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应力波入射至软弱薄层后发生多重反射和透射现象,因波形叠加使反射和透射系数计算变得复杂。弹簧模型可以有效简化应力波在软弱薄层的多重反射和透射过程,给出反射和透射系数计算公式。通过建立考虑应力波在软弱薄层内多重反射和透射的实体模型,引入h/λ和Kn/Zω两个无量纲量分别描述应力波在软弱薄层传播过程中的几何特性和力学特性,讨论垂直入射条件下实体模型和弹簧模型的反射、透射系数变化规律。研究结果表明:当软弱薄层厚度与应力波波长相当时,应力波在软弱薄层的多重反射和透射过程引起透射系数和反射系数成“锯齿形”波动,波动周期和软弱薄层与岩层的阻抗比成线性关系;当软弱薄层厚度小于应力波波长时,随Kn/Zω值增加,采用实体模型和弹簧模型计算的透射系数逐渐接近,基于两者透射系数的差值确定等效门槛值ξ,ξ和软弱薄层与岩层的阻抗比成线性关系。
The multiple reflections and transmission phenomena occur when stress waves are incident on weak thin layers, which complicates the calculation of reflection and transmission coefficients. The spring model can effectively simplify the multiple reflections and transmission processes of stress waves in weak thin layers, and gives the formula of reflection and transmission coefficient. By establishing a solid model considering the multiple reflection and transmission of stress wave in a weak thin layer, two dimensionless quantities, h / λ and Kn / Zω, are introduced to describe the geometric and mechanical properties of the stress wave propagation in a weak thin layer respectively. The Law of Reflection and Transmission Coefficient of Solid Model and Spring Model under Vertical Incidence. The results show that when the thickness of the soft thin layer is equal to the wavelength of the stress wave, the transmission and reflection coefficients of the stress wave become “zigzag” When the thickness of weak thin layer is less than the wavelength of stress wave, the transmission coefficient calculated by solid model and spring model approaches gradually with the increase of Kn / Zω value, and the equivalent transmission coefficient is determined based on the difference between the two transmission coefficients The threshold ξ, ξ and the resistivity ratio of weak thin layer and rock formation are linear.