Evolution Of Fractured Rock Mass Energy And The Damage Characteristics Experimental Study Under Cyclic Loading

Rock mass is discontinuous media, there are large amounts of fractures and holes inside, which make rock behave anisotropic. Extension and connection among joints and fractures under external loads not only have significant effects on rock mechanical characters, but also be the main cause of local deformation. So, correctly analyzing the mechanical character and local deformation process of fracture rock has an important engineering significance. The nature of rock damage is the result of energy dissipation and release from the view of energy, and studying mechanical features from this point could reflect rock deformation rule factually.Based on the similar material simulation basalt brittle material, make different crack Angle and length of single fissure samples and the double fracture of the spatial distribution of different samples.With PIV high-speed particle imaging velocimetry method as a means of observation, with independent research and development "YY-L600 biaxial compression test system for biaxial cyclic compression test.Analyzed the crack sample through the local process of mechanical properties, deformation and crack model.From energy point of view, to study the energy evolution regularity of fracture specimens in the loading process, characteristics and damage characteristics of energy consumption.The main results were as follows:(1) The prefabricated crack effect on the mechanics and strength characteristics of the specimens, the same load condition, the peak intensity of complete sample was obviously higher than that of crack sample peak intensity.Starting recycling value, the combination of the confining pressure and fracture form the axial stress-strain curve of specimen have little impact on the overall form, but will affect the sample peak strength, crack strength/peak intensity ratio;(2) The precast single crack and double the specimen failure process roughly experienced four stages: initial consolidation stage, elastic deformation stage, the secondary crack initiation and propagation, prefabricated crack extending, around the secondary cracks accelerate specimen failure as a whole.Double fracture specimen with single fracture specimen, the crack of time early, large-scale crack through earlier than single fracture specimens, the peak intensity is lower than that of single frac-ture specimens;(3) Single crack crack and double the wing crack, the crack in the extension process are coplanar secondary crack and secondary crack, but the single fracture crack upright tilt secondary cracks in the middle of the prefabricated crack, this is a double fracture specimens do not have, double crack crack prefabricated in up and down the middle area of rock bridge in the form of shear crack, and not to the vertical tension crack, the main reason is that crack spacing, the smaller the stress concentration effect makes no vertical tension crack formation of rock bridge;(4) According to the different forms of fracture mechanics crack and crack extension failure process, can be single and double fracture specimen under biaxial cyclic loading conditions, a shear crack propagation mode is divided into extensional transfixion compound penetration and shear through three categories, according to the final transfixion crack types, each of the categories and can be subdivided into several classes.Corresponds to the crack extension penetration model, sample of failure mode can be divided into three categories, both the tensile damage model, the shear failure model and a compound damage model;(5) Single crack specimens and the specimens, the cyclic loading process, the energy evolution presents the nonlinear growth trend, energy present different in the different stages of the deformation and failure form of transformation.Energy dissipation characteristics of the specimens were the major influencing factors of the crack length, crack Angle, length of rock bridge, the combination and loading confining pressure five aspects;(6) Different geometry size and the combination of fracture specimens, the limit of energy storage.Under the condition of the same confining pressure, the limit of specimen storage starting value of the correlation is not obvious, and the crack Angle and crack length has a larger effect on the limits of sample storage.Sample the limit of the energy storage and its compressive strength has good correlation, the higher the compressive strength, specimen can release the strain energy stored in front of the damage, the greater the both, with the increase of compressive strength of specimens of the larger the limit storage;(7) Specimen with different deformation stages corresponding to different energy evolution.From the point of failure form, failure pattern and the specimen after the peak energy concentration degree release has a good correspondence.On the failure pattern of it, before the peak of dissipation energy, the more the more extended development inside the rock crack, rock specimen damaged is smaller, the higher the fragmentation, degree of a fracture specimen broken both: zhang cut compound damage specimens, the largest of the shear specimens, minimal tension damage specimens;(8) Single crack specimens and the specimens its damage variable and the axial stress curve is nonlinear, and the curve of each specimen with similar form, with the continuous increase of stress, the damage variable of the specimens.The relationship between the damage variable D and axial can be expressed as: 。...