新浇混凝土爆破振动损伤累积规律模拟试验研究

Simulation experimental research on damage accumulation law of new concrete under multiple blasting vibration loads

针对新浇混凝土振动损伤累积问题,利用振动试验系统开展了新浇混凝土爆破振动损伤累积模拟试验,并进行了受振混凝土强度与耐久性检测试验。结果表明:新浇混凝土振动损伤值累积过程可分为降低、快速增长和基本稳定3个阶段,且累积损伤值随着振动速度的增大而增大。振动速度v≤1. 0 cm/s时,超声波波速发展经历快速增长、缓慢增长和稳定3个阶段,最大波速随振动速度的增大而增大,振动损伤劣化效应不显现,混凝土的强度和耐久性提高。振动速度v≥1. 5 cm/s时,超声波波速发展出现损伤劣化降低过程而呈现为4个阶段,峰值波速和稳定波速均低于基准试块的相应波速,且都随着振动速度的增大而减小;振动损伤劣化效应从第2阶段开始显现,并在第3阶段宏观显现,振动速度达到3. 5 cm/s时,损伤从第1阶段即宏观显现;混凝土的强度和耐久性降低,且高强混凝土损伤劣化程度较普通混凝土明显。试验条件下新浇混凝土安全振动速度应控制在1. 5 cm/s以下,龄期12 h以前,振动速度不宜超过2. 0 cm/s。

To address the blasting vibration induced damage accumulation of new concrete,a test on blasting vi-bration induced damage accumulation of new concrete was carried out by the vibration test system,and the test of strength and durability of vibrated concrete was also carried out.The experimental results show that the blasting vibration induced damage accumulation has experienced three stages including the reduction stage,rapid growth stage and stability stage,and the cumulative damage value increases with the increase of vibration velocity.When the vibration velocity is less than 1.0 cm/s,the development of ultrasonic wave velocity has experienced three stages including the rapid growth stage,slow growth stage and stability stage,the maximum ultrasonic wave velocity increases with the increase of vibration velocity,the damage deterioration effect of vibration loads does not appear,and the vibration loads can improve the compressive strength and durability of the concrete.However,when the vibration velocity is greater than1.5 cm/s,the development of ultrasonic wave velocity has experienced four stages because of the appearance of damage deterioration and reduction process,both the peak and steady ultrasonic wave velocity are lower than the corresponding wave velocity of the virgin specimens,and both decrease with the increase of the vibration velocity,the damage deterioration effect of vibration loads begins to appear in the second stage and appear macroscopically in the third stage,when the vibration velocity reaches 3.5 cm/s,the damage deterioration effect appears from the first stage.The compressive strength and durability of concrete are decreased,and the damage deterioration degree of high strength concrete is more obvious than that of ordinary concrete.Under the test conditions,the safety vibration velocity of new concrete should be controlled below 1.5 cm/s,and the vibration velocity should not exceed 2.0 cm/s before the age of 12 h.