复合煤岩变形破裂应力-电荷-温度耦合模型研究

Stress-charge-temperature coupling model of composite coal-rock in deformation and fracture

为探究复合煤岩力学性质与电荷、温度信号内在联系,从大同忻州窑矿具有典型煤岩动力灾害特征煤层,提取顶板岩、煤样、底板岩按照1∶1∶1比例制备复合煤岩试样,采用0.1,0.3,1.0mm/min三种不同加载速率对煤岩试样进行单轴加载破裂实验,研究复合煤岩试样单轴加载变形破裂过程中电磁、电荷、温度信号变化规律。试验结果表明:电磁辐射脉冲、电荷感应、温度在复合煤岩试样失稳破坏前均出现明显的前兆变化特征;加载初期电磁辐射、电荷感应信号较弱,随着加载应力水平的增加,两个信号逐渐增强,在临近峰值应力前信号达到最强,具有较强的一致性,两者呈二次相关性,系数在0.8以上;相对于电磁辐射信号变化特征,电荷感应信号的持续时间较短,信号特征为阵发性的,当以0.1mm/min速率加载时,电荷感应信号最强,0.3,1.0mm/min速率加载时信号变化率随加载速率增大而增大;温度总体呈阶跃式、台阶式上升趋势,在峰值前达到最大值。结合复合煤岩破裂SET(stress-electricity-thermal)耦合模型,推导电磁辐射脉冲数与电荷感应电压之间的数学关系,构建了SCT(stress-charge-thermal)耦合模型。针对12组试样进行试验,数据拟合结果表明:SCT模型参数n,b′的数据拟合精度较SET耦合模型m,b稍高,复相关系数基本均在0.9以上,具有较高契合度。试样产生的电磁辐射、电荷感应及温度变化与自由电荷、内部微破裂、摩擦等因素有关。在煤矿现场电荷感应检测受干扰相对于电磁辐射要小很多,故可考虑采用SCT耦合模型对煤岩动力灾害进行预测预报。

To explore the relationship between the mechanical properties of composite coal-rock and charges,temperature signals,the roof slate,coal sample and floor rock were extracted from the Datong Xinzhouyao mine with the typical coal-rock dynamic fault characteristics of coal seam.The coal-rock samples consist of roof rock,coal seam and floor rock in proportion of 1∶1∶1.The uniaxial compression experimental investigation was conducted in three different loading rates of 0.1,0.3 and 1.0 mm/min respectively.This paper discusses the variation law of electromagnetic emission (EME),charge and temperature during the process of coal-rock uniaxial loading deformation and fracture.The experimental results demonstrate there are obvious precursor signals of in-duced-charges,electromagnetic emission pulse and temperature before the rupture of the unstable coal-rock.The EME and induced-charges signals are weak at the initial stage of loading.Both signal strengths gradually increase with the increase of loading stress,and reach the strongest values before the peak stress.Both signals have strong consistency.There is a quadratic polynomial relationship between the EME and charge-induced,and the multiple correlation coefficient is above 0.8.Compared with the variation characteristics of the EME signal,the duration of the charge-induced signal is shorter and the signal characteristics are paroxysmal.When the loading rate is 0.1 mm/min,the induced-charges signal is the strongest,at 0.3 and 1.0 mm/min.The loading rate is higher and the change rate of induced-charges become greater.The temperature presents an increasing tendency of step type,and reaches the maximum before the stress peak.Based on the SET (stress-electricity-thermal) coupling model,the mathematical relationship between the EME pulses and the charge-induced voltage was derived.The SCT (stress-charge-thermal) coupling model was built.According to the test of 12 sets of samples,the data fitting results show that the experimental data fit the SCT coupling model parameters n,b′,the multiple correlation coefficients are all above 0.9.Its accuracy is slightly higher than the SET coupling model parameters m,b .The EME,induced-charges signals and temperature produced by composite coal-rock are connected with free charge,internal fracture,friction and other factors.In the coal mine,the signal disturbance degree of induced-charges is smaller than the EME.Therefore,the SCT coupling model could be considered to predict and prevent the coal-rock dy-namic disaster.