煤矿矿井混凝土井壁腐蚀的调查与破坏机理

Investigation and destruction mechanism on corrosion of concrete shaft in coal mine

为研究煤矿矿井混凝土井壁腐蚀破坏机理,结合黄淮地区井筒破裂实例,采用超声回弹法对井壁过水面、干湿交替面及未过水井壁混凝土进行腐蚀深度及回弹强度的检测,并通过SEM,EDS,XRD对不同深度被腐蚀的井壁混凝土进行微观分析,研究环境介质对水泥石中C-S-H凝胶结构的影响。结果表明:垂深304.8 m至马头门位置的井壁混凝土破坏严重,井壁混凝土的强度由原来的C30降低到10~15 MPa;马头门附近四含水过水面的井壁混凝土受到了溶解性腐蚀,水化产物Ca(OH)2,Aft等基本消耗殆尽,大部分C-S-H已被分解,其主要物相是Ca CO3以及少量的低碱度的水化硅酸钙凝胶;垂深346~430 m过水的井壁外附着黑色糜烂状沉积层,主要是水泥石中C-S-H凝胶碳化生成的无胶凝性的硅胶和结晶度较差的Ca CO3;地下水中的SO2-4和Na+对井壁混凝土的腐蚀主要是膨胀性的化学腐蚀,生成的钙矾石、石膏以及析出的芒硝、石盐结晶体,产生较大的膨胀压力,可导致井壁混凝土胀裂而成片剥落。

In order to study the corrosion mechanism of shaft concrete in a coal mine,Huanghuai region,the ultrasonic rebound method was used to check the corrosion depth and rebound strength of the wall over water,wet and dry alternating surfaces and shaft concrete.The wellbore fracture examples at Huanghuai region were applied for the analysis of concrete corrosion.The micro-analysis of the shaft concrete in different corrosion depths was conducted by SEM,EDS and XRD,in order to investigate the impact of environment media on the C-S-H gel structure in cement.The results show that the shaft concrete is seriously damaged from the vertical position of 304.8 m to the ingate,and its strength is reduced from C30 to 10-15 MPa.The shaft concrete over water near ingate is dissolved corrosion.The hydration products of Ca(OH)2and Aft is almost exhausted.Also,most of the C-S-H is broken down.The main phase is Ca CO3 and a small amount of low alkalinity of hydrated calcium silicate gel.The shaft wall with water in vertical depth of 346 m to 430 m attaches the black erosion deposition layer which is mainly non-gelling silica and Ca CO3 with poor crystallinity generated by carbonization C-S-H gel in cement stone.The corrosion of SO2-4and Na+in groundwater on theshaft concrete is mainly the expansion chemical corrosion.The ettringite,gypsum,precipitated mirabilite and halite crystal will produce greater pressure to cause the shaft concrete spalling and flaking.