鄂尔多斯盆地是我国煤炭储量最大、煤质优良的富煤区，盆地腹部为厚度达数百米至上千米的巨厚白垩系含水砂岩层覆盖。近年来，随着盆地周边煤炭开采逐渐向腹地延伸，巨厚白垩系覆盖区侏罗系煤炭开采的一些矿井，发生了严重的突泥溃砂事故，给煤炭安全开采造成严重威胁。通过地质理论分析和区域露头地质调查，认为白垩系底部与中侏罗系顶部接触带(K1/J2)存在古风化壳，具备突泥溃砂的地质组成条件。进一步测试分析了古风化壳岩体结构、物质组成、粒度组成、水理性质，进行了点荷载强度试验和原位大型剪切试验；表明古风化壳岩性以泥质砂岩、泥岩为主，岩体结构在垂向上具有全风化土壤层、强风化碎石层、中-弱风化裂隙块石层的分带特征，天然状态下粒度组成以角砾为主，浸水后泥砂颗粒含量明显增大，遇水存在不同程度的泥化、崩解、碎裂性质，总体属于含泥砂量较高的软弱破碎岩体，岩体强度较低，整体性质与松散泥质砂性土类似，是区域上白垩系覆盖区煤炭开采突泥溃砂的主要物质来源。分析了K1/J2古风化壳下采动突泥溃砂的综合水文工程地质条件，给出了隐伏古风化壳识别方法，提出了K1/J2古风化壳下采动突泥溃砂灾害评价工程地质模型。

The Ordos basin is a coal rich area with the largest coal reserve and good coal quality in China. The central part of the basin is covered by a huge water bearing Cretaceous sandstone layer with a thickness of hundreds of meters to thousands of meters. In recent years, as coal mining around the basin has gradually extended inward, some serious mud sand inrush accidents have occurred in some of the Jurassic era coal mines in the thick Cretaceous coverage area, posing a serious threat to the safety of coal mining. Through the analysis of geological theory and regional outcrop geological survey, the authors found that the paleoweathered crust at the bottom of the Cretaceous and the top of the Middle Jurassic (K1/J2) has the mud sand inrush structural composition conditions. Further testing and analysis of paleoweathered crust rock mass structure, material composition, grain size composition, water physical property, point load strength test and in situ large scale shear test have been carried out. The result shows that the lithology of the paleoweathered crust is dominated by argillaceous sandstone and mudstone,and the rock mass structure has the zoning characteristics of fully weathered soil layer, strongly weathered gravel layer, and medium weathly weathered fractured rock layer in the vertical direction. The composition is dominated by breccia, and the content of mud sandy particles increases significantly after immersion in water. When encountering water, there are different degrees of argillization, disintegration, and fragmentation. The paleoweathered crust is generallya soft and broken rock mass with high mud and sand content, the rock mass has low strength, and the overall properties are similar to loose argillaceous sandy soil. It is the main material source of mud sand inrush in coal mining in the Cretaceous covered area. This paper has analyzed the comprehensive hydrological engineering geological conditions of mud sand inrush under the K1/J2 paleoweathered crust, provided the identification method for the concealed paleoweathered crust, and proposed an engineering geological model for the evaluation of mining mud sand inrush disaster under the K1/J2 paleoweathered crust.

1 K1/J2古风化壳突泥溃砂物源的地质成因

   1.1 K1/J2古风化壳地层结构

   1.2 K1/J2古风化壳典型露头岩性结构特征

2 K1/J2古风化壳的物理力学性质

   2.1 粒度组成和矿物成分

   2.2 水理性质

   2.3 力学性质

3 突泥溃砂物源的识别

4 K1/J2古风化壳下采动突泥溃砂工程地质模型

5 结论