With the development of urban accelerated construction, “urban disease” is becoming more and more prominent, and the development and utilization of underground space is more and more important. By transforming the mode of urban development, scientifically planning the development and utilization of underground space, drawing on international successful experience and paying attention to the development of quality, we can realize the multifunctional utilization of underground space development, realize the “urban diseases” such as urban disaster, traffic congestion, air pollution and urban inland inundation, and take the construction of underground pipe gallery and sponge city construction as an opportunity to resolve the existing problems in the construction of legal system and the reform of management system in a timely manner, realize the harmonious coexistence of man and nature, promote the construction of urban ecological civilization towards a new height, and promote the construction of beautiful cities.

In recent years, in some super-long water diversion tunnels, construction methods of multi-headed excavation using multiple TBMs have emerged, forming the characteristics of TBM cluster tunneling. The northern Xinjiang Water Supply Phase II Project is a typical representative. The geological condition of this project is extremely complex. Tunnel  construction is faced with many disaster risks such as collapse, water inrush, soft rock deformation with high groundwater, and TBM jamming. There are many high-risk sections and it is of great necessary to carry out geological forward-prospecting. In views of the construction characteristics of TBM cluster and the challenges faced by geological forward-prospecting, the geological conditions and major disaster risks of the project were analyzed, and the features of commonly used geological forward-prospecting techniques were compared. The applicability of forward-prospecting methods under TBM cluster construction conditions as well as the corresponding technical challenges were discussed in detail, and the countermeasures were proposed accordingly. The development direction of TBM geological forward-prospecting technology was further discussed. Recommendations were proposed from the following five aspects: expert decision-making and fusion diagnosis of forward-prospecting for TBM clusters, robust and efficient real-time geological forward-prospecting technology, correct utilization and construction permit of geological forward-prospecting results, TBM intelligent excavation based on “transparent” geological rock mass information and standardization of TBM geological forward-prospecting, etc. These recommendations will be focused and deployed in advance, which will provide guidance for future forward-prospecting in tunnel construction with TBM cluster.

Hydraulic tunnels are widely adopted for water conveyance purpose in the mountainous region of western China. The tunnels usually pass through various stratum with complex occurrence environment and geological conditions, including active faults. Currently, both domestic and foreign codes and regulations regarding tunnel design fail to provide any specifications and recommendations on design philosophy and countermeasures for tunnels crossing active faults and therefore potential threat is posed on the long term stability of water conveyance tunnels. Based on the definition, the classification and the influences of active faults to tunnels, the engineering examples were collected and comprehensive comparisons were made. Totally ten cases regarding tunnels crossing active faults were summarized and the emphasis was placed on the discussion of the design philosophy adopted in each case. It was found that the primary countermeasures consists of four approaches, which were setting up flexible connection section, enlarging excavation dimension, using tubes placed inside the tunnel, and application of composite lining or new materials. Then, the adaptability evaluation of countermeasures for tunnels crossing active faults was reviewed. Some concerning topics and their research progress were summarized and commented. The issues that required further study and improvement were mentioned. Finally, combining the research project “Disaster mechanism of surrounding rock mass and lining structure and countermeasure technology for tunnels crossing active fault”, which was a research program of the National Key Research and Development Program “Efficient Use of Water Resources”, the problems of tunnels crossing active faults were discussed and the potential achievements were prospected.

The deep-buried tunnel has the characteristics of high in-situ stress, high osmotic pressure and rich sources of disasters. These factors can significantly increase the risk of water-inrush. Drilling-and-blasting excavation method must be adopted in some sections. The water-inrush in drilling-and-blasting excavated deep-buried tunnel are commonly characterized by concealment, complexity, suddenness and destructiveness and the disaster mechanism is more complicated. There are still some problems in the existing researches, such as the detection and identification of disaster source are inaccurate, the constructed disaster mechanism is unclear, the prevention and control of malignant disasters are inadequate. The existing theories and technologies are not fully applicable anymore, thus, the prevention and mitigation of geological hazards are the key scientific issues remained to be solved. The existing research status are analyzed from three aspects: the advanced geological prediction, the disaster mechanism of water-inrush, and the evolution and mitigation of constructed disaster. Three suggestions were put forward about the key points and directions of the research on the water-inrush in deep tunnel. First of all, it is necessary that comprehensive application of big data analysis and the latest research results of other subjects in order to achieve quantitative and accurate detection. Furthermore, the catastrophic model of disaster sources should be established from the perspective of energy storage and release. The occurrence conditions and emergency mechanism of engineering disasters need revealing. In addition, the method of calculating the safety of impermeable silt layers should be developed and the existing research results also should be applied to practical engineering. Last but not least, the risk assessment theory of the water-rich soft rock section of deep-buried tunnel should be studied seriously. According to the actual conditions of the tunnel, the different technologies of disaster control should be combined organically to maximize the benefits of technology, economy, resources and environment.

At present, China is the country with the greatest scale and difficulty in the construction of tunnels and underground projects. Fault fracture zone, water-rich sand strata and other water-rich soft strata have become the most common unfavorable geologic bodies in the construction of underground engineering. Grouting is the main method to treat water-rich soft strata. Based on the characteristics of the project team, the latest research progress in grouting reinforcement theory, simulation test and grouting control method in water-rich soft strata was introduced. In terms of grouting reinforcement theory, considering the layered characteristics and space attenuation characteristics of reinforced soil, a quantitative method for calculating the reinforcement effect of splitting grouting was established by synthesizing the performance parameters and spatial distribution of grouting veins, compacted strata and undisturbed strata. What's more, considering the inhomogeneity of the retention space of cement particles caused by filtration effect in sand layer, a quantitative strength calculation method of grouting reinforced composition ground was established for the permeation grouting form of plane radial flow. On this basis, the spatial attenuation characteristics of grouting strength were revealed. In the aspect of simulation test of grouting reinforcement, a simulation test system for grouting after water inrush and mud inrush of tunnel was developed. The rule of priority filling and diffusion in cavities and soft broken areas and the law of multi-sequence split grouting diffusion in closed space strengthened area were summarized. A visual simulation test system for splitting grouting was developed, which could reveal the variation rule of split channel shape with time during grouting. The influence range of splitting and compaction grouting under test conditions was obtained. In terms of grouting control methods, the corresponding grouting control methods for muddy fault fracture zone and water-rich sand layer were put forward respectively, which could provide effective guidance for grouting engineering practice in water-rich weak stratum.

Deep underground rocks are in a complex geomechanical environment featuring high in situ stress, high temperature, and high osmotic pressure. The mechanical responses and failure mechanisms of deep rocks under dynamic loading due to excavation, blasting and earthquakes cannot be explained by traditional rock mechanics theories due to these factors. In recent decades, significant progress has been made in the characterization of dynamic properties of rocks, including compression, tension, fracture and shear. Due to the complex geomechanical environment of deep rocks, extension of these investigations to deep rocks is desirable by considering high in situ stress, high temperature and high osmotic pressure, which is a critical issue in deep rock engineering. This study reviewed existing rock dynamic studies considering such three factors, summarized the influence of these factors to dynamic responses of rocks. Experimental systems, data analytical methods, and experimental results were summarized. In the last, future directions in deep rock dynamics were proposed.

For the problems facing by Qinling Tunnel South TBM Project of the Hanjiang-Weihe Water Diversion, such as TBM tunneling difficulty in high-strength high-abrasion stratum and heavy cutter consumption, the tunneling parameters and cutter consumption in the first 2 000 m TBM trial tunneling section were studied to put forth problems with some tunneling parameters, including overlarge thrust, excessive penetration, small rotation speed and over-low torque, which would shorten the service life of the hob and limit TBM tunneling speed. It was found that there were not enough cutters near 43# cutter position of the cutterhead, the areal abrasion resistance was inadequate, slag was not removed off from the cutterhead in time, and the secondary wear of the cutter was serious, which all contributed to heavy cutter consumption too. The high-strength hard rock breaking test by hob indicated that rock could be broken efficiently when the cutter edge spacing ranged from 80 mm to 130 mm, but if the ratio of cutter edge spacing to penetration(S/p)was 25~30, TBM would have a lower rock-breaking specific energy and a higher rock-breaking efficiency. The scaled-down-hob wear test in high-abrasion stratum showed that there existed a critical penetration in rock breaking by hob, at which the mass loss rate would increase sharply. It was also found that using rounded-edge hob could lower the hob wear efficiently. The obtained results could provide reference and basis for design of TBM cutterhead and cutter, and control of tunneling parameter for tunneling in high-strength high-abrasion stratum in Hanjiang-Weihe Water Diversion and other projects.

The heat treated-high strength steel bar have many advantages,such as high strength,good ductility,high strength ratio, good welding and cold bending performance, etc. It could effectively reduce the amount of steel bars and improve the project quality, and was successfully applied in civil engineering at home and abroad. However, the application of heat treated-high strength steel bar has limited study in the tunnel engineering. Based on the railway and highway tunnel construction, field tests of heat treatment high-strength lattice girders was carried out. By comparing the results, the supporting performance of high-strength lattice girders and I20b steel was analyzed. The result showed that settlement and convergence between high-strength lattice girders test section and I20b steel was reduced 7%~30%, and the surrounding rock pressure was close. But the steel stress of high-strength lattice girders was higher than I20b steel. Because of better combination between lattice girders and shotcrete, high-strength lattice girders ultimate bearing capacity was bigger than I20b steel, and steel material consumption of high-strength lattice girders was about 36% less than I20b steel. So high-strength lattice girders had good social and economic efficiency.

During the construction of large-span loess tunnel, surface cracking, settlement deformation, support invasion and landslides are easy to occur, which makes the construction of large-span loess tunnel extremely difficult. Based on the pier-beam tunnel, the largest-span highway loess tunnel excavated in the world at present, the combination of field measurement, theoretical analysis and numerical simulation was used to analyze the deformation law of large-span loess highway tunnel. Combined with the relevant research results and engineering practice experience of support design of single loess tunnel and two-lane loess tunnel, the structure type of the initial support was put forward, and structural force and stability of initial support were studied. The results showed that the convergence at the upper step and the maximum excavation line could be divided into four stages when the three-step method was adopted. The convergence rate at the upper step was faster than that at the maximum excavation line, and the final convergence value at the maximum excavation line was about three times of that at the upper step. As the distance between the settlement curve and the face increases, the settlement value increased continuously and the growth rate slowed down. Within the range of 1D, 1D to 2D, 2D to 3D and 3D to 4D from the palm surface, the settlement values generated by each measuring point were 49%, 23%, 12% and 6% of the maximum settlement values, respectively. The large-span loess tunnel colud ensure the stability of the tunnel structure by adopting the composite structure of “steel frame+shotcrete+steel mesh+anchor bolt(pipe)+longitudinal connection bar”. The double-sided guide pit method was adopted in the construction of the tunnel entrance section, the three-step retaining core soil method in the construction of the tunnel body section, and the stability control technology of the large-span loess tunnel strengthened by steel pipe grouting was adopted in the tunnel bottom with low bearing capacity in the shallow section.

Taking the strong concealment of seepage pressure along the water channel in inrush water disaster of deep buried rock as the background, based on the ideal generalizability of stress state of the anti-water-inrush rock mass, a large scale physical simulation test system for inrush water with high pressure and large flow was developed. The model size of this system was 1 800 mm×300 mm×300 mm. By using the plug-type uniform pressure servo loader, the geostress with the range of 0~6 MPa could be imposed on the model boundary, which could effectively reduce the negative effects induced by uneven loading and stiffness mismatch on the test results. The high pressure water source(2 MPa)was composed of a group of high pressure nitrogen tanks and a water irrigation system with large capacity constant pressure. Due to high sensitive characteristics of gas and liquid composite loading, both large flow recharge and high water pressure maintenance after catastrophe could be realized. A complete set of testing technology, including similar materials, model placement, and data acquisition, had been developed. A “four-in-one” boundary water proof method of “water proof cement+waterborne polyurethane+epoxy resin+auxiliary water proof belt” had been proposed, from which, the problem of high pressure water seal on the boundary of similar material was effectively solved. Then, a series of indoor tests on the typical disaster induced structures, with respect to various geological defects of different formation and scale, in-situ stress level and direction, water inrush pressure, as well as the filling medium characteristics, were conducted. Combined with the multi-field coupling numerical simulation, a spatio-temporal evolution theory model of seepage pressure and hydraulic gradient along the water channel was put forward. The inherent mechanism of progressive inrush channel conduction was preliminarily revealed.

It is an important way to prevent engineering disaster by using monitoring data to carry out tunnel collapse warning. On the basis of characteristic analysis of typical deformation monitoring curves, four stages of collapse deformation were summarized, and a quantitative early warning model with accumulated deformation, deformation rate and acceleration as the index was established. Then the level of safety management based on collapse precursor was determined. Combining quantitative monitoring with qualitative phenomena, a comprehensive early-warning model of tunnel collapse was established, which was applied to the tunnel engineering of Yakang Expressway. The application results showed that the model possessed better accuracy and practical value.

The isolated pile technique was adopted in a practical foundation project in Nanchang. Based on this project, numerical modeling simulations built with ABAQUS were combined with the observed data to study the protection effect of isolated piles on adjacent subway tunnel when the foundation pit was proceeded. The influences of horizontal location as well as buried depth of the isolated piles on internal stress and diameter variation of lining in existing tunnel during excavation were studied, based on the analysis on several sets of numerical models. A significant influence of the horizontal location on internal stress of the lining has been observed, a shorten gap of the isolated piles to the tunnel implied an improved protection effect. In addition, the deformation of the lining could be greatly suppressed by setting the isolated piles and more prominent effect on horizontal deformation compared with that on vertical direction. A further analysis indicated that the buried isolated piles performed better than the exposed ones. In general, the buried isolated piles with shortened pile length could be used in practical engineering to reduce the project cost.