Study On Energy Conversion Of Post-peak Fractured Rock Mass Failure And The Supporting Characteristics Of Fiber Shotcrete

During the process of excavation of surrounding rock in tunnel engineering, surrounding rock always continuously exchange energy with the initial supporting structure. Under the influence of in situ stress and blasting load, the original micro cracks and cracks of post-peak cataclastic surrounding rock mass develop further with the new cracks emerging. Due to random distribution of cracks, traditional stress-strain concepts hardly make an accurate analysis and couldn’t provide scientific reference for subsequent initial support design. In this paper, the deformation characteristics of post-peak fractured rock mass is studied from the viewpoint of energy balance. According to relevant researches on the failure process of rock fractures, it shows the whole system energy changes well explain the stability of surrounding rock mass and internal mechanism of deformation and failure of post-peak fractured rock. Aim to the problem that deformation of post-peak fratured surrounding rock easily leads to local destruction of the initial support structures, this article based on the energy dissipation theory and by means of UDEC numerical simulation tool, fixes on fiber sprayed concrete combined with indoor tests and field tests to study the deformation characteristics of post-peak fractured rock mass and the supporting technology of fiber sprayed concrete applying into initial support structures in tunnel engineering. The main research contents of this article can be divided into four parts as following:(1) The complete stress-strain curve of rock mass is divided into two types and unified into the same one mathematical formula by an deep account of energy conversion while the post-peak fractured rock mass in the loose circle of surrounding rock in tunnel engineering is considered as the research object. And the failure criterion of deformation of post-peak fractured surrounding rock mass is further put forward.(2) By the means of FISH programming language, the failure criterion based on strain energy density theory is introduced into numerical simulation software UDEC to fulfill simulation of the whole failure process of post-peak fractured rock mass. And it’s verified by comparison of results of indoor tests and simulations, which offers well support for researches on the supporting influence of fiber sprayed concrete.(3) A new type of steel fiber sprayed concrete is invented based on indoor tests by optimizing the ratio and length of steel fiber. And necessary mechanical properties of steel fiber sprayed concrete is researched and put forward. At last, it’s fully studied on the supporting influence of steel fiber sprayed concrete in the circumstance of post-peak fractured surrounding rock by the improved UDEC program.(4) A new type of separated sprayed concrete construction technology is put forward by improving traditional technology combined with field tests. And supporting effects of new steel fiber sprayed concrete is analyzed to determine its optimal thickness as part of initial support structures in tunnel engineering.