Amount Of Water Flow Research Articles

Prediction of water inflow and analysis of surrounding rock stability in unfavorable geological mountain tunnel

During the construction of a mountain tunnel, water inflow and rock instability are common occurrences due to unfavorable geological conditions, posing serious threats to construction safety. This study focuses on a proposed mountain tunnel and employs multiple formulas to predict potential water inflow during excavation. Based on the amount of water inflow and deformation of surrounding rocks, comprehensive determinations are made for the thickness of grouting rings and permeability coefficients. The results demonstrate that: 1) Different formulas yield slightly varied outcomes but overall trends remain consistent; considering various calculations, the normal water inflow for this tunnel is approximately 115.5908×103 m3/d with a maximum at 210.9100×103 m3/d 2) Increasing grouting ring thickness or decreasing permeability coefficient can effectively reduce water inflow, but the reduction range is gradually narrowed. 3) Pre-grouting curtains have an evident effect in enhancing stability; however, their effectiveness decreases with increased thickness. 4) Taking into account both safety and economic factors, it is recommended that the grouting ring thickness be set at 8 m with a permeability coefficient equaling one 100th that of surrounding rocks for this tunnel project.

Case Study and Risk Assessment of Water Inrush Disaster in Qingdao Metro Line 4

Water inrush is one of the most frequent and catastrophic hazards in tunnel engineering, and poses serious threats to the safety of engineering and personnel. This paper presents a case study of a water inrush and ground collapse in the Qingdao Metro Line 4, which caused a cave-in with the diameter and depth of about 30 m and 6 m, respectively. Based on the field data and numerical modelling, the causes of the disaster were analyzed. A numerical model was used to analyze the changes of surface settlement, vault settlement and water pressure during the tunnel excavation. The results of the study indicate that the cause of this disaster was the failure of the tunnel vault surrounding rock caused by the weakening of the tunnel surrounding rock and water pressure, which in turn triggered the water inrush in the tunnel and caused a large volume of surface collapse. As the tunnel was excavated from the slightly weathered area to the strongly weathered area, the vault settlement increased, and the influence zone expanded towards the surface due to the continuous decrease in the strength of the surrounding rock. In particular, a negative pore water pressure zone was formed in a certain area around the tunnel during the water inrush. The negative pressure zone caused the surrounding groundwater to converge here, leading to an increase in the amount of water inflow, which also increased the scope and scale of the impact of this disaster. A risk assessment method for water inrush in tunnels is proposed. According to the geological and engineering characteristics of Qingdao area, the evaluation index system of tunnel water inrush risk was established. An RBF neural network was improved by gray correlation analysis and a PAM clustering algorithm to establish the tunnel water inrush risk assessment model. Comparing the evaluation data with the actual data, the prediction data of a traditional RBF neural network and a BP neural network, the accuracy and reliability of the model were verified. This study has value in reducing the occurrence of water inrush in a composite formation tunnel.

MICROHYDRO POWER PLANT FOR THE COMMUNITY

Micro Hydro Power Plant is an implementation of the green energy initiative, which is to encourage renewable energy. The Caturanom village area, Parakan District, Temanggung Regency, Central Java Province has a hydropower source that has not been maximally utilized. Meanwhile, electricity needs for integrated businesses, livestock, fisheries, agriculture, and waste processing require electricity supply. The research objective is to analyze micro hydro power plants that can be used for the operation of a sustainable integrated business. The research method begins with literature study, field study, designing, manufacturing, and testing its performance. The power of the water flow with the head and the amount of water flow has the potential to generate electricity with a cross flow turbine. The results of the research on the installation of micro hydro power plants with a working power of 8.1 [kWatt] with a head of 10 [m]; discharge 126 [liters/second]. Micro-hydro power plants are used to provide cheap and environmentally friendly electrical energy supplies to meet the operational needs, monitoring and control of Integrated Enterprises covering agriculture, animal husbandry, fisheries, and waste processing. The economic impact caused by the application of this micro-hydro power plant technology is that it is able to increase income, economy and welfare of integrated businesses through lowering production costs, increasing quantity, quality, and competitiveness of horticultural cultivation production. Meanwhile, the social impact caused by Integrated Enterprises and the surrounding community are becoming more concerned with the importance of renewable sources of electrical energy and technology for using clean, environmentally friendly, and sustainable energy.

Closed-form solution for determination of pore pressure field around horizontal wellbore

Wellbores are usually located in saturated geological layers. The determination of pore water pressure field around the wellbore is necessary during the design calculation and drilling stages. This paper presents analytical approach to determine the pore water pressure field around a horizontal wellbore at deep geological layer that exhibits heterogeneous, isotropic or transversely isotropic behavior. Thus, the wellbore is considered to be in an infinite medium. The pore water pressure at the well wall, equal to the drilling mud pressure, together with the pore water pressure at infinity is assumed to be constant. The closed-form solutions are based on the theory of fluid transport in porous medium and the conformal mapping technique of the complex variable method. The closed-form solutions are established with the condition of transient fluid flow for the case of isotropic medium and with the condition of steady state fluid flow for the case of transversely isotropic medium. The accuracy of the closed-form solutions is validated by numerical solutions based on the finite element method. The obtained solutions can be used as tools to determine quickly and accurately the pore pressure field around the horizontal wellbore, which serves to evaluate the stability of the well wall in preliminary design of the wellbore, as well as the amount of water inflow into it. Furthermore, the closed-form solutions are also considered as reference solutions to evaluate the accuracy and reliability of numerical models.

Research of characteristics of the flow part of an aerothermopressor for gas turbine intercooling air

Complex gas turbine schemes with air intercooling are usually used to bring the compression process of working fluid in compressor closer to isothermal one. A promising way to realize it is to use an aerothermopressor. The aerothermopressor is a two-phase jet apparatus, in which the highly dispersed liquid (water) is injected into the superheated gas (air) stream accelerated to the speed closed to the sound speed value (Mach number from 0.8 to 0.9). The air pressure at the aerothermopressor outlet (after diffuser) is higher than at the inlet due to instantaneous evaporation of highly dispersed liquid practically without friction losses in mixing chamber and with an increase in pressure of the mixed homogenous flow. The liquid evaporation is conducted by removing the heat from the air flow. In the course of the experimental research, the operation of the aerothermopressor for gas turbine intercooling air was simulated and its characteristics (hydraulic resistance coefficients, pressure increase, and air temperature) were determined. Within contact cooling of air in the aerothermopressor, the values of the total pressure increase in the aerothermopressor were from 1.02 to 1.04 (2–4%). Thus, the aerothermopressor use to provide contact evaporative cooling of cyclic air between the compressor stages will ensure not only compensation for pressure losses but also provides an increase in total air pressure with simultaneous cooling. Injection of liquid in a larger amount than is necessary for evaporation ensures a decrease in pressure losses in the flow path of the aerothermopressor by 15–20%. When the amount of water flow is more than 10–15%, the pressure loss becomes equal to the loss for the “dry” aerothermopressor, and with a further increase in the amount of injected liquid, they are exceeded. The values of errors in the relative increase of air pressure in the aerothermopressor measurements not exceeded 4%. The results obtained can be used in the practice of designing intercooling systems for gas turbines.

Result of the influence for center pivot irrigation machine operations on rain intensity

The impact of two parameters - the pressure regulator X1 at the nozzle and the speed of the machine X2 for the amount of water flow through the sprinkler (Y, mm) experiment were determined by 8 mm diameter nozzles. The experiment was carried out in the laboratory of “Design of Irrigation and Equipment” used by “Sprinkler’s uniformity distribution measuring equipment” at the School of Engineering and Technology of MULS. In order to determine the rain intensity of low pressure sprinkler nozzle, mathematical statistical methods was used and it was found that the maximum amount of water supplied by the sprinkler nozzle is 1.727 mm/min with a maximum pressure of 30 PSI and a minimum speed is 1 m / min with a minimum flow rate of 0.313 mm/min. At a pressure regulator value of 20 PSI, the speed was a maximum of 3 m/min.

IMPROVING THE METHOD OF DETERMINING THE VALUE OF WATER LEVELS IN VERTICAL WELLS OF GROUP WATER COLLECTION

Purpose. Reconstruction of water supply systems to meet the increased water needs of consumers is a complex, time-consuming and expensive task. Reconstruction options include expanding existing water intakes or building new ones anywhere in the existing water supply network. The variety of options is accompanied by changes in water consumption in the sections of the networks and, importantly, in the flow distribution. The introduction of additional sources into the existing water supply systems requires a detailed study of the factors affecting the technical characteristics of the systems and responsible for the economic component of the project. Methodology. The influence of the determining factors on the total head losses in the water distribution network during the reconstruction of the water supply system is analyzed. An algorithm for finding the optimal network points for connecting an additional power source is proposed, which includes determining the optimal flow distribution and the corresponding technical changes for each selected option; total capacity of pumping stations and heads; analysis of the complete set of the water supply system of the accepted options; an economic analysis of the construction investment and operating costs that will accompany the operation of the water supply system design options. Findings. The choice of the optimal connection points for additional power sources depends on the amount of water flow in the network sections and the flow distribution. It is shown that the nodes of the end sections of the network most correspond to the conditions for searching for optimal points and can be fed from different directions, depending on the amount of additional flow. With an additional water flow rate no more than two nodal flow rates, the total head losses in the network sections are minimal. When an additional flow rate of more than two nodal flows enters the final node, an increase in head losses is observed, which can have critical values depending on its increase. The introduction of additional water flows into the network, which exceed two nodal ones, requires the use of intermediate network nodes located at sections with a higher throughput as connection points. Originality. The analysis of the factors influencing the choice of points of connection of additional power sources of the water supply network during its expansion is carried out. The analysis of the points was carried out with limited ranges of the values of water consumption of additional feeding − less and equal to the nodal ones, two and three times larger than the nodal ones. The ways of finding the optimal option for choosing a network node as a point of connection of additional power are shown. Practical value. The use of the analysis results will make it possible to most effectively search for the optimal variant of reconstruction of water supply systems, take into account the influence of determining factors on the characteristics of networks with changes in water consumption and flow distribution. The use of the analysis results will make it possible to most effectively search for the optimal variant of reconstruction of water supply systems, take into account the influence of determining factors on the characteristics of networks with changes in water consumption and flow distribution.

Influence of Segmented Rolls on Homogeneity of Cooling in Continuous Casting

This paper deals with secondary cooling in a continuous caster. In particular, it deals with cooling inhomogeneity caused by spray arrangement and segmented rolls used for leading the strand. The cooling section is placed under the mold. Segmented rolls are supported by bearings in several places across the strand. Sprayed water can flow in the gaps between rolls where the bearing pocket is located. The main question that was experimentally studied is how this geometry with segmented rolls can influence homogeneity of cooling. Two experimental approaches developed for this study were applied, and both used full-scale geometrical configuration. The first one was a cold test where water flow and water distribution were observed using a transparent board with the studied surface structures (rollers and bearing pockets) and four spraying nozzles. The second one was a cooling test using a heated steel plate with rolls and bearing pockets. Cooling homogeneity was studied based on the temperature distribution on the rear side of the sample, which was recorded using an infrared camera. Homogeneity of cooling distribution was experimentally studied for three levels of cooling intensity that are used in typical cooling sections in plants. The hot tests showed that the bearing pockets do not provide significant cooling inhomogeneity despite the fact that a large amount of water flows through the gap between the rollers (which has been observed in cold tests).

Changes of water exchange cycle in Lake Taihu (1986-2018) and its effect on the spatial pattern of water quality

针对太湖水体交换周期近十余年发生的变化，本文收集整理了1986—2018年太湖水文巡测、汛期水文巡测数据以及太湖流域沿江城市引水量、流域降雨量变化数据，基于太湖出入湖水量的变化研究了太湖水体交换周期的变化及原因，并对交换周期变化对水质空间格局的影响进行分析.结果表明：太湖入湖水量有显著上升，2007年以来平均每年入湖水量增长30.8亿m³/a.水体交换周期显著下降，2007年以后约为184 d，相比2007年前下降了26 d.太湖流域及各水利分区近70年来，除去2015和2016年，降雨量无显著变化，主要入湖区下垫面变化造成的入湖水量增加估算在每年2.0 m³左右.太湖入湖水量增加主要集中在湖西区，与沿江口门引水量明显相关.相比2007年前，沿江口门引水量年均增长28.9亿m³/a，而这期间太湖入湖水量增量与这一引水有关.入湖水量的增加开始影响太湖存在的“西浊东清”水质结构，水体交换周期缩短会使东西太湖水质出现均化的现象，东部太湖水质会出现下降的趋势.;In view of the changes of Lake Taihu water exchange cycle in recent ten years, this paper collected and sorted out the hydrological survey data of Lake Taihu from 1986 to 2018, the water diversion quantity change of cities along the Yangtze River in Taihu Basin, rainfall change data of the basin, studied the changes and reasons of Lake Taihu water exchange cycle based on the changes of water inflow and outflow in Lake Taihu, and analyzed the effect of the change of water exchange cycle on water quality spatial pattern. The results show that the inflow of Lake Taihu has increased significantly, with an average annual inflow of 3.08 billion m³/a from 2007. The water exchange cycle has dropped significantly. It is about 184 days after 2007, which is 26 days lower than that before 2007. Over the past 70 years in the Taihu Basin and various water conservancy divisions, except for 2015 and 2016, there has been no significant change in rainfall. The increase in the amount of water inflow into Lake Taihu caused by changes in the underlying surface of the main lake inflow area is estimated to be about 2.0 m³/a. The increase of water inflow into Lake Taihu is mainly concentrated in the west of Lake Taihu, which is obviously related to the water diversion along the Yangtze River. Compared with that before 2007, the water diversion volume along the Yangtze River has increased by 2.89 billion m³ on annual average, and the increase in the amount of water inflow into Lake Taihu during this period is related to this diversion. The increase of water inflow into Lake Taihu began to affect the water quality structure of “Turbid in the West and Clear in the East”. The shortening of the water exchange cycle will homogenize the water quality of east and west Lake Taihu, and the water quality of the east Lake Taihu will show a downward trend.

A novel analytical method incorporating valve pressure for the controlled drainage of transport tunnels

A novel drainage method using pressure valves to regulate the water pressure acting on the support system of transport tunnels is proposed in order to reduce water inflow and protect the local groundwater environment as much as possible. A complete analytical solution to the problem is further derived to assess the water pressure borne by the support system (assuming pressure valves are installed in the side ditches of the tunnel). No assumptions need to be made about the water penetrating the lining. Under this premise, the amount of water inflow is balanced by the water pressure acting on the tunnel lining to ensure the safety of the lining. To restrict the water inflow to the maximum amount allowed, using our novel drainage method allows the thickness of the grouted zone to be significantly reduced compared to conventional methods and, therefore, reduces costs and speeds up the construction process. Results predicted using our analytical solution are in excellent agreement with those derived via field monitoring and numerical (finite element) modeling. The relative errors are less than 0.15%, suggesting that our analytical solution is a reliable way of assessing the seepage expected in our novel drainage system.

Analisis Ketersediaan Air DAS Sausu Untuk Kebutuhan Air Pada D.I. Sausu Bawah, Kabupaten Parigi Moutong

This study aims to grasp and analyze the water availability in Sausu Watershed and the need of water in Lower Sausu Irrigation Scheme. The research begins with data collection and hydro-climatological analysis to determine whether the water is enough or not enough to be used during a hydrological period. To obtain the comparison between the needs and availability of water, a hydro-climatological analysis and calculation of water need are carried out. Methods that used namely the Penman Modification method and the F.J Mock method. Penman modification method is used to calculate monthly evapotranspiration (ETo) by taking into account climatological factors such as air temperature, wind speed, solar radiation and relative humidity. By applying the F.J.Mock method for calculating the water availability, the amount of water flow from the rain, characteristics of the drainage area and evapotranspiration can be calculated. Based on the results of data analysis for Sausu watershed area of 568.64 km², it shows that the average value of water availability in the lower intake for 1 year is app. 30.19 m³/sec with the maximum value of app. 48.149 m3/sec and the minimum is app. 4.134 m3/sec. Whereas the maximum water demand in the Lower Sausu irrigation scheme is app. 1.77 m³/sec with the minimum of 0.04 m3 /sec and the average is app. 0.49 m3/sec. It can be concluded that the water availability in the Sausu River Basin is sufficient to meet the water needs of the Lower Sausu Irrigation Scheme throughout the year, or there is a continuous surplus.

Substantiation of rational relationships of main parameters of the rock washing-out process when applying GD-300 hydraulic monitors at Kuzbass open pits

The need to use hydraulic technology for washing out quaternary bedrock, as well as heterogeneous rocks previously piled in hydraulic-mine dumps located above commercial coal reserves, requires the use of modern high-performance equipment. As such equipment, it is advisable to use the new GD-300 hydraulic mining giants – monitors, which are designed, manufactured and tested at Kuzbass open pits. In order to increase the performance of hydraulic monitors at Kuzbass open pits, the following dependencies are determined in the article: changes in the amount of water flow through the hydraulic monitors on the nozzle diameter and the pressure in front of it; changes in the amount of solid rock washed out by the hydraulic monitor ‒ solid flow on the nozzle diameter at various values of the pressure in front of it; changes in the solid flow on the pressure in front of the nozzle.

Coupling the water-energy-food-ecology nexus into a Bayesian network for water resources analysis and management in the Syr Darya River basin

The widespread uncertainty regarding future changes in climate, socioeconomic conditions, and population growth have increased interest in water-energy-food-ecology nexus-based frameworks in relation to the analysis of water resources. A challenge for modeling the water-energy-food-ecology nexus is how to reduce the multidimensional and codependent uncertainties and measure the complicated casual relationships effectively. We propose a methodological solution to the problem, and this solution is demonstrated in this case as an extension to the previous water resource optimization framework. We coupled the water-energy-food-ecology nexus into the Bayesian network, which provides a formal representation of the joint probabilistic behavior of the system, and the method was applied to water resource use analysis and management in the Syr Darya River basin, a transboundary and endorheic basin that has contributed to the Aral Sea ecological crisis as a result of unreasonable water use. The annual scale data of four periods, 1970–1980, 1980–1991, 1991–2005, and 2005–2015, were introduced into the Bayesian network. Before the disintegration of the Soviet Union, the amount of water inflow into the Aral Sea was sensitive to increases in irrigation for agricultural development, increases in water storage of the upstream reservoirs and stochastic runoff. After the disintegration of the Soviet Union, the amount of water inflow into the Aral Sea was sensitive to the inefficient irrigation water use in the downstream areas of Uzbekistan and Kazakhstan and the water storage of the reservoir located upstream of Kyrgyzstan. The change resulted from unresolvable disputes between water use for power generation in the upstream area and irrigation in the downstream area. Comprehensive scenario analysis shows that, in the short term, it would be useful to improve the proportion of food crops, improve the efficiency of water use in relation to salt leaching and irrigation, and prevent drought damage. In the long term, based on the increased use of advanced drip irrigation technology from 50% to 80%, the annual inflow into the Aral Sea will increase significantly, reaching 6.4 km3 and 9.6 km3, respectively, and this technology is capable of ameliorating the ecological crisis within the basin.

Development of Simulink Model to Investigate Control Structure, Safety, and Stability of a Water Brake System at Main Engine in House 5 Laboratory: Warnemünde

A water brake loads the diesel engine will set desired work points and work curves. So that can find a safe point and control safety. After this, the essential system component will be created the model in block diagram and the block diagram will be simulated with Simulink. This requires a model of combustion machine and its control as well as break system and its control. The valve angle also affects the amount of flow or discharge of water which resides in the brake system. The amount of water flow in the brake system affects the amount of load that will be accepted by the main engine. The model is to be validated with measured data. To define load characteristics for a parallel operating visualization, these load characteristics are to be simulated. The results of the modeling were to know PI controller parameters to control the main engine. In the investigation, then simplify the process of modeling results are displayed in the form of a curve. Where in the curve we can see the performance of the engine and brake system so that the operation of the main engine will get maximum condition within safe limits.

Особенности многолетней динамики гидрохимических показателей водохранилищ Нижней Волги и реки Урал (на примере Саратовского, Волгоградского и Ириклинского водохранилищ)

The article considers the long-term dynamics of organic matter, biogenic and toxic elements in the reservoirs of the Lower Volga (Saratov and Volgograd) and the Ural River (Iriklinskoe), differing in geographical location, morphometric and hydrological characteristics. In the Ural reservoir, in contrast to the Lower Volga reservoirs, lower concentrations of mineral nitrogen, silicon, as well as indicators characterizing allochtonic organic matter, and a higher level of total and easily oxidable organic matter are recorded. There are differences in the seasonal and spatial dynamics of the ingredients. Despite the differences in the hydrochemical regime of the reservoirs under study, the synchronicity of the main indicators characterizing the trophic status of the aquatic ecosystem (total, easily oxidable and allochthonic organic matter, and nitrate nitrogen), as well as the amount of water flow through the corresponding hydroelectric facilities was revealed. Studies of the structure of a multidimensional array of general hydro/chemical indicators by the method of principal components revealed the universality of the processes occurring in reservoir ecosystems, the basis of which is surface runoff and seasonal changes.

Analytical solution for the limiting drainage of a mountain tunnel based on area-well theory

Water seepage from a tunnel may induce the drawdown of the groundwater table and destroy vegetation and the ecological environment in the tunnel area. One of the primary objectives in tunnel engineering is to develop effective methods to estimate the amount of the limiting drainage of a mountain tunnel. Based on the area-well theory, a groundwater seepage model of a tunnel is established. Due to the model and groundwater dynamics, the equation describing the relationship between the amount of water inflow and drawdown of the groundwater table for a tunnel is derived under unsteady flow conditions. After the ecological groundwater table for vegetation is introduced, a method of calculating the amount of the limiting drainage for a mountain tunnel is proposed to prevent the drawdown of groundwater table from exceeding the ecological groundwater table required to support vegetation. According to the proposed method, the three-dimensional form of the groundwater drawdown funnels and the influence scope of tunnel water inflow are determined. The rainfall recharge amount Wt within the influence scope is obtained based on the rainfall infiltration coefficient method, and the value is compared to the total groundwater discharge Q. These values Wt and Q are then equated through adjusting the unit groundwater inflow q0. The values less than or equal to q0 can be determined as the limiting drainage value of groundwater for the tunnel, and the groundwater table will not drop and balances the groundwater and the vegetation ecological environment. The results and case study show that the proposed method exhibits good agreement with actual conditions and is suitable for use in tunnel construction.

Prediction of Water Inflow in Subsea Tunnels under Blasting Vibration

The subsea tunnel of Qingdao metro line 1 has been excavated using the drill and blast method. Blasting vibration during tunneling may cause larger water inflow and even severe security risks and considerable economic losses. However, the prediction of water inflow in subsea tunnels under blasting vibration still remains a challenging problem. Thus, this paper proposes an approach combining tests and numerical calculations for analyzing this problem. The approach is developed by analyzing the mechanical and deformation characteristics of the surrounding rock through a laboratory triaxial compression test and then establishing the strain softening constitutive model of the surrounding rock. Based on the elastic compression theory of porous media and the cubic law of fractured rock mass, we establish and analyze the evolution model of the permeability characteristics during the damage process of the surrounding rock. Then, a Fast Lagrangian Analysis of Continua in 3 Dimensions (FLAC3D) is used to verify the rationality and accuracy of the model. According to the actual blasting design scheme, the surrounding rock constitutive model, and the permeability characteristic evolution model, the blasting process and water inflow of the subsea tunnel is simulated. The amount of water inflow in the subsea tunnel calculated by using the permeability coefficient under blasting vibration (PCuBV) is compared with the measured water inflow and the amount of water inflow calculated by using the exploration permeability coefficient (EPC) and the initial permeability coefficient (IPC) of the surrounding rock. The results show that the prediction of water inflow quantity under blasting vibration is both closer to reality and more reasonable than existing models.

The Novel Design to Prevent a Water Meter Damage from Freezing Using Bellows Tube

Water meters are widely used to monitor and measure the amount of water flow. However, most of them experience blockage or breakage in winter. These detrimental effects are attributed to increasing volume and pressure inside applications by phase transition from water to ice. As a result, it is required to replace or repair water meters every winter with additional cost and time. In order to avoid damage and reduce a burden with these problems, new type of water meter should be developed. Therefore, this study proposes renovated structure adopting bellows tube to protect damages from freezing with cost effective way and analyzes its impacts by means of finite element analysis (FEA). Compared to the general water meter, the revised structure has superior ability to absorbing increased pressure and volume by phase change as expanding volume of bellow tube in longitudinal direction. In addition, optimal dimensional parameters of bellows tube are derived using multi objective genetic algorithm (MOGA).

Water inflow forecasting for tunnel considering nonlinear variation of permeability coefficient

To assess the water inflow which is more suitable to the actual conditions of tunnel, an empirical correlation about the permeability coefficient changing with depth is introduced. Supposing that the surrounding rock is heterogeneous isotropy, the formula for calculating water inflow of tunnel with the nonlinear variation of permeability coefficient is deduced. By the contrast analysis with the existing formulas, the presented method has the similar value to them; moreover, the presented method has more simple form and easy to use. Due to parameter analysis, the water inflow decreases after considering the nonlinear variation of permeability coefficient. When the attenuation coefficient a>0, the water inflow increases first till reaches the maximum at a certain depth, then decreases and is close to 0 finally if deep enough. Thus, it is better to keep away from the certain depth where it is with the maximum water inflow for safe operation and economical construction, and reduce the water damage. Based on the analysis, the radius of tunnel has less impact on the amount of water inflow, and the water inflow just increases by 6.7% when the radius of tunnel increases by 1 m.

A method to estimate concrete hydraulic conductivity of underground tunnel to assess lining degradation

The determination of the degradation state of underground concrete tunnels is a crucial issue for maintaining and monitoring the performance of these infrastructures. In particular, if the tunnel is totally or partially submerged, concrete deterioration and consequent changes in both lining thickness and hydraulic conductivity can have dramatic effects on the amount of water inflow, leading to an increase in maintenance costs as well as to possible interruption of the infrastructure serviceability. The hydraulic conductivity of the concrete lining is here proposed as a proxy of the overall degradation state of the structure, being this property directly correlated to porosity and to the presence of interconnected fissures and cracks.The aim of this study is to propose a simple and completely non-destructive method to estimate the hydraulic conductivity of tunnel lining concrete. Provided the availability of easy-to-collect in situ geometrical and hydrogeological data (i.e. tunnel geometry, water inflow, water table level), the method relies on a back analysis to estimate the hydraulic conductivity of the concrete, performed via the finite element method to solve the seepage equations in porous media. Ground Penetration Radar technique is coupled to the modelling approach to gain accurate data about the current lining thickness.The proposed method has been applied to the study of a real case of underground tunnel, used to prove the model reliability. Moreover, once estimated the hydraulic conductivity and thickness of the concrete, the model can be used to generate curves linking the total water inflow in the tunnel as a function of the groundwater level variations, allowing a real-time monitoring of the current hydraulic state of the infrastructure.This methodology, which can be considered of general validity and easy to be extended for the study of any underground tunnel, provides a simple and effective tool useful to prioritize maintenance works and to evaluate the consequences of different hydraulic scenarios.