In this review, the tunnel engineering geological disasters were firstly reported, and then the simulation applications of tunnel engineering related to RFPA were summarized. The following main conclusions were that during the construction of tunnel engineering, the tunnel engineering of main geology disaster types including solid geological disasters, quasi fluid geological disasters and fluid geological disasters; the RFPA numerical methods in tunnel engineering construction related rock mechanics and failure characteristics of acquiring, under the condition of excavation of tunnel damage simulation, bedding rock tunnel excavation simulation, dynamic tunnel under the condition of failure simulation, simulation and partition of deep surrounding rock fracture under the action of seepage tunnel stability analysis were carried out in such aspects as widespread application; at present, RFPA has made important progress in the aspects of calculation accuracy, calculation scale and calculation speed, parallel computation of large-scale solution process, construction of numerical computing cloud platform and so on. It is believed that with the continuous development of technology and program, RFPA numerical calculation method will be more widely used in tunnel engineering simulation.

On the basis of theoretical analysis in the framework of specific energy, the main factors of such an interaction were summarized as: the size and the spacing distance of cutters, mechanical properties of stratum, and penetration. A method for design of scaled model tests of tunneling process, by means of shield boring machines, was proposed. The diameter of cutterhead was reduced, while the size and the spacing distance of cutters, the stratum, and the penetration were kept as the same as they were on site. Such a method was applied to a model test of the tunneling of the Cancer Hospital Metro Station of Shenzhen Line 14. This station was the first application of a new construction method which was characterized by that the station was firstly excavated by a small shield boring machine and then re-excavated by a larger one. The results of the model test allowed for predictions of the axial forces and the torque moments of the prototype cutterhead. The predicted values agree well with the monitored ones on site. This underlines the reliability of the proposed method for design of the model test. The originality of this work was highlighted by the quantitative relations between the quantities of the model and the prototype shield boring machines, which provides a reliable method for design of a model test of tunneling by means of shield boring machines.

Contact detection and computation efficiency has always been the key problem of three-dimensional discontinuous deformation analysis(3D-PEDDA), which is one of the most powerful numerical methods. Contact detection suffers from low efficiency, contact indeterminacy, and the incapability to deal with concave blocks. The efficiency of the entire DDA program is also one of the most crucial bottlenecks. This paper introduced the multi-cover method and the last entrance plane method to deal with lacking of efficiency and indeterminacy of contact detection, as well as the local convex decomposition method for concave polyhedron. In addition, in order to improve the computational efficiency, 3D explicit DDA was adapted to unify data reading and writing mode, and parallelized by adding precompile instructions. In order to expand to high-performance cloud computing and supercomputers, the new 3D-PEDDA programs were all developed on Linux system, and preliminary experiments were carried out on a simple cloud virtual machine. Numerical examples verified the efficiency and accuracy of the newly developed parallel 3D-PEDDA, and it is promising that it can be easily extended to high-performance virtual machines or supercomputers to realize the analysis of large-scale projects.

The application of 4D-LSM in rock blasting was studied. The fundamental principles of 4D-LSM in tunnel surrounding rock blasting were introduced, including system equations, non-reflective boundary conditions and rock fracturing model based on multi-body failure criterion. Aiming at the blasting of tunnel surrounding rock, 4D-LSM was used to establish the surrounding rock vibration analysis model, single hole blasting model and surrounding rock damage model under blasting. On the basis of different tunnel blasting design schemes, these models were processed through geometric simplification and boundary condition simplification to realize the quantitative analysis of the peak load velocity of the key points of the tunnel blasting surrounding rock for the given blasting scheme. Aiming at the problem of single-hole free-surface blasting, the simulation effects of DLSM and 4D-LSM were compared, and the advantages of 4D-LSM in dealing with large dynamic deformation and failure of rocks were demonstrated. The numerical modelling of surrounding rock damage zone depth under different blasting design parameters was realized by 4D-LSM. The safety classification and ranking of different blasting schemes were realized through the prediction and analysis of particle vibration velocity and damage zone depth predicted by 4D-LSM. The optimization of the tunnel rock blasting design could be realized by quantitative sensitivity analysis and ranking of blasting safety based on numerical simulation by using 4D-LSM.

The subway tunnel disaster recognition based on image processing is affected by the occlusion on the surface of the subway tunnel segment, which leads to inaccurate disaster feature recognition. In order to reduce the influence of occlusion on disaster recognition, according to the characteristics of various occlusions on the surface of the subway tunnel, the Mean-shift target tracking algorithm was used to determine the center position of the occlusion and then determine its area. The cascade classifier was used to quickly identify the occlusion and mark all the occlusions. This method could quickly identify and mark the occluded objects in the subway tunnel segment image. When there was no accurate identification, the algorithm would intelligently prompt and record the unidentified image for subsequent artificial auxiliary marking. Experiments showed that this method could quickly batch process subway tunnel segment image. In the disaster identification of subway tunnel, the influence of shelter area can be avoided, and it has certain engineering practicability.

Based on a power pipe tunnel project in Xiasha, Hangzhou, 3D finite element software ABAQUS was used to conduct numerical simulation of parallel pipe jacking process, the effects of successive pipe jacking staggered distance and mud-water pressure on soil settlement were studied.The maximum settlement was located directly above the center line of parallel pipe jacking and deviates from the leading pipe. The settlement caused by the descending pipe was 1.5 times that of the leading pipe; when the mud pressure was close to the static earth pressure, the settlement was the smallest; with the increasing of the staggered distance between the leading pipe and the descending tube, the soil settlement generally decreased. Meanwhile, the soil settlement generated by jacking was about 2 times as much as that generated by separate jacking. After the cross distance exceeded 4.31 times of the outside diameter of the pipe joint, the settlement had little change.

In order to efficiently treat the suspended solids with small size in the wastewater discharged during tunnel construction in karst area, the pollutants in the tunnel construction wastewater from Guilin to Liucheng Expressway were analyzed. Based on the concept of micro-flocculation filtration method, suspended solids with small size in wastewater were treated by coagulation-filtration process.The results showed that the main pollutants in the tunnel sewage were suspended solids and hydrogen ion concentration. Polymericferric sulfate silicatewas used as green flocculant, the flocculated wastewater was directly filtered, which could effectively remove at least 65% of the suspended solids with small size in water. For the wastewater with suspended solids content of 25, 50, 100 mg/L, the removal rates of suspended solids are 65.52%~68.47%, 79.06%~80.91%, and 85.19%~88.85%, when the precipitation time in 0~5 minutes, respectively.It can be seen that the precipitation process has little effect on the removal of suspended solids with small size. Therefore, it is suggested to cancel the precipitation process in wastewater treatment and directly adopt the flocculation-filtration process to efficiently treat the suspended solids with small size in the tunnel sewage.

This study aimed to enhance shield muck by incorporating foam agent and active magnesium oxide. The fluidity, bleeding rate and compressive strength of the improved soil under different foam agent and active magnesium oxide content were obtained by fluidity, bleeding rate and compressive strength test. It was showed that the improved flowable backfill soil exhibited excellent fluidity and solidified strength. By adjusting the content of foam agent and active magnesium oxide, the flowable backfill soil with fluidity ranging from 180 mm to 320 mm, bleeding rate below 5%, and 28-day compressive strength between 0.6 MPa and 1.2 MPa could be obtained.

The paper reviewed the experimental research progress of prefabricated drilling and high stress real-time drilling in analyzing the mechanism of drilling pressure relief(DPR)for preventing rockburst disasters from the perspectives of macroscopic(mechanical behavior characteristics, failure characteristics, energy evolution)and microscopic(crack evolution), and elaborated on the rationality and effectiveness of DPR for preventing rockburst disasters. Theoretical research and experimental analysis had confirmed that DPR was a key technology for relieving high stress and high energy in deep surrounding rocks, providing a reference for optimizing the application of DPR to prevent rockburst. High stress real-time drilling test method was a more scientific new research method that revealed the internal mechanism of DPR to prevent rockburst. Based on this, six development directions had been proposed for the experimental research on the mechanism of rockburst induction and the current technical conditions of multifunctional testing systems to analyze the mechanism of DPR to prevent rockburst: developing high-stress drilling rig test equipment compatible with true triaxial test systems; considering disturbance factors in high-stress real-time DPR simulation tests; simulating real-time DPR test after excavation of deep tunnels(roadway)("3D six-sided loading-single-sided unloading-real-time DPR" test); constructing an analytical model for the energy evolution of surrounding rock under 3D high stress real-time DPR; exploring the relationship between the spatial size effect of pressure relief drilling and the stress field and internal energy dissipation mechanism of surrounding rock; establishing a computational model for rockburst prevention by DPR in large-scale high-stress surrounding rock based on numerical simulation software.

The underground caverns of a hydropower station under construction are large in scale, with high side walls and large span.The deformation, stress evolution and plastic zone distribution characteristics of surrounding rock mass during layered excavation of underground caverns were studied by numerical simulation method, and the deformation and failure mechanism of surrounding rock mass was analyzed based on the results. Results showed that the failure of surrounding rock mass in the early excavation of the caverns was dominated generally by stress, and gradually changed to dominated by structural plane with the increase of excavation face. The numerical simulation results revealed the failure characteristics of hard rock with high in situ stress under the influence of structural plane, which could provide reference for the formulation of excavation measures and support design of caverns.