关键词: 锚杆(索), 应力波, 数值模拟, 锚固质量, 缺陷段, 饱满度, 激发方式

Abstract: 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. Length 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 v₀ 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 bottom 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 positions of section change and bottom of anchorage body, so it is conducive to engineering applications.

Key words: rock bolt (cable), stress wave, numerical simulation, anchorage quality, defective segment, plumpness, excitation mode