考虑区域地应力特征的裂隙煤岩流固耦合特性实验

Testing on fluid-solid coupling characteristics of fractured coal-rock mass considering regional geostress characteristics

通过位移反演方法对区域地应力特征进行理论分析,建立研究煤岩内部裂隙时空演化规律的力学实验系统,设计了区域地应力作用下裂隙煤岩流固耦合计算模型,初步揭示裂隙煤岩流固耦合特性。通过地应力的现场监测,验证了位移反演方法的准确性,垂直地应力与最小水平主应力数值稳定,受开采扰动影响,最大水平主应力出现局部性突增。借助数字化X射线摄影系统,给出了不同载荷下内部裂隙场DR扫描图像,发现随外载增大煤岩内主裂隙持续扩展,且裂隙场形态分别为共轭型与X型。矢量化处理裂隙场信息并导入耦合计算模型,分析不同工况下耦合模型的渗流参数变化情况,初步得出裂隙煤岩流固耦合特性:外载增大将导致煤岩内部微裂隙进一步相互贯通扩展并出现宏观破裂,这是裂隙煤岩孔隙率与渗透率持续性增加的本质原因,且流速最大区域迁移过程可表征裂隙煤岩次生裂隙分布特点,主裂隙内水体流速最大且随注水压力的增大,水体流速不断增加,较大的流速一般发生在具有较大水力梯度的细小裂隙位置处。同时,出口流速特征表现为出口流速分量的最大值均位于煤岩两侧并随着外载的增大而增加。

A displacement back method was used to analyze regional geostress characteristics in this research.A new mechanical experimental system was adopted to provide a mechanism on spatio-temporal evolution of internal crack in both coal-rock masses.A simulation model on the fluid-solid coupling of fractured coal-rock mass was built up for uncovering the fluid-solid coupling characteristics with considering the regional geostress characteristics.The authors also offered in-situ geostress monitoring to verify the accuracy of the displacement back method.The values of both vertical geostress and minimum horizontal principal stress remained stable.The maximum horizontal principal stress increased suddenly at local region due to excavation disturbance.DR scanning images of internal cracks with various loading values were offered by digital X-ray system.It showed that the main cracks in the coal-rock masses was propagating continuously when the external loading remained growing.Shapes of crack field in both coal and rock mass were conjuga-ted type and X type.Crack-field data being vectorization processing needed to import in fluid-solid coupling model.The authors got the traits of all seepage parameters in different experimental settings.The traits indicated the fluid-solid coupling characteristics of fractured coal-rock mass.Essential reason for resulting in the propagation and connection of external micro-cracks is increscent external loadings,which leads the macroscopic fracture of the coal-rock mass and value increment of porosity and permeability.Transport process of maximum velocity region represents the distribution characteristics of induced cracks.Crest value of flow velocity is at the main crack and in direction proportion to water inject pressure.Tiny crack has larger hydraulic gradient and the value of flow velocity here is also greater than the one at other position.The features of outlet area velocity indicate the maximum value of flow velocity at the exit lies in two sides of the model and increase with the increment of loading value.