弱胶结充填型断层破碎带岩体渗流特性

Characterizing seepage behavior of weakly cemented filling fault fracture zone

  • 摘要: 弱胶结充填断层破碎带在采掘扰动和地下水渗流作用下易发生突水事故,给深部资源开采带来极大威胁。断层破碎带的胶结充填特征直接控制着流体运移和渗流通道形成,有必要深入研究胶结充填特征对断层破碎带渗流特性的影响规律。因此开展了不同Talbot级配指数n的断层破碎带三轴渗流试验,采用CT扫描分析了断层破碎带在渗流前后的微细观结构变化特征,通过基于CT扫描数据的数值模拟研究了弱胶结充填断层渗流特性。结果表明:围压通过改变断层破碎带结构而影响渗透性,围压升高使得断层破碎带内部孔隙和裂隙被压缩,弱胶结充填断层破碎带渗透系数随围压增大而减小;Talbot级配指数n和含石率越大的断层破碎带其内部连通性和渗透性越好,更易形成渗流通道,反之Talbot级配指数n越小的断层破碎带孔隙率和孔隙连通性越低,渗透性能越弱,更难形成渗流通道;地下水渗流将使断层破碎带内部球状孔隙减少,扁平状孔隙增加,导致逐渐形成渗流通道;断层破碎带内部孔隙方位角和极角变化可反映渗流路径的改变;在地下水渗流作用下断层破碎带骨架间将逐渐形成优势渗流通道,进而形成突水通道,Talbot级配指数n对断层破碎带发生突水的涌水量影响显著,涌水量随着Talbot级配指数n的增大呈现先增大后减小的趋势。

     

    Abstract: Water inrush accidents caused by weakly cemented filling fault fracture zone often occur under mining disturbance and groundwater seepage, posing a great threat to deep resource exploitation. The characteristics of cemented filling within the fault fracture zone directly control fluid migration and the formation of seepage channels. Identifying its impact on the seepage characteristics of fault fracture zones is of great importance in revealing the mechanism of water inrush from faults. Therefore, triaxial seepage tests were conducted on fault fracture zones with different Talbot function power exponent n values. CT scanning was used to analyze the microstructural changes of the fault fracture zone before and after seepage, and numerical simulations based on CT scanning data were conducted to study the seepage characteristics within weakly cemented filled fault fracture zones. The research results indicate that confining pressure affects permeability by altering the structure of fault fracture zones. The increase in confining pressure leads to the compression of pores and fractures within the fault fracture zone, and the permeability coefficient of weakly cemented filled fault fracture zones decreases with increasing confining pressure. The internal connectivity and permeability of the fault fracture zone is better and higher with the higher of the Talbot function power exponent n and rock content. Conversely, the porosity and pore connectivity of the fault fracture zone is lower with the lower value of the Talbot function power exponent n. Groundwater seepage will reduce the spherical pores inside the fault fracture zone and increase the flat pores, leading to the gradual formation of seepage channels. Moreover, the changes in the azimuth and inclination angles of pores within the fault fracture zone can reflect alterations in the internal seepage pathways. Under the action of groundwater seepage, dominant seepage channels will gradually form between the skeletons of fault fracture zones, leading to the formation of water inrush channels. The Talbot function power exponent n value has a significant impact on the water inflow of water inrush through the fault fracture zone. The water inflow of water inrush exhibits a trend of first increasing and then decreasing with the increase in the Talbot function power exponent n value.

     

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