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Seismic vulnerability of tunnels and underground structures revisited
... 13 Therefore, the seismic design of such a structure must adhere to factors that are distinct from those that govern the construction of structures located above ground. 5,8,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] While evaluating the transverse racking response of rectangular cut-and-cover tunnel structures: there are two approaches that can be used to assess transverse response (racking deformation) in rectangular tunnels 5,13,16,30,31 : (1) a streamlined analytical method, (2) a more complex numerical modeling strategy. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Numerical modeling can be used depending on the complexity of the soil-structure system, the subsurface conditions, the level of seismic danger, and the significance of the structures. ...
... 5,8,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] While evaluating the transverse racking response of rectangular cut-and-cover tunnel structures: there are two approaches that can be used to assess transverse response (racking deformation) in rectangular tunnels 5,13,16,30,31 : (1) a streamlined analytical method, (2) a more complex numerical modeling strategy. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Numerical modeling can be used depending on the complexity of the soil-structure system, the subsurface conditions, the level of seismic danger, and the significance of the structures. Numerical modeling should be taken into consideration in particular situations where straightforward analysis approaches are less useful, more ambiguous, or inconclusive. ...
... To represent this phenomenon, a triangular pressure distribution was implemented in the model, following the approach described. [13][14][15][16][25][26][27][28][29] The method developed by Wang et al. 13 was used for the calculation of racking deformation, along with the approach, was utilized. [13][14][15][16][25][26][27][28][29] The necessary foundational data required for this analytical method is outlined as follows. ...
The increasing number of private cars, public transportation vehicles, and pedestrians, as well as the absence of adequate space for these ground amenities, are one of the primary causes of traffic congestion and accidents in the Kathmandu Valley. Investigations have indicated that the Kathmandu Valley has the greatest traffic accidents despite the heavy presence of the government and its agencies there. Most teens and young adults suffer injuries while using motor vehicles. The study's primary objective is to foresee and prevent such complications by planning for sufficient subsurface infrastructure (a cut‐and‐cover rectangular tunnel) for the Kathmandu Valley's transportation network. The overlying pressure, lateral earth pressure, live load, uplift pressure, and live surcharge are some of the forces acting on the tunnel, creating unique stress and moment zones. The tunnel meets the following geometric requirements: (a) Each of the tunnel's two cells has a clear span of 10 m and a clear height of 5.5 m. The side walls, inner walls, top slab, and bottom slab are all 700 mm thick. Soil has built up to a height of 4 m over the tunnel's roof. The analytical method is used in the tunnel segment's analysis. Furthermore, the designed tunnel has been evaluated for stability, considering the deflection and shear resistance. The analysis indicates that the tunnel meets the stability requirements. This implies that the structure is capable of withstanding the applied forces without excessive deflection. Non‐linear dynamic time history analyses of the El Centro earthquake and the Gorkha earthquake were computed. From the El Centro earthquake, the maximum displacement was 23.63 mm at 10.59 s, and from the Gorkha earthquake, the maximum displacement was 16 mm at 0.19 s for the modeled structures.
... Figure 2-6. 204 case histories of shaking-induced damages from 10 earthquakes were re-analysed by /Power et al, 1998/ including data from 1989Loma Prieta, 1993Hokkaido, 1994Northridge and 1995 ...
... g (hypocentral distance 18-35 km) and damage due to shaking would be expected. /Power et al, 1998/ estimated PGA to around 0.6 g. The Rokko tunnel in granitic rock, one of the very famous tunnels in granitic rock in Japan, is of special interest. ...
... The three cases with Heavy Damage are all from the 1923 Kanto earthquake, Japan, where damage may have been due to landsliding. The damage classification used in the published paper is unfortunately not very precise /Revised afterPower et al, 1998/. ...
... Seismic performances of tunnels have been extensively studied (e.g. Duke and Leeds, 1959;Dowding and Rozen, 1978;Owen and Scholl, 1981;Sharma and Judd, 1991;Power et al., 1998;Wang et al., 2001;Chen et al., 2012;Wang and Zhang, 2013;Yu et al., 2013Yu et al., , 2016aLai et al., 2017). Currently, several global databases are available. ...
... Sharma and Judd (1991) compiled a database with 192 cases during 85 earthquakes. Power et al. (1998) used the previous database to study the performance of bored tunnels, adding cases from more recent earthquakes (e.g. the 1995 Kobe earthquake). After investigating 10 strong earthquakes, Chen et al. (2012) established a database for the damage situation of 81 mountain tunnels. ...
Accurate seismic assessment and proper aseismic design of underground structures require a comprehensive understanding of seismic performance and response of underground structures under earthquake force. In order to understand the seismic behavior of tunnels during an earthquake, a wide collection of case histories has been reviewed from the available literature with respect to damage classification, to discuss the possible causes of damage, such as earthquake parameters, structural form and geological conditions. In addition, a case of Tawarayama tunnel subjected to the 2016 Kumamoto earthquake is studied. Discussion on the possible influence factors aims at improving the performance-based aseismic design of tunnels. Finally, restoration design criterion and methods are presented taking Tawarayama tunnel as an example.
... Table 1 The correlation of damage degree and peak ground acceleration (ALA, 2001) PGA(g) All Tunnels DS=1 DS=2 Damage cases of tunnel structures documented by H. Dowding & Rozen (1978), as shown in Figure 1 which was revised by Göran Bäckblom (2002), suggest that no damage should be expected if the peak surface accelerations are less than about 0.2g, and only minor damage will be experienced between 0.2 and 0.4 g. According to the extended database of Owen& Scholl(1981), little damage would be expected for rock tunnels for peak ground accelerations below 0.4 g, as can be indicated from Figure 2. Sharma & Judd (1991) further updated the previous database and concluded that no damage or minor damage occurred for PGA less than 0.15 g, which can be shown by Figure 3. Focusing on the damage induced by earthquake shaking other than by ground failure or fault movement, Power et al(1998) removed the relatively poorly documented cases as well as those caused directly by the other two seismic effects, and simultaneously added some recent cases, and then concluded that ground shaking caused less damage for PGA less than 0.2 g, some cases damaged ranging from slight to moderate damage with PGA between 0.2 g and 0.5 g, and some other cases suffered slight to heavy damage when PGA exceeded 0.5 g, as shown in Figure2. Besides, the case of 1923 Kanto earthquake with PGA equal to 0.2 g suffered heavy damage probably due to landsliding other than ground shaking. ...
... ALA(2001) studied 217 bored tunnels which suffered strong ground motions and obtained the correlation of damage degree and peak ground acceleration, as shown in Table 1, and it can be concluded that the general tendency is almost correspondent to previous conclusions. More recently, Corigliano(2007) updated the data derived from the post earthquake surveys after Chi-chi(Taiwan) and 2004 Niigata (Japan) earthquakes based on the database developed by Power et al(1998), and by his investigation, the influence of PGA on damage did not show a clearly increasing trend, which might be induced by the uncertainty involved in the calculation of PGA using empirical attenuation relations. However, it can be inferred from Figure 3 that almost no damage occurred for PGA less than 0.15g, the threshold of PGA leading to moderate damage was 0.25g, while heavy damage occurred when PGA exceeded 0.35g. ...
... Some of the prominent work documenting seismic damages of tunnels and underground facilities have been carried out by Dowding and Rozen (1978), Owen and Scholl (1980), Sharma and Judd (1991) and Power et al. (1998). Dowding and Rozen (1978) investigated 71 tunnels following earthquakes in America and Japan. ...
... It was also found that the damage levels decreased for tunnels constructed in competent rocks. Similar observations were made by Power et al. (1998) with regard to the performance of underground facilities following the 1995 Hyogoken-Nanbu (Japan) and the 1995 Northridge (U.S.) earthquakes. Table 1 collates past seismic performances of tunnels highlighting the major observations and conclusions. ...
Severe cases of damages of mountain tunnels following 1995 Hyogoken-Nanbu (Japan), 1999 Chi-Chi (Taiwan), 2004 Mid-Niigata Prefecture (Japan) and 2008 Wenchuan (China) earthquakes have challenged the traditional belief of tunnel structures being seldom damaged in seismic events. These experiences are a reminder that seismic behaviour of mountain tunnels must be further studied in detail. Such investigations assume greater significance as more number of tunnels are being planned to be constructed to meet the infrastructural needs of mountainous regions all around the world. In this paper, seismic damages of mountain tunnels have been reviewed. Prominent failure patterns have been identified based on the case histories of damages. Damages in the form of cracking of tunnel lining, portal cracking, landslide induced failures, uplift of bottom pavement, failures of sidewalls, shearing failure of tunnel liner and spalling of concrete have been majorly observed. Based on the damage patterns and earthquake data, main factors leading to instabilities have been discussed. Probable failure mechanisms of mountain tunnels under seismic loading conditions have been explained. Seismic analyses of a circular lined tunnel in blocky rock mass have been carried out through discrete element based approach. The significant role of different seismic parameters like frequency, peak ground acceleration has been identified. Moreover, effect of tunnel depth on the seismic response of tunnels has been investigated. It is believed that the present study will help in advancing the present state of understanding with regard to the behavior of tunnels under seismic conditions.
... The review of damage suffered by underground structures due to earthquakes (i.e. Dowding & Rozen (1978), Owen & Scholl (1981), Sharma & Judd (1991), Power et al. (1998), Wang et al. (2001), etc.) confirms that these structures are less vulnerable than above-ground facilities. In particular, Dowding & Rozen (1978) grouped damages of underground structures due to earthquakes into three main categories: ...
... The American Lifelines Alliance (ALA, 2001) provides empirical fragility curves for tunnels in rock (bored) and soil (cut and cover) tunnels considering two possible conditions for construction quality: poor-to-average and good. The curves are based on the PGA database gathered by Power et al. (1998). ...
Underground structures are critical elements in transportation and utility networks. The worldwide growing need to further expand these networks has determined a renewed interest for studying the vulnerability of underground structures to earthquake loading. Fragility curves constitute a powerful tool for assessing the seismic vulnerability of structures. A few fragility relationships have however been specifically derived for underground structures.All of them use as a measure of strong motion intensity the Peak Ground Acceleration (PGA). However PGA shows almost no correlation with the damage potential of ground motion to a structure, particularly underground structures. In this paper empirical fragility curves are proposed for deep tunnels using as a measure of ground motion intensity the Peak Ground Velocity (PGV), which is known to be better
correlated to damage.
... Thus, neglecting an appropriate seismic assessment can produce problems during tunnel construction in earthquake-prone regions (Hashash et al., 2001;Iida et al., 1996;Tsinidis et al., 2020). Several contributions have been made to achieve seismic criteria for tunnel design, such as the relative flexibility of the tunnelground system (Wang, 1993), or other analytical (Bobet, 2003), experimental (Chen & Shen, 2014;Power et al., 1998), and numerical approaches (Chakraborty & Kumar, 2013;Esmaeilzadeh Seylabi et al., 2018;Sahoo & Kumar, 2012). However, few researchers have addressed the impact of seismic loading on tunnel face stability, and analyses were often conducted only in the context of rock tunnels (Pan & Dias, 2018) or using upper-bound (i.e., unsafe) limit analysis formulations without considering the effect of seismic loading on the assumed failure mechanism (Huang et al., 2020;Saada et al., 2013). ...
... Most of the studies expressed the importance of shotcrete rock interaction under static conditions, and the seismic performance of the same still lacks clarity. This lack of understanding in the area has intrigued various scientists around the world with the damage in underground openings because of seismic loading [9][10][11][12][13][14][15][16][17]. The active tunneling and underground works going around the world, along with the seismic damage occurring in deep-buried structures as observed in the Wenchuan earthquake with a moment magnitude (Mw) of 8.3, led to the interest in the study [13]. ...
Shotcrete as a permanent support system is common for many underground openings. However, the performance of the same under seismic loading conditions has not been thoroughly considered, especially in jointed rock tunnels. This paper presents a numerical study using the two-dimensional distinct element modeling (DEM) technique to understand the performance of shotcrete in jointed rock tunnels under seismic loading conditions. The study analyses the spalling of the shotcrete under actual earthquake conditions. The normal force and bending moment acting on the shotcrete have been studied for the presence of joints under static and seismic loading. The increased spalling in the intersection regions between rock joints and shotcrete was observed in the study with localization of stress and moment concentrations. Parametric studies have also been conducted to analyze the effect of joint, shotcrete and seismic factors on the stability of shotcrete. The studies indicated spalling under the action of seismic loads commonly near points of intersection between shotcrete and joint. The position of spalling along with the forces and moments acting on the shotcrete has been found to be highly influenced by incoming wave frequency and amplitude.
... Therefore, it is of utmost importance to study the seismic behaviors of tunnel portals and improve their seismic stability. The failure of tunnel portals have been observed and reported during several famous strong earthquakes, including the 1989 Loma Prieta earthquake [2,7], 1995 Kobe earthquake [8,9], 1999 Chi-Chi earthquake [10,11] and 2008 Wenchuan earthquake [12][13][14], and since then the seismic behaviors of tunnel portals therefore becomes an hot topic and arouses much attention. Numerous researchers have investigated the seismic response of tunnel portals. ...
... Several studies of tunnel performance during earthquakes have been published [12,13], and of particular use are reviews of the performance in large earthquakes in Taiwan [14,15]. When damage to mined sections of tunnels was observed, these were indicated to be situations where: ...
Wellington city is characterised by steep hilly terrain, and as such several tunnels have been constructed since the beginning of the last century to provide critical transport access in the city. These tunnels are still used today as part of the city’s transport routes, while also being an integral part of the city’s history and heritage. Wellington is among the most seismically active areas in New Zealand. Three major active faults located within the Wellington Region and the proximity to the subduction zone are the main contributors to the high seismicity. The aging tunnels were designed and constructed prior to the advent of earthquake design standards and are subject to deterioration. Hence, they require maintenance and strengthening to ensure operational integrity and resilience to earthquake and other hazard events. Authorities have been supported by the authors in managing the risk through identifying key vulnerabilities, and prioritisation and implementation of strengthening measures. Best practice investigation and strengthening techniques have been applied through the process to ensure resilience and cost effectiveness. The paper presents case histories that highlight the value of investigations and assessment in understanding the risks, and novel strengthening measures developed to enhance resilience while preserving the heritage of the tunnels. Case histories include the seismic strengthening of the Hataitai Bus Tunnel, the Northland and Seatoun road tunnels and the investigation and assessment of the iconic Wellington Cable Car tunnels.
... These tunnels are vulnerable owing to the heterogeneous geological structure along with the presence of high seismic activity. The study on the vulnerability of tunnels under seismic loading has been of great interest among researchers under various geological conditions [1][2][3][4][5]. The recent earthquake events like the 1999 Chi-Chi earthquake in Taiwan [6] and the 2008 Wenchuan earthquake in China [7] revealed that seismic activity has the potential to damage the support system of the tunnels. ...
Tunnels are the most important infrastructure components as it plays a major role in public infrastructure, water transport and the production of hydroelectric power. The constant variation in the geological conditions affects the tunnel stability which can be achieved using flexible rock support methods. The analysis and understanding of the prevalent complex rock mass in a region which is highly seismically active is a challenge and necessary for the successful execution of any tunnelling project. Therefore, a pseudo-static approach has been studied to understand the impact of earthquakes on circular tunnels using the Phase 2 software. The rock mass surrounding the tunnel is modeled using the continuum approach and continuum with interface approach where joints were incorporated in the model as an interface. For this study, a tunnel model with specification (diameter-6 m, depth-100 m) with a Q range of 1–30 was used to examine the impact of rock mass quality. The study revealed that while the seismic load remains unchanged, the magnitude of the axial force on the liner and the net increase due to seismic loading referred to as seismic axial force, increase as the rock mass quality decreases. The diameter of the circular tunnel at a depth of 100 m is increased from 6 to 24 m at an interval of 6 m to check the influence of the tunnel diameter under the seismic loading. It was observed that the seismic axial force decreases with the tunnel diameter for the rock mass Q = 1 (“very low” rock class) and strong rock, it is comparatively small.
... This can induce damage in the tunnel structure, as observed after recent and historic seismic events (e.g. Dowding & Rozen, 1978;Sharma & Judd, 1991;Power et al., 1998;O'Rourke & Liu, 1999;Corigliano, 2007). The earthquake effect on the tunnel lining is also shown by experimental evidence from centrifuge models of tunnels undergoing shaking in the transverse section (e.g. ...
The paper is focused on the assessment of seismic fragility curves for circular tunnels under moderate to severe earthquakes with the aim of improving the reliability of the risk assessment of underground infrastructural networks. Non-linear two-dimensional dynamic analyses were performed on different tunnel and soil configurations by using the finite-difference method implemented in Flac2D software. The applied input motions were selected considering their amplitude and frequency content variability. The response accelerations and predominant frequencies computed at ground level, above the tunnel, were compared with the corresponding free-field results to distinguish the effects attributable to the tunnel presence from those due to the site amplification. Tunnel safety was assessed through fragility curves, taking into account the dependence of tunnel lining bending resistance on the axial force variation during the earthquake. The more effective intensity measure was investigated correlating the tunnel performance to peak ground accelerations and peak ground velocities computed at the ground level and at the bedrock depth, respectively. The resulting fragility curves showed a satisfying matching with the empirical ones, generated on the basis of the observed seismic damage on tunnels.
... And according to the extended database of Owen & Scholl, little damage would be expected for rock tunnels for peak ground accelerations below 0.4g, as indicated in Figure 3 [6]. IOP Focusing on the damage induced by earthquake shaking other than by ground failure or fault movement, Power et al. removed the relatively poorly documented cases as well as those caused directly by the other two seismic effects, and simultaneously added some recent cases [7]. They concluded that ground shaking caused less damage for PGA less than 0.2g, some cases damaged ranging from slight to moderate damage with PGA between 0.2g and 0.5g, and some other cases suffered slight to heavy damage when PGA exceeded 0.5g, as shown in Figure4. ...
... Based on previous statements the "minor damage" is expected when the value of PGA ranges between 0.19 g and 0.5 g and corresponding thresholds for PGV range approximately between 20 cm/s and 90 cm/s, also Power [5] proposed a damage classification based on PGA. For ground shaking less than about 0.2 g very little damage occurred in tunnels; in the range of about 0.2 g to 0.5 g, some cases of damage were reported, ranging from slight to heavy (serious damage only occurred in an unlined tunnel and in a tunnel with timber or masonry linings); for PGA exceeding 0.5 g there were a number of instances of slight to heavy damage (serious damage occurred only in a tunnel with unreinforced concrete lining). ...
The use of underground space for various needs has seen a significant growth in recent year. This possibility is also reflected in the concept of construction underground nuclear facilities. Based on previous experience , success in the future might be bound to such as smaller nuclear facilities by some named as Small Modular Reactors (SMRs). Suitable locations at appropriate depth taking advantage of the natural barrier properties afforded by the good quality bedrock have important influence on providing appropriate natural circumstances for SMRs. Underground sitting can provide superior protection compared to that of a surface serviced sitting in many critical situations and subsequent devastating consequences for the operation of a nuclear facility. Complicated underground complex needed for a nuclear power system need special attention calling for dedicated investigations and also research on such as issues as earthquake hazard, although the latter seems to be documented being advantageous already. The paper will present a case that clearly shows the obvious advantages of the use of underground space for current available nuclear technologies and assessments of seismic loads influences on nuclear underground structures.
... However, recent large earthquakes have revealed that underground structures can suffer severe damages or even collapse during strong seismic excitations (Hashash et al., 2001;Pitilakis and Tsinidis, 2014). A number of studies documented the observed damage of tunnels in various earthquakes (Dowding and Rozan, 1978;Giannakou et al., 2005;Iida et al., 1996;Jiang et al., 2010;Kitagawa and Hiraishi, 2004;Li, 2012;Lu and Hwang, 2008;Nakamura et al., 1996;Owen and Scholl, 1981;Power et al., 1998;Sharma and Judd, 1991;Shen et al., 2014;Wang, 1985;Wang et al., 2009;Yamato et al., 1996;Yashiro et al., 2007;Yu et al., 2016Yu et al., , 2013. A review of seismic damage of mountain tunnels and possible failure mechanisms was systematically presented by Roy and Sarkar (2017). ...
... Its performance under seismic condition is hardly analyzed. However, the failures of tunnels under seismic loading have been reported in the literature (Dowding & Rozen, 1978;Kaneshiro, Power, & Rosidi, 2000;Owen & Scholl, 1981;Power, Rosidi, & Kaneshiro, 1998;Sharma & Judd, 1991). Hence, it is important to study the effect of seismic loading on tunnels. ...
The studies on the performance of tunnels under static loads are reported extensively in the literature but their performances under dynamic loads are limited. The present study highlights some of the important aspects of jointed rock tunnels during seismic loading. The literature review provides a shake table experimental study of a jointed rock tunnel. A Universal Distinct Element Code (UDEC) model is developed from this shake table experiment. The model tunnel is subjected to a scaled input motion of the 1985 Mexico earthquake. The numerical results are validated systematically with the findings of the shake table experiment. Further, the developed numerical model is used to perform parametric studies to understand the effect of in-situ stress, joint angles, joint stiffness, and joint friction angle on the deformation and stability of the tunnel under the same earthquake input motion. It is observed that some joint angle combinations form a wedge that yields excessive deformation and subsequently a complete failure. An exponential decrease in deformation occurred in the tunnel as the joint stiffness increases. It is found that the shallow tunnels are more susceptible to damage under the action of earthquake loads. Keywords: Tunnel, Jointed rocks, Seismic loading, UDEC
... Several additional reviews of tunnel performance during earthquakes have been published since Dowding and Rozen (1978), including Powers, Rosidi, and Kaneshiro (1998), and being particularly important the reviews performed after large earthquakes in Taiwan (Wang et al., 2001), Japan (Kosugi, Hatsuku, & Shimonishi, 2011;Yashiro, Kojima, & Shimizu, 2007), and China (Lin & Chai, 2008;Li, 2011). These additional data points have confirmed that tunnels can actually behave quite well during earthquakes, but that their response is more complex than initially expected. ...
The tunnel industry has considered that tunnels, especially tunnels in rock, are naturally resistant to earthquake action, including faulting, shaking, deflection and ground failure. As the number of case histories of tunnels subject to earthquake action has increased, the industry has started to recognize that, although tunnels in rock have good resistance against earthquakes generating peak ground accelerations (PGA) lower than 0.5g, it is important to include the dynamic forces and displacements generated by seismic ground motions in the design process to obtain a more reliable design. These additional earthquake forces impact the final design, potentially requiring changes to the ground support and additional reinforcement of the concrete lining, as illustrated by case histories presented in this paper
... The development of appropriate ground motion parameters, including peak accelerations and velocities, target response spectra, and ground motion time histories, is briefly described by (Hashash et al., 2001). Based on previous statements the "minor damage" is expected when the value of PGA ranges between 0.19g and 0.5g and corresponding thresholds for PGV range approximately between 20 cm/s and 90 cm/s, also (Power et al., 1998) proposed a damage classification based on PGA. For ground shaking less than about 0.2g very little damage occurred in tunnels; in the range of about 0.2g to 0.5g, some cases of damage were reported, ranging from slight to heavy (serious damage only occurred in an unlined tunnel and in a tunnel with timber or masonry linings); for PGA exceeding 0.5g there were a number of instances of slight to heavy damage (serious damage occurred only in a tunnel with unreinforced concrete lining). ...
The use of underground space for various needs has seen a significant growth in recent years; several mega cities are considering the potential of going underground. This possibility is also reflected in the concept of construction nuclear facilities and power stations underground. Based on previous experience, success in the future might be bound to such as smaller nuclear facilities by some named as Small Modular Reactors (SMRs). Suitable locations at appropriate depth taking advantage of the natural barrier properties afforded by the good quality bedrock have important influence on providing appropriate natural circumstances for SMRs. Such circumstances provide confinement associated with safety and physical security. Underground siting can provide superior protection compared to that of a surface serviced siting in many critical situations and subsequent devastating consequences for the operation of a nuclear facility. Complicated underground complex needed for a nuclear power system need special attention calling for dedicated investigations and also research on such as issues as earthquake hazard, although the latter seems to be documented being advantageous already. The paper will present a case that clearly shows the obvious advantages of the use of underground space for current available nuclear technologies.
... Experiences gained through the large earthquakes such as in Kobe, Japan (1995), Kocaeli, Turkey (1999) and Chi-Chi, Taiwan (1999) show that underground structures have suffered significant damage due to seismic loading (Sitar, 1995;Iida et al., 1996;Power et al., 1998;Kaneshiro et al., 2000;Hashash et al., 2001;Wang et al., 2001). These damages are mostly caused by fault actions, slope failures, liquefaction-induced floatation or sinking and by racking or ovaling deformations (Wang, 1993, Hashash et al., 2001. ...
Seismic safety of buried structures has become increasingly important over the past two decades, especially after the destructive earthquakes such as in Kobe, Japan (1995), Kocaeli, Turkey (1999) and Chi-Chi, Taiwan (1999). Some of the embedded structures including pipelines, subways and tunnels collapsed or suffered severe damage in those earthquakes due to inappropriate design. The main difficulty in seismic design is the incorporation of soil-structure interaction effect governed by the relative stiffness (flexibility ratio) between the soil and the embedded structure. This study aims to clarify the effect of flexibility ratio on the dynamic response of rectangular structures buried in dry sand. For that purpose, a series of dynamic centrifuge tests were conducted on two types of box-shaped models with different rigidities under various harmonic motions. The results reveal that the magnitude of dynamic lateral earth pressure and sidewall deformation is highly dependent on the flexibility ratio of the embedded structure. Based on the flexibility ratios, racking deformations observed in centrifuge tests and racking deformations estimated through analytical approaches were evaluated in a comparative manner.
... Some researchers used case studies and field observations (Finno et al. (1989), Tan & Li (2011), Ou and Chiou (1993), Wong et al. (1997), Ou and Lin (1998)) some of them used numerical and analytical studies (Finno and Harahap (1991), Whittle et al. (1993)) and few of them used both field observations and numerical analysis (Kung (2009), Ou et al. (1996), Wang et al. (2012)). Also the effect of seismic movement was reported by Sharma and Judd (1991), Power et al. (1998), and Kaneshiro et al. (2000). In this study static and dynamic performance of supporting system was evaluated by investigating lateral deformations and ground settlements in the excavation area located between Mecidiye-Belediye stations, which is a part of Tandogan-Kecioren (M4) line (Figure 1-b). ...
In this study a braced excavation support system of a subway station is evaluated under two cases: (1) Lateral soil pressure caused by excavation and overburden load (2) Seismic load. The substructure is instrumented and the lateral deformations and settlements are observed during excavation and construction of substructure.
A three dimensional finite element model of the substructure is developed and verified using field observations. The structural model is used to calculate the seismic response of the substructure. A bracing system which consists of secant piles and tie-back anchors is introduced to the substructure and seismic performance is examined. Results of three dimensional finite element analysis showed that predicted lateral deformations and vertical movements have similar patterns with measured results and these movements is almost three times under seismic load comparing to static case.
... The support requirements can vary from no support at all to fairly heavy steel sets. The data collected by Power et al. [21] indicate that the support systems, especially reinforced concrete lining and permanent steel support, improve the seismic capacity of the tunnels. The comprehensive analysis studied by Li [16] indicates that with increased lining thickness, the internal stresses increase; also the stress difference between the lining and surrounding rock increases, and the degree of stress concentration in surrounding rock and the amplification factor that defined as the ratio of tunnel response to rock response tend to increase. ...
This study proposes a new damage classification criterion to classify and quantify tunnel damage based on data collected from major earthquakes. The factors influencing seismic damage of mountain tunnels are studied and discussed, including seismic parameters, structural information, and ground conditions. Seismic risk assessment of tunnels is important for an effective disaster management plan. A risk-based assessment technique is proposed as a way to quantify the seismic risk of tunnels. The efficacy of the proposed method is illustrated using data from the 2008 Wenchuan earthquake.
... The study started with compilation of information by literature surveys, internet searches and by sending circular letters to around 60 organizations over the world asking for cooperation and possible information. Several previous compilations, for example Dowding [4], Power [5], Asakura [6] were re-visited. The data base used in Sharma [7] was also kindly provided by Prof. Judd and utilized. ...
... The latter requirement is quantified by imposing restrictions on the maximum developing eccentricity e lim = M max /T max , where M max is the bending moment in the cross-section and T max is the axial hoop force. Unlike conventional reinforced concrete liners, which have been proven to suffer less from earthquakes compared to aboveground structures [4,5], significant damage to unreinforced tunnel linings has been recorded during the Kobe (1995) and the NiigataChuetsu (2004) earthquakes in Japan, which has a long tradition in using unreinforced concrete for tunnel linings678. Although the damage distribution in the tunnel networks suggested that unreinforced tunnel linings can indeed survive earthquake effects under certain conditions, transient seismic wave propagation is recognized to be an important load case to be considered during their analysis and design. ...
... The data collected by Power et al. (1998) indicate that the stronger the shield support system is, especially reinforced concrete lining and steel lining, the better the seismic capacity of the tunnel. The comprehensive analysis submitted by Shunzo (1984) indicates that stone-lined or plain concrete-lined tunnels show cracking due to the unsymmetrical pressure generated after earthquake forces because of their low-moment, tensile, and shearresistance capacity. ...
A total of 81 mountain tunnels that were damaged in 10 strong earthquakes are studied. They are classified into six typical
damage characteristics: lining cracks, shear failure of lining, tunnel collapse caused by slope failure, portal cracking,
leaking, and deformation of sidewall/invert damage. Further study and discussion are carried out on influencing factors for
mountain tunnels, including seismic parameters, structural information, and rock conditions. Suggestions are also made regarding
seismic resistance and reduction.
Sivok-Rangpo Rail Line Project (SRRP) is traversing along the Teesta River Valley through the seismically active Darjeeling and Kalimpong Hills in between MBT and MCT of Darjeeling-Sikkim Himalaya (DSH). Therefore, many environmentalists and geologists claimed that this project dominated by tunnels may invite natural disasters and the tunnels will not be safe under seismic events. From the studies like empirical correlations between measured peak ground accelerations (g) and observed damage in tunnels, the following tendencies have been revealed: (a) up to a peak acceleration of 0.2 g, slight damage, (b) from 0.2 g to 0.6 g, serious damage in unlined tunnels and in tunnels devoid modern lining, (c) from 0.6 g to 0.9 g, serious damage on tunnels having plain concrete lining (unreinforced). Though most severe earthquakes in Sikkim and adjoining areas had peak ground acceleration ranges from 0.15 g to 0.45 g only, which indicate that the modern lined tunnels constructed by NATM are very much safe under massive earthquakes, and NATM designs have all considerable factors for earthquake-induced ground movement in them. The transportation tunnels ensure less damage to the environments and biodiversity and are also used to avoid instable slopes which fail during earthquake-induced ground vibration. Therefore, tunnels are considered as safe and useful in sustainable infrastructural developments in this seismically active Himalayan region.
Underground structures must be able to support both static overburden and seismic loads. Previous work has found that the dynamic amplification of stress waves impinging on a tunnel is negligible when the wave length (λ) of peak velocities is at least eight times larger than the width (B) or diameter (D) of the opening. This condition is applicable to tunnels located far from the seismic source, where the predominant frequencies range between 0.1 and 10 Hz. While such statement has been used and verified for underground structures placed in linear-elastic ground under dry or drained conditions, the effect of input frequency (f) on the seismic response of tunnels placed in nonlinear ground has not been well investigated, especially when undrained conditions apply. Two-dimensional dynamic numerical analyses are conducted, using FLAC 7.0, to evaluate the effect of frequency on the seismic response of deep circular tunnels placed in nonlinear ground under drained and undrained loading. It is assumed that the liner remains elastic, and that plane strain conditions apply. For the ground, an elastoplastic constitutive model is implemented in FLAC. It is found that the effect of input frequency is negligible for λ/D ratios larger than eight to ten, which, given the geometry of the tunnels investigated, correspond to frequencies f ≤5 Hz. Pseudo-static numerical analyses are also conducted for a much smaller and less expensive model, and the results are compared with those of the dynamic analyses. Differences smaller than 2% are found, which suggests that pseudo-static analyses may be sufficient to evaluate the drained or undrained seismic response of deep tunnels placed in nonlinear ground far from the seismic source.
The zones where tunnels through the active faults are proved to be seriously damaged because of the fault dislocation which could be due to strong earthquakes. A steel reinforced rubber joint with flexibility and ductility is proposed in this paper. An experimental investigation of the responses and the damage patterns of the tunnel lining with the joints under normal faulting is presented. The results showed the damage of the lining with the joints in the model test was mainly concentrated in the fault areas because of the joints’ adjustment. No obvious shear failure was found in this test. Then, a nonlinear three-dimensional finite element (FE) model, using concrete damaged plasticity model, was performed to simulate the tunnel linings with the proposed joints and without joints under normal faulting. The numerical results show that the tunnel with the joints had step-like displacements without big relative displacement compared to the tunnel without joints. The joints efficiently decreased the maximum relative displacement between lining segments. The extent of the tensile damage area of the lining affected by normal fault was longer than that of the compressive damage area. And the tensile damage area was larger than the compressive damage area for either the lining with the joints or the lining without joints. There was no obvious difference in damage to the lining with and without joints in areas under compression loading. The joints efficiently decreased the extent of the damage in the zone with tensile stresses. The comparisons between the numerical predictions and experimental results show a good agreement.
Tunnels constructed in soft soils are vulnerable to earthquake-induced ground shaking in seismically active regions. Since typically the tunnelling depth is shallow and lies within the soft ground zone, there is a need for a complete understanding of tunnel behavior in soft soil. A wide range of case histories and various approaches adopted in seismic analysis of tunnels have been reviewed here. Seismic effects on tunnels and factors influencing damages to tunnels due to earthquakes are summarized in this article. In addition, the effects of various parameters on seismic behavior of shallow tunnel in soft soil were investigated in the present study. A fully nonlinear plane strain analysis was performed using finite element (FE) program to examine the effects of input ground motion, shape of tunnel, and tunnel–soil interface conditions on the seismic behavior of tunnel. Prior to parametric study, an approach for calibration of stiffness and Rayleigh damping parameters are discussed. It was observed that the realistic field scenario can be simulated in numerical modeling with calibrated stiffness and damping ratio after conducting site-specific ground response analysis. Available analytical results are compared with developed numerical results. Circular tunnels are found to perform better than other shapes during earthquake condition. Full-slip interface produces higher bending moment in tunnel compared to no-slip tunnel–soil interface condition. Maximum dynamic earth pressure occurs at shoulder of tunnel. The major findings here focus on the complex deformation modes and lining forces of tunnel during earthquake shaking, which can be used for design of tunnels in soft soil.
In the modern world, the underground tunnels and tunnelling facilities are becoming an integral part of the transportation and environmentally preferred means of providing infrastructure. In view of increasing importance, the current study has been carried out to investigate the seismic performances of tunnel structures assessed by investigating seismic vulnerability of underground tunnels. The paper also evaluates the need for seismic design for a communication (road) tunnel located in Zone V, India, based on physical parameters and structural setting. Source parametric data gathered for the earthquakes during the period from CE 1500 to 2012 have been analysed and reported in this work. The study adopts the secondary data collection methodology (i.e. the information obtained from the secondary sources like newspaper, magazines, and Internet). The study also analyses the spatiotemporal variation in b-value and observed that most severe earthquake is located close to high b-value domains. In the analysis correlation between the magnitude and time interval, reduced variate was observed to be low in the final forecast. The findings from this study indicate that within the project life a maximum magnitude (Mw) of earthquake value 8.6 is likely to occur. Therefore, provision of the seismic coefficient is recommended in this tunnel.
An earthquake fault rupture generates two types of ground motion: permanent quasi-static dislocations and dynamic oscillations, characterized by strong pulses. This study investigates tunnel’s response to two different conditions using a 2D finite element program; the first one has a static dislocation corresponding to different earthquake magnitudes, while the second combines near-field seismic motions with three specific peak ground accelerations along with permanent dislocations. The impulsive ground motions affect the lining response further to other influential factors such as fault type and dip angle, making changes in sectional forces, displacement, and shear distortion of the lining. Moreover, pulse intensity, period, and frequency content are effective characteristics of impulsive motions that change in final response of the lining, subjected to subsequent static dislocations. Based on the second condition, at low PGAs, the pulse type is more effective to final response of the lining, due to forward and backward momentum specifications in impulsive motions. For earthquakes with high PGA and larger values in nearfield parameters, both the pulse type and period are effective. The tunnel displacement increases at PGAs as large as 0.7 and 1g, unlike the low PGA as large as 0.35g, because of increasing soil stress and plastic strain, respectively. © 2017, Academy of Sciences of the Czech Republic. All rights reserved.
A review of seismic damages suffered by underground structures shows that most tunnels were located near active faults. In a near field seismic event, the rupture of an earthquake fault generates large ground displacements referred to "fling step" effects. The present study investigates the response of tunnel to static fault displacement according to different earthquake magnitudes by using a 2D finite elements program. The results indicate that the fault mechanism, tunnel position, amount of slip, and earthquake magnitude have significant effects on tunnel lining response, making considerable changes in sectional forces, displacement, and shear distortion on tunnel lining. Reverse faults have more effects on sectional forces of lining comparing to normal faults. The displacement of the lining section under reverse faults is greater than the one under normal faults, except for earthquake magnitudes greater than Ms 7. The shear distortion of the lining section under normal faults located in hanging wall side (i.e. moving bottom boundary of faulting) is higher than the one in footwall side (i.e. fixed bottom boundary of faulting). This is opposite for reverse faults. Finally, in normal mechanism, the recommended safe distance from fault tip is smaller than that of reverse mechanism. 060
In order to analyze the influential factors of tunnel damages induced by an earthquake, the relative data of four tunnels seriously affected by the Wenchuan earthquake were collected and analyzed statistically, as well as calculated and verified through ANSYS software modeling. The results show that the main influential factors include the earthquake parameters (earthquake wave peak acceleration), the surrounding rock grade, overburden, faults intersecting with the tunnel, special tunnel structures, and so on. The damage to the lining is more serious if the earthquake wave peak acceleration is high, the rock mass is of a low grade, or the tunnel passes through faults. The damage to the lining is inversely proportional to the overburden depth. Stress easily concentrates at the special structures of a tunnel, resulting in worse damage.
Natural analogues are defined for this report as naturally occurring or anthropogenic systems in which processes similar to those expected to occur in a nuclear waste repository are thought to have taken place over time periods of decades to millennia and on spatial scales as much as tens of kilometers. Analogues provide an important temporal and spatial dimension that cannot be tested by laboratory or field-scale experiments. Analogues can be used in a qualitative mode to provide a means of understanding complex or abstract processes or in a quantitative mode to test models. Analogues provide one of the multiple lines of evidence intended to increase confidence in the safe geologic disposal of high-level radioactive waste. Although the work in this report was completed specifically for Yucca Mountain, Nevada, as the proposed geologic repository for high-level radioactive waste under the U.S. Nuclear Waste Policy Act (and it is referred to as such throughout this report), the U.S. Geological Survey believes that the applicability of the science, analyses, and interpretations is not limited to a specific site. The work is important as a contribution not only to investigations of future waste-disposal options, such as the assessment of alternative sites or solutions, but also as a contribution to scientific investigations unrelated to waste disposal. Isolation of radioactive waste at a mined geologic repository would be through a combination of natural features and engineered barriers. In this report we examine analogues to many of the various components of the Yucca Mountain system, including the preservation of materials in unsaturated environments, flow of water through unsaturated volcanic tuff, seepage into repository drifts, repository drift stability, stability and alteration of waste forms and components of the engineered barrier system, and transport of radionuclides through unsaturated and saturated rock zones. Hundreds of delicate and easily destroyed artifacts and biological materials have been well preserved both in natural (for example, caves and rock shelters) and in manmade (for example, tombs and mines) underground openings. The maintenance of a stable microclimate is a critical feature in making caves suitable for long-term preservation. The survival of metal artifacts over prolonged periods of time is related to the corrosion-resistant properties of metals and metal alloys, the development of protective passive film coatings with the onset of corrosion, and sequestering artifacts with water, which is enhanced by the location of artifacts in arid to semiarid environments. Numerous examples demonstrate that both natural and manmade underground openings can exist for thousands of years in a wide variety of geologic settings, even with minimal or no engineered supports. Examination of these openings also leads to the conclusion that seismic events at or near a mined repository are not likely to cause significant damage to the emplacement tunnels. As a consequence, the tunnels should be expected to be a long-term hydrologic feature. Analogues add valuable insight to understanding long-term waste-form degradation processes through the record left behind in secondary minerals and groundwater chemistry. In addition, measurement of the concentration of fission products as tracers in rock and groundwater surrounding uraninite provides a satisfactory approach to estimating natural dissolution rates, as was tested at a number of sites that demonstrated a more rapid dissolution rate under oxidizing conditions. Models predict that much of the water percolating through the unsaturated zone will be held in the wall rock of tunnels by capillary forces rather than entering the tunnels as seepage. Analogues in natural and manmade underground openings demonstrate the tendency for water that does become seepage to run down the walls of underground openings rather than drip from the ceiling; thus, not all seepage would affect stored waste. In the event of waste mobilization and migration away from the emplacement drifts, the rate of radionuclide transport through the unsaturated zone is determined by the percolation flux and by the hydrologic properties and sorptive properties of the tuff units. Fractures act both as transport pathways and as places of retardation at a number of unsaturated analogue sites, including the Idaho National Laboratory, near Idaho Falls; Peña Blanca, Mexico; Akrotiri, Greece; and volcanic tuff-hosted uranium deposits in northern Nevada. In the saturated zone, advective transport along fractures has been identified as a more significant transport mechanism than matrix diffusion in all the analogue sites studied, although matrix diffusion may account for loss of lead in uraninites at Oklo, in Gabon. The Poços de Caldas site in Brazil highlighted the importance of amorphous phases in suspension or as coatings on rock as the principal sorptive surfaces for many trace elements in solution. Some of the fixing processes appeared to be irreversible over long time scales. Sorption onto fracture coatings, particularly calcite, also efficiently retards uranium transport in fractures at Palmottu, Finland, and El Berrocal, Spain. Matrix diffusion in crystalline rock is generally limited to only a small volume of rock close to fractures, but even a small volume can make a significant difference in radionuclide retardation. In most studies of natural systems, a proportion of the total uranium, thorium, and rare earth elements (REE) in the groundwater was associated with colloids. Colloid transport appears to be an important factor for migration of thorium in one open unsaturated system, Steenkampskraal, in South Africa, but not in another, Nopal I, in Mexico. Colloidal transport of uranium was shown to be minimal at the analogue site in Koongarra, Australia, where filtration of colloids appears to be effective. Observations from the Nevada Test Site lend support to the concept that radionuclide transport in the saturated zone can be facilitated by colloids; but so far, no natural analogue studies have quantified the importance of this process. The emplacement of heat-generating waste in a geologic repository located in the unsaturated zone will cause perturbations to the natural environment through heat transfer, as well as by associated geochemical and geomechanical changes taking place in the repository near-field and altered-rock zones. The unsaturated conditions, lower temperatures, and much lower fluid-flow rates predicted for the Yucca Mountain system should result in less extensive water/rock interaction than is observed in geothermal systems. Evidence from fossil hydrothermal systems indicates that mineral alteration resulting from flow of hot fluids through fractures extends only a few centimeters from the fracture wall into the matrix. Simulations indicate that only small reductions in fracture porosity (4-7 percent) and permeability (less than 1 order of magnitude) will occur in the near field as a result of amorphous silica and calcite precipitation. Changes in permeability, porosity, and sorptive capacity are expected to be relatively minor at the mountain scale, where thermal perturbations will be reduced. The Yucca Mountain Project has applied analogues for testing and building confidence in conceptual and numerical process models and has less frequently used analogues to provide specific parameters in total system performance assessment (TSPA) models. Analogues have been widely used as model validation of aspects of Yucca Mountain characterization. In conclusion, natural and anthropogenic analogues have provided and can continue to provide value in understanding features and processes of importance across a wide variety of topics in addressing the challenges of geologic isolation of radioactive waste.
A theoretical method for studying the dynamic response of a circular lined tunnel with an imperfectly bonded interface subjected to plane P-waves is presented in the paper. The wave function expansion method was used and the imperfect interface was modeled with a spring model. Two cases were discussed in the paper. In the first case rock is harder than the lining and vice-versa in the second case. The results indicated that the variation in the stiffness of the interface has much influence on the distribution of dynamic stress concentration factors (DSCF) in the rock and the lining. The imperfection of the interface has a more noticeable influence on the DSCF in the rock mass and the lining at high frequency incident wave's scenario than low frequency incident wave's scenario. The resonance scattering phenomena can be observed when the bond is extremely weak. Limiting cases were considered and a good agreement with the solutions available in the literature was obtained.
Seismic safety of underground facilities such as pipelines, culverts, subways and tunnels becomes an essential requirement for sustained economic and social development. Many engineers earlier thought that the underground structures had been inherently safe against earthquakes, but then, especially after the failure of some underground facilities during 1995 Kobe, Japan, 1999 Kocaeli, Turkey and 1999 Chi Chi, Taiwan earthquakes the safety evaluation of underground structures has become a major concern of the engineers. This research aims to investigate the dynamic response of box shaped underground structures buried in dry sand. For this purpose, a series of centrifuge tests were carried out under harmonic sinusoidal motions by considering the nonlinear behavior of both structure and surrounding soil. Hence, response of model ground and deformation of the buried models were examined with special reference to the dynamic soil structure interaction. A specific variable considered in this study is the rigidity of buried box structures. Three different models with varying rigidities were used in the tests. Different deformations schemes of the sidewalls were analyzed under harmonic motions. Results of the centrifuge experiments were evaluated and compared to the predictions obtained from closed-form solutions recommended in the literature.
Major earthquakes such as Kobe (1995), Kocaeli (1999) and Chi–Chi (Taiwan) have shown that underground structures have suffered significant damage due to dynamic loading. Therefore, recently, much priority has been given to seismic safety of underground structures located in earthquake-prone regions. There is, however, not much experimental research on the dynamic response of buried structures. This research aims to better understand the dynamic behavior of relatively flexible rectangular underground structures embedded in dry sand. To achieve this purpose, a series of dynamic centrifuge tests were conducted on a box-shaped flexible underground structure under harmonic motions with different accelerations and frequencies. Thus, response of soil and buried structure model was examined considering the dynamic soil structure interaction. Accelerometers were placed in the soil and on the buried structure model to evaluate the shear strain and acceleration response. Moreover, a special attempt was made to investigate the racking deformations by installing extensometers inside the tunnel model. Measurements obtained from those extensometers were compared with the predictions of analytical solutions. Results show that, Penzien’s approach gives reasonable estimates of racking deformation for the rectangular shaped flexible underground structure.
Isolation layer is one of the countermeasures to enhance seismic safety of tunnels. Its behavior under earthquake is affected by many factors such as shape of the tunnel, stiffness of the isolation layer and the characteristics of the input motion. However, current knowledge on the effects of these parameters on the seismic behavior of isolation layer is limited to lack of experimental data. This paper focuses on the mechanism of isolation layer, especially the efficacy of input motion frequencies on the seismic behavior of a square tunnel with isolation layer around its outer surface. Dynamic centrifuge tests were carried out on model tunnels which took isolation layer as seismic countermeasure using input motion of sinusoidal waves of different frequencies. Actual records of ground motions, magnified to approximate 15 g peak acceleration, formed the basis of the excitations to verify the actual efficacy. Due to the difference between model material (aluminum alloy) and prototype material (concrete), the similar flexural deformation law and the similar axial deformation law could not be satisfied simultaneously. Given the fact that cross-sectional moments were one of the main factors that influenced the safety of tunnels under dynamic loadings, the similar flexural deformation law was accepted in model preparation. The results show that the bending strains of tunnel with isolation layer around its outer surface are lower than those of tunnel without isolation layer, which indicates that isolation layer has positive effect on moment reduction, especially at corners. Increasing of the input motion frequency decreases the dynamic cross-sectional bending moments. In addition, isolation layer has little influence on frequency contents of acceleration response of tunnel. This study has clarified the mechanism of isolation layer on shock absorption, which is proved to be an effective method to improve the safety of tunnel against earthquake.
This paper presents an elastoplastic finite element analysis of the seismic response of tunnels constructed in soft soils. The behavior of the soil material is described using a cyclic elastoplastic constitutive relation involving both isotropic and kinematic hardening. The paper is composed of three parts. The first part includes a brief presentation of the numerical model used in the analysis; the second one concerns analysis of the seismic response of a tunnel constructed in a soft soil; the last one presents a study of the influence of the plasticity and soil dilatancy on the seismic response of tunnels. Analyzes show that the plastic deformations induce an important reduction in the seismic-induced bending moment in the tunnel, while the soil dilatancy moderately affects the bending moment in the liner.
Calculations made by the U.S. Department of Energy's Yucca Mountain Project as part of the licensing of a proposed geologic repository in southwestern Nevada for the disposal of high-level radioactive waste, predict that emplacement tunnels will remain open with little collapse long after ground support has disintegrated. This conclusion includes the effects of anticipated seismic events. Natural analogues cannot provide a quantitative test of this conclusion, but they can provide a reasonableness test by examining the naturally occuring and anthropogenic examples of stability of subterranean openings. Available data from a variety of sources, combined with limited observations by the author, show that natural underground openings tend to resist collapse for millions of years and that anthropogenic subterranean openings have remained open from before recorded history through today. This stability is true even in seismically active areas. In fact, the archaeological record is heavily skewed toward preservation of underground structures relative to those found at the surface.
Underground facilities are an integral part of the infrastructure of modern society and are used for a wide range of applications, including subways and railways, highways, material storage, and sewage and water transport. Underground facilities built in areas subject to earthquake activity must withstand both seismic and static loading. Historically, underground facilities have experienced a lower rate of damage than surface structures. Nevertheless, some underground structures have experienced significant damage in recent large earthquakes, including the 1995 Kobe, Japan earthquake, the 1999 Chi-Chi, Taiwan earthquake and the 1999 Kocaeli, Turkey earthquake. This report presents a summary of the current state of seismic analysis and design for underground structures. This report describes approaches used by engineers in quantifying the seismic effect on an underground structure. Deterministic and probabilistic seismic hazard analysis approaches are reviewed. The development of appropriate ground motion parameters, including peak accelerations and velocities, target response spectra, and ground motion time histories, is briefly described. In general, seismic design loads for underground structures are characterized in terms of the deformations and strains imposed on the structure by the surrounding ground, often due to the interaction between the two. In contrast, surface structures are designed for the inertial forces caused by ground accelerations. The simplest approach is to ignore the interaction of the underground structure with the surrounding ground. The free-field ground deformations due to a seismic event are estimated, and the underground structure is designed to accommodate these deformations. This approach is satisfactory when low levels of shaking are anticipated or the underground facility is in a stiff medium such as rock. Other approaches that account for the interaction between the structural supports and the surrounding ground are then described. In the pseudo-static analysis approach, the ground deformations are imposed as a static load and the soil-structure interaction does not include dynamic or wave propagation effects. In the dynamic analysis approach, a dynamic soil structure interaction is conducted using numerical analysis tools such as finite element or finite difference methods. The report discusses special design issues, including the design of tunnel segment joints and joints between tunnels and portal structures. Examples of seismic design used for underground structures are included in an appendix at the end of the report.
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