, establishes the cusp catastrophe model with cumulative AE energy represent damage, uses this model to analyze cusp catastrophe damage under the process of cyclic loading failure and monotonic loading failure, and further describs the four phases law of the rock damage failure under cyclic load in this paper;7) Through analyzing the correlative dimension of rock AE sequence under the monotonous load and cycle load, this paper shows that the dimension of AE sequence is decrease on the process of rock failure.8) This paper shows that the displacement sequence of this slope has characteristics of fractal and chaos by analyzing monitoring data of displacement sequence of a mine open pit slope. Using the way of the nearest neighbor of chaotic system time sequence state space, this paper forecasts the displacement sequence of this slope.