粗粒土颗粒多点接触下的破碎准则研究

Breakage Criterion of Coarse Grained Soil Particles Under Multiple Points Contact

室内多采用2点加载的单颗粒破碎试验获取岩石颗粒的破碎强度,而在实际工程中颗粒大多处于多点接触受力状态,单颗粒破碎试验获得的颗粒强度是否适应多点接触破碎判别需要深入研究。以凝灰岩室内试验的弹性模量、泊松比、单轴抗压强度和巴西劈裂抗拉强度作为基准标定平节理模型的细观力学参数,用标定后的参数建立岩石颗粒的平节理模型试样。首先进行单颗粒破碎试验的数值模拟,分析颗粒在2点加载下的破坏过程;随后随机挑选100个加载构型,模拟颗粒受到不同接触力数量作用下的颗粒破碎,分析多点接触下最大主应力准则、平均主应力准则、八面体剪应力准则和最大接触力准则的适用性。结果表明:岩石颗粒在单颗粒破碎试验中的破坏过程有弹性阶段、裂纹稳定扩展阶段、劈裂破碎阶段;当颗粒处于多点接触受力状态,最大接触力准则判断颗粒破碎仍然适用。

The indoor 2 points loading particle breakage test is mostly used to obtain the crushing strength of particles.However,particles are mostly in multiple points contact state in practical engineering.Whether the particle strength obtained from the 2 points loading test is suitable for particles needs to be further analyzed.The elastic modulus,Poisson's ratio,uniaxial compressive strength and Brazilian splitting tensile strength of tuff are used to calibrate the micromechanical parameters of the flat joint model.The flat joint model sample of rock particle is established with the calibrated parameters.Firstly,the numerical simulation of single particle breakage test is carried out to analyze the failure process of particles under 2 points loading.Subsequently 100 loading configurations are randomly selected to simulate the particle crushing process under multi-contact,and the applicability of maximum principal stress criterion,average principal stress criterion,octahedral shear stress criterion and maximum contact force criterion under multi-contact is analyzed.The results show that the failure process of rock particle in single particle breakage test has elastic stage,stable crack propagation stage and splitting crushing stage;while the particle is under multi-contact,the maximum contact force criterion is still suitable to judge particle breakage.