基于应力波法的锚杆(索)锚固质量动力检测数值模拟研究

Numerical Study on Dynamic Testing of Anchorage Quality of Rock Bolt( Cable) by Stress Wave Method

锚杆(索)大量应用于边坡工程加固,为保证锚杆(索)发挥作用,一般采用应力波法对其锚固质量进行检测,检测的2个主要指标是:锚杆(索)长度和缺陷段的位置。为此,在ANSYS/LS-DYNA中建立锚固体应力波动力分析模型,将小锤对锚杆(索)的敲击作用等效为小锤按一定激发速度v0与锚杆(索)的碰撞,并在锚杆(索)端头断面中点采集应力波信号。经算例与理论研究成果对比,验证了数值模型的可行性,同时,分析了小锤弹性模量和激发速度v0的取值对应力波信号的影响,研究了应力波法判别缺陷段位置的准确性,及对比了端头激发与端头和底端同时激发这2种方式在锚杆(索)质量检测中的适用性。研究结果表明:1小锤弹性模量的增大仅对初始应力波信号有增强作用,对经锚固体底端一次反射回的应力波信号影响不大,而小锤激发速度v0的增大对初始和经锚固体底端一次反射回的应力波信号均有利,且与后者成线性比例关系;2应力波法对锚固体缺陷段位置的判别较为可靠,且缺陷段越饱满判别准确性越高;3端头和底端同时激发方式缩短了反应锚固体断面变化处和底端位置的应力波信号时间,因而有利于工程应用。

Rock bolt （cable） is widely used in slope reinforcement. To ensure rock bolts （cables） work effectively, the stress wave method is generally adopted to detect anchorage quality. I^ength of rock bolt （cable） and position of defective segment are two main indicators of detection. In this research, dynamic model of stress wave of anchorage body is established in ANSYS/LS-DYNA. The percussion effect of hammers on rock bolt （cable） is presumed to be equivalent to the collision between hammer with a certain speed v0 and rock bolt （ cable）, and stress wave signal is gathered on midpoint of rock bolt （cable） top section. Feasibility of the numerical model is verified by comparing with the results of theoretical studies in examples. Moreover, the effect of elastic modulus and excitation speed vo of hammer on stress wave signal is analyzed, and the accuracy of defective segment position detected by using stress wave method is studied. The applicability of two excitation modes （ excitation on top and excitation on top and bot- tom simultaneously） in the detection is compared. Results reveal that： （1） Increasing the elastic modulus of hammer only affects the initial stress wave signal, but has little effect on stress wave signal reflected once back from the bottom of anchorage body; while the increase of excitation speed v0 of hammer is conducive to both the signals and is linearly proportional to the latter. （2） It is reliable to use stress wave method to detect the defective segment position of anchorage body, and the detection accuracy is higher when defective segment is more complete. （3） The mode of excitation on top and bottom simultaneously shortens the time of stress wave signal reflecting the posi- tions of section change and bottom of anchorage body, so it is conducive to engineering applications.