不同含水率条带煤柱稳定性研究

煤层的富水性明显影响高应力作用下条带煤柱的稳定性,为研究含水率对条带煤柱蠕变特性的影响,首先对不同含水率的煤样进行蠕变试验,结果表明,含水率对煤样蠕变特性具有明显的影响,含水率越大,煤样的蠕变变形量越大,其蠕变门槛值、蠕变强度及蠕变系数越低。蠕变试验拟合结果表明,采用改进的Burgers模型能够较好地描述煤的蠕变力学特性。以蠕变试验结果为基础,采用FLAC~(3D)数值模拟软件对不同含水率条带煤柱的蠕变特性及稳定性进行了模拟分析。随含水率增大,应力峰值距煤壁距离增加,煤柱塑性区增大;同时,煤柱垂直应力变小,蠕变变形量增大,其承载能力降低,煤柱进入长期稳定状态的时间加长。数值模拟结果表明,在其他条件相同的情况下,煤柱含水率为0.78%,1.07%及1.36%时,煤柱塑性区宽度分别为10,12,16 m,其进入长期稳定状态的时间分别为18,24及36个月。

Study on stability of strip coal pillar with different moisture content

The stability of strip coal pillar under high stress is obviously affected by water abundance of coal seam. In order to study the influence of moisture content on creep characteristics of strip coal pillar, creep tests of coal specimens with different moisture content have been carried out firstly, and the results have revealed that moisture content has obvious influence on creep characteristics of coal speci-mens, to be more specific, with the increase of moisture content, the creep deformation gets bigger, but the creep threshold value, the creep strength and the creep coefficient get lower. The fitting results of creep tests have shown that the creep mechanical properties of coal can be well described with the im-proved Burgers model. Based on the creep test results, the creep characteristics and stability of strip coal pillar with different moisture content have been analyzed with the FLAC3D numerical simulation soft-ware. With the increase of moisture content, the distance between the peak stress position and the strip coal pillar boundary will increase, so will the plastic zone of the strip coal pillar;meanwhile, the vertical stress of coal pillar and the creep deformation will decrease, but the bearing capacity of coal pillar will reduce, and the time the strip coal pillar using to gets into long-term stability state will in-crease. The simulated results have indicated that when the moisture content is 0.78%, 1.07%and 1.36%, the widths of plastic zone of the strip coal pillar are 10, 12 and 16 m respectively and the period the strip coal pillar gets into long-term stability is 18, 24 and 36 months respectively when other conditions re-main unchanged.