Li Junwei, Xu Fei, Wang Tianmu, Shi Songtao
School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, China.
Key Laboratory of Large Structure Health Monitoring and Control, Shijiazhuang Tiedao University, Shijiazhuang 050043, China.
Materials (Basel). 2022 Aug 24;15(17):5829. doi: 10.3390/ma15175829.
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 mm, 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.
为了探究管片的开裂规律和破坏特性，开展了盾构管片开裂的模型试验。利用声发射检测技术和裂缝张开位移（CMOD）研究了管片微观和宏观的裂缝演化过程。根据声发射信号和CMOD，以数值形式反映管片开裂过程中产生的特征，直接体现管片开裂各阶段的演化特性。基于声发射能量和CMOD建立了管片开裂损伤模型，以确定管片的断裂损伤程度。结果表明，管片开裂可分为三个阶段，且在每个开裂阶段声发射检测结果和CMOD均有不同程度的变化。这证明声发射采集结果和CMOD均可作为损伤程度的评价指标。声发射能够准确识别裂缝演化过程，且屈服强化是裂缝损伤演化的重要阶段。该阶段损伤数据点占所有损伤数据点的76.83%，损伤数据点的发生率为0.225 s，损伤区域的数据点密度为3.219×10 mm，大于其他两个阶段。管片开裂损伤模型能够有效反映管片开裂程度，为实际管片开裂评估提供参考。
