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In order to ensure the safety of the Daling tunnel with extralarge section and small space, the three-dimensional model of blasting dynamic simulation had been established and verified. Then, the model was used to analyze the influence of the surrounding rock characteristics and blasting design parameters on the blasting vibration of the first hole, and the analysis of the sensitivity of each factor was carried out. The results showed that blasting of the second hole had a serious impact on the safety of the first hole lining structure. Based on the safety threshold and analysis of sensitivity, the explosive velocity, charge density, and digging length were selected as the key parameters affecting the safety of the tunnel structure. Meanwhile, the corresponding engineering measure was taken based on the results of sensitivity and the actual situation on site, and, after that, the maximum PPV of the right wall of the first hole had been reduced to 9.3 cm/s, which effectively guaranteed the safe construction of the tunnel.

This paper presents a case study of a large ground collapse (30.6 m long, 25.5 m wide, and 6.0 m deep) and water inrush and mud outburst (10540.8 m3) in the Qingdao line 4, China. This disaster caused a loss of life and property, and construction delay. After the catastrophe, the remedial measures had to be taken to guarantee the stability of the tunnels when tunnel advance resumed. Based on the geological survey and numerical modelling, the main causes of this disaster were summarized as the low strength of strata, high water pressure, stress concentration, the coupling interaction between seepage force and ground and, as a consequence, also the crash of the slice of strongly weathered tuff. Eventually, potential energy, which was derived from the collapse bodies, was transformed into kinetic energy and developed this disaster. After this disaster, a set of remedial instruments including filling the ground cave-in, reinforcing the advance core ahead of tunnel face, and conducting the porepoles to form a protective shell were proposed. After the tunnel advance resumed, these remedial instruments validated by employing monitoring data were effective to tackle this disaster.

Traditional primary support made of reinforced concrete is widely applied but can bring many problems. Therefore, to study the mechanical behavior of corrugated-plate structure as primary support, several finite-element simulations in different sizes, shapes and elements were carried out. Besides, to ensure the exactness and practicability, a verification experiment and a BP neural network for prediction were done. The result shows that the outcome of beam-element and shell-element model is similar and the main deformation and stress is respectively down and compressive. And the difference between horseshoe-shaped and circular tunnel is small in aspect of vertical displacement and stress. Then, when t (thickness) increases, d (maximum vertical deformation) and s (maximum stress) decrease more and more slowly. When w (width) ascends, d and s improve more and more slowly. When h (height) becomes bigger, d declines more and more slowly and s goes down slowly, fast and slowly again. The outcome of the experiment conforms with the simulation. Next, by BP neural network, using top load and t, w, h to predict d and s is feasible and efficient. It performs better when predicting d. This paper can provide reference for the application of corrugated-steel-plate structure as new-type primary support.