低频机械振动含瓦斯煤体积应变变化规律研究

Change law of volume strain on gas filled coal under low frequency

为研究低频机械振动对含瓦斯煤体积应变的影响,建立煤体孔隙瓦斯压力、吸附膨胀力、振动衰减应力作用下煤体体积应变变化方程。以10,20,30 Hz振动1,2,3,4,5 h后的煤体试件单轴抗压强度变化试验检验方程所反映的规律性,发现振动频率相同,振动时间越长,试件单轴抗压强度越低,计算应变越大;振动时间相同,振动频率越小,试件单轴抗压强度越高,计算应变越小。分析认为振动使煤体孔隙率变大,应变变大,从而单轴抗压强度降低。振动时间相同,振动频率越大,单轴抗压强度越低,试件孔隙率就越大,试件应变就越大;振动频率相同,振动时间越短,单轴抗压强度越高,试件孔隙率就越小,试件应变就越小。且无论频率为何值,单轴抗压强度均随时间的增加而降低,表明试件孔隙率均随时间的增加而变大,试件应变均随时间的增加而增大,抗压强度所反映出的应变变化与计算得出的应变规律相一致。方程计算值能较好地反应低频机械振动作用下不同振动频率、振动时间影响煤体应变变化规律。

To study the influence of low-frequency disturbance load on volume strain of gas-filled coal, the equation for change of volume strain of coal under porous pressure of coal, absorption strength and decreasing vibration stress is established. Then the rules depicted by the above equation are verified by changes of uniaxial compressive strength of samples which are vibrated for 1, 2, 3, 4, 5 hours under the action of frequency of 10, 20, 30 hz. It is found that under the constant vibrating frequency, with the increase of he vibrating time, the uniaxial compressive strength of samples gradually decreases, and the calculated strain increases. Under the constant vibrating time, with the decrease of the vibrating frequency, the uniaxial compressive strength of samples gradually increases, and the calculated strain decreases. The analysis shows that the vibration makes coal porosity increases, then the strain becomes larger, so the uniaxial compressive strength declines. Under the same vibrating time, when the frequency increases, the uniaxial compressive strength declines, the porosity increases, and the strain also becomes larger. However, under the same frequency, when the vibrating time gets shorter, the uniaxial compressive strength becomes greater, the porosity gets smaller, and the strain also becomes smaller. Whatever the value of the frequency gets, the uniaxial compressive strength decreases with the increasing time, which indicates that the porosity and the strain both increase with the increasing time. The variation of strain reflected by the compressive strength is the same as that of the calculated strain. The calculated values satisfactorily reveal influence of different frequencices and time ranges on strain changes under low frequency.