高压水射流破岩能量耗散与释放机制

从应力-应变角度建立的高压水射流破岩准则,其精确度取决于对屈服应力的表述,由于表达式中不含材料参数,不能精确计算高压水射流破岩参数,而从能量角度建立的岩石强度理论具有更好的适用性和准确性。开展了基于能量耗散和释放机制的高压水射流破岩机理,理论研究了自由射流段速度分布特征,分别计算了等速核区和射流边界层扩展区动能,建立了不同靶距处射流动能计算模型。高压水射流冲击破岩能量表征为冲蚀坑的形成和岩体的体积破坏;射流能量耗散于剪切面的扩展和滑动,储存弹性势能的释放导致岩体的整体体积破坏。根据岩石的统一能量屈服准则,建立了高压水射流破岩能量准则。通过砂岩、灰岩和花岗岩的单轴压缩应力-应变曲线得出3种岩石的材料参数,计算每种岩石的剪切应变能和体积应变能,得出射流破岩临界速度。根据高压水射流冲击破岩实验结果修正了考虑喷嘴流量系数的高压水射流破岩能量准则,该准则能够较为精确的计算射流破岩速度。且岩体的破坏形态证明从能量角度研究破岩机理更为适合。

Mechanism on energy dissipation and release of rock breakage with high pressure water jets

If the criterion of rock breakage with high pressure water jets is developed based on stress strain,the precision of the criterion depends on the function type of yield stress.And the precision is not high enough for rock breakage with high pressure water jets,because of being lack of critical rock parameters.But if the criterion is developed based on energy,its precision will be high enough and its applicability will be general.The paper studied the mechanism of rock breakage with high pressure water based on energy dissipation and release.The kinetic energy of potential core area and boundary layer was calculated based on the velocity distribution of free jet,and then the kinetic energy calculation model of high pressure water jets was developed.The rock breakage energy of high pressure water jets represented the formation of erosion pit and volumetric fracture of rock.Part of energy dissipated fracture propagation and slip plane.And part of energy reserved as elastic potential energy in rock,which leaded to the volumetric fracture of rock.According to the unified energy yield criterion of rock,the energy criterion of rock breakage with high pressure water jet was developed.The primary rock parameters of sandstone,limestone and granite were tested by uniaxial compression experiment.Then the shear strain energy and volumetric energy of three type rocks can be calculated respectively.So,the critical speed of high pressure water jets can be figured out.According to the experimental results of rock breakage,the energy criterion of rock breakage with high pressure water jet was amendment,combining with the discharge coefficient of nozzle.The amended criterion was more precise for coal breakage with high pressure water jets.And the failure mode of rock proved that the energy criterion was more suitable for the mechanism of coal breakage with high pressure water jets.