高预应力和围岩加载速率对高强高韧锚杆钢变形行为的影响研究

Effects of high prestress and rock loading rate on deformation behaviors of highstrength and high-toughness steel for rock bolts

在深部地下工程中,新型金属支护材料的研发和应用越发引起人们的关注与重视。然而,关于预应力和围岩加载过程对高强高韧锚杆钢的影响规律尚不清楚,亟待进行相关研究。以具有极高地应力区的木寨岭公路隧道为工程背景,结合以物理机制为基础的晶体塑性模型,以NPR钢为例,研究高预应力和围岩加载速率对高强高韧锚杆钢塑性变形行为的影响规律。研究结果表明,围岩加载速率是影响锚杆钢材料应变量的主要因素,锚杆钢材料的最终应变量和变形弛豫均会随围岩加载速率的降低而不断增加。当围岩加载速率控制在10^(−2)MPa/s以下时,可以明显增强锚杆钢材料的大变形能力。当预应力大于600 MPa时,材料会出现明显的应变弛豫现象。当预应力增加到800 MPa以上时,材料会出现应力弛豫现象,这可能会导致锚杆的预应力损失,需要引起注意。研究结果为高强高韧锚杆钢在高地应力难支护工程上的应用提供理论依据和技术指导。

In deep engineering,the development and application of novel metallic materials has attracted many attentions.However,the influence of prestressing process and rock loading process on high-strength and hightoughness steel for rock bolts remains still unclear,and relevant research is urgently required.Muzhailing highway tunnel with extremely high in-situ stress area was taken as the engineering background,combined the physically based crystal plasticity model,and NPR steel was taken as an example to study the effects of high prestress and rock loading rate on the plastic deformation behaviors of high-strength and high-toughness steel.The results show that the rock loading rate plays a major role on affecting the strain capacity of bolt steel,and the ultimate strain and deformation relaxation of bolt steel will increase with the decrease of the rock loading rate.It is found that the large deformation capacity of bolt steel can be significantly enhanced when the rock loading rate is controlled lower than 10^(-2)MPa/s.In addition,there will be obvious strain relaxation phenomenon for bolt steel as the prestress is higher than 600 MPa.The bolt steel will exhibit stress relaxation as the prestress increases higher than 800 MPa,which may result in the loss of prestress for rock bolt and should be paid attention.The research results provide theoretical basis and technical guidance for practical application of high-strength and high-toughness steel for rock support engineering in high in-situ stress field.