循环冲击状态下砂岩力学及损伤特性研究

Study on mechanics and damage characteristics of sandstone under cyclic impact state

为研究循环冲击状态下砂岩力学及损伤特性,本文采用分离式Hopkinson压杆试验装置对红砂岩进行不同入射幅值的循环冲击试验,通过Weibull分布统计损伤模型分析了红砂岩损伤演化规律。研究结果表明,以90 MPa入射应力进行循环冲击试验时,随着循环冲击次数的增加,动态强度先增大后减小,最大应变以及平均应变率则先减小后增大,第一次冲击有助于提高红砂岩的抗压强度;随着入射幅值的增大,当以100 MPa、110 MPa、120 MPa入射应力冲击时,动态强度、变形模量和循环次数逐渐减小,最大应变和平均应变率逐渐增大。基于Weibull分布的损伤模型可以反映此材料的损伤演化特性,累积损伤随着冲击次数的增加而增大,累积单位体积吸收能与累积损伤规律具有较好的一致性,岩样出现失稳破坏为大块时的累积损伤值在0.8左右,没有明显的变化。研究结果为矿山岩体安全防护及正确评价岩石稳定性提供理论依据。

In order to study the mechanics and damage characteristics of sandstone under cyclic impact state,a separate Hopkinson pressure bar test device is used to carry out cyclic impact tests on red sandstone with different incident amplitudes.The damage evolution law of red sandstone is analyzed by Weibull distribution statistical damage model.The research results show that when the cyclic impact test is carried out with an incident stress of 90 MPa,as the number of cyclic impacts increases,the dynamic strength first increases and then decreases.The maximum strain and the average strain rate first increase and then decrease.The first impact helps to improve compressive strength of red sandstone.As the incident amplitude increases,the incident stress is impacted at 100 MPa,110 MPa,and 120 MPa,the dynamic strength,deformation modulus and cycle times gradually decrease,and the maximum strain and average strain rate gradually increase,the damage model based on Weibull distribution can reflect the damage evolution characteristics of this material.The cumulative damage increases with the increase of the number of impacts.The cumulative unit volume absorbed energy has good consistency with the cumulative damage law,and the rock sample appears when the instability failure is large,the cumulative damage is around 0.8,and there is no obvious change.The research results provide a theoretical basis for the safety protection of mine rock masses and the correct evaluation of rock stability.