In the presence of heavy rainfall on the earth’s surface, a series of water-induced problems often appear in karst tunnels, such as lining cracks and invert uplift. An effective method of alleviating ...these problems is the adjustment of the tunnel drainage scheme. In this study, three waterproofing and drainage optimization schemes were studied using numerical simulation and model tests. Numerical results show that, when the conventional waterproofing and drainage scheme is adopted in water-rich karst tunnels, the water pressure at the tunnel invert cannot be effectively reduced by the drainage system. When the water head height of the tunnel crown is 50 m and the distance between circumferential drainage blind pipes is reduced from 5 to 2 m, the rate of water pressure reduction at the invert from 21 to 27%. When a longitudinal drainage blind pipe is added at the bottom of the invert, the rate of reduction is increased to 84%; however, it is increased to 96% when the central drainage ditch is set at the bottom of the invert. Therefore, placing the central drainage ditch at the bottom of the invert has the most significant effect on reducing the water pressure. Model test results indicate that when the water head height of the tunnel crown is 12 m, the reduction rates of water pressure at the invert corresponding to the placement of a central drainage ditch at the bottom of the invert are 66%. The model test results were found to be consistent with numerical results.
From a global perspective, karst geological disaster has great influence on the tunnel construction. Once it is not handled properly, the karst problems in the tunnel area will cause great disaster, ...such as water inrush, mud gushing and collapse, etc. These karst disasters seriously affect the construction progress of the tunnel, resulting in equipment damage, casualties, and so on. The construction of Yichang–Wanzhou (YW) railway tunnel has created a miracle in the field of Chinese tunneling. The geology of tunnel area is quite complex, the karst disaster is remarkable, and the engineering construction is extremely difficult. In this paper, the karst characteristics, unfavorable geological disasters, and treatment methods of YW railway tunnel were analyzed systematically. The YW railway tunnel and Zhengzhou–Wanzhou (ZW) railway tunnel are both located in the Qinling-Daba (QB) mountainous area, and the regional geological conditions of them are very similar. Therefore, the research in this paper can be extended to the QB mountainous area, thus providing a reference for the construction of ZW railway tunnel. The investigation can also provide reference for the similar engineering.
This Express Letter reports three methane explosion accidents during tunnel construction in Southwest China. In recent years, tunnel construction of China is developing rapidly. The geological ...conditions of the tunnel passing through are extremely complex, especially, tunnels in coal strata increase rapidly, what's worse, many methane explosions occur during the tunnel construction. The backgrounds, causes and rescue operation of three methane explosion accidents situation are studied. Furthermore, we proposed relevant measures to prevent methane explosions of tunnels.
Sandy soil liquefaction is common phenomena in engineering construction. However, in fact, saturated or nearly saturated loess liquefaction is also common phenomenon in loess area. In recent decades, ...large earthquakes around the world are frequent, loess is widely distributed worldwide, and loess liquefaction is one of the hot issues in loess dynamics. China has the most typical loess landform in the world, and Chinese scholars have done in-depth research on loess liquefaction. In this paper, the phenomena, mechanism, influencing factors, microscopic characteristics, evaluation methods and prevention methods of loess liquefaction in China are reviewed systematically. At the same time, improvement of loess saturation technology and new theory of loess liquefaction proposed by Chinese scholars are also analyzed. The results indicated that damages of foundations, landslides and collapses are the main phenomena of disasters caused by loess liquefaction; shear capacity of soil particles due to friction is close to zero during loess liquefaction; the main influencing factors of loess liquefaction are effective confining pressure, load frequency, cyclic stress ratio, saturation, over consolidation ratio; most of soluble salts have been dissolved, which is one of the main causes of loess liquefaction, and structure of loess particles has also been destroyed; evaluation methods of loess liquefaction mainly include the standard method and the Seed–Idriss simplified discriminant method; pore water pressure and strain conform to “A type curve” in loess liquefaction; pile foundation reinforcement, dynamic consolidation, chemical treatment are the main prevention methods of loess liquefaction.
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.
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.
A great concern for the safety of large cross-section tunnels, which are being or to be built in the loess strata of China, is attracted. Generally, loess is a multi-phase porous medium and develops ...complex stress and strain variation while executing a tunnel project. Another problem is that the soil surrounding both tunnel arches is subjected to a complex loading due to the double excavation. To obtain an in-depth knowledge of the mechanism of tunnel deformation induced by the twin-tunnelling, we conducted comprehensive centrifuge tests, which can simulate and reproduce strictly the action process of twin-tunnelling. Through the model tests, the response of twin-tunnelling on loess stratum deformation was obtained. The investigations showed that with the increase of tunnel spacing, the stratum deformation distribution near the vault changes from a single-peak V shape to a double-peak W shape. Additionally, the height of the stratum pressure arch effect increases significantly. The settlement of the preceding tunnel is slightly larger than that of the latter tunnel, and the twin-tunnelling effect gradually decreases with the increase of tunnel spacing. Through comparative analysis of the different combinations of tunnel spacing and tunnel interval, the interaction between two tunnels with different spacing and interval during tunnelling was investigated, further optimizing the reasonable tunnel spacing and construction steps, as well as providing reference for tunnel route selection in the loess strata.
The rapid development of high-speed railway tunnels has resulted in the increased application of ballastless track slabs. However, floor heave induces ballastless track slab deformation as a result ...of surrounding rock pressure, imposing serious challenges to the safety of railway systems. In this study, the characteristic of floor heave was analyzed based on field monitoring data. A new tunnel lining structure was then proposed to reduce the effect of floor heave on the slab track. The stress and deformation characteristics of the lining structure under different floor heave loads were analyzed through three-dimensional load structure numerical simulation, and the adaptability of the new tunnel lining structure was numerically studied. The results show that the floor heave typically occurred in the deep-buried sections of tunnel and the maximum floor heave was less than 50 mm during the operation of high-speed railway tunnels. When the new type of tunnel lining was adopted, the influence of the floor heave on the slab track was very small due to the reserved groove of the upper part of the invert and the high rigidity of the steel-reinforced concrete slab, thus effectively reducing the deformation of the tunnel floor heave. This research can be beneficial in the structural design of high-speed railway tunnels and the prevention of tunnel floor heave.
Building information modelling (BIM) can be applied to tunnel engineering to address a number of problems, including complex structure, extensive design, long construction cycle and increased ...security risks. To promote the development of tunnel engineering in China, this paper combines actual cases, including the Xingu mountain tunnel and the Shigu Mountain tunnel, to systematically analyse BIM applications in tunnel engineering in China. The results indicate that BIM technology in tunnel engineering is currently mainly applied during the design stage rather than during construction and operation stages. The application of BIM technology in tunnel engineering covers many problems, such as a lack of standards, incompatibility of different software, disorganized management, complex combination with GIS (Geographic Information System), low utilization rate and poor awareness. In this study, through summary of related research results and engineering cases, suggestions are introduced and an outlook for the BIM application in tunnel engineering in China is presented, which provides guidance for design optimization, construction standards and later operation maintenance.
The present study compared the expression of activity-regulated cytoskeleton-associated protein (ARC/Arg3.1) in the lateral geniculate body between form deprivation amblyopia kittens and normal ...kittens to examine the significance of ARC/Arg3.1 in the lateral geniculate body in the pathogenesis of amblyopia.
Twenty kittens were randomly divided into an experimental group (n = 10) and a control group (n = 10). Black opaque covering cloth was used to cover the right eye of kittens in the experimental group. Pattern visual evoked potentials (PVEP) were detected weekly in all kittens. The expression of the ARC/Arg3.1 gene was detected by immunohistochemistry and in situ hybridization, and apoptosis of lateral geniculate body cells was detected by TUNEL.
PVEP detection showed that at the age of 5 and 7 weeks, the latency of P100 in the right eye of the experimental group was higher than that of the other three groups (P < 0.05), and the amplitude of P100 was lower than that of the other three groups (P < 0.05). The expression of ARC/Arg3.1 protein (P < 0.05) and mRNA (P < 0.05) in the lateral geniculate body of the experimental group was significantly lower than that of the control group. The level of neuronal apoptosis in the experimental group was higher than that in the control group (P < 0.05). The expression of the ARC/Arg3.1 gene was negatively correlated with the apoptosis level of lateral geniculate body neurons.
The expression of ARC/Arg3.1 is associated with monocular form deprivation amblyopia and apoptosis of lateral geniculate body cells.
PDF
