基于离散元数值模拟的冰川冰抗剪强度特性及影响因素研究

STUDY ON SHEAR STRENGTH CHARACTERISTICS AND INFLUENCING FACTORS OF GLACIER ICE BASED ON NUMERICAL SIMULATION OF DISCRETE ELEMENTS

在现场调研和直剪试验标定的基础上,通过PFC2D数值模拟分析了纯多晶冰、冰岩嵌固体、岩屑冰和碎石冰4类冰川介质的抗剪强度及温度、岩屑含量、碎石含量与粒径的影响,进行了试验验证。结果表明:(1)纯多晶冰沿最大剪应力面产生剪切破坏,冰岩嵌固体沿冰岩接触面发生剪切破坏,破裂面较为平整;而岩屑冰和碎石冰的剪切破坏特征与颗粒含量和粒径有关,破裂面凹凸不平。(2)抗剪强度随着温度的升高而降低,-40~-10℃时基本呈线性下降,而-40℃以下和-10℃以上时影响则更为显著,其中内摩擦角对于温度的响应相比黏聚力更为敏感。(3)抗剪强度随着岩屑或碎石含量的增加而增大,含量从0增加到20%时对内摩擦角的影响较大、对黏聚力的影响较小,而含量从60%增加到80%时对黏聚力的影响比对内摩擦角的影响更为显著,含量20%~60%时两者皆呈线性增大。(4)随着碎石粒径的增大,内摩擦角先增大、后减小,黏聚力则先减小、后增大,碎石粒径12.5mm左右时分别达到最大值和最小值。研究结果对于揭示冰崩机理及灾害防治具有科学价值和现实意义。

Based on field investigation and direct shear test calibration,PFC2D numerical simulation was used to analyze the relationship between shear strength and temperature,rock debris content,gravel content,and particle size of polycrystalline ice,ice-rock mixture,rock debris ice,and gravel ice.Experimental verification was carried out.The results show that:(1)The shear failure of crystalline ice occurs along the maximum shear stress surface,and the shear failure of ice-rock mixture occurs along the contact surface of ice-rock.Their fracture surfaces are flat.The shear failure characteristics of rock debris ice and gravel ice are related to particle content and particle size,and the fracture surface is uneven.(2)The shear strength of glacier ice decreases with the increase of temperature.It decreases linearly at-40℃to-10℃,while the influence is more significant below-40℃and above-10℃.The internal friction angle is more sensitive to temperature than cohesion.(3)The shear strength increases with the increase of rock debris or gravel content.When the content increases from 0 to 20%,it has a greater influence on the internal friction angle and a smaller influence on the cohesion.When the content increases from 60%to 80%,the effect on cohesion is more significant than that on the internal friction angle.When the content is 20%to 60%,both of them increase linearly.(4)With the increase of gravel particle size,the internal friction angle increases first and then decreases,while the cohesion decreases first and then increases.When the gravel particle size is about 12.5mm,it reaches the maximum and minimum values,respectively.The research results have scientific value and practical significance for revealing the mechanism of ice avalanche and disaster prevention.