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中南大学学报(自然科学版)

Journal of Central South University

第46卷    第12期    总第256期    2015年12月

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文章编号:1672-7207(2015)12-4625-09
基于特征线法的锚杆(索)锚固质量应力波检测方法
邓东平,李亮,赵炼恒

(中南大学土木工程学院,湖南长沙,410075)

摘 要: 将由锚杆(索)和外围注浆体组成的锚固体等效成一维弹性杆件,采用应力波特征线法,并根据应力波在突变断面处的入射、反射和透射关系以及初始与边界条件,得到应力波传播过程中的应力和速度。通过计算锚固体的复合弹性模量和质量密度以获得应力波在其传播的波速,并按传播时间的对数螺旋衰减规律对求得的应力波应力和速度进行修正。考虑均匀断面全长注浆型、存在自由段非全长注浆型和存在缺陷段全长注浆型这3种锚固体,及由端头发射端头接收和底端发射端头接收2种应力波信号处理方式,得到简便判断锚固体断面变化处位置和锚杆(索)长度所需的脉冲信号时间,并推导出由锚固体断面变化处和底端反射(或透射)回的应力波的速度计算公式。在算例中,研究脉冲信号时间、应力波衰减系数、外围注浆体的混凝土强度等级、锚杆(索)自由段和锚固段交界面位置及缺陷段注浆饱满度对应力波法检测锚固体质量的影响,同时,分析实测锚杆(索)长度误差影响因素。研究结果表明:满足简便判断锚固体质量的脉冲信号时间范围很小;锚固体外围注浆体的混凝土强度等级对端头接收到的应力波的速度信号影响较小;锚固体断面变化处仅对由该位置反射回的应力波的速度信号有一定影响;缺陷段的饱满度越低,经缺陷段和锚固段交界面处反射后在端头接收到的应力波的速度信号越强,而由底端反射(或透射)回的应力波的速度信号越弱;缺陷段的饱满度对实测锚杆(索)的长度影响较大。

 

关键字: 应力波;特征线;锚固体;衰减系数;脉冲时间;饱满度;锚杆(索)长度

Stress wave method to detect anchorage quality ofanchor (cable) based on feature line method
DENG Dongping, LI Liang, ZHAO Lianheng

School of Civil Engineering, Central South University, Changsha 410075, China

Abstract:The anchor body composed of anchor (cable) and peripheral grouting body was equivalent to a one-dimensional elastic rod, stress and velocity of stress wave in communication process were gotten through adopting feature line method of stress wave and according to the initial and boundary conditions and the relationship between incidence, reflection and transmission when stress wave spread to mutant section. Propagation velocity of stress wave in anchor body was attained by calculating composite elastic modulus and mass density of the anchor body. Stress and velocity of stress wave gotten by feature line method was amended according to stress wave attenuated by the way of logarithmic spiral law with propagation time of signal processing mode. The two kinds of stress waves (stress wave launched and received by top of rod, and stress wave launched by bottom of rod and received by top of rod) was considered when studying three types of anchor body. i.e. full-length grouting type with uniform cross-section,non-full-length grouting with presence of free segment and full-length grouting with presence of defective segment, pulse signal time required to easily judge position of changed section and length of anchor (cable) in anchor body was gotten, and the formula for calculating velocity of stress waves reflected (or transmitted) back from change place of anchor body’s cross-section and bottom of rod was derived. In some examples, impact of pulse signal time, attenuation coefficient of stress wave, concrete strength grade of peripheral grouting body, position of interface surface between free segment of anchor (cable) and anchoring segment, and grouting plumpness of defective segment on quality of anchorage body detected by using stress wave method were studied. Influencing factors of deviation in aspect of measured length of anchor (cable) were analyzed. The results show that range of pulse signal time that can easily judge quality of anchorage body is very small. Concrete strength grade of peripheral grouting body has little effect on speed signal of stress wave received by the top of rod. Changed cross-section of anchorage body only has effect on speed signal of stress wave reflected from its position. The lower plumpness of defective segment, the stronger speed signal of stress received by the top of rod and reflected by interface surface of anchoring segment, and the weaker speed signal of stress wave reflected (or transmitted) back from the bottom of rod. Plumpness of defective segment has great effect on the measured anchor (cable) length.

 

Key words: stress wave; feature line; anchorage body; attenuation coefficient; pulse time; plumpness; length of anchor (cable)

中南大学学报(自然科学版)
  ISSN 1672-7207
CN 43-1426/N
ZDXZAC
中南大学学报(英文版)
  ISSN 2095-2899
CN 43-1516/TB
JCSTFT
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