Numerical Study On Mechanism Of Fracture In Deep Underground Engineering

Development of the national economy will depend on the exploitation of energyand mineral resources in a very long period of time. With the increase of miningintensity and demand for mineral resources, the resource of shallow grounddecreasing day by day, development and utilization of deep underground engineeringhas become an inevitable trend, people are becoming more concerned about this field,especially in mining engineering, tunnel engineering, energy storage, nuclear wastedisposal engineering and other fields. Meanwhile, the rock mechanics problemsencountered in the development of deep underground has gradually become a focus invarious countries.The rockmass occurrance environment of deep underground engineering is ratherspecial, it mainly displays in the complex environment with high ground stress, highosmotic pressure and high temperature. Some extraordinary response phenomena areproduced during deep excavation, including the phenomenon of tension andcompression fields alternating generated, the phenomenon of zonal disintegration andlayered fracture phenomenon. Analysis of the relevant phenomena of deep rockextraordinary response, and provide a reasonable explanation on the mechanism. Thiswill provide an important theoretical basis for deep excavation and support designtheory, it has a very important practical significance.According to the special geological environment of deep rock, It is consideredthat the mechanism of deep rockmass located in the post-peak stage, the paper selectthe strain softening model to reflect the characteristics of the deep rock, and establishcalculation model to simulate and analysis the layered fracture. The paper mainlyconsiders the influence to the layered fracture caused by post-brittleness of rock,temperature stress, rock dilatancy angle, axial ratio of oval-shaped cavern and otherfactors. The main contents are as follows:Firstly, based on domestic and external documents about the deep rockextraordinary response phenomenon, expounds systematically the definition of "deep"in the deep underground engineering, summarizes the basic characteristics of deeprock, moreover, summarize and elaborate the extraordinary response phenomenonobserved in the practical project, analysis the relationship and difference betweenvarious phenomena.Secondly, according to the basic features of deep rock, establish the calculation model using the strain-softening model. Combined with the summary about theproducing law of layered fracture from other literatures, maintaining the original rockstress is larger than the uniaxial compressive strength, analysis the influence to thebroken mode of cavern, stress field and displacement field caused by post-brittlenessof rock (the slope of the stress drop stage). Observe whether there will be layeredfracture and the critical threshold when this phenomenon occurs, summarizes theresearch results and explain the mechanisms of layered fracture.Finally, by take the rock which has produce layered fracture phenomenon as theresearch object, analysis the factors that may affect the development of layeredfracture. Study the effects of temperature stress and rock stress field coupling, rockdilatancy angle and axial ratio of oval-shaped cavern on layered fracture phenomenon,a better understanding of the regularity and characteristics of layered fractureoccurred in deep rock will be presented.