Search

The construction of traffic network brings opportunities to the development of tunnel construction technology. At present, the construction of rock tunnels is still dominated by drilling and blasting. There are some problems in conventional blasting, such as over and underexcavation, damage of surrounding rock, large blasting vibration, and high content of tunnel dust. The energy-concentrated hydraulic blasting technology (ECHBT) combines the advantages of energy-concentrated blasting technology (ECBT) and hydraulic blasting technology (HBT) and makes up for the defects of conventional blasting. This paper summarizes the principle of ECHBT and its application effect in tunnel construction in China. In addition to solving the problems existing in conventional blasting technology, ECHBT can also improve tunneling efficiency, can be used in special stratum tunnels, and can save construction costs. However, there are also some factors affecting the blasting effect in practical applications, which need to be paid attention to. At present, there is little theoretical research on ECHBT; with the further improvement of optimization research, it can be expected to be more widely used in the field of tunnel construction.

The reasons, prevention, and control of loess disaster are of great concern in practice. In recent years, Xi’an city, China, has taken the leadership in large-scale construction of subway lines in the loess strata. To study the structural response of the tunnel in loess region under local hydrodynamic environment, an experimental testing in 1g as well as a numerical simulation were performed, in which the achieved results were verified and were found to be in good agreement. Furthermore, the results showed that when the water outlet point is above the lining, the overall stress of the lining is “peanut shell,” as the water pressure of the outlet point decreases, the tensile stress of the top and bottom of the lining increases, while the compressive stress on both sides decreases; the channel form of the flow to the lining changes with the variation of the position of the water outlet point. It is worth mentioning that in the process of water gushing, the closer to the water source, the greater surface subsidence is, and there is a positive correlation between water pressure and surface subsidence. This study is of significant benchmark for the construction, maintenance, and prevention of tunnel in loess strata under the influence of water environment.

Over the past couple of decades, as a new mathematical tool for addressing a number of tough problems, fractional calculus has been gaining a continually increasing interest in diverse scientific fields, including geotechnical engineering due primarily to geotechnical rheology phenomenon. Unlike the classical constitutive models in which simulation analysis gradually fails to meet the reasonable accuracy of requirement, the fractional derivative models have shown the merits of hereditary phenomena with long memory. Additionally, it is traced that the fractional derivative model is one of the most effective and accurate approaches to describe the rheology phenomenon. In relation to this, an overview aimed first at model structure and parameter determination in combination with application cases based on fractional calculus was provided. Furthermore, this review paper shed light on the practical application aspects of deformation analysis of circular tunnel, rheological settlement of subgrade, and relevant loess researches subjected to the achievements acquired in geotechnical engineering. Finally, concluding remarks and important future investigation directions were pointed out.

In the past few decades, as a new tool for analysis of the tough geotechnical problems, artificial neural networks (ANNs) have been successfully applied to address a number of engineering problems, including deformation due to tunnelling in various types of rock mass. Unlike the classical regression methods in which a certain form for the approximation function must be presumed, ANNs do not require the complex constitutive models. Additionally, it is traced that the ANN prediction system is one of the most effective ways to predict the rock mass deformation. Furthermore, it could be envisaged that ANNs would be more feasible for the dynamic prediction of displacements in tunnelling in the future, especially if ANN models are combined with other research methods. In this paper, we summarized the state-of-the-art and future research challenges of ANNs on the tunnel deformation prediction. And the application cases as well as the improvement of ANN models were also presented. The presented ANN models can serve as a benchmark for effective prediction of the tunnel deformation with characters of nonlinearity, high parallelism, fault tolerance, learning, and generalization capability.

The classical shell theory (CST) without considering the shear deformation has been commonly used in the calculation of shells structures recently. However, the impact of theory of plates and shells subjected to the shear deformation on the calculation is increasingly pronounced along with the wide use of composite laminated structures. In this paper, based on first-order shear deformation theory (FSDT) of cylindrical shells, the displacement control differential equation of moderately thick cylindrical shells has been obtained, so has been the edge force at longitudinal of the shells. Meanwhile, a group of unit force is introduced to deduce the displacement of edge beam under the action of edge force. A join condition of moderately thick cylindrical ribbed shells is established according to the continuity of displacement as well. Most notably, the displacement analytical solution of bending problems of moderately thick cylindrical ribbed shells is obtained, which has profound theoretical significance for further improving the analytical solution of moderately thick cylindrical shells.

Because of the particularity of the environment in the tunnel, the rational tunnel illumination system should be developed, so as to optimize the tunnel environment. Considering the high cost of traditional tunnel illumination system with high-pressure sodium (HPS) lamps as well as the effect of a single light source on tunnel entrance, the energy-saving illumination system with HPS lamps and LEDs combined illumination in road tunnel, which could make full use of these two kinds of lamps, was proposed. The wireless intelligent control system based on HPS lamps and LEDs combined illumination and microcontrol unit (MCU) Si1000 wireless communication technology was designed. And the remote monitoring, wireless communication, and PWM dimming module of this system were designed emphatically. Intensity detector and vehicle flow detector can be configured in wireless intelligent control system, which gather the information to the master control unit, and then the information is sent to the monitoring center through the Ethernet. The control strategies are got by the monitoring center according to the calculated results, and the control unit wirelessly sends parameters to lamps, which adjust the luminance of each segment of the tunnel and realize the wireless intelligent control of combined illumination in road tunnel.

Structural health assessment is one of the key activities in maintaining the performance of a tunnel during its service life. Due to the development of modern detection technology, comprehensive structural health assessment system is being established for operating tunnels. To evaluate the actual operational state of Shitigou tunnel, overall detection of the liner crack, tunnel seepage, and liner void was conducted by employing the modern detection technology, such as crack width monitoring technology, concrete strength monitoring technology, and electromagnetic wave nondestructive monitoring technology. Through the statistical analysis of the detection results, the distribution characteristic, development law, and damage grade of structural defects were obtained. Tunnel liner cracks are mainly located on the middle wall; serious water leakage is encountered on the side wall, middle wall, and vault; the strength of foundation and liner structure of left tunnel does not meet the design requirement; the liner voids are mostly located at the tunnel entrance section, especially, on the tunnel vault; and the proportion of influence factors of structural defects should be considered. The research results presented for this study can serve as references for effective design and health assessment of existing multiarch tunnel projects.

Compared with electrical strain gauges, fiber Bragg grating (FBG) sensing technology is a relatively novel method for tunnel structural health monitoring, which has a number of advantages including high accuracy, multiplexing, electromagnetic interference resistance, and good repeatability. In order to study the internal force of the tunnel liner and detect the potential safety hazards, series of strain monitoring tests of a loess tunnel, taking into account the complex stress and strain variation of the loess during tunnelling, were performed by employing the tandem linear FBG sensor arrays controlled by the wavelength division multiplexing (WDM) technology. The concrete strain has obvious linear characteristics over time in the early stage and then gradually tends to a stable value. Moreover, after the necessary temperature compensation, loess tunnel structure safety was assessed through the analysis of real-time strain and internal force of the liner concrete, and the FBG monitoring data and safety assessment results indicate that the safety factors of various liner sections all meet the code requirements, which verify the safety and stability of the tunnel liner structure. The FBG sensors-based in situ monitoring technology can be well applied in the loess tunnel structure safety assessment.

The performance of the ground treatment is always critical for a tunnel excavated in unstable stratum. Laodongnanlu Xiangjiang Tunnel (Changsha, China) across the Xiangjiang River will be constructed in a sandy gravel ground which is characterized by loose structure, extensive porosity, elevated sensitivity, poor stability, and a high groundwater table. Permeation grouting will be employed to improve the bearing capacity and mitigate groundwater movement into the excavation. In order to seek suitable injection parameters and grouting method, a field trial of vertical grouting was conducted in the sandy gravel stratum in river floodplain. A series of tests focusing on grout material, grouting sequence of boreholes, injection pressure, and grouting volume were performed to improve the sandy gravel mass strength and reduce water permeability. The examination of the results obtained during water pressure testing and core drilling on completion of the grouting trial successfully demonstrated that the specified injection criteria had led to an expected effect. Grouting control method of this saturated sandy gravel stratum was concluded after the test, which would contribute to the future pregrouting work during the tunnelling.