厚松散层底部土层抗渗透破坏突水溃砂研究

Study on water and sand burst for anti-seepage failure of thick loose layer bottom soil

为了探究厚松散层底部土层抗渗透破坏特征,以兴隆庄煤矿巨厚松散层薄基岩下开采四采区浅部资源为工程背景,通过对上、下2组土样进行颗粒级配、微观测试、抗渗透试验、安全临界水头高度理论计算等综合分析,探究山西组3煤层上覆含水层发生突水溃砂的临界条件。研究发现:土样的颗粒级配及颜色变化差异较大,粒径小于0.075 mm的细粒土的质量分数,上组的不到30%,而下组的高达70%;上组土样以长石为主,长石质量分数超过90%,结构疏松,SiO_(2)质量分数高,属于典型的砂性土类;下组土样以高岭石为主,质量分数超过70%,结构致密,Al_(2)O_(3)质量分数高,属于典型的黏性土类;确定了不同裂缝宽度下临界水压及临界水力坡度量化取值,随着裂缝宽度不断增加,临界水压和临界水力坡度均呈现逐渐下降的趋势,当裂缝为20 mm时,均出现明显拐点;理论类比计算了安全临界水头高度,初步确定了研究区第四系底部含水层允许安全水头高度为54~70 m,通过与实际水头值对比,分析认为正常开采条件下该区域不会发生突水溃砂渗透破坏事故。

In order to explore the seepage failure of thick loose layer bottom soil,the ultra-thick loose layer in the fourth shallow mining area of Xinglongzhuang Coal Mine is set as an example.Based on the particle grading,microscopic testing,anti-seepage test and the theoretical calculation of the safe critical head height in two groups soils.the critical conditions of water inrush and sand collapse in the overlying aquifer of No.3 coal seam in Shanxi formation are investigated.It is found that the particle grading and color changes of the two groups soil samples have significant differences.The percentage of particle size(less than 0.075 mm),the upper group soil is lower than 30%,while the lower group soil is up to more than 70%.The upper group soil falls into the type of feldspar,with feldspar accounting for more than 90%.The structure is loose and the content of SiO_(2) is high,thus belonging to the typical sandy soil type.The lower group soil is mainly kaolinite,accounting for more than 70%.With compact structure and high Al_(2)O_(3) content,they belong to typical clay soil.The quantized values of critical water pressure and critical hydraulic gradient at different crack widths are obtained.With the increasing of crack width,both critical water pressure and critical hydraulic gradient show a gradual decline trend,and an obvious inflection point appears at 20 mm crack.The safe critical water head height was calculated theoretically.The allowable safe water head height of the bottom aquifer of the Quaternary is preliminarily obtained between 54 m and 70 m.Compared with the actual water head value,the analysis showed that the sand collapse and penetration failure would not occur in this area under normal mining conditions.