The paper aimed to investigate the natural mechanism for this water inrush and mud outburst disaster in certain subway tunnels by energy theorem. The fundamental reason why this disaster was so large(approximately 11 679 m³)was that the equilibrium of the surrounding rock around the tunnel face was broken, and thus the volume of potential energy was transformed into kinetic energy and released instantaneously. Based on the field survey, some reasons were concluded as follows: the geological tectonic profile seemed like a “funnel”, where stress concentration was obvious; the tunnels crossed the bottom of the “funnel”; the weak and thin strongly-weathered tuff with many cracks located on the crown; the “funnel” stratum could collect a large amount of rainwater, and before this disaster, the rainfall resulted in the medium-coarse sand being saturated, so the water-head rose, seepage force increased, and the surrounding rock was weakened. These conditions could be classified into DI space. It could be seen from the numerical simulation that, the tunnel face applied by seepage force was unstable when strengthened by leading injected conduit whereas by taking account of the influences of seepage function, the tunnel face strengthened by steel piles could keep stable. By comprehensively analysis, it could conclude that the natural reasons for this disaster were that the combined effects consisting of increasing water pressure, concentrated stresses, seepage forces, applied to the degrading rocks, and then the potential energy transforming into kinetic energy formed this disaster on a large scale.

The geometric model of the deep tunnel was established according to the spatial constraint of the excavation face, and the corresponding stress field distribution was obtained. The visco-elasto-plasticity of the rock mass was simulated by the Nishihara model. The excavation disturbance(D)and geological strength index(GSI)were considered to analyze the rock deformation, access to the law of rock deformation. Results showed that the smaller the original rock stress, the better the quality of rock, the smaller excavation disturbance, the smaller creep deformation rate was in the phase II. In addition, the influence of the excavation surface advancing velocity on displacement of surrounding rock was also analyzed. The larger the advancing speed, the greater the changing intensity of the tunnel surrounding rock displacement. Advancing speed did not affect the ultimate displacement of surrounding rock when the original rock stress was relatively small. On the contrary, when the original rock stress was relatively large, the faster the advance speed, the greater the displacement of surrounding rock.

Based on the in-situ expansion project of Jinjishan tunnel in Fuzhou 2nd ring road, the row-hole blasting was simplified to the triangular blast load and then applied upon the centerline of row-hole according to the detonator time-interval. The whole process of millisecond blast in the left head face of left tunnel was carefully studied by the refined numerical simulation, and the blast-induced vibration effect upon the surrounding tunnels was well focused. As far as pedestrian tunnel was concerned, the peak velocity of frontward side was 5~13 times to its counterpart of backward side, and the vertical-direction peak velocity at the frontward side wall reached to 4.55 cm/s. On the other hand, the vibration effect of right tunnel was negligible, since the existing cavity within left tunnel could hamper the propagation of vibration wave significantly. The field monitoring at the frontward side wall was also carried out, whose three-dimensional velocity histories generally coincided with the results from numerical simulation. The time-interval among peaks coincided with the delay of detonators, while the peak velocity was 10%~30% greater than its counterpart calculated by numerical simulation.

Aiming at the problems of subjective deviation, language ambiguity and incomplete information in the evaluation of green construction of tunnels in Karst area, a fuzzy comprehensive evaluation model for tunnel green construction was established based on extension analytic hierarchy process and grey system theory. The extension interval judgment matrix was used to deal with the subjective fuzziness of the index weight of green tunnel construction, the grey system theory was used to consider the index scores of multiple experts under the influence of incomplete information, and the comprehensive evaluation weight vector was obtained by combining the two, so as to improve the accuracy of the evaluation results.Through computer programming language Python development based on the model algorithm evaluation software, the software was applied to the green construction evaluation of the Dongqi Tunnel from Guilin to Liucheng Expressway, the evaluation results showed that the green construction grade of Dongqi Tunnel was good, and the performance of water pollution and material saving needed to be improved. The evaluation results were consistent with the actual situation of the Dongqi Tunnel construction site. The proposed model provided a new reference for the green construction evaluation of similar tunnels in Karst area.

The quantitative relationship between the seepage defects and several influencing factors was studied based on the various types of inspection data of a highway tunnel in Yunnan Province, China. Based on the survival analysis method, a Weibull damage accumulation model was established for predicting the leakage of tunnel developing with influencing factors and time. The reasonability of the physical meanings of model parameters was discussed, and followed by the validation of the accuracy of model prediction. The research found that the order of importance for the influencing factors of seepage defects were: the existence of cavity behind the lining, the grade of surrounding rock, whether neighboring the deformation joint, and operating time, respectively; in addition, according to the model prediction, the leakage of tunnel could continually increase over time, so it was suggested to adopt maintenance measures such as water sealing treatment. This research provided a new method for diagnosing the major influencing factors and predicting the future development of tunnel defects.

In view of the characteristics of Chongqing Metro Station, such as large section, weak surrounding rock and great interference of cross construction, the mechanical properties and supporting measures of surrounding rock of super large section tunnel reserved middle rock column were studied. Based on Protodyakonov's theory, considering the influence of middle rock column, the calculation span of natural equilibrium arch was modified, and the calculation method of surrounding rock stress of reserved rock column was deduced, which was verified by actual case and numerical simulation. In order to improve the stability of surrounding rock, temporary steel support was added to the middle rock column, and the finite element software was used to simulate the support scheme and removal time of the reserved middle rock column. Considered the surrounding rock deformation, stress and site construction situation, the analysis showed that, temporary horizontal support adopted a layer of temporary horizontal bracing design.On the basis of meeting the deformation and stress of surrounding rock, it saved materials and reduces costs.It also improved the efficiency of construction. After the temporary support was removed after the invert construction, the vertical displacement of the vault of the tunnel, the horizontal displacement of the arch waist and the maximum vertical stress were the smallest when compared with the other two removal times.

Relying on the actual engineering case of grouting water plugging in water-rich fractured rock of Qingdao Metro, the field test of the applicability of grouting materials was carried out. The applicability of regular cement slurry, cement-sodium silicate slurry, and superfine cement slurry under the water yield standard requirements of two inspection holes, 0.2 L·min^-1·m^-1 and 0.01 L·min^-1·m^-1, was studied. Suggestions for water plugging grouting materials in water-rich fractured rock that match the requirements of different standards were proposed. The applicability of the grouting material was verified by means of Borehole TV and actual excavation verification. Research indicated: it was difficult to meet the requirements of waterless operation by using regular cement slurry alone(the water yield from the borehole was less than 0.01 L·min^-1·m^-1), but after repeated grouting, the water yield from the borehole could meet the requirement of no more than 0.2 L·min^-1·m^-1. Cement-sodium silicate slurries had a short gel time, which could effectively limit the diffusion scope of the slurry. By coordination application of regular cement slurry and cement-sodium silicate slurry, the grouting effect was significantly better than regular cement single-liquid slurry; The superfine cement slurry had low particle size, which could effectively fill the micro-fracture space in the water-rich fractured rock and improve the water plugging efficiency of the tunnel surrounding rock. The use of regular cement slurry, cement-sodium silicate slurry and superfine cement slurry to carry out advanced curtain grouting of water-rich fractured rock could meet the requirements of tunnels waterless operation. The research results could provide a basis for the treatment design of grouting and field construction in water-rich fractured rock.

Four shield tunnels with different burial depths of Jinan Railway R1 and R2 are under the bridge of Beijing-Shanghai High-speed Railway at the same construction section, and in order to reduce the influence of shield construction on the pile foundation of High-speed Railway, the isolation piles were formed by the bored piles and cyclone piles between the interval structure and bridge piles. Based on this, the isolation and protective effect of the isolation piles on the different burial depths of the shield tunnel construction was studied by numerical analysis. The calculation results showed that the application of isolation piles between the new shield tunnel and adjacent high-speed rail bridge pile foundation could effectively reduce the range of influence of tunnel construction and reduce the impact of tunnel construction on adjacent pile foundation; the greater the tunnel burial depth within the range of pile lengths of adjacent piles, the greater the impact of tunnel construction on them, and the more significant the protection effect of isolation piles on them.

Based on the project of Nanning Metro Line 5 undercrossing Guangxi University Station of Line 1 in Xinguang Section, FLAC^3D software was used to study the stability of the excavation face of the shield tunnel undercrossing the water-rich gravel stratum of the station bottom plate at ultra-close distance. The influence of support stress ratio and groundwater level on the stability of excavation face was explored, and the appropriate supporting pressure control value of excavation face was given as the technical guidance for field construction. The research showed that with the decrease of the support stress ratio, the horizontal displacement of the soil on the excavation face increased continuously, and its deformation conformed to the development trend of the soil plastic zone. The failure mode of the excavation face in the water-rich gravel stratum was wedge-shaped ahead of the excavation, and the failure area gradually developed to the bottom plate of the existing station structure. After the instability and failure of the excavation face, the bottom plate of the station structure and the soil belowed the bottom plate form the free surface; with the increase of groundwater level, the supporting stress ratio of instability failure of excavation face increased, and the stability of excavation face decreased significantly. The earth pressure should be controlled above 111 kPa when crossing station.

To ensure the safety of tunnel construction and operation of the Yujingshan Tunnel of Chenggui Railway, the overall stability of the dark river cave system was evaluated and analyzed, and a comprehensive remediation plan of “dark river diversion-cave backfill-cave wall protection” was proposed. The results of the optimization test and the monitoring of the internal force of the protection structure were applied to the remediation process. The field construction practice showed that the above remediation could guide the Yujingshan Tunnel to traverse the giant dark river cavern safely and efficiently, and could provide experience reference for the design and construction of similar karst tunnels.