上海交通大学学报

上海交通大学学报

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基于离散元法的砂岩力学性能及渗透特性模拟研究

  

  1. 长安大学 公路学院，西安 710064
  • 基金资助:
    国家自然科学基金资助项目（52178310，52478384），陕西省杰出青年科学基金项目（2025JC-JCQN-026），陕西省创新能力支撑计划资助项目（2023-CX-TD-35）

Simulation Study on Mechanical Properties and Permeability Characteristics of Sandstone Based on Discrete Element Method

  1. School of Highway, Chang’an University, Xi’an 710064, China
  • About author:王二博（1995—），博士生，从事隧道与地下工程方向研究

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摘要： 为了研究水-力耦合作用对砂岩力学性能及渗透特性的影响，基于颗粒流离散元数值计算平台，提出了一种采用有限差分法离散化求解渗流场的数值计算方法，并综合考虑了裂隙的产生对渗透率的影响。通过开展不同渗透水压作用下砂岩试样水-力耦合数值试验，得到结论如下：随着水压与围压比值的增加，砂岩试样的力学强度和弹性模量呈指数式减小，泊松比和渗透率分别近似呈线性和指数式增长。当水压与围压比值为0.03~0.40时，岩样力学强度下降约为0.8%~4.8%，渗透率增长约为2.2%~8.0%；当水压与围压比值为0.40~0.75时，岩样力学强度下降约为3.9%~20.3%，渗透率增长约为15.0%~85.3%；水-力耦合作用下试样内强接触力链主要集中在剪切破裂滑移带附近，且呈现出“枝晶”结构特征；随着渗透水压的增加，拉剪裂纹数目演化曲线由S形增长转变为台阶式增长，其中主要以张拉裂纹为主，且裂纹主要沿着渗流速度场的强弱分布整个岩样；水-力耦合作用弱化了颗粒胶结强度，削弱了试样积累弹性应变能的能力，而增强了峰值应力处能量的耗散能力，且岩样内能量的耗散、裂纹的增长与渗透特性呈正相关。本文所提出的数值计算方法可为离散元模拟岩石水-力耦合效应提供一种新思路。

关键词: 水-力耦合, 力学性能, 渗透特性, 破坏模式, 离散元法, 有限差分法

Abstract:

In order to study the influence of hydraulic coupling on the mechanical properties and permeability characteristics of sandstone, a numerical calculation method using finite difference method to discretize the seepage field and the influence of crack formation on permeability was proposed based on the particle flow dispersion element numerical calculation platform. By conducting numerical experiments on the hydraulic coupling of sandstone samples under different osmotic pressures, the following conclusions were drawn: As the ratio of water pressure to confining pressure increases, the mechanical strength and elastic modulus of sandstone samples decrease exponentially, while Poisson's ratio and permeability increase approximately linearly and exponentially, respectively. When the ratio of water pressure to confining pressure is 0.03 to 0.40, the mechanical strength of the rock samples decreases by about 0.8% to 4.8%, and the permeability increases by about 2.2% to 8.0%. When the ratio of water pressure to confining pressure is 0.40 to 0.75, the mechanical strength of rock samples decreases by about 3.9% to 20.3%, and the permeability increases by about 15.0% to 85.3%. The strong contact force chain in the samples under hydraulic coupling is mainly concentrated in the vicinity of the shear rupture slip zone, and shows the characteristics of “dendritic” structure; With the increase of osmotic pressure, the evolution curve of the number of tensile-shear cracks changes from an S-shaped growth to a stepwise growth, which is mainly dominated by tensile cracks, and the cracks are mainly distributed along the strength of the seepage velocity field throughout the rock samples; The hydraulic coupling weakened the particle cementation strength and weakened the ability of the samples to accumulate elastic strain energy, while enhancing the ability to dissipate energy at the peak stress, and the dissipation of energy within the samples and the growth of cracks were positively correlated with the permeability characteristics. The numerical calculation method proposed in this article can provide a new approach for discrete element simulation of rock hydraulic coupling effects.

Key words: hydraulic coupling, mechanical properties, penetration characteristics, destructive mode, discrete element method, finite difference method

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