风沙滩地区煤层采动下潜水位恢复时间影响因素敏感性分析

Sensitivity analysis of factors affecting the phreatic water level recovery time caused by underground coal mining in wind-blown sand area

西北风沙滩地区煤层采动潜水微渗漏易诱发潜水位发生不同程度的恢复,其恢复时间影响因素敏感性对于矿区生态地质环境保护意义重大.为此,结合井流模型,建立了煤层采后潜水微渗漏下潜水位恢复预计模型;分析了煤层采动下潜水位恢复时间的影响因素;结合正交试验方法,模拟探究了煤层开采及采后恢复过程中潜水渗漏量演化规律,预计了潜水位恢复到采前潜水位埋深的30%,50%,80%所需的时间,并通过极差分析和矩阵分析厘清了潜水位恢复时间影响因素敏感性.结果表明:从地层结构、水文地质和采矿条件等角度确定了潜水位恢复的主要影响因素为基岩厚度T_(b)、红土厚度T_(c)、黄土厚度T_(l)、潜水埋深b、含水层厚度T_(a)、含水层渗透系数K和煤层采厚T_(co);潜水发生轻微渗漏的情况下,煤层采后恢复过程中潜水渗漏量整体呈现下降的趋势,采后恢复初期渗漏量下降速度较快,在1~2个月期间下降幅度减少、之后趋于稳定至基本不渗漏;当潜水位恢复到30%时,各因素敏感性次序为:T_(a)>K>T_(c)>b>T_(l)>T_(b)>T_(co);当潜水位恢复到50%和80%时,各因素敏感性次序均为:T_(a)>K>b>T_(l)>T_(c)>T_(b)>T_(co);影响因素最敏感的两项为T_(a)和K,在水位恢复程度较少的情况下T_(c)的敏感性相对较大,当水位恢复程度超过50%后b的敏感性则相对较大;T_(co)和T_(b)的敏感性相对较小.采前潜水含水层的渗透系数及厚度越大,潜水位恢复所用时间越短.

The phreatic micro-leakage caused by underground coal mining is prone to induce varying degrees of the phreatic level recovery in the wind-blown sand beach area of northwest,China.The sensitivity of factors affecting the recovery time is of great significance for the ecogeological environment protection of the mining area.Therefore,combined with the well flow model,aprediction model for the recovery time of phreatic water level under phreatic microleakage after coal mining was established.The factors influencing the recovery time of phreatic water level were analyzed.By combining the orthogonal experimental method,the evolution law of phreatic leakage during coal seam mining and post mining recovery process was simulated,and the time required for the post mining phreatic water level to 30%,50%,80%of the pre-mining phreatic water level buried depth was estimated.Furthermore,the sensitive factors influencing the recovery time of phreatic water level were determined using range analysis and matrix analysis.The results show that the main influencing factors for phreatic water recovery have been determined from the perspectives of stratigraphic structure,hydrogeologic and mining condition like bedrock thickness T_(b),laterite thickness T_(c),loess thickness T_(l),the buried depth of phreatic water level b,aquifer thickness T_(a),aquifer permeability coefficient K,and coal seam mining thickness T_(co).Under the condition of phreatic micro-leakage,the overall phreatic water leakage during the post mining recovery process shows a decreasing trend.In the initial stage of post-mining recovery,the leakage rate decreases rapidly,and after one to two months,the decline rate decreases and stabilizes to almost no leakage.When the phreatic water level is restored to 30%of the pre-mining phreatic water level buried depth,the sensitivity order of each factor is T_(a)>K>T_(c)>b>T_(l)>T_(b)>T_(co).When the phreatic water level is restored to 50%and 80%of the pre-mining phreatic water level buried depth,the sensitivity order of each factor is T_(a)>K>b>T_(l)>T_(c)>T_(b)>T_(co).The two most sensitive influencing factors are T_(a)and K,and the sensitivity of T_(c)is relatively large when the degree of phreatic water level recovery is less,and the sensitivity of bis relatively large when the degree of phreatic water level recovery exceeds 50%.The sensitivity of T_(co)and T_(b)is relatively small.The greater the permeability coefficient and thickness of the pre-mining phreatic water aquifer,the shorter the time required for the recovery of the phreatic water level.