It is well known that anchor rods and prestressed anchor cables (rods), as important components of the protection and reinforcement system, are widely used in foundation projects such as tunnels, roadways, foundation pits, and slopes. Especially in China's rapid development of high-speed railways, in the construction of tunnels, slopes, etc., rock anchor cables and anchor rods have been widely used, and it is obvious that quality assurance is very important. However, due to the weathering of the rock mass and the influence of groundwater, various aging and deterioration phenomena (such as prestress relaxation, etc.) will inevitably occur in anchor cables and anchor rods. On the other hand, because it is a hidden project, if the construction quality is not well guaranteed, such as insufficient length, inadequate grouting, or even insufficient tension, it will seriously reduce the stability of the structure, causing significant social and economic losses.
In the "Quality Acceptance Standards for Construction of Railway Tunnel Engineering" (TB 10417-2018) and "High Quality Acceptance Standards for Construction of High-speed Railway Tunnel" (TB 10753-2018) newly issued and implemented in February 2019, it is clearly stipulated that: The cementation and anchoring quality of the rod shall meet the design requirements. Inspection methods: check the construction records, check the impact elastic wave method, and pull or drill when necessary.
Carefully compare the original "High Quality Railway Tunnel Construction Quality Acceptance Standards" (TB 10753-2010) regulations, and the new version of the regulations has revised the inspection method of anchor bolts (sound wave reflection method) to shock elastic wave method.
What kind of shock elastic wave is mentioned in the verification?
Shock elastic wave: The elastic wave generated in the target material by mechanical shock is called shock elastic wave. There are generally two methods for the generation of shock elastic waves, namely, the impact of external forces and the internal damage of objects. The impact elastic wave in the non-destructive testing field is generated by hitting the test object with an external force such as a hammer or other excitation device. The signal characteristics are phase, amplitude, time domain or frequency domain by using the propagation characteristics of the impact elastic wave such as reflection and transmission Analysis can detect the mechanical properties of materials and the soundness of structures, and is called the shock elastic wave method.
There is a "shock elastic wave" inspection method in the railway tunnel anchor mark inspection. Is there a corresponding inspection procedure?
"Technical Specifications for Anchor Bolt Support of Railway Tunnels" edited by China Railway Second Academy is about to be promulgated. The code clearly specifies the testing methods for anchor bolts. The non-destructive testing of anchor bolt anchorage quality should adopt the impact elastic wave method, which is consistent with the new railway inspection method.
As the above specifications have not been officially promulgated, the current anchor testing generally refers to the “Non-destructive Testing Regulations for Anchors of Water Conservancy and Hydropower Projects” (DL / T 5424-2009) issued by the National Energy Administration or the “Anchor Anchors” issued by the Ministry of Housing and Urban-Rural Development Technical Specification for Quality Nondestructive Testing "(JGJ / T 182-2009). The non-destructive testing methods for anchor bolt anchoring quality described in these two regulations are "sound wave reflection method".
What are the similarities and differences between the shock elastic wave method and the acoustic wave reflection method?
The DL / T 5424-2009 procedure defines the acoustic reflection method as: applying transient or steady-state excitation loads to the exposed end of the bolt, measuring the acceleration or velocity response time-history curve, and performing analysis in the time and frequency domains. Detection method for evaluating the anchor bolt anchoring quality.
The JGJ / T 182-2009 protocol defines the acoustic reflection method as: a nondestructive testing method that uses an excited acoustic signal, measured acceleration or velocity response curve, analyzes based on wave theory, and evaluates the anchoring quality of the bolt.
As mentioned earlier, the shock elastic wave is a concept of a cluster wave with a wide frequency range and does not specifically refer to a certain component wave. According to the detection needs, the vibration mode can be changed to obtain signals in different frequency domains to meet the test requirements. The detection requires the extraction and analysis of a certain component wave in the wave group, and the detection purpose has been achieved. Therefore, in engineering applications, the shock elastic wave detection method is more and more accepted by the public. In addition to TB 10753-2018 explicitly using the "shock elastic wave method", the "Technical Specification for Detecting Concrete Defects by the Impact Echo Method" (JGJ / T 411-2017) also made a clear definition of "shock elastic wave".
The "sound wave" in the "sound wave reflection method" generally refers to the elastic wave in the frequency range of 20 Hz to 20 kHz, and mainly refers to the P wave or S wave component therein, that is, the shock elastic wave contains the "sound wave" in the "sound wave reflection method", so As far as the detection medium is concerned, the "shock elastic wave method" test anchor rod quality meets the "sound wave reflection method". As far as the operation requirements are concerned, the two are basically the same.