Study On Mechanical Properties Of One - Dimensional Addition And Unloading Of Limestone

The studied title is come from National Science Foundation Project "Deep roadway excavation and unloading induced rock burst mechanism (51264018)" mainly aimed at HUIZE lead-zinc mine to horizontal slice stoping and backfilling mining method for engineering background and the stope "pillar" is as the research object.According to the loading and unloading pathof rock,the rock were under uniaxial compression and uniaxial cyclic loading and unloading experiments at different loading and unloading path, respectively, from the strength characteristics and deformation of the deformation and strength properties of rocks, acoustic emission characteristics and failure modes, etc. Mechanical properties and mechanism of instability are revealed by rock mining areas, mainly finished the following work:(1) By analyzing the peak intensity of rock samples in each group and the number of loading and unloading in the test of constant stress of the lower grade under cyclic loading and unloading test, using polynomial fitting function it can be obtained the result that show there are certain rules to follow in the relationship of peak intensity and cyclic loading and unloading times about limestone in the test of constant stress of the lower grade under cyclic loading and unloading test.(2) Uniaxial cyclic loading and unloading experiments were performed and the stress-strain curve of groups of experiment research suggests that mutually uncorrelated overlap and they will form the varied shape of plastic-loop. Along with the increase of cycling times, the loop area size of each test presents certain regularity, and there is a continuous backward "migration" phenomenon.(3) To contrast each cycle test mechanical properties, the size of the different mechanical parameters, such as limestone peak strength, elastic modulus and poisson’s ratio which were measured under the Uniaxial cyclic loading and unloading experiments, were greatly influenced by different unloading paths and cycles, and the limestone specimen deformation for the first time caused by the different loading and unloading way will directly affect the final peak strength size and deformation characteristics of limestone.(4) The different acoustic emission test were researched, when the cycle number increases 1 to 2 times, the AE energy accumulation will appear linear increase phenomenon, acoustic emission ringing count also increased significantly, rock’s damage moment will have a lot of elastic energy, demonstrated that the mining limestone brittleness is larger, the occurrence of rock burst orientation is relatively obvious.(5) The failure modes of limestone in different tests are compared. The conclusion shows that:the failure mode is single under one load-unload test. Under the stepped cycle load-unload test, the failure modes are complex. Indicating that under different load-unload paths, the damage degree and the failure mechanism of limestone present different characteristics.