In order to further study the mechanism of coal and gas outburst and solve the safety problem of coal mining, the research group had made new progress in similar system and physical simulation experiment.Based on the energy model of coal and gas outburst and the classical gas-solid coupling model, the similarity criterion of coal and gas outburst was established, and the similar materials of high absorption gas bearing coal, ultra-low permeability rock and intrinsically safe gas were developed to ensure the scientificity and accuracy of the physical simulation experiment; six sets of basic test instruments, such as the visualized constant volume solid gas coupling tester, the circumferential displacement test system, the coal particle gas emission tester, the gas expansion energy tester, the rock triaxial mechanical penetration tester, and the similar material permeability tester, had been developed to realize the accurate and comprehensive measurement and control of the coal rock gas characteristics under the specific conditions of high pressure gas; based on the comprehensive action hypothesis and basic theory, a multi-scale quantitative simulation experiment system of coal and gas outburst aiming at tunnel excavation induced outburst was developed, which could realize the real simulation of tunnel excavation induced outburst with three adjustable factors of in-situ stress, gas pressure and coal rock mass characteristics;it had innovated the functional technology and method technology. Taking the “6.12” outburst accident of Xinzhuangzi mine in Huainan as the prototype, the experiment simulation of coal and gas outburst induced by driving and uncovering coal under the condition of large-scale model loading, inflation and pressure maintaining had been successfully realized for the first time in the world.

FRP-PCM is a new reinforcing method of tunnel lining using fiber reinforced polymer grid as reinforced material and polymer cement mortar as cementitious material. Based on the finite difference method, a numerical model of tunnel lining with back cavity defect was established. The FRP-PCM method was numerically applied to reinforce the deterioration tunnel lining using. Four design factors including FRP type, loosening pressure, surrounding rock grade and tunnel lining health degree were considered to conduct the numerical simulation. The reinforcement effect of FRP-PCM method on tunnel lining in operation was discussed quantitatively. FRP-PCM reinforcement could improve lining stiffness and strength through arch axial stress and plastic damage of the lining. It could resist the lining deformation to a certain extent, thereby reducing lining failure possibility. The reinforcement effect became more obvious with the improvement of FRP type. In order to quantitatively evaluate the reinforcement effect of the FRP-PCM reinforcement, section repair rate was proposed. Results showed that the higher the degradation level of the tunnel lining was, the more effective the FRP-PCM method was. Besides, suitable type of FRP bars could be selected according to loosen pressure, lining degradation degree and expected section repair rate.

This paper was based on the engineering practice of a large karst cave(this cave was revealed during the construction period)in the upper part of a high-speed railway tunnel in June 2019. The main situation of revealing karst cave and its change countermeasures, disasters and emergency measures during the operation period was introduced, and the mechanism of karst cave evolution disaster was analyzed through the inspection of each stage during investigation, design and construction. A consultation scheme combining “arch protection + strong blocking + reserved drainage + consolidation and lightweight compact backfilling” was put forward, which was on the basis of pointing out the shortcomings of the two drainage tunnel renovation schemes. The feasibility, working conditions, construction period, investment, risks, environmental impact and effect prediction was compared with the drainage tunnel scheme. A three-dimensional mode was established by FLAC3D to check the safety of tunnel. The research results were as follows: The karst cave with filling type was changed into water-filled and water-flowing type due to the construction tunnel. And water flowed into the karst cave by the type of runoff, which was formed by the dissolution gap, dissolution tank, pipeline between the surface and the karst cave during seasonal heavy rainfall. The disaster was formed by sediment entering the tunnel with the karst cave water-filled and water-flowing; the runoff field hydraulic channel was formed by the medium between the karst cave and the tunnel under the action of seasonal karst cave water-filled and water-flowing or even short-term pressure. The consultation scheme of “arch protection + strong blocking + reserved drainage + consolidation and lightweight compact backfilling” had significant advantages over the drainage tunnel scheme in terms of environmental protection, investment control, construction period and construction risks. It would necessarily lead to the evolution of disasters within a certain period of time after the completion of tunnel, by taking groundwater observation and water quantity estimation during the construction period as the basis for disposal of large karst caves and ignoring the induced evolution prediction of groundwater force field caused by engineering activities. So the disaster was appeared only after one and a half years of operation because of failure to maintain and construct the artificial drainage channel of groundwater with maintenance function. In addition, it was suggested that special measures of unit separation water prevention and drainage should be implemented for water-rich sections or potential water-rich sections when new tunnels were built.

Long tunnel in homogeneous stratum was studied, which was simplified to a beam on elastic foundation. Soil-structure interaction was simulated by normal and tangential spring. Analytical solution of longitudinal seismic response was derived by solving governing differential equations. Through the analysis of the analytical solution of the internal force response, the calculation method of the maximum internal force response required for the longitudinal seismic design was put forward, which could be used to calculate the most unfavorable longitudinal response of long tunnel. On the basis of numerical calculation, the correctness of the analytical solution was verified. In addition, the analytical solution could intuitively give the correlations among the key parameters. Through parametric analysis, influence laws of incident angle, incident wavelength and relative stiffness ratio on longitudinal seismic response of tunnels were obtained. Analysis showed that as the wavelength of incident wave increased, the bending moment response first increased and then decreased, and the shear force and axial force response decreased. If the incident angle increased from 0° to 90°, the shear response decreased, while the bending moment and axial force first increased and then decreased. As the relative stiffness ratio increased, internal force response was reduced, but the displacement response of the structure and the deformation of tunnel structure would appear larger, which should be considered in the structural design. On this basis, a reasonable design and calculation method of longitudinal seismic response analysis of long tunnels was put forward, which could provide guidance for longitudinal seismic design of long tunnels.

Based on a series of exploration and practice in the process of tunnel construction of Haoji railway, the management measures about onsite check and optimization of construction drawings, change design, headmans responsibility system for project quality, monitoring measurement, and application of tunnel tooling equipment were presented. These measures could provide system support for the construction of the tunnel project safely and rapidly. In the aspect of design optimization, design parameters optimization about the inner contour of tunnel structure, the type of inverted arch structure and the supporting structure of auxiliary tunnel were introduced. These optimization measures could ensure the safety of tunnel supporting structure and the rationality of project cost. In the aspect of technical innovation, the type of steel frame of initial support, combination form of initial support, the type of composite lining structure, new type of initial support structure of resistance limiter, and large section horseshoe shield were introduced. Moreover, the scientificity and rationality of the tunnel support structure were guaranteed effectively through scientific research and experimental research. The above mentioned management measures, design optimizations, technological innovations can provide reference for tunnel construction in the future.

In order to deal with the problem from the large difference in the stress release rate of shield tunnels in different strata and the difficulty to accurately define the stress release rate in numerical calculations, it was studied about the correlation between the loss of the stratum and the stress release rate of the shield tunneling process. A method was proposed, which defined the stress release rate by taking the over-excavation of the cutterhead as the control index, and the application time of the shield shell, grouting, segment supporting and other processes was corresponding to the specific stress release rate. The geometric and physical mechanical parameters of the shield-soil clearance and the overlying stratum in the engineering background were combined, a high-simulation calculation method for the whole process of tunneling with shield tunneling machine was established to realize fine simulation of disturbance deformation. The comparison between the calculation results and the monitoring results proved the correctness of the research method. The simplified calculation method based on the comprehensive control parameters of the stress release rate accurately simulated the stratum deformation of the entire shield construction process in soil texture and improved the calculation accuracy, which could quickly complete the accurate prediction of the shield construction process.

The security problems such as misalignment of the pile foundation and excessive deformation of the bridge are existed during the excavation of the shield tunnel of the Hangzhou Metro Line 3 at a very close distance to cross the viaduct pile foundation shield. The theoretical calculation method of soil movement model and the numerical simulation method of Midas GTS soft were used to calculate the construction of shield tunnels, and the ground settlement and pile foundation inclination during shield construction were analyzed. The results showed that, when the left or right line tunnels were excavated separately, the maximum settlement occurred at the tunnel vault and above the ground surface,and the settlement would gradually decrease to both sides. The theoretical calculation of the settlement was similar to the numerical simulation; after the completion of the excavation of the two-line tunnel, the maximum settlement occurred at the surface position between the two tunnels;the excavation of the left and right line tunnels caused the left and right swing excursion of the middle row pile foundation; the cutter parameters and the distance between the tunnel face and the pile foundation were the main factors affecting the deviation of the pile foundation; in addition, the shield and rock mass gap, the strength of the secondary grouting material after the segment affect the ground deformation to a certain extent, and indirectly affect the gradient of the pile foundation.

In order to solve the problem of EPB(earth pressure balance)shield muck accumulation and transportation impact on the urban environment, relying on the shield tunnel project in a work area of Hangzhou Metro Line 10, for the clay soil layer, the shield muck reuse was proposed as synchronous grouting material. In the scheme, the slurry performance was tested by uniform test method. Linear regression and single factor analysis were performed on the test results. Among them, the 28 d compressive strength and the 2 d hardening rate were both increased significantly with the increase of the proportion of muck, while the 3 h bleeding rate decreased accordingly. It was found that when the water-binder mass ratio was 0.65, the cement-sand mass ratio was 0.7, the residue mass fraction was 5%, and the cement mass fraction was 30%, all the parameters of the slurry met the requirements. The influence of each factor on the key performance indicators of the slurry was explored to provide a new idea for the reuse of earth pressure balance shield muck.

This study aimed at the present situation of domestic construction in weak rock tunnel was used "close type" of the cave-in, combined with the tunnel construction emergency rescue practice experience, put forward a new idea of tunnel construction capsule, through science and technology research, development and manufacture of the tunnel construction capsule device, filled the domestic blank of tunnel construction life-saving equipment, to solve the weak rock tunnel was closed and rescue personnel trapped after a cave-in of the rescue, could greatly reduce or even eliminate this kind of accident caused casualties, for the effective guarantee for the safe construction in weak rock tunnel, could be applied in the similar engineering.

For the longitudinal cracks on the top surface of inverted arch of a loess tunnel which located at Lanzhou South Ring Expressway, the mechanism and development process of the tunnel floor heave were analyzed by means of in-situ deformation monitoring and numerical simulation. Through the observation of the vertical settlement on the top surface of the inverted arch filling, and the simulation results with the focus on the stress of the uneven settlement of the inverted arch, we found the main cause of the cracks was that the tensile stress in the middle of the inverted arch exceeded the tensile strength of the concrete. Combining the analysis results and the actual working conditions, we formulated the construction scheme as locking anchor pipes and reinforced concrete pavement. And the effectiveness of the scheme had been verified in practice. The research results not only guided the field construction, but also provided a basis for optimizing the support system of loess tunnel, and also a reference for similar engineering constructions.

Based on the large well method, through the in-depth study of the influence mechanism of the suspended water stop curtain, combined with the groundwater seepage theory, the theoretical calculation formula of the foundation pit water inflow under the condition of suspended dewatering was derived. Through the numerical calculation of the engineering example, this method had high precision, and the suspended dewatering condition was efficiently and accurately estimated with the limited known conditions in the early stage of the foundation pit, therefore the current foundation pit dewatering design theory could be improved and perfected.

Based on a foundation pit project in Jingdezhen near an underground shelter, a finite element model was established using MIDAS software to simulate the excavation process of the foundation pit. The simulation results were compared with monitoring data to verify the accuracy of the finite element model. On this basis, the earth pressure, displacement and internal force of the anchoring structure of the pull-anchor foundation pit were studied, and the influence range of the underground shelter was obtained by comparing the influence of different horizontal distance underground shelters on the deformation of the supporting structure. The results of the study indicated that the earth pressure behind the pile would decrease and then increase when there was an air-raid shelter. The earth pressure at the top of the air-raid shelter began to decrease and the bottom began to increase 55 kPa; when the foundation pit was excavated to the depth of the air-raid shelter, the maximum horizontal displacement value of the enclosing pile was reduced by 15% compared with that without the air-raid shelter, the influence range of underground shelter on the foundation pit was about 2.5D(D is the diameter of the underground shelter). Both the maximum bending moment point and the reverse bending point would show a downward trend, and the maximum bending moment value would increase with the increase of the excavation depth. The maximum bending moment was increased by 20%.