某核电厂软岩地基动态力学参数特征试验研究

  目的]  循环荷载会影响岩石的强度和力学性质，目前核电工程中等风化砂岩的动态参数研究相对较少。  方法]  以某核电厂软岩地基中等风化砂岩相关物理参数统计得出物理参数与深度的规律，随后利用MTS三轴试验机进行频率为1 Hz的不同应力幅值循环加、卸荷载试验，得出中等风化砂岩的动力学参数的规律。  结果]  研究表明:90个中等风化砂岩的取样深度与波速呈幂函数关系，随着深度的增加，砂岩的波速也随之增加，砂岩的密度基本在2.50 g/cm3左右。不同应力幅值循环加、卸荷载试验给出了中等风化砂岩试样在单轴下的滞回环形态、轴应变、阻尼比及动弹模的变化规律:增加循环次数，试样轴应变增加，塑性变形不断增大，滞回环的面积逐渐增加，内部裂隙不断扩展发育，循环所消耗的能量逐渐增大。滞回环的形态皆为尖叶状，在应力减少或者增加的转折点处滞回曲线呈尖状而非圆状，说明试样对应力的变化反应迅速，在应力转折时试样的塑性应变较小。随着动应变增加，试样动弹性模量逐渐减少，阻尼比逐渐增加。动弹性模量、阻尼比与动应变呈线性关系。拟合曲线相关系数R在0.92以上，具有良好相关性。  结论]  试验研究成果对核电厂软岩地基的动态参数测定和评价具有很好的工程参考意义。

Experimental Research on Dynamic Characteristic Parameters of Soft Rock Foundation in a Nuclear Power Plant

  Introduction]  Cycle load has effect on the rock strength and mechanical characteristics and China still lack the research on dynamic characteristic parameter of mechanism of medium weathering sandstone.  Method]  According to test physical parameters of 90 medium weathering sandstones, the deep and velocity of sonic were presented as power founction, then MTS machine was used to conduct cyclic load test in different amplitude obtain the sample′s law of hysteretic cycle, dynamic elastic modulus, axial strain and damping ratio in axial cyclic load.  Result]  The results show that the velocity is increasing with the increasing of the depth. The density of sample approximate 2.50 g/cm3. The axial strain and plastic displacement are increasing with the increasing of rounds. The increasing area of hysteretic cycle means that rock inner cracks is creating continuously resulting to increasing consumption of energy.The form of hysteretic cycle is same as sharp leaf and what it′s sharp but not around in the time of increasing stress or decreasing stress means that the sample reflection of changing stress is rapid and the plastic displacement in the time of changing stress is little relatively. The dynamic elastic modulus is increasing and damping ratio is decreasing with the increasing of dynamic strain. The math relations between either elastic modulus or damping and dynamic strain is presented as linear. The correlation coefficient R2 is almost above 0.85 showing good relevance.  Conclusion]  This work provides some guidance for further study on testing and evaluation of dynamic characteristic parameters for soft rock foundation of nuclear power plant.