According to the structure form of room and pillar goaf in gypsum mine, the mechanical model of pillar roof composite supporting structure was established in this research. Based on the cusp catastrophe theory and energy dissipation theory, the energy dissipation relationship of the support structure was analyzed, and a new instability criterion of the support system was derived by introducing the control parameters α and β. On this basis, the study of blasting caving was carried out. The influence of row spacing and hole depth on blasting caving was analyzed using ANSYS/LS DYNA software. The blasting influence range, stress wave attenuation and vibration velocity attenuation indices are obtained, and the blasting parameters such as the optimal distance and depth of blast holes between pillars and roof were optimized. Based on the results of theoretical analysis and numerical, combined with the engineering geological conditions of Dahan gypsum mine, the practical study of blasting caving was carried out. The caving scheme and caving sequence was determined, then the blasting caving effect was analyzed. The caving effect was found to be good, and the applicability of the theoretical model is verified.
A three-layer theoretical model is used to calculate the lee wave of a real example occurring over Blue Ridge in Pittsburgh, in which the maximum vertical velocity is 0.11 m s^-1. Based on this, the influence of changes in the thickness and values of the Scorer parameter in each layer are analyzed. It is shown that the influence of each layer parameters on the lee-wave amplitude is different, and the amplitude is more sensitive to the changes in the lower layer. Since the environment changes can affect the Scorer parameter profile, the influence of the environment on the amplitude is studied. The results show that the amplitude will decrease in the daytime because of solar heating, and increase at night because of radiational cooling, according to observational data. The case is also simulated by the Advanced Regional Prediction System (ARPS) model. The simulated amplitude is 0.089 m s^-1, which is close to the calculated result. Numerical sensitivity experiments are performed to test the former calculated experiments. The simulated results are consistent with the analytically calculated results. 相似文献