基于赵固一矿上覆巨厚冲积层多含水层（组）薄基岩的特点，冲积层下部砂砾含水层水压达到4.0 MPa，为高水压含水层。为确定基岩性质对顶板突水溃砂的影响，保证多含水层（组）薄基岩区的正常回采，对水文勘察孔所取基岩岩样进行点荷载、干燥饱和吸水率和室内崩解试验，通过分析岩样各项试验指标随深度的变化曲线，确定基岩性质及其对留设防砂煤柱的影响。试验表明：基岩风化深度超过20 m；距离冲积层底界面0～6.5 m垂深范围内的泥类岩干燥饱和吸水率大于15%，遇水崩解多呈泥状、碎岩片和碎块泥，隔水性能良好，可以有效弥合采动裂缝，可以作为防水煤柱的保护层；冲积层底界面下部0～11.4 m的风化泥岩强度低于4.0 MPa的冲积层下部细砾含水层水压力，防砂煤柱的保护层不能全部由风化泥岩构成，提出防砂煤柱保护层厚度需要大于11.4 m；砂岩耐崩解性强，干燥饱和吸水率远小于泥类岩，阻隔水性能较差，防水煤柱保护层不可以全部由风化砂岩构成。风化砂岩强度大于4.0 MPa的冲积层下部砂砾含水层水压，可以有效抵御上覆水头压力。

Based on Zhaogu No. 1 Mine’s characters that are the overlying thick alluvium, multi-aquifers (groups) and thin bedrock, the water pressure of the gravel aquifer under the alluvial layer reaches 4.0 MPa, defined a high-pressure aquifer. To determine the influence of bedrock properties on roof water inrush and sand bursting, and ensure the normal mining around the thin bedrock area under groups, there were tests, point loading, dry saturated water absorption rate and indoor disintegration, of bedrock samples taken from hydrological survey holes to determine those properties and influence on retaining sand-proof pillars by analyzing the variation curves of various indexes of them with depth. The experiments’ results showed that the weathering depth of bedrock exceeds 20 m; the dry saturated water absorption rate of mudstone in the vertical depth ranging of 0−6.5 m from the bottom interface of the alluvial layer is greater than 15%. The mudstone exposed to water features muddy disintegration, broken rock fragments and mud blocks, which means it is good water-proof performance of effective bridging mining cracks and a protective layer for waterproof coal pillars; as the strength of weathered mudstone below the alluvial layer 0 to 11.4 m is lower than it of the fine gravel aquifer in the lower that of 4.0 MPa, the sand control coal pillar’s protective layer that is greater more than 11.4 m is cannot be entirely composed of weathered mudstone; due to strong resistance to disintegration and lower dry saturated water absorption rate of sandstone, the protective layer cannot be entirely composed of weathered sandstone. The compressive strength of weathered sandstone, when it is higher than 4.0 MPa, can effectively resist the overlying water head pressure.