采煤工作面底板水视电阻率全方位探测方法

深部煤层开采受下伏灰岩水害威胁日益严重,探测采煤工作面底板富水区是保障安全生产的一项重要工作。目前,矿井电法是富水区探测的主要手段之一,但存在对富水区定位不准的问题。为进一步提高对采煤工作面底板岩层富水区的判定精度,在充分分析单巷电法和双巷电透视法优缺点的基础上,通过对视电阻率观测与反演方法的改进,提出视电阻率全方位探测方法。以全空间球状模型为例,给出了球状模型外空间中任意三极装置的视电阻率表达式。针对采煤工作面内侧、巷道和外侧底板不同位置的5个低电阻率模型,分别计算了全方位和双巷透视视电阻率数据,通过三维反演分别获得了采煤工作面底板岩层的电阻率图像,对比可见:①在平面上,前者的低阻核心区与5个模型位置一致;后者的低阻核心区与工作面内侧及巷道底板的3个模型位置一致,而与工作面外侧底板的2个模型位置存在误差,误差系数分别为1.0和2.0,反映工作面外侧模型距离巷道越远,误差则越大;②在垂向上,两者对模型深度的判定均存在不同程度的误差,但相比而言,前者定位误差小,对模型深度的判定更准确。分析结果表明在全方位视电阻率反演过程中,单巷测深数据与双巷透视数据之间能够相互约束,促使低电阻率球状模型的准确归位,体现了全方位视电阻率探测方法的优越性。工程实践进一步表明了该方法的准确性和可靠性。

An all directional detection method of apparent resistivity for water from the floor strata of coalmining face

Deep coal seam mining is increasingly threatened by the water damage of underlying limestone.Detecting the water rich area of coal mining face is a major task to ensure safe production.At present,the mine electrical method is one of the main means of detecting the water rich area,but there is a problem of inaccurate positioning of water rich area.In order to solve this problem to improve the detecting accuracy for the water rich area of the floor rock of coal mining face,based on the analysis of the advantages and disadvantages of the one roadway electrical method and two roadway electrical penetration method,the omni directional detection method of apparent resistivity was proposed by improving its observation and inversion method.Taking a full space spherical model as an example,the apparent resistivity expression of any pole dipole system in the outer space of spherical model was given.For the five low resistivity models at different positions on the inside,edge and outside floor of coal mining face,the apparent resistivity data were calculated by the omni directional and two roadway penetration method respectively.Through the three dimensional inversion,the rock resistivity images in the floor of coal mining face were obtained respectively.The comparison of these images shows:① In the horizontal section,the former’s core low resistance areas are one to one correspondence with the center positions of five models;the latter’s core low resistance areas are consistent with the center positions of the three models that located in the inside and edge floor of coal mining face,and have distance error with the center positions of the two models that located in the outside floor of coal mining face,and the error coefficients are 1.0 and 2.0 respectively,which reflects that the farther the model located in the outside of coal mining face is from the roadway,the larger the error.② In the vertical section,both of them have various degrees of error in determining the depth of the models,but in contrast,the positioning accuracy for the models from the former is higher than the latter’s,because of its small error.The above analysis results show that the one roadway sounding data and the two roadway penetration data can constrain each other to promote the accurate homing of the spherical model with low resistivity during the omni directional apparent resistivity data inversion.As a consequence,the omni directional apparent resistivity detection method has greater superiority to the conventional electrical methods,and an engineering practice further demonstrates the accuracy and reliability of the method.