The assembled external quick mounting rack system is a new type of support structure suitable for fixing electromechanical equipment and pipelines in metro shield tunnel. It has the advantages of simple process, green environmental protection and no damage to tunnel segments. Based on the engineering example of Fuzhou Metro Line 5, the load-bearing performance of the assembled external quick mounting pylon system is studiedby means of field static test and finite element software simulation. The study shows that: (1) The safety performance of the metro shield tunnel assembled external quick-mounted hanger system can be satisfied by considering the safety factor of 3 times under static load; (2) Local stress concentration occurs at the load action, the intersection of long bolt and groove, and the intersection of groove and lug at the hand hole of concrete pipe slice. The maximum stress point is located at the top of the long bolt, but the maximum stress is less than the allowable stress of the material; (3) When the load acts on the OCS crossbeam, the deformation of long bolt has the greatest influence, but has little influence on the deformation of concrete segment, lug and longitudinal connecting bolt.

Experiments were conducted to investigate the effects of bacterial suspension concentration and pH on calcium carbonate production and the flocculation latency phase during microbially induced carbonate precipitation (MICP) reinforcement of tailings sand. The effectiveness of this method in reinforcing tailings sand was evaluated using tests for permeability, water retention, resistance to raindrop erosion, wind erosion resistance and penetration. By analyzing the influence of pH on urease activity and the equilibrium of the carbonate system, and observing the microstructure of tailings sand through scanning electron microscope and X-ray diffraction tests, the mechanism of MICP reinforcement of tailings sand at low pH was revealed. Results showed that the MICP method at low pH significantly improved the mechanical properties of tailings sand. After a single spray treatment, the wind erosion mass of tailings sand was reduced to zero, and the permeability coefficient decreased by an order of magnitude. Additionally, the raindrop and wind erosion mass of tailings sand treated with a high-concentration bacterial suspension at pH = 4 was also reduced to zero. Low pH temporarily inhibited urease activity and disrupted the carbonate system equilibrium, delaying calcium carbonate precipitation. This allowed calcite to uniformly fill the intergranular pores of tailings sand, cementing the sand particles together. This research presents a novel approach to tailings dam reinforcement and tailings sand treatment, elucidating its reinforcement mechanism and offering theoretical and experimental support for the application of low-pH MICP reinforcement of tailings sand.

Aiming at the problem of insufficient time-frequency resolution of tunnel blasting vibration signal, a time-frequency image enhancement algorithm based on convolutional neural network is applied, through the time-frequency image enhancement of the measured tunnel blasting signal, the aggregation range of the blasting signal energy in the time-frequency domain is captured, and the real signal reflecting the blasting characteristics is reconstructed; according to the real signal, the initiation time of detonator in blasting network is accurately distinguished, and the characteristics of tunnel blasting detonator disaster source are identified.The analysis shows that the time-frequency image enhancement algorithm based on convolutional neural network can effectively suppress the cross-terms in the signal, retain the auto-terms of the signal to the greatest extent, and improve the energy aggregation and time-frequency resolution of the blasting signal; The mixed use of different batches of detonators is the main disaster causing factor of tunnel safety.Supervision should be strengthened to realize safe and efficient tunnel construction.