The Gob Roof Dynamic Instability Mechanism Research

China is a multi-earthquake country, most of the gobs are located in the seismicarea. With the development of the society, the land resources are increasingly barren,more and more engineering construction needs to consider the influence ofunderground mined-out area, this also gradually becomes a problem in engineeringconstruction. The effective way to protect and strengthen surface buildingseconomically and reasonably is to analyze the seismic deformation stability of the gobroof. There has important theoretical significance and application value of this subjectresearch for making full use of land resources and realizing sustainable development ofthe gob.This paper uses the ANSYS finite element analysis program to establish themodel of the gob roof, which is divided into a single rock mass model and amulti-layer rock mass model. Qianan wave, Lanzhou wave and Taft wave are chosen toload, then the analysis of dynamic response rule of the gob roof model under thecondition of different seismic wave and peak value. The main work and conclusionsare as follows after summarizing the paper:1. The natural vibration period and formation of the structure were determined bythe modal analysis, it is concluded that the natural vibration period and structure of thestructure is closely related based on the calculation of different constraints anddifferent rock mass model, that is the natural vibration period when all sides areimposed constraints is smaller than that of four bottoms are imposed constraints, thenatural vibration period of the multi-layer rock mass model is larger than a single one.2. The single rock mass model and multi-layer rock mass model are imposed threeseismic waves with different peak values, it is concluded that the vertical displacementof the model is proportional to the peak wave. The corresponding vertical displacementof the single rock mass model are0.004m,0m and0.112m, the multi-layer rock massmodel are0.013m,0m and0.109m under the condition that the peak value of Qiananwave, Lanzhou wave and Taft wave is70cm/s2. For this computing example, the Taftwave is the most unfavorable waveform under the condition of small earthquakes.3. For this computing example, the influence on the model under horizontalseismic wave is greater than the vertical one under the condition of single rock mass model, and the influence is quite the opposite under the condition of multi-layer rockmass model.4. The maximum peak value that the Qianan wave, Lanzhou wave and Taft wavecan be imposed are respectively180cm/s2,220cm/s2and80cm/s2under the conditionof single rock mass model; they are120cm/s2,200cm/s2and70cm/s2under thecondition of multi-layer rock mass model, for this computing example, the maximumseismic wave peak value that can be imposed under multi-layer rock mass model issmaller than that of single layer model.