Catastrophe Analysis of Underground Cavern´s Roof under Motorcade Loads

A vehical load is always regarded as a centralized harmonic load on beam model. To motorcade loads, when the beam´s span is small and the spaces among vehicals of motorcade is also small, the motorcade load can be looked on as a full- distributed harmonic load on the roof. In this paper, the underground cavern´s roof was looked on as Euler-Bernoulli´s beam model and the motorcade load was regarded as the full distribution harmonic load. The catastrophe model of the roof was built and the necessary and sufficient condition of roof failure and the calculation formula of roof´s safety thickness were built. Taken the cavern roof of Wengfu phosphate mine for example, the safety thickness of the roof was obtained. The analysis shows the roof´s stability depends on the dead weight, engineering structure characteristics, attribute of rock mass except the vibration intensity and frequency. The roof fails more easily when the vibration amplitude is greater .The roof´s thickness increases with the vibration frequency closed to nature frequency .The roof is more stable when the rock strength is bigger and more integral.