循环荷载下岩-砼复合试件疲劳破坏与能量演化研究

Research on Fatigue Failure and Energy Evolution of Rock-Concrete Composite Specimens

在地下洞室开挖过程中,围岩-衬砌支护结构长期受到钻孔爆破等施工扰动产生的周期性荷载影响,使支护体系面临着失稳破坏的潜在风险.对此,制作了混凝土与砂质板岩的复合试件,探讨围岩-衬砌复合试件在不同应力水平单轴循环荷载下的疲劳损伤特性,揭示围岩-衬砌复合试件的能量演化规律.试验结果表明:复合试件的单轴抗压强度介于纯砼和岩石试件中间,且更接近于纯砼试件,其力学性能随砼强度的增大而增强;在单轴循环加卸载条件下,复合试件破坏以沿二者接触面的剪切破坏为主,相较于单轴压缩试验结果,其内部裂纹得到充分扩展,破坏更为彻底;循环加卸载过程中复合试件内部储存的弹性应变能占比较高,耗散能较低,而在临近破坏前,耗散能突增,可为围岩-衬砌结构的失稳预测提供依据.

During the excavation of underground caverns,the surrounding rock-lining support structure is affected by periodic loads caused by construction disturbances such as drilling and blasting for a long time,which makes the support system face the potential risk of instability and damage.Therefore,composite specimens of concrete and sandy slate were made,the fatigue damage characteristics of the surrounding rock-lining composite specimens under uniaxial cyclic loading at different stress levels were discussed,and the energy evolution law of the surrounding rock-lining composite specimens was revealed.The test results showed that:the uniaxial compressive strength of composite specimens was between pure concrete and rock specimens,which was closer to that of pure concrete specimens.The mechanical properties of composite specimens increase with the increase of concrete strength.Under uniaxial cyclic loading and unloading conditions,the failure mechanism of composite specimens was mainly shear failure mechanism along the contact surface of the two materials.Under the condition of uniaxial cyclic loading and unloading,the failure of the composite specimen is mainly the shear failure,compared with the uniaxial compression test results,the internal cracks were fully expanded,and the overall strength was reduced,and the failure was more complete;The elastic strain energy stored in the composite specimen during the whole cycle was higher and the dissipation energy was less;close to failure,the proportion of dissipation energy increased sharply,which can provide basis for instability prediction of surrounding rock-lining structure.