Research on the Evolution of Shield Segment Cracks Based on Acoustic Emission and CMOD

Abstract

In order to explore the cracking law and failure characteristics of segments, a model test of shield segment cracking was conducted. The microscopic and macroscopic crack evolution process of the segment is studied by using acoustic emission detection technology and crack opening displacement (CMOD). According to the acoustic emission signal and CMOD, characteristics generated in the process of segment cracking, in the form of numerical value, the evolution characteristics of each stage of segment cracking are directly reflected. Based on acoustic emission energy and CMOD, the segment cracking damage model was established to determine the segment fracture damage degree. The result shows that segment cracking can be divided into three stages, and the acoustic emission detection results and CMOD have different degrees of change in each cracking stage. This proves that both the acoustic emission acquisition results and CMOD can be used as evaluation indicators of damage degree. Acoustic emission can accurately identify the crack evolution process, and the yield strengthening is an important stage of crack damage evolution. The damage data points in this stage account for 76.83% of all the damage data points, the occurrence rate of damage data points is 0.225 s, and the density of data points in the damaged area is 3.219 × 10−4 mm3, which is larger than the other two stages. The segment cracking damage model can effectively reflect the segment cracking degree and provide a reference for the actual segment cracking assessment.

Assessment of the Service Status of the Tunnel Structure Adjacent to the Station

“…These factors were analyzed using a fault model tree, categorizing problems into three main factors: predesign, construction, and post-operation management [5]. The overall reduction in segment stiffness due to crack presence has been further confirmed through similar model tests [6].…”

Analysis of seepage-damage coupling in Shield tunnel concrete lining under high hydraulic pressure

“…With the operation of the shield tunnel, there are more and more diseases on lining, such as breakage, cracks, leakage, segment dislocation, erosion, differential settlement, etc. [1] , which have a serious effect on the durability of segment and long-term performance of tunnel structure. The high hydraulic pressure on the cross-river or cross-sea tunnels makes seepage not be neglected.…”

Study on the Fracture of a Shield Segment in a Fully Excavated Hard Rock Section under the Influence of Construction Loads

“…Fracture not only affects the normal use of the supporting structure but also significantly reduces the impermeability and frost resistance of components. An excessively wide fracture will accelerate the corrosion of steel bars, thus reducing the bearing capacity of components and often causing serious safety hazards [1][2][3]. Due to the many adverse effects of fractures, China spends considerable manpower and financial resources on the prevention and repair of segment fractures every year, resulting in enormous economic losses and resource waste.…”