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Water Ingress Assessment for Rock Tunnels: A Tool for Risk Planning
Abstract
There are four classical analytical methods being used to estimate water inflow into tunnels. These are Goodman method, Heuer and Raymer method, Heuer Analytical method, and IMS method. Geological data, ground and groundwater information, and permeability data were collected along and in the vicinity of the tunnel alignment in order to prepare a geological longitudinal section together with a rock quality assessment along the tunnel. Rockmass permeability histogram chart, rock mass quality versus permeability chart, were prepared. Water inflow to the tunnel was estimated using the above methods together with the available information of geology, rock quality, rockmass permeability and water table. Potential high water inflow zone was identified of the tunnel to propose additional ground investigation works and probe drill during tunnel construction. Based on the assessment results, early risk planning should be carried out to ensure that the tunnel construction works are proceed in a safe manner, particularly for high water inflow sections of the tunnel.
... Many engineering activities involve tunnels, where water inflow is a challenging issue during the whole process of design, construction and operation (Chen et al., 2020;Kaufmann and Romanov, 2020;Kong, 2011;Nikvar Hassani et al., 2018). Overestimating water inflow into a tunnel leads to an overconservative design of the drainage system (Zhang et al., 2020c), while an underestimate would lead to serious geological disasters, such as mechanical instability (Bizjak and Petkovsek, 2004;Zhang et al., 2015) and mud and water inrush (Li et al., 2017), as well as secondary destruction of the ecological environment (Cheng et al., 2019a;Preisig et al., 2014). ...
... Despite the flexibility of the simulation method, the analytical method cannot be fully replaced by the simulation method. This is not only because the simulation method needs good knowledge of the hydrogeological setting (Perrochet, 2005) but also because the prediction of water inflow into a tunnel must be efficient in case of emergency (Kong, 2011;. Time-consuming simulation modeling is obviously impractical when water inrush accidents occur, and a fast estimation of water inflow for treatment decisions needs to be conducted. ...
Water inflow into a tunnel is usually estimated by assuming that the flow follows the linear Darcy’s law. However, fluid flow in fractured-rock aquifers is prone to deviation from Darcy’s law and gives rise to nonlinear flow phenomena due to significant inertial losses. This non-Darcian effect is seldom considered when evaluating water inflow into the tunnel in a fractured-rock aquifer. In this study, we investigated an analytical method for predicting water inflow into a tunnel considering the non-Darcian effect. A series of numerical simulations for water inflow into a tunnel were conducted with different combinations of parameters, where non-Darcian flow was considered and characterized by the Forchheimer’s law. Based on the numerical results and an ingenious parameter integration method, a semi-empirical model was developed to analytically predict water inflow into a tunnel where the flow is under non-Darcian flow regime. The semi-empirical model includes the classic theoretical formula for predicting water inflow and the Forchheimer equation for describing non-Darcian flow. In this context, the non-Darcian effect on water inflow into a tunnel can be quantitatively estimated. This developed model has a concise expression satisfying dimensional consistency with the parameters having sound physical meaning, and it can be successfully reduced to the classic formula under the Darcy flow regime. The validity of this semi-empirical model was confirmed by numerical results, showing a high fidelity in predicting water inflow into a tunnel. By means of this proposed model, the error induced by neglecting non-Darcian effect was estimated for a large number of real engineering cases, which rapidly increased as a power function with the magnitude of water inflow into the tunnel. The necessity of considering the non-Darcian effect when calculating water inflow was thus proven, especially for massive tunnel gushing. The proposed model and the method used in this study can provide guidance for accurately predicting water inflow into a tunnel under a complex non-Darcian flow regime.
... Most of the employed methods and approaches make assumptions which do not fully reflect the real situations of the rocky areas in which tunnels are built. 89 This allows the application of Darcy's law and the establishment of many analytical, semi-analytical, empirical and semi-empirical equations. In reality, in heterogeneous rocky environments, Darcy's law should not be used. ...
Groundwater inflow into tunnels is always a salient topic in Hydrology, Hydraulic Engineering, Hydrogeology, Rock Engineering and allied sciences. In fact, tunnels particularly built below the groundwater table, often face groundwater inflows during their excavation, and even sometimes after they are put into operation. These inflows, habitually regarded as unpredictable geological hazards, cause instabilities in the surrounding rocks of tunnels, and lead to considerable damages such as injuries, loss of lives, and huge-scaled economic expenses. It is argued that groundwater conditions are of decisive significance for the design and running of tunnels. Therefore, accurate prediction or evaluation of groundwater inflows into tunnels is of paramount importance. Such prediction, although it is still challenging, has been broached by many researchers with diverse methods. However, a state-of-the-art review of these methods has not yet been presented. This paper reviews the assessment methods of groundwater inflows into tunnels built in rocky media. The results mainly include analytical, semi-analytical, empirical, semi-empirical, numerical, machine learning, and other methods used in the field. This was made possible by selecting and analysing relevant scientific articles published by various worldwide Journals. In addition, some recommendations and future trends are pointed out. This paper can provide useful references in understanding groundwater inflows prediction in different points of view and their limits in terms of applicability and accuracy.
... In rock mechanics, groundwater level (GWL) or the water table is included for the purpose of tunneling (Goodman et al. 1965;Moon and Fernandez 2010;Kong 2011;Farhadian and Katibeh 2017). Bearing capacity solutions in rock masses have been classically based on empirical solutions (Bishoni 1968;Carter and Kulhawy 1988;Goodman 1989;Bowles 1996) and highly influenced by local conditions and the characteristics of the tests. ...
... In rock mechanics, groundwater level (GWL) or the water table is included for the purpose of tunneling (Goodman et al. 1965;Moon and Fernandez 2010;Kong 2011;Farhadian and Katibeh 2017). Bearing capacity solutions in rock masses have been classically based on empirical solutions (Bishoni 1968;Carter and Kulhawy 1988;Goodman 1989;Bowles 1996) and highly influenced by local conditions and the characteristics of the tests. ...
The presence of the groundwater level (GWL) at the rock mass may significantly affect the mechanical behavior, and consequently the bearing capacity. The water particularly modifies two aspects that influence the bearing capacity: the submerged unit weight and the overall geotechnical quality of the rock mass, because water circulation tends to clean and open the joints. This paper is a study of the influence groundwater level has on the ultimate bearing capacity of shallow foundations on the rock mass. The calculations were developed using the finite difference method. The numerical results included three possible locations of groundwater level: at the foundation level, at a depth equal to a quarter of the footing width from the foundation level, and inexistent location. The analysis was based on a sensitivity study with four parameters: foundation width, rock mass type ( m i ), uniaxial compressive strength, and geological strength index. Included in the analysis was the influence of the self-weight of the material on the bearing capacity and the critical depth where the GWL no longer affected the bearing capacity. Finally, a simple approximation of the solution estimated in this study is suggested for practical purposes.
... Additionally, several geological assessment models were developed to assess the risk of water inrush hazards (e.g. Kong, 2011;Meng et al., 2012;Li et al., 2018a). Wu et al. (2015) proposed the "three maps-two predictions" method to evaluate the water inrush risk, where "connectivity zoning map", "water abundance zoning map" and "comprehensive zoning map" were used to predict the "discharge component not related to mining" and "mine discharge under mining conditions". ...
Water and mud inrush is one of the most important geohazards in underground engineering. The paper presents a state-of-the-art review of the current understanding of this type of geohazard. Emphasis is placed on recorded the geneses and evolution processes of water and mud inrush, as well as relevant prevention methods. In particular, the geneses of this inrush hazard are initially discussed, by providing hazard cases during the past several decades. This is followed by a review of the various forming processes and corresponding research methods (including theoretical, numerical, experimental methods) for water and mud inrush, which can be used to pave the ways for hazard prevention and future research. Subsequently, the paper provides a summary of relevant hazard prevention methods employed by academics and practitioners, followed by a short discussion on the achievements and limitations of each method. Throughout the presentation, the current overall gaps in understanding water and mud inrush hazards are identified in an attempt to stimulate further research in these promising directions by the research community.
... Therefore, these methods might overestimate or underestimate the amount of groundwater inflow into the tunnel due to the geological complexities and the aforementioned assumptions. Farhadian et al. [33] and Kong [34] have proved that where (1) the water flows around the tunnel are not radial, (2) the rock mass contains variant bedding around the perimeter of the tunnel, and (3) the estimated permeability coefficient of the rock mass is imprecise, analytical evaluation of the groundwater inflow into the tunnel will not be reliable. Table 2 illustrates the analytical solution given by several researchers. ...
The main objective of this study is to estimate the amount of groundwater inflow into the Dorud-Khorramabad railway tunnel. To this end, in the first place, existing approaches of predicting groundwater inflow into the tunnel were reviewed. According to the literature, up to now, a wide range of approaches have been proposed in order to predict the groundwater inflow into the tunnel which can be classified into three distinct groups including analytical solutions, empirical equations, and numerical modeling. Analytical solution and empirical equations are mainly developed based on the given hypotheses and specific data sets, respectively, and should be applied just in similar conditions. On the other hand, results obtained from numerical modeling are generally dependent on a wide range of parameters. Literature review revealed that one of the most effective parameters on the numerical modeling results is the model extent which not only controls final results but also affects numerical runtime. Hence, a sensitivity analysis is performed in order to investigate the effect of model extent on numerical results. The results demonstrated that increasing model extent is along with decreasing the groundwater inflow rate and for a large model extent (greater than 1000), the amount of groundwater inflow tends to a constant value. In the second part, analytical solutions and finite element numerical modeling are applied for estimating the amount of groundwater inflow into Dorud–Khorramabad railway tunnel. The results indicate that the groundwater inflow into the tunnel, based on analytical methods, gives higher values than the numerical modeling. The reason for this difference may be justified by assumptions and simplifications in analytical methods, accordingly, it can be inferred that if the appropriate model extent selected, the results of the numerical model based on the fact in the project can be more reliable.
... Two types of filled karst caves, with water and with water-mud mixture, in front of the tunnel face are studied to estimate the required thickness of the supporting rock stratum in order to prevent water and mud inrush under earthquake action [13]. Zhang [14], Zheng [15], Kong [16], Shin et al. [17], and Cao et al. [18] derived the analytical solution of water pressure acting on the lining or rock tunnels. Zhang et al. [19] suggested a new set of analytical solutions for predicting the effect of grouting on ground and shield tunnel behavior as a consequence of steady water inflow into a tunnel in saturated clay based on relative permeability of the tunnel lining and grouting material to the surrounding soil. ...
This study gives two new analytical solutions to the tunnel by high-pressure water in the cavern. Firstly, it deals with the analytical solution for the seepage inflow in unsupported karst aquifer tunnels considering the boundary condition. Secondly, it focuses on the study of the seepage force and gives the reduction coefficient of lining water pressure. A comparison of the analytical solution and the finite element software shows a curve relationship as the relevant permeability coefficient β increases. The results show that the analytical solution and numerical solution are consistent. As d increases, β decreases gradually. β increases as rw increases or the grouting circle and initial support become thinner or the secondary lining becomes thicker. In summary, the analytical solution of β can be used to predict the seepage inflow and the seepage force of the actual engineering.
... Long tunnels constructed for highway and rail transportation, energy generation and water transmission are challenging engineering structures. Complex geological conditions (Shaterpour-Mamaghani et al. 2015;Jack and Lyall 2019;Maleki et al. 2020;Sandford and Mason 2020), ingresses of high-pressure water and tunnel collapses (Apaydin et al. 2019a;Gong et al. 2018;Alp and Apaydin 2019;Kong 2011), and the presence of thermal water and gas (Wenner and Wannenmacher 2008;Yao et al. 2018;Chen et al. 2020) all increase the difficulty of these projects. Tunnel-boring machines (TBMs) are preferred over conventional drilling methods, but most long tunnels are not completed within the timescale predicted in the tender contract (Alp and Apaydin 2019). ...
The Gerede tunnel is one of the large inter-basin projects in Turkey. As with many long tunnels, some predictions, envisaged in the project report and the tender contract have not realized in this tunnel. Completion of the tunnel delayed more than two times than the tender contract. Unexpected complex geological-tectonic-hydrogeological conditions and TBM selection are the main reasons for this long delay. There were some discrepancies between the predicted in the project and the actual geology. Groundwater pressure encountered was much more than expected. Plastic clays in the limestone and breccia and loose agglomerates with high water pressures in the faults decreased the advance rate and even caused long stoppages several times. Even worse, one of the three double shield TBMs stuck in the tunnel and could not be recovered. The last quarter of the tunnel was excavated more slowly but without severe problems, by a modified EPB type TBM. As a result, TBM type, drive direction, length, route, cost and completion date of the Gerede tunnel changed.
... 25 Accurate estimation of discharge into tunnels is of great importance for risk assessment of water inrush and mud flow induced by tunnel excavation in karst aquifers, 26 and for design of drainage system during construction and/or operation. 27 Numerous efforts have been devoted to the evaluation of discharge into tunnels with analytical models, [28][29][30][31] numerical simulations [32][33][34][35] or synthetical approaches. 26,36,37 These models and approaches, however, are either developed based on the Darcy's law, or lack of an elaboration for the flow regime in karst aquifers with field data support. ...
... Conventionally, there are four classical analytical methods to estimate groundwater inflow into https://doi.org/10.1016/j.tust.2019.103136 Received 10 May 2019; Received in revised form 12 September 2019; Accepted 4 October 2019 tunnels (Kong, 2011): (1) Goodman method (Goodman et al., 1965); (2) Heuer and Raymer method (Heuer, 1995;Raymer, 2001); (3) Heuer Analytical method (Heuer, 1995(Heuer, , 2005; and (4) IMS method (McFeat-Smithet al., 1985). However, analytical solutions are difficult to estimate groundwater inflow under complex geological conditions. ...
... Because of this, an increasing number of tunnels will be built in karst regions, and water and mud inrush disasters will occur more frequently Li et al. 2015a;Zhao et al. 2013;Ling et al. 2015). Water and mud inrush can increase the risks of construction and significantly increase the difficulty of construction (Kong 2011;Li et al. 2012;Meng et al. 2012;Wang et al. 2016;Zhou et al. 2015;Li et al. 2017b, d). It can also cause significant casualties and economic losses, and can produce negative social impacts Wang et al. 2004;Zarei et al. 2012;Zhang et al. 2011). ...
A new slice-based method is proposed for calculating the minimum safe thickness for a filled-type karst cave. A computational slice model of the filling medium is put forward with the assumption that the filling medium is in a limit equilibrium state on a straight-line sliding surface. The force expression is calculated, and the most dangerous sliding surface is identified. For intact and fractured resistant bodies, theoretical formulas for the minimum safe thickness are deduced from the tension strength and shear strength criteria of the rocks, respectively. A case study is analyzed, and several influencing factors are discussed. The results show that the cohesion of the filling medium has no effect on the angle of the sliding surface, and the angle of the sliding surface increases by 1.5° if the internal friction angle increases by 3°. The force that filling medium acts on the resistant body decreases nearly linearly with increasing cohesion and decreases nonlinearly as the internal friction angle increases. The minimum safe thickness decreases nearly linearly as the cohesion or internal friction angle of the filling medium increases. As the tensile strength of the resistant body increases, the minimum safe thickness decreases nonlinearly. The minimum safe thickness increases nonlinearly with increasing load. Compared to an intact resistant body, the minimum safe thickness for a fractured resistant body is larger. The method proposed in this paper provides an efficient and reasonable way to explore the mechanism by which filling medium inrush to the tunnel face of a karst tunnel occurs.
... As one of the most dangerous geological disasters, the water inrush in tunnels has been paid much attention and studied using various methods. Besides the four classical analytical methods, namely Goodman method (Goodman et al., 1965), Heuer and Raymer method (Heuer, 1995;Raymer 2001), Heuer Analytical method (Heuer, 1995 and2005) and IMS method (McFeat-Smith et al., 1985), some other solutions were also proposed to estimate the water inflow in tunnels with different geological conditions, such as the hydraulic conductivity gradient method (Zhang and Franklin, 1993), the exact analytical solution (Kolymbas and Wagner, 2007), the semi-analytical method base on classical groundwater theory (Hwang and Lu, 2007), the combination method based on the classical ones (Kong, 2011), and the ground dynamics method (Jin et al., 2016). However, all the analytical solutions are based on given hydrogeological assumptions and are unable to predict water flow in complex hydrogeological conditions . ...
This paper presents an improved assessment system to evaluate the risk of water inrush in tunnels in carbonate karst terrain based on extension assessment method. This system considers the karst geological conditions and selects nine main factors as evaluation indices that influence the water inrush in tunnels. The evaluation indices are quantitatively graded into four risk grades based on their values or expert judgement. The same-feature matter-element, classical domains, and sectional domains are constructed based on the nondimensionalization of the risk grades of the evaluation indices. The integrated weights for the evaluation indices are composed of the objective weights computed from measured values and the subjective weights derived from the Fuzzy Analytical Hierarchy Process (FAHP). The water inrush risk level of the evaluation object is recognized by the correlation analysis. The variable characteristic value makes it possible to further distinguish the water inrush risk of different objects having the same risk level. The accuracy of the assessment results of this proposed extension assessment system was verified by applying it in two engineering cases. This extension assessment system provides a practical tool to assess the risk of water inrush in tunnels in carbonate karst terrain.
... The evaluation index of water inrush was put forward in tunnels (Li et al. 2013a). There are four classical methods for the analysis of water inrush (Kong 2011), namely, the Goodman method (Goodman et al. 1965), IMS method (McFeat-Smith et al. 1985), Heuer and Raymer method (Heuer et al. 1995;Raymer et al. 2001) and Heuer Analytical method (Heuer et al. 1995(Heuer et al. , 2005. Furthermore, the risk classification system of water inrush and mud inrush was put forward in tunnels, which is combined with a qualitative and quantitative evaluation (Mao et al. 2010). ...
Water inrush is a major geological hazard that threatens the safety of karst tunnels. The risk assessment of water inrush is necessary in tunnel engineering. A new model based on intuitionistic fuzzy analysis was proposed to assess the risk of water inrush, which considered the subjective and objective weights of influencing factors. Seven factors were selected to constitute the set of evaluation attributes, namely, formation lithology, unfavourable geological conditions, groundwater level, landform and physiognomy, modified strata inclination, contact zones of dissolvable and insoluble rock, and layer and interlayer fissures. The proposed model was applied in a typical karst tunnel, Xiakou tunnel in China. The sensitivity of the changes in the index weights was analyzed. The results showed that the water inrush risk of section XJK0 + 110 to XJK0 + 060 in Xiakou tunnel was evaluated as grade I (high risk). The risk assessment results were more sensitive to the index weights of landform, formation lithology, and contact zones of dissolvable and insoluble rock than to those of the other indices. Landform was the most sensitive index. The obtained results were identical to the practical findings, and the rationality and feasibility of the model was verified. Intuitionistic fuzzy analysis is a new method for the quantitative risk assessment of water inrush in karst tunnels.
... Water ingress is a key issue affecting the construction and operating phases of drained tunnels (Anagnostou, 1995;Arjnoi et al., 2009;Kong, 2011). Moreover, some researchers have determined that most tunnels eventually act as drains (Atkinson and Mair, 1983;Wongsaroj et al., 2007). ...
... Thus, analytical solutions over/underestimate groundwater inflow to the tunnel since the geological media is very complex and the aforementioned assumptions are unrealistic. Moreover, analytical methods have difficulty in predicting groundwater inflow to the tunnel if: (1) water flow around the tunnel is not radial, (2) variations in rock mass bedding in the perimeter of the tunnel, (3) imprecise rock mass permeability estimation (Farhadian et al., 2012;Kong, 2011). In the following, a short description of the main contributions is outlined. ...
The objective of this study is to make a comparison among different methods used for evaluation of steady state groundwater inflow to a shallow circular cross section tunnel. These methods include: analytical solutions, empirical methods and numerical modelling. Analytical formulas provide an estimation of inflow rate based on some simplifying assumptions which are somehow unrealistic. Therefore, their results are over/underestimated. Empirical methods are presented based on the experiences of different tunnel projects and they mostly provide an appropriate qualitative estimation; while, their quantitative predictions are not desirable. Despite analytical and empirical approaches, numerical modelling is a suitable tool for solving complex geomechanical and hydrogeological conditions. Hence, their results are more reliable and precise for designation of efficient drainage systems. In this study, groundwater inflow into Tabriz Metro-Line 2 (TML2) is evaluated by means of these methods and their results were compared. The results indicated that all of the methods provide consistent results, however, it is inferred that in the absence of sufficient data, Raymer equation can provide more reliable estimation of inflow rate for shallow tunnels in comparison to other analytical and empirical solutions due to its higher correlation with numerical results.
... Many scholars have done a lot of research on the risk assessment of tunnel collapse and water inrush (Bukowski 2001;Kong 2011;Li et al. 2015;Li and Li 2014;Meng et al. 2012;Yazdani-Chamzini 2014). Zhang et al. (2009) developed the theory and method of water inrush risk assessment of high risk karst tunnel, and then established the quantitative evaluation method of water inrush risk and the mechanism of the four color warning. ...
In the process of tunnel construction, many kinds of geological disasters are frequently occur. Among them, tunnel collapse is one of the most serious geological disasters. Seven controlling factors were determined by analyzing 76 large or medium tunnel collapses in China. By means of synthesizing all kind of index parameters, grey relational coefficients were calculated based on grey correlation theory. Entropy weight method was used to compute the weight coefficients. And a comprehensive risk evaluation model of tunnel collapse was established based on entropy weight and grey relational degree. The paper gives the correctional coefficients depending on rainfall conditions during construction of the tunnel. At last the collapse risk level of tunnels was obtained. Based on the actual project cases of risk assessment, the results indicated that the comprehensive risk evaluation model of tunnel collapse was scientific and reasonable. And it was shown that the method was easy to master and has a great significance on engineering practice.
... Although it is difficult to accurately predict water inrush probability and discharge rate of tunnels, many investigations consisting of analytical, empirical, and numerical approaches have been presented within the last few decades. Three classical analytical methods are often used to estimate water inflow into tunnels (Kong, 2011): (1) Goodman method (Goodman et al., 1965); (2) Heuer and Raymer method (Heuer, 1995;Raymer, 2001), and (3) IMS method (McFeat-Smith et al., 1985). Analytical solutions can be rapid and useful. ...
... One of the interesting points mentioned by Goodman et al. (1965) is the slight increase of water inflow with an increase in tunnel diameter. This equation is developed based on the following assumptions; the radius flow, no bedding in the rock, and accurate prediction of equivalent permeability (Kong 2011 Parameters * According to increase the joint angle (clockwise or anti-clockwise) can increase or reduce the flow. ...
The high volume of water inflow into tunnel plays a significant role in the design of drainage systems and exerts bio-environmental effects. In engineering practice, analytical and empirical methods that are commonly used to estimate water inflow in sedimentary rock masses, lack sufficient accuracy. The geostructural anisotropy in a fractured rock has a great impact on water inflow. In discontinuous media, anisotropy and heterogeneity of the fractured rock masses are highlited. Hence, these methods are not efficient to calculate water inflow to tunnel in such media, due to the assumed isotropic hydraulic coefficient. In this regard, an empirical formula is developed in this study for hydraulic conductivity in the fractured rock masses for analytical methods, alternately used to predict water inflow. To achieve this, a discrete network flow model was performed. The simulation resulted in a dataset that is helpful in developing hydraulic conductivity empirical formula for well-known Goodman equation. The geostructural parameters, such as the joint orientation, aperture, spacing and joint interconnectivity were included to determine this formula. The acquired empirical equation was utilized in the evaluation of groundwater inflow to middle-depth Amirkabir tunnel in north of Iran. In comparison to the observerd flow, analytical methods resulted in higher overestimation, especially in the sites with high anisotropy. However, empirical model led to a better estimation of water inflow to tunnel.
... -Variations are in rock mass bedding in the perimeter of the tunnel. -Imprecise rock mass permeability estimation is made (Kong 2011;Farhadian et al. 2012). ...
In order to prevent problems like casualties, delays in tunneling procedure, and increasing tunneling costs, predicting groundwater inflow into tunnels and designing an efficient drainage system are necessary. Several analytical solutions exist in the literature, but they cannot accurately estimate groundwater inflow due to simplifying assumptions. Numerical methods, however, are increasingly used to predict groundwater inflow with higher accuracy. This study is aimed at predicting the steady state groundwater ingress into Tabriz line 2 metro tunnel (TML2: a shallow urban tunnel) by considering model dimensions as critical factors in the numerical analysis process. A 2-D numerical finite element analysis of steady state groundwater inflow was performed along the tunnel based on geological and geotechnical investigations. Water inflow into TML2 was then estimated based on optimum model dimensions. The total amount of groundwater inflow into TML2 was estimated to be 7013.6 l/min. The maximum cumulative water inflow into the tunnel was also predicted to occur between 15.55 and 16.25 km in the tunnel with a 4754 l/min inflow rate, which demands an effective drainage program. Finally, for validation of the methodology groundwater inflow values obtained through 2D finite element analysis were compared to those calculated with a well-known inflow evaluation method (Raymer solution).
... After analysis on the possible factors that cause water inrush, Bukowski (2011) proposed a risk assessment system to predict water harzard in Upper Silesian Coal Basin Mines using typical factors and designed it as the basis for a more detailed, expert system which can be applied in different geological and mining conditions. Four classical analytical methods are often used to estimate groundwater inflow into tunnels: (1) Goodman method; (2) Heuer and Raymer method; (3) Heuer Analytical method; and (4) IMS method (Mohamed 2003, Kong 2011). Moreover, with the application of GIS, Bayesian Network and comprehensive fuzzy assessment, the fuzzy TOPSIS method has been adopted in assessment of tunnel construction and water inrush (Fouladgar et al. 2012, Matthias et al. 2012, Wang et al. 2012, Li and Li 2014). ...
Water inrush makes time extended, instruments destructed, and casualty increased, which is the biggest threat for safe construction of tunnels in karst areas. A software system for risk assessment of water inrush was established with considering eight risk factors, including groundwater level, unfavorable geology, formation lithology, topography, strata inclination, excavation, advanced geological prediction, and monitoring. In the present software system, fuzzy mathematics and Analytical Hierarchy Process (AHP) were used to quantitatively describe the risk levels for each factor. The influence degree of each factor to water inrush was assigned an objective weight and a subjective weight, and the proportion of the two weights in the risk assessment was defined as weight distribution. The objective weights of the risk factors were obtained from more than 100 water inrush instances in karst tunnels, whereas the weight distribution was totally derived from expert field assessment and subjective weights were determined by using AHP in the risk assessment. Two case studies of karst tunnels were applied to check the reliability of the proposed software system, and the comparisons between the software assessment and practical excavation yield good consistency. Therefore, the software system can appropriately be used in practice to forecast water inrush in karst tunnels.
In hard-rock tunnels, most of the inflow comes from a small portion of the tunnel length, some of the inflow comes from a large portion of the tunnel, and much of the tunnel is dry. The total inflow accumulates as the sum of all the inflows. Zagros tunnel passes through different formation and in a part of its route cuts the limestones with the karstic potential. In this paper based on the geological investigation, observed and measurement water seepage into tunnel in recorded sections using the numerical modeling, (The Universal Distinct Element Code (UDEC)), the water ingress into tunnel has been estimated. Results show that the large portion of water inflow is from the fault zones and karstic zones.From the amount of groundwater inflow point of view, the results show that amount of 50% of tunnel length can be classified as a low risk and around of other 50% has a high risk and critical conditions.
The problem of water inrush is commonplace in underground constructions. This paper using the thin plate model studied the critical thickness of tunnel aquifuge. According to the extreme equilibrium principle, the formula for calculating the minimum safe thickness of aquifuge was deduced. It further argued that the calculated plate thickness is just the minimum safe thickness of aquifuge, where the stress from underground water pressure is equal to the extreme stress supported by the extreme stress of the aquifuge. Through applying the formula to the practical cases, the authors concluded that the derived formula relatively conforms to the real constructions and can be applied into real tunnel engineering. Then after analysis and summary, the conditions and ranges of formula application were also obtained.
Collapse was one of the typical common geological hazards during the construction of tunnels. The risk assessment of collapse was an effective way to ensure the safety of tunnels. We established a prediction model of collapse based on Bayesian Network. 76 large or medium collapses in China were analyzed. The variable set and range of the model were determined according to the statistics. A collapse prediction software was developed and its veracity was also evaluated. At last the software was used to predict tunnel collapses. It effectively evaded the disaster. Establishing the platform can be subsequent perfect. The platform can also be applied to the risk assessment of other tunnel engineering.
Water inrush and mud outburst always restricts the tunnel constructions in mountain area, which becomes a major geological barrier against the development of underground engineering. In view of the complex disaster-causing mechanism and difficult quantitative predictions of water inrush and mud outburst, several theoretical methods are adopted to realize dynamic assessment of water inrush in the progressive process of tunnel construction. Concerning both the geological condition and construction situation, eleven risk factors are quantitatively described and an assessment system is developed to evaluate the water inrush risk. In the static assessment, the weights of eight risk factors about the geological condition are determined using Analytic Hierarchy Process (AHP). Each factor is scored by experts and the synthesis scores are weighted. The risk level is ultimately determined based on the scoring outcome which is derived from the sum of products of weights and comprehensive scores. In the secondary assessment, the eight risk factors in static assessment and three factors about construction situation are quantitatively analyzed using fuzzy evaluation method. Subordinate levels and weight of factors are prepared and then used to calculate the comprehensive subordinate degree and risk level. In the dynamic assessment, the classical field of the eleven risk factors is normalized by using the extension evaluation method. From the input of the matter-element, weights of risk factors are determined and correlation analysis is carried out to determine the risk level. This system has been applied to the dynamic assessment of water inrush during construction of the Yuanliangshan tunnel of Yuhuai Railway. The assessment results are consistent with the actual excavation, which verifies the rationality and feasibility of the software. The developed system is believed capable to be back-up and applied for risk assessment of water inrush in the underground engineering construction.
Engineers may encounter unpredictable cavities, sinkholes and karst conduits while tunneling in karst area, and water inrush disaster frequently occurs and endanger the construction safety, resulting in huge casualties and economic loss. Therefore, an optimal classification method based on grey system theory (GST) is established and applied to accurately predict the occurrence probability of water inrush. Considering the weights of evaluation indices, an improved formula is applied to calculate the grey relational grade. Two evaluation indices systems are proposed for risk assessment of water inrush in design stage and construction stage, respectively, and the evaluation indices are quantitatively graded according to four risk grades. To verify the accuracy and feasibility of optimal classification method, comparisons of the evaluation results derived from the aforementioned method and attribute synthetic evaluation system are made. Furthermore, evaluation of engineering practice is carried through with the Xiakou Tunnel as a case study, and the evaluation result is generally in good agreement with the field-observed result. This risk assessment methodology provides a powerful tool with which engineers can systematically evaluate the risk of water inrush in karst tunnels.
A veracious and feasible method is presented to systematically evaluate the risk of water inrush in karst tunnels. The methodology consists of two attribute recognition models: one is used in design stage, and the other one is applied in construction stage. Based on the principles of scientificity, rationality, operability and representative, several influence factors are selected as evaluation indices. In order to meet the requirement of the data format of attribute mathematical theory, a couple of evaluation indices are modified and quantitatively graded according to four risk grades through expert evaluation method. The weights of evaluation indices are rationally distributed by comprehensive assignment method, and the attribute measure functions are constructed to compute single index attribute measure and synthetic attribute measure. A confidence criterion is adopted to discern the risk grade of water inrush. Comparisons of the results derived from the present method and a case study are made. The results of the comparisons indicate that the evaluation results obtained from the proposed method are generally in a good agreement with the field-observed results. This risk assessment methodology provides a powerful tool for systematically assessing the risk of water inrush in karst tunnels.
About this book
This book describes the stage by stage development of a new method for predicting the penetration rate (PR) and the advance rate (AR) for tunnel boring machines based on an expanded version of the Q-value, termed QTBM. Some 145 TBM tunnels totalling about 1000 km in length were an-alysed and some simple formulae are developed from the results to esti-mate PR and AR from the QTBM value, or to back-calculate QTBM from performance data. Logging methods, empirical TBM tunnel support de-sign, and numerical verification of support are also treated in this slim but practical book on TBM tunnelling.
Penetration rates as high as 10 m/hr, but occasionally as low as 0.1 m/hr, are a function both of the machine and rock mass interaction, and of the cutter force and rock strength interaction. Actual advance rates that could be as high as 5 m/hr for one day, or as low as 0.005 m/hr (while stuck for several months in a major fault zone) are quantitatively ex-plained.
This book is a useful source of reference for consultants, contractors and owners of TBM tunnels, and for those involved with feasibility stud-ies, machine and support design and follow-up of tunnel progress. Among the geotechnical community, the book will be useful for geolo-gists, engineering geologists and rock mechanics engineers, and for all civil engineers who have a professional interest in TBM tunnelling.
Engineering Classification of Rock Masses for the Design of Tunnel Support An analysis of some 200 tunnel case records has revealed a useful correlation between the amount and type of permanent support and the rock mass qualityQ, with respect to tunnel stability. The numerical value ofQ ranges from 0.001 (for exceptionally poor quality squeezing-ground) up to 1000 (for exceptionally good quality rock which is practically unjointed). The rock mass qualityQ is a function of six parameters, each of which has a rating of importance, which can be estimated from surface mapping and can be updated during subsequent excavation. The six parameters are as follows; theRQD index, the number of joint sets, the roughness of the weakest joints, the degree of alteration or filling along the weakest joints, and two further parameters which account for the rock load and water inflow. In combination these parameters represent the rock block-size, the interblock shear strength, and the active stress. The proposed classification is illustrated by means of field examples and selected case records. Detailed analysis of the rock mass quality and corresponding support practice has shown that suitable permanent support can be estimated for the whole spectrum of rock qualities. This estimate is based on the rock mass quality Q, the support pressure, and the dimensions and purpose of the excavation. The support pressure appears to be a function ofQ, the joint roughness, and the number of joint sets. The latter two determine the dilatency and the degree of freedom of the rock mass. Detailed recommendations for support measures include various combinations of shotcrete, bolting, and cast concrete arches together with the appropriate bolt spacings and lengths, and the requisite thickness of shotcrete or concrete. The boundary between self supporting tunnels and those requiring some form of permanent support can be determined from the rock mass qualityQ.
The geology of Hong Kong consists largely of granites and volcanic tuffs comprising rock masses of low permeability with higher zones of permeability being dictated by the presence of tabular shear zones and major (persistent) jointing. As a result water inflows experienced in over 200kms of land based rock tunnels have encountered anisotropic water inflow conditions that are difficult to predict. Recent problems identified from the driving of tunnels at depth under the harbour have focused attention on construction delays experienced from water inflows in rock tunnels located below large water sources. In particular, excessive downtime is being experienced for probing and grouting ahead of advancing TBM faces. This paper presents several case histories that clearly illustrate the nature and quantity of water inflows that are encountered in local tunnels; presents a new method of predicting water inflows using empirical methods; discusses typical construction problems and identifies control and remedial measures necessary to manage the risks involved.
Tunnelling conditions prevailing in Hong Kong are discussed in conjunction with the steps necessary to achieve successful construction of underground projects. Experience is drawn from all major bored tunnel projects initiated in the territory in the last six to eight years. The works comprise the excavation of shafts, tunnels and caverns in soft ground, mixed face and hard rock conditions. Emphasis is given to the geotechnical aspects of these projects and to the various processes required to excavate in adverse ground conditions. The advantages of issuing interpretative geotechnical reports to contractors are discussed, together with a method of defining Ground Reference Conditions for rock tunnelling in the local terrain.
Engineering Classifications of jointed rock masses
- Zt Bienawski
Estimating rock tunnel water inflow
- R Heuer
Landslide Preventive Works at Po Shan Road, Mid-levels for Contract No
- Hong Kong
Predicting groundwater inflow into hard-rock tunnels: estimating the high-end of the permeability distribution
- Jh Raymer