Change law of gas content under low-frequency vibration

To study the effect of low-frequency disturbance load on gas volume, a formula for gas content considering coal porosity pressure, absorption strength and decreasing vibration stress is established. Meanwhile, the absorption capacity formula is verified by using vibrating and absorption instruments. The tests indicate that under the constant vibrating frequency, when the vibration time extends, the porosity and free-state gas increase, so gas content increases. Under the constant vibrating time, when the frequency speeds up, the porosity expands and gas content increases. Under frequency of 20 Hz and 10 Hz, D-value of content moves up, while under frequency of 30 Hz and 20 Hz, D-value of content moves down. The vibration expands the porosity inside the samples, thereby the gas content accumulated. When the frequency moves up to 10, 20 and 30 Hz, the porosity expands and the gas content is accelerates accordingly. The proposed formula significantly reveals the change law of gas content under different frequencies and time ranges.