Drainage Tunnel Research Articles

A new-designed system for continuous measurement of radon in water

On-line continuous monitoring of radon concentration in water is of great significance for its environmental application as a radioactive tracer, for example, as a potential precursor for earthquake forecast and volcanic eruption. To realize on-line continuous measurement on radon in complex water body, a compact measurement system mainly consisted of a simple degassing device and an electrostatic radon monitor is newly developed. The sensitivity of the measurement system is 73 ± 5 cph/(Bq/L), and the detection limit is 0.04 Bq/L with a 60-min cycle at 25 °C water temperature. Intercomparison measurements with RAD H2O were performed both in laboratory condition and in field, and consistent results within the error range were achieved. To test the developed measurement system, a continuous monitoring of radon concentration in water in the drainage tunnel of Mount Jinping was performed for 3 months. The arithmetic mean of radon concentration in water is 0.34 ± 0.09 Bq/L, varying in the range of 0.04–0.60 Bq/L during the period. Several rapid decreases of radon concentration in water were observed, which might be attributed to the increase of rainwater mixing in the drainage tunnel caused by heavy rainfall. The stability of long-term operation of the system enables it to be widely used in the field of radon in water as a tracer.

CFD-DEM modeling of geotextile clogging in tunnel drainage systems

In this study, a coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) method we used to investigate the hydraulic deterioration of a geotextile due to clogging in tunnel drainage systems. Initially, a framework was developed to generate and test a numerical representation of a typical non-woven geotextile. Following model validation, we carried out parametric analysis to examine the effect of fine content, crack angle, and groundwater inflow. The results showed a general trend of pressure increase associated with increasing both the crack angle and fine content. This increase was found to decay at larger crack angles and high content of fines. Interestingly, increasing groundwater inflow was found to had minimal effect on the final deposition of the clogging particles. Finally, an approximate semi-analytical model was developed to describe the pressure increase due to clogging. The model was able to provide a good match with the data obtained from the numerical analysis.

A new sustainable energy based freeze proof method for drainage system in cold-region tunnels: A case study of Tianshan Shengli Tunnel

In order to solve frost damage problems in cold-region tunnels, a new sustainable energy based freeze proof method for tunnel drainage system is proposed. The method is applied to Tianshan Shengli Tunnel, China as a case study to show the concept and details of tunnel drainage system ground heat exchangers (GHEs) including calculation of active heating length and maximum heating load, design of heat extraction in cross tunnel, the segmented design method. Long-term performance of tunnel drainage system GHEs is also fully discussed. Multi-field simulations are performed to achieve corresponding thermal responses of the tunnel drainage system GHEs. Results show that anti-freezing measures provide an initial heating length 900 m of the drainage system at the entrance of Tianshan Shengli Tunnel during full life cycle. When the tunnel drainage system GHEs are employed, the heating length can be reduced to 600 m. Maximum total heating load of the tunnel drainage system in heating period is 84.40 kW. The calculation method of segmented heating load is suggested for precise prevention and control of frost damage in cold-region tunnels, owing to varying tunnel air temperature with the distance from the tunnel entrance. The use of boiler heating in winter will enhance the compensation between operation and recovery period and provides good long-term performance. This study provides a potential reference for antifreeze design of cold-region tunnels utilizing geothermal energy.

Influence of alternating electric field on crystallization of tunnel drainage pipes-based on indoor orthogonal test

The blocking of tunnel drainage pipe caused by crystals from groundwater calcification is prone to bring about lining cracking and water leakage. In this paper, in order to prevent tunnel drainage pipes from the crystallization, this study proposed a method to prevent the binding of Yin and Yang ions based on the alternating electric field. For the purpose of concluding the crystallization rules of drainage pipes and verifying the feasibility of this method, an indoor orthogonal test was adopted to study the crystallization rules and anti-crystallization efficiency of three drainage pipes under three alternating electric fields at three voltages (6 V, 9 V, 12 V) and at three flows (34.7 ml/s, 76.9 ml/s and 192.0 ml/s). The results showed that: During the test, all the three voltages can reduce the crystallization of drainage pipes, and the anti-crystallization efficiency of all the three tested pipes was optimal at 6 V under each of three alternating electric fields, reaching 22%, 25%, 7%, respectively. Case 2 had the best anti-crystallization effect at 6 V. The reason is that, at 6 V, the crystals had the loosest and minimum grains and the largest interplanar spacing, so they were inclined to be discharged through the pipe under the water flow. At 34.7 ml/s, Case 2 had the best anti-crystallization effect at 12 V; At 76.9 ml/s and 192.0 ml/s, Case 2 had the best anti-crystallization effect at 6 V. The alternating electric field can prevent the tunnel drainage pipe from crystallization and blocking, and different drainage pipes in the alternating electric fields should be selected based on according to the groundwater in tunnel.

Spatiotemporal Impact on Vegetation by Tunnel Discharging in the Jinping II Hydropower Station: Evidence From the NDVI and GPP Monitoring Dataset of 2001–2019

An impact on vegetation by tunnel discharging has been a critical point for underground constructions around the world. The Jinping II hydropower station in China possesses the world’s largest karst diversion tunnel group and discharged massive groundwater during the construction period. This study assessed the effects on vegetation in the karst and non-karst areas at different stages before construction (2001–2003, BC), during construction (2004–2014, DC), and after construction (2015–2019, AC) based on the Normalized Difference Vegetation Index (NDVI) and the gross primary productivity (GPP) dataset of the moderate resolution-imaging spectroradiometer (MODIS). The regional median results of the NDVI and GPP showed that the whole vegetation was little changed by massive tunnel drainage throughout BC, DC, and AC. The NDVI and GPP were locally decreased in the first 3 years, and then recovered to the original level within next several years. Notably, the NDVI and GPP of the karst area (20 and 50% in the total area) were decreased more significantly than those of the non-karst area (8 and 20% in the total area). The factors controlling vegetation change are the development of karst and fractures, which are the conduits of groundwater flow. Therefore, massive groundwater discharge is the primary influence leading to the vegetation deterioration in the Jinping II hydropower station. The research would provide a vital reference for vegetation protection of large-scale underground construction in the world.

Strainburst Control in Deep Tunnels Using a Slotted Excavation Method

Strainburst is the most common type of rockburst in deep excavations, which sometime result in heavy losses. This research studies the feasibility of a conceptualized destressing method for strainburst control. In this method, the rock is destressed by cutting slots at the excavation boundary. First, a circular tunnel is modeled and the stress distribution around the tunnel is calculated. In a separate model, a slot is added to the tunnel wall. Results show that when the slot is added to the model, the rock at the tunnel wall destresses, and the stress concentration zone transfers to a distance farther away from the wall. Also, the analysis of the failure zone around the tunnel and the velocities of the failed element nodes show that the failure in the slotted tunnel is less violent compared with the tunnel without the slot. Secondly, a parametric study is conducted to find the optimum dimensions of the slot. Finally, the rockburst damage in Jinping II drainage tunnel is simulated and then the application of the proposed destressing method for strainburst prevention in this tunnel is studied. Comparison of the modeling results with the field rockburst observations of the drainage tunnel shows that the proposed destressing method can be considered as a potential tool for strainburst control in deep excavations.

Influence of liquid accelerators on shotcrete in karst area tunnels

Tunnel constructions built in karst areas are liable to calcium leaching, which can lead to CaCO3 deposits in tunnel drainage pipes and water gutters, resulting in the blockage of tunnel drainage systems. This research aimed to analyze the influence of liquid accelerators on shotcrete in karst area tunnels. To achieve this, the present study investigated the influence of accelerator type and the karst water environment on the degradation behaviors of shotcrete. More specifically, the calcium leaching processes of hardened cement pastes incorporated with various liquid accelerators were analyzed, and the tunnel drainage system blockage mechanism was expounded in terms of shotcrete lining. The results showed that the compressive strength of shotcrete decreased most significantly in a karst water environment, while the mass of shotcrete decreased most significantly in a flowing water environment. The shotcrete combined with an aluminum sulfate-based alkali-free liquid accelerator performed best in the attack test, and its maximum compressive strength decreased by only 0.33%. The accelerator can change the composition and microstructure of cement hydration, thus altering the deterioration resistance of shotcrete. In terms of shotcrete lining, calcium leaching can increase the pH value and calcium ion concentration of groundwater, resulting in the formation and crystallization of CaCO3.

Development and Application of a New Reduction Coefficient of Water Pressure on Sub-Sea Tunnel Lining

Limited drainage tunnels face pore water pressure, water inflow, and permeability challenges. At present, there is little systematic analysis and research on the lining water pressure of sub-sea tunnels, and there is a lack of verification of relevant engineering examples and field monitoring data. Based on the numerical simulation method, this paper discusses the lining water pressure and its reduction coefficient of the horseshoe section tunnel, which is verified by an engineering example. Based on many numerical simulations, the recommended value of the water pressure reduction coefficient considering the thickness of the grouting ring and grouting effect is put forward. The stress law and safety of tunnel lining under different water reduction coefficients are studied, and the safety of lining is evaluated combined with the measured data of lining stress. The results show that the numerical simulation has been well verified. Considering the water pressure according to the water pressure reduction coefficient method proposed in this paper can ensure the structural safety of tunnel lining. The method of lining water pressure reduction coefficient proposed in this paper can provide a reference for the subsequent lining design of the sub-sea tunnel.

Calculation of the Allowable Drainage of Parallel Tunnels Based on Ecological Environment Protection

To determine a reasonable value of parallel tunnel drainage, a steady-flow calculation model is established. The differential equilibrium equation of seepage is established, and the equation of the falling funnel curve in a steady state with drainage parameters is solved by using boundary conditions. The maximum drawdown depth of the control point is used to calculate the allowable discharge of the tunnel. Then, the curve equation of the falling funnel is determined, the volume of the drainage funnel is calculated, and the total discharge in the steady state is calculated according to the water storage coefficient. Finally, the theoretical formula is verified based on an engineering case and numerical simulation. Considering the actual engineering geology and hydrogeological conditions of the tunnel site, the total drainage, allowable drainage, and initial support bearing head height calculated with the proposed method are different from the actual measurements collected on site by 10%, 18.9% and 13.6%, respectively. Therefore, the calculation method can provide a reference for similar engineering.

Governing beyond capacity

ABSTRACTHow are disasters made into routine, even banal parts of everyday life? In Mexico City the spatiality and temporality of disasters have become an object of dynamic governmental manipulation. The city's water engineers use a vast drainage tunnel system to strategically transform what would otherwise be catastrophic flooding of the city center into a slow‐moving, spatially diffuse, and ultimately routine environmental problem for the poor on the urban periphery. Furthermore, to prevent unrest, the engineers deliberately modulate flooding within the thresholds of what populations can perceive and bear. This technopolitical work, which I callcalibration, has emerged as a crucial means of governing beyond capacity, of maintaining social control even amid the unfolding of a disaster that has exceeded a government's capacity to prepare for or prevent. [disaster,government,engineering,infrastructure,flooding,water,space,temporality,Mexico]

Tunnelgeothermie – Ein Überblick

AbstractTunnel geothermal systems hold the potential to promote decarbonization of the building heating and cooling sector. They can be integrated into existing infrastructure, resulting in low additional costs. In addition, these systems have large contact areas with the ground leading to larger heat fluxes. However, tunnel geothermics is relatively unknown and rarely used. Thus, the objective of this study is to provide an overview of the two primary tunnel geothermal system types as well as their application and potential. Open hydrothermal systems use the tunnel drainage water as a heat source, whereas closed absorber systems harness the heat flux from the subsoil and the warm tunnel interior via heat exchangers. The evaluation of the global application of existing and planned tunnel geothermal systems shows that all open systems are currently located in mountainous regions with a thick rock overburden. In contrast, closed absorber systems are mostly installed in urban tunnel infrastructures. The spatial distribution of geothermal tunnel systems has a focus in central Europe with Switzerland, Germany and Austria being the countries with the highest number of installed systems. Finally, this study also presents a brief summary of existing methods to determine the geothermal potential of tunnels.

Mechanism and Application of Blasting Technology Using Phase-Difference Vibration Mitigation on Adjacent Railway Tunnel

The blasting vibration velocity is a widely used controlling index for the safety assessment of tunnel structures. How to reduce the impact of blasting vibration on the operation of adjacent railway tunnels is worth studying. In this paper, the initial phase-difference of blasting using phase-difference shock absorption is derived from the propagation theory of the blasting stress wave. When the initial phase-difference is Δφi = ±(2n + 1)π (n = 1, 2, 3, …), the peak particle velocity (PPV) in the tunnel structure is decreased to the minimum. On the basis of blasting theory using phase-difference shock absorption, the blasting parameters were designed for the No. 2 drainage tunnel excavated which adjacent a railway tunnel from Guiyang to Changsha, and it carried out 4 times blasting tests. It was found that the PPV of the railway tunnel structure in X, Y, and Z directions reduced by 64.6%, 66.25%, and 81.26%, respectively, which compared with the conventional blasting with the same total quality. Meanwhile, the amount of overbreak and underbreak can be controlled within 5%. The results show that the effect of blasting technology using phase-difference vibration mitigation is obvious, which is able to match with the design requirements for the tunnel excavation contour. The blasting technology using phase-difference vibration mitigation can be achieved via controlling the blasting time interval accurately. Moreover, it is beneficial for enriching and developing the blasting vibration control technology.

Stochastic modeling of groundwater drawdown response induced by tunnel drainage

Tunnel designers persistently experience issues regarding the impact of tunnel drainage on groundwater that can affect the safety of tunnels. From an environment-oriented approach, tunnel drainage affects the groundwater table and leads to alterations in the ecological environment in the long term. Accordingly, novel methods have been established to estimate drainage-induced drawdown concerning groundwater balance and environmental factors. However, the existing methods ignore the spatial characteristics of hydrogeological parameters and complex topography, leading to over-simplification of the groundwater flow; moreover, they lack a strategy to represent drawdown uncertainty. This paper presents a stochastic modeling method for inferring drainage-induced drawdown predictions conditional on tunnel inflow estimates. The method uses a numerical groundwater model to include the rock mass properties, fault zones, and complex topography of the tunnel area. The stochastic model processes the outcomes of the numerical model conditional on the absolute error of groundwater inflow based on Bayes' theorem. The contributions of the proposed method are as follows: (1) The method considers complex topography such as an inclined water table, fault zones, and rock type distribution. Accordingly, the groundwater simulation results indicate that the spatial distribution of rock types determines the magnitude of drawdown. Furthermore, the drawdown response was irregular and variable along the tunnel axis. (2) The Bayesian method allows the prediction of drawdown estimates with minimum data before tunnel construction with approximate drainage. The predictions can be updated using additional data during construction. (3) The application of the predictions is made flexible by arranging absolute error intervals, in which the decision-maker may consider the uncertainty of the parameters on the predicted solutions. The stochastic model was applied to a tunnel project in a poorly sampled ungauged mountainous catchment. The method provides information on parts of the tunnel that have the most significant potential impact with minimal input. The proposed method can be extended for long-term environmental impact assessment of tunnels by including surface features such as soil type, land use, and land cover.

Research on Seepage of Jointed Rock Mass of Tunnel and Limited Discharge of Grouting

In underground engineering such as tunnel engineering, the condition of surrounding rock such as water-containing jointed rock mass is a common engineering geology. For broken, water-containing surrounding rock, the reasonable measures to prevent and drain water has always been a key issue. Based on the statistical information of the structural surface of the surrounding rock of the Hongtuzhang tunnel, DIPS software was used to classify the structural plane of the tunnel. Based on the statistical analysis of the occurrence, size, and density of the structural plane, the two-dimensional structural plane network model of the rock mass was established, and the permeability tensor (K1 = 1.61 × 10−6 m/s, K2 = 5.78 × 10−7 m/s) was calculated. Consider the worst orientation, the permeability tensor (K1 = 1.61 × 10−6 m/s) was selected to calculate the grouting design. Based on the theory of limited discharge, the influence of parameters of permeability coefficient ratio n and thickness of grouting layer Tg on the tunnel water inflow and lining external water pressure was analyzed. The recommended value of tunnel drainage was 3.0 m3/m∙d, then the corresponding grouting circle parameters were put forward (permeability coefficient ratio n = 100, thickness of grouting layer Tg = 8 m).

Railway Alignment Optimization Based on Multiobjective Bi-Level Programming Considering Ecological Impact

Railway projects frequently pass through ecologically fragile regions and result in various ecological damages. The railway alignment determining the layout of structures plays an important role in ecological protection. This paper presents a railway alignment optimization model based on multiobjective bi-level programming (MBRAO). The upper level of MBRAO is a horizontal alignment optimization for the minimization of investment and ecological impacts from tunnel drainage and train noise. A multiobjective evolutionary algorithm based on decomposition (MOEA/D) solves the horizontal alignment optimization and naturally maintains population diversity. The lower level of MBRAO is a vertical alignment optimization for investment minimization. A self-adaptive differential evolution (DE) algorithm adjusting essential parameters based on optimization status solves the vertical alignment optimization efficiently. MBRAO is applied in multistage at both levels to find the suitable numbers of horizontal and vertical points of intersection. This paper introduces three kinds of vertical feature data generated corresponding to horizontal feature data to define different site modification costs on the bridge, subgrade, and tunnel structures. A real-world case study at Wolong Reserve is studied to verify the effectiveness of MBRAO based on a customized geographic information system (GIS).

Effect of a magnetic field on water crystallization in tunnel drainage pipes in karst areas

Effect of a magnetic field on water crystallization in tunnel drainage pipes in karst areas

Construction Safety Risk Assessment of Large-Sized Deep Drainage Tunnel Projects

Frequent extreme climate events and rapid global urbanization have amplified the occurrence of accidents such as waterlogging or the overflow of pollution in big cities. This has increased the application scenarios of large-sized deep drainage tunnel projects (LSDDTPs). The scientific and accurate evaluation of the construction safety risks of LSDDTP can effectively reduce the corresponding economic losses and casualties. In this paper, we employed the hierarchical holographic model to construct the safety risk list of LSDDTPs in terms of the risk source and construction unit. Based on social network analysis, we then screened key indicators and calculated the weights of all secondary indicators from the correlation between risk factors. We subsequently developed a construction safety risk assessment model of LSDDTPs based on the matter-element extension method. The Donghu Deep Tunnel Project in Wuhan, China, was selected as a case study for the proposed method. The results of empirical research demonstrated that eight indicators (e.g., failure to effectively detect the change of the surrounding environment of the tunnel project) were key factors affecting the construction safety risk of IV, which is within the acceptable risk level. Our proposed model outperformed other methods (the fuzzy comprehensive evaluation, analytic hierarchy process, entropy weight method, and comprehensive weight method) in terms of scientific validity and research advancements.

Laboratory Experimental Study on Influencing Factors of Drainage Pipe Crystallization in Highway Tunnel in Karst Area

The crystalline blockage of tunnel drainage pipes in a karst area seriously affects the normal operation of drainage system and buries hidden dangers for the normal operation of the tunnel. In order to obtain the influencing factors and laws of tunnel drainage pipe crystallization in a karst area, based on the field investigation of crystallization pipe plugging, the effects of groundwater velocity, drainage pipe diameter, drainage pipe material, and structure on the crystallization law of tunnel drainage pipe in karst area are studied by indoor model test. The results show that: (1) With the increase of drainage pipe diameter (20–32 mm), the crystallinity of drainage pipes first increases and then decreases. (2) With the increase of water velocity in the drainage pipe (22.0–63.5 cm·s−1), the crystallinity of the drainage pipes gradually decreases from 1.20 g to 0.70 g. (3) The crystallinity of existing material drainage pipe is: M3 (poly tetra fluoroethylene) > M2 (pentatricopeptide repeats) > M4 (high density polyethylene) > M1 (polyvinyl chloride); M8 (polyvinyl chloride + coil magnetic field) is used to change the crystallinity of drain pipe wall material. (4) When the groundwater flow rate is 34.5 cm·s−1, M1 (polyvinyl chloride) and M8 (polyvinyl chloride + coil magnetic field) can be selected for the tunnel drainage pipe. The research on the influencing factors of tunnel drainage pipe crystallization plugging fills a gap in the research of tunnel drainage pipe crystallization plugging. The research results can provide a basis for the prevention and treatment technology of tunnel drainage pipe crystallization plugging.

Roadkills of Lowland Tapir Tapirus terrestris (Mammalia: Perissodactyla: Tapiridae) in one of its last refuges in the Atlantic Forest

Highways limit the movement and dispersion of wild animals and contribute to their loss due to roadkills, leading to the isolation and decline of populations, increasing the risk of local extinction. The Lowland Tapir Tapirus terrestris is the largest neotropical herbivore-frugivore, and despite its wide distribution in South America it is threatened with extinction. In this study we report six roadkill events of tapirs between 2014 and 2019 in a section of a federal highway crossing the mosaic of Atlantic Forest reserves called Sooretama, one of the last tapir refuges in southeastern Brazil. The traffic in this area is heavy with inadequate speed control, while exotic fruit trees growing along the highway attract wild animals. Water drainage tunnels serve as passageways for some species, including tapirs. However, the tunnels located under the highway are not continuously maintained, reducing its effectiveness. The loss of at least one tapir per year can have serious long-term consequences for one of the last viable lowland tapir populations in the entire Atlantic Forest. Emergency measures are required to avoid vehicle-tapir collisions.

Water pressure evolution and structural failure characteristics of tunnel lining under hydrodynamic pressure

With the frequent occurrence of heavy rainfall, the lining cracking, leakage, and buckling collapse accidents of water-rich mountain tunnels are becoming increasingly prominent. A large amount of surface water rushing into the tunnel in a short time and exceeding the drainage capacity of the tunnel is an important reason for the occurrence of water pressure diseases. To ascertain the failure characteristics of the lining structure under the condition of surface rainfall recharge and tunnel drainage, we designed a seepage model test system. The evolution law of water pressure behind lining, vertical displacement of invert and failure characteristics of structure under water pressure were studied. On this basis, the influence of the optimized drainage tunnel structure on the water pressure of the lining was further studied. The results show that the water pressure of the lining invert cannot be effectively reduced through the drainage system when the conventional drainage scheme is adopted, and the invert deforms and gradually cracks and fails under the action of hydrodynamic pressure. The cracking sequence of the lining structure is the invert center, the sidewall foot, the vault, and the sidewall. The type of cracks is mainly longitudinal, supplemented by circumferential and oblique. When the optimized drainage scheme is adopted, the water pressure at the bottom of the invert and the uplift displacement of the structure are significantly reduced, ensuring the safety of the lining structure.