Rockburst disaster is one of the prominent problems faced by deep underground engineering. Microseismic (MS) monitoring techniques can be used to warn of rockburst in tunnels to provide scientific basis for rock burst prevention and control measures. Described in this paper, is an MS monitoring system based on MS source location with hierarchical strategy implemented in the tunnel group of the Jinping II hydropower station in Sichuan Province, China. The spatiotemporal distribution of MS events was analyzed in the construction process and the size effect of rockburst risk discussed by statistical analysis and numerical calculation of rockburst in seven tunnels. The results show that the active period of microseisms and the high-incidence period of rockburst are within 1.5 h after the rock disturbance. The MS events within 1D from the tunnel wall are the most intensive and are mainly concentrated near the heading face, the side wall, and the left spandrel. At the construction site, the accuracy rate of rockburst prediction is 61.8%, of which the accuracy rate of the medium and strong rockburst is 80.3%. Based on field statistics of rockburst, the increase of the tunnel excavation section size can reduce the rockburst strength to a certain extent, which is consistent with the numerical simulation results.

The problem of large deformation is very prominent in deep-buried tunnel excavation in soft rock, which brings serious potential safety hazards and economic losses to projects. Knowledge of the stress field distribution and deformation law is the key to ensuring rational design and safe construction in large deformation tunnels of soft rock. As described in this paper, theoretical analysis, numerical simulation and field monitoring were employed to investigate the surrounding rock stress and displacement state in the Dongsong hydropower station in Sichuan Province, China. The results show that the short-bench construction method can effectively control the deformation of surrounding rock and range of the plastic zone. In order to reserve enough working space, the optimum bench length in the actual construction was 10 to 14 m. The peripheral displacement and plastic radius decreased with the increase of tunnel support strength and the advance of supporting time. The displacement can be effectively controlled by applying the second lining in time at a position about twice the diameter of the hole (16 m) from the working face. A reasonable reserved deformation should be adopted to avoid secondary expanding excavation. The values of different positions in the tunnel laterally and longitudinally may be different, and adjustments are needed according to the actual situation.

The problem of large deformation is very prominent in deep-buried tunnel excavation in soft rock, which brings serious potential safety hazards and economic losses to projects. The knowledge of deformation law and support measures is the key to ensure the rational design and safe construction in a large deformation tunnel of soft rock. This paper describes rock physical and mechanical tests and field monitoring is employed to investigate the cause and development process of large deformation in Dongsong hydropower station in Sichuan Province, China. The results show that the free expansion rate of the rock sample is 20.0%, the average expansion stress of the rock sample is 11.0 kPa, and the expansibility of the rock is low. Large deformation of surrounding rock mainly comes from the dilatancy effect with high geostress and relaxation deformation with weak support. Shotcrete sealing exposed surrounding rock, and early strength support avoiding water immersion are useful to deal with the three main factors (weathering, water and confining pressure) that affect the strength of surrounding rocks. The second lining applied in time can effectively limit the further development of stress and deformation of initial support, and prevent the cracking and large deformation of concrete. Clearance convergence is suggested to be the main monitoring work in construction, because of its advantages of intuitive results, easy quality assurance of instrument installation and high accuracy.

The anchor bolt is a key point of tunnel design in bedded rock mass. The previous theory of anchorage support falls does not fulfil engineering requirements, and the stability of bedded rock must be addressed by empirical methods. To investigate the bolt anchoring performance for bedded rock mass under different anchoring methods, the rock failure mode under shear and tensile stresses in bedded rock was examined in this paper. The results showed that bolt anchoring for rock is achieved mainly through the bonded restoration of surrounding rock near the drill holes by means of an anchoring agent and the supporting resistance provided by the bolt body. It was observed that the strength parameters of bedded rock were increased under the anchoring effect. Full anchoring bolts were especially effective. In addition, it was observed that, in the absence of bolts, the failure form changed from shear to split. In the case of bolting, the failure plane occurred parallel to the bolt’s axis. The shearing began along the interface between the hard and soft rock bedding. Compared to end bolt anchoring, full-length bolt anchoring was more capable of offering an anchoring effect. The latter offered a greater increase in the strength and greater shear-bearing capacity of the rock, which ultimately enabled the rock to bear more load.

At present, the damage caused by steel corrosion to structures has become a serious problem all over the world. In order to study the mechanical behaviors of tunnel lining structure system under the corrosive environment to rebars, first, the bending tests were performed to investigate the crack propagation behavior and structural bearing capacity of the reinforced concrete bending members degraded by corrosion. Secondly, the pull-out tests were performed to investigate the degradation of bonding strength between corroded rebars and the concrete. Finally, on the basis of the findings from the pull-out tests, a 3-D finite element bond-slip model of reinforced concrete lining structure has been established to simulate the changes of bearing capacity and durability of tunnel reinforced concrete lining under different corrosion degrees. The research has revealed: Rebar corrosion is the most important factor affecting concrete and steel corrosion. As the conversion rust rate increases, the ultimate drawing force continues to decrease. With the increase of the corrosion rate, the deflection of the specimen when it is destroyed becomes smaller, the cracking load becomes smaller and the bearing capacity also decreases. As the degree of corrosion increases, the overall deformation of the tunnel increases, and the overall safety of the lining structure decreases. The corner position is the most prone to problems after the lining structure is corroded, so pay more attention. As well, the safety of the lining structure will be basically lost when the final corrosion rate of the steel bars is greater than 30%. The findings of this research can be used to evaluate the corrosion degree of tunnel reinforced concrete lining structure and support the durability design of new tunnel concrete lining structure.