【摘 要】
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爆破开挖过程中,爆炸产生振动波及冲击波会对衬砌混凝土造成一定的损伤,在多次爆破振动下,损伤会不断的累积,最终降低结构体性能指标,进而影响到衬砌结构的安全性及使用性。因此本文紧密结合衬砌混凝土多次爆破振动损伤问题,依托于北京云龙山隧道工程,基于强度损伤理论,采用现场监测、室内模拟试验和数值分析相结合的方法,对爆破振动下衬砌混凝土振动损伤特性进行研究。首先采用现场监测手段分析振速及主振频在爆破振动作用
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爆破开挖过程中,爆炸产生振动波及冲击波会对衬砌混凝土造成一定的损伤,在多次爆破振动下,损伤会不断的累积,最终降低结构体性能指标,进而影响到衬砌结构的安全性及使用性。因此本文紧密结合衬砌混凝土多次爆破振动损伤问题,依托于北京云龙山隧道工程,基于强度损伤理论,采用现场监测、室内模拟试验和数值分析相结合的方法,对爆破振动下衬砌混凝土振动损伤特性进行研究。首先采用现场监测手段分析振速及主振频在爆破振动作用下的衰减规律,并根据现场测试数据采用爆破振动模拟试验对混凝土试块的强度损伤特性进行分析,为进一步研究衬砌混凝土结构上各位置的应力和位移变化特性,最后利用数值模拟方法对其进行研究分析,主要的研究工作及成果如下:(1)利用萨式公式对振速及主振频线性拟合后,得到爆破振动衰减规律预测公式;同时利用量纲分析原理建立相似准数方程得出主振频关于振速的预测公式,并利用现场观测数据验证了其有效性。(2)短龄期混凝土受爆破振动扰动后,其单轴抗压强度根据龄期的变化会有一个先增长后降低的过程;多次爆破振动下,混凝土在多次爆破振动下,其强度损伤将会累积,利用线性回归方法对爆破损伤累积与振动次数的关系进行拟合,得到混凝土强度损伤累积随受振次数的变化关系式,可通过混凝土的受振次数对其强度损伤进行预测。(3)同一断面衬砌混凝土上最大拉应力出现在拱脚处,并且随着爆心距的增大,衬砌混凝土的拉应力逐渐变小。爆心距20m处的最大拉应力值要大于28h龄期的C25混凝土的抗拉强度;在爆心距60m处的最大拉应力才能够小于12h龄期的C25混凝土的抗拉强度,表明最大拉应力基本不会对爆心距大于60m的位置造成受拉破坏,可将其称之为安全距离。通过对爆破振动下衬砌混凝土的损伤特性进行研究,为基于衬砌混凝土损伤的爆破振动预测和控制提供前提条件和研究基础。
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