毛乌素沙漠区多个近地表含水层支撑着区域生态环境、生产和生活，开展保水采煤研究势在必行。而“保水安全厚度”计算作为保水采煤研究的核心内容，由于各近地含水层的性质以及所处垂向位置的差异，导致了针对毛乌素沙漠区的保水安全厚度计算方法适用范围有限、缺乏统一性。通过分析毛乌素沙漠区内含隔水层在垂向和平面上的展布特征、水文地质性质，结合不同区域内的工程地质条件和开采方法，探讨了保水安全厚度的定义。将煤层之上地层划分为目标保护层、预测导水段(导水裂隙带发育段)和等效保水段(由有效黏土隔水层和基岩层组成的保水段)。利用水均衡法分析了黏土隔水层与基岩层间的保水性能关系，通过“保水比例系数”形成了黏土隔水层与基岩层间统一的等效保水段计算方法。建立了具有能够适用毛乌素沙漠区内“沙-基(岩)型开采区”、“沙-土-基(岩)型开采区”、“沙-土-洛(洛河组含水层)-基型开采区”、“烧变岩型开采区”等主要不同地质条件的保水安全厚度计算模型。根据导水裂隙带的发育高度与黏土隔水层、基岩层间的导通特征以及煤水间距与保水安全厚度的大小关系，制定了煤层开采影响的自然保水区、一般失水区和严重失水区的分区标准。并以榆神矿区小保当煤矿为例，应用建立的统一模型确定了小保当井田内砂-基型和砂-土-基型开采区内的保水安全厚度，并据此评价了煤层开采对潜水含水层的影响。所建立的保水安全开采厚度计算模型以及开采分区评价标准具有良好的适应性，也为保水采煤研究中有关保水安全厚度的计算和煤层开采对上覆含水层的影响评价提供了新思路。

Multiple near-surface aquifers in Mu Us desert are regarded as critical supports of region ecological environ-ment,production and life. It is urgent to study on water-preserved coal mining. However,as the core content of water-preserved coal mining research,due to the various characteristics and the vertical position of the aquifers,some “water-retention thickness” calculation methods have limited application scope and lack unity. Characteristics and hydrogeo-logical properties of aquifer and aquiclude at horizontal and vertical distribution in Mu Us Desert are analyzed. Combined with the engineering geological conditions of different area and mining methods,the definition of water-retention thickness is discussed. The whole layer above the coal is divided into three parts:target protection aquifer,predicted water diversion section and equivalent water-retention section (consist of active bedrock and clay aquiclude,main wa-ter-retention section). Water equilibrium principle is adopted to analyze the water-retention characteristics of bedrock and clay aquiclude. “ Water retention proportional coefficient” is applied to determine the water-retention thickness calculation method in bedrock and clay aquiclude. Combined with the computing of predicted water diversion section, the model to calculate the water-retention thickness is established which can be applied to the regions of “ sand-clay-Luohe aquifer-bedrock”,“sand-clay-bedrock”,“sand-bedrock” and “burnt rock”. According to the positional relation between the water diversion and bedrock,clay aquiclude,scale relation between the altitude from the target protection aquifer to coal and water-retention thickness,the zoning standards for natural water-retention areas,general water loss areas and severe water loss areas are formulated. Besides,the established model is put into use in Xiao Baodang coal mine of Yulin-shenmu coalfield to calculate the water-retention thickness,where the “sand-clay-bedrock” and “sand-bedrock” regions distribute. In addition,the coal mining influence to the unconfined aquifer is evaluated. The calcula-tion model of water-retention thickness and the zoning evaluation standards of mining have a good adaptability. A new idea for the calculation of water-retention thickness and the evaluation about the influence of coal mining on the overly-ing aquifer is also presented.