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Effect of Repeated Blast Loading On Damage Extent of Penstock Tunnels In Heavily Jointed Rockmass - A Case Study
Ramulu, M. (Central Institute of Mining & Fuel Research) | Sitharam, T.G. (Department of Civil Engineering, Indian Institute of Science) | Choudhury, Pb (Central Institute of Mining & Fuel Research) | Raina, AK (Central Institute of Mining & Fuel Research) | Chakraborty, A.K. (Central Institute of Mining & Fuel Research)
ABSTRACT The detonation of explosive charges releases large quantities of energy that can produce deformations in the vicinity of blasting site. Extensive data are available on blasting in general and on the behavior of surface structures subjected to blast vibrations. However, only limited information is available on the effect of blast induced dynamic forces on underground structures like tunnels and caverns. This paper deals with the research work carried out at Koldam Hydroelectric Power Construction Project (KHEPP) on the effect of repeated blast vibrations on the jointed rock mass. Multiple rounds of blasts were conducted at the penstock tunnels and at the excavation site for powerhouse foundation. The damage caused by blast induced vibrations can be categorized into two types: i) near-field damage due to high frequency vibrations when the blast is occurring in the close proximity and ii) far-field damage due to low frequency vibrations when the blast is occurring relatively farther distances. The near-field damage was assessed by analytical damage models based on the ground vibrations. The far-field damage was assessed by measuring deformations of borehole extensometers and by borehole camera inspection surveys before and after the repeated blasting. Peak particle velocities generated by blast rounds were recorded by installing triaxial geophones near the borehole extensometers and borehole camera inspection holes. Damage assessment instrumentation was carried out at both the sides of penstock tunnel wall as another objective of the study was to compare the extent of rock mass damage with different joint orientations. The study reveals that repeated dynamic loading imparted on the jointed rock mass from subsequent blasts, in the vicinity, resulted in damage even at 23–26% of critical peak particle velocity. The far-field damage due to the repeated blast loading, after 56 rounds, was 77% of the near-field damage. It was also found that the far-field damage due to the repeated blast loading at the tunnel wall with 1500 joint orientation is 74% more than the damage at tunnel wall with 200 joint orientation. The results of the study indicate that repeated blast vibrations, even at less than critical vibration levels can cause damage problems to the structures in jointed rock mass. The paper stresses the need for consideration of the effect of repeated blast loading for comprehensive damage assessment as well as for fixing the threshold vibration limits to avoid the blast induced damage. 1. INTRODUCTION Blasting produces seismic waves similar to those produced by earthquakes, but with relatively high frequency and low amplitude and the degree of structural damage depends on the total energy of explosion, distance from the source, and the character of the medium. Blast induced damage weakens a rock mass, potentially leading to stability problems in the underground excavations. The blast damage problem is more severe and vulnerable for the jointed rock mass in underground excavations (Singh and Xavier, 2005). Unfortunately, there are no specific safety guidelines available for the blasted tunnels with regards to the threshold limits of vibrations caused by repeated blasting activity in the close proximity.
ABSTRACT Back-analysis is a systematic procedure to determine model parameters using measured response. The use of back-analysis is particularly appropriate for tunnel constructions where more information on the ground characteristics and response become available as the construction progresses. Back-analysis requires an algorithm to find a set of input parameters that will minimize the difference between predicted and measured performance. This paper presents one such algorithm based on Simulated Annealing (SA). The specific method belongs to a general class of heuristic based methodologies for locating global solutions for non-linear optimization problems. SA presents certain advantages when dealing with highly non-linear ground response and subsequent non-linear behavior of a multi-variable error function to be minimized. The SA-based back-analysis procedure is implemented in the commercially available computer code FLAC. The performance of the proposed method is illustrated by its application to the modeling of the Heshang Tunnel in China. 1 INTRODUCTION Computational models for geotechnical applications have undergone major improvements in the past several decades. Computational models can be used in a performance-based engineering design and evaluation of geotechnical structures by providing detailed evaluation of damage and estimated consequences. However, determination of model parameters remains to be the "Achilles heel" of computational modeling (Brown et al. 2002). This is particularly true due to significant uncertainties in material properties and loads encountered in geotechnical engineering. Geological, geophysical, in situ and laboratory investigations needed in analysis and design are time consuming and expensive, and are carried out extensively only for very important projects. Direct measurements of field response can provide faster and more economical means of determining model parameters and for improving the reliability of model predictions. The determination of parameters required in computational models using measured response is referred to by different terms, including back-analysis, parameter or system identification, inverse analysis and model updating. In contrast to forward analysis where response is predicted given the required input data (e.g., material parameters and loads), back-analysis involves determining the input parameters given the response (i.e., from field measurements). Back-analysis requires an algorithm to find a set of input parameters that will minimize the difference between predicted and measured performance (e.g., in terms of deformations or stresses). Back-analysis is particularly suited for underground constructions such as tunneling where more information on the ground characteristics and response become available as the construction progresses. Back-analysis requires an algorithm to handle the minimization of the difference between predicted and measured response, which is expressed in terms of an error or objective function. Methods of back-analysis can be broadly classified as direct and gradient based optimization techniques. Direct optimization methods exploit the vector relation between two successive solutions, and perform linear combinations of sequential solutions and attempts to find the local optimum. In gradient-based methods, the infinitesimal change of the solution path and the corresponding gradient are used to control the solution processes. Usually such methods may offer higher solution precision at the expense of the calculation run time required for the estimation of the first or second order derivatives
ABSTRACT Presently the survey of absolute displacements of targets fixed at the tunnel wall is the state of the art in performance monitoring of tunnels. Monitoring data are used to assess the stabilization process of the tunnel, more recently also for the short term prediction of the ground conditions ahead of the face. The displacements do not substantially vary in rock mass conditions with nearly constant properties and influencing factors. On the other hand, changes in the rock mass structure or properties result in changes in the displacement characteristics. For nearly constant conditions, the displacement trends show minor fluctuations within a certain normal range, due to minor variations in the rock mass properties. Deviations from this range are clear indicators for changing conditions ahead of the face or outside of the tunnel. To identify such trend deviations the normal range of the trend lines becomes crucial. Geostatistical methods allow an automatic identification of trends along the tunnel. Using data from completed tunnel projects a "reference trend table" can be established. By comparing actual observed trend characteristics to this reference table changing ground conditions ahead of the face can be identified and hence, the change in the displacement characteristics and magnitudes can be predicted. 1 INTRODUCTION The uncertainties in the geological conditions and ground parameters require an observational approach for safe and economical tunnel construction. Several conditions must be fulfilled for a successful application of the observational method (Peck 1969, Schubert 2008). One of the requirements is the assessment of possible behaviors and the establishment of their acceptable limits during design. This includes the identification of potential failure modes, as well as the determination of deformation characteristics and magnitudes. As the ground in general is all but homogeneous, continuous, and isotropic, simple homogeneous models usually do not provide enough insight to establish a realistic "normal behavior" for structured and heterogeneous ground conditions. It is also unrealistic to think that sophisticated numerical models can be used for an entire project during the design. A reasonable way to produce expected realistic ground behaviors is to first use simplified models to determine the range of expected displacements, and then modify the results with the help of expert knowledge. During construction the measurement results contain all influences of the ground structure, stresses, and interaction between ground and support. The previously established characteristic behaviors for certain conditions are compared to the monitoring results. In case of agreement it can be established that the observed behavior is "normal". Deviations from the expected behavior can have various reasons. One may be that the behavior during design was not assessed correctly. In this case, a refinement of the model is required. Another reason for behavior deviating from the expected can be a change in the ground conditions ahead of the face. It is meanwhile well known that trends of displacement vector orientations can be used to predict changing ground conditions ahead of the face (Schubert & Budil 1995, Steindorfer 1997, Jeon et al. 2005).
Ground Reaction Curves of a Tunnel Excavated In a Good Quality Rock Mass Showing Different Types of Post-failure Behaviour
Liang, Weiguo (Taiyuan University of Technology) | Zhao, Yangsheng (Taiyuan University of Technology) | Dusseault, Maurice B. (Earth and Environmental Sciences Department, University of Waterloo)
The costs of ground support and reinforcement in underground works and tunnels is significant, but even more costly would be a support failure or a tunnel face collapse. The authors of this paper have been working in the development of techniques to obtain Ground Reaction Curves (GRCs) for tunnels excavated in brittle and strain-softening (or strength weakening) continua, as well as in the post-failure dilatant behaviour of rock masses. This study is an extension towards brittle behaviour of the work on strain-softening rock masses presented in the ISRM International Congress by members of the group. This particular study regards a tunnel excavated in a good quality rock mass, being estimated all of its significant parameters and its ground reaction curve obtained for increasing levels of model complexity and realism. To determine the residual strength parameters of the rock mass, the GSI system approach has been used. After the different models had been built, the integration techniques for strain softening behaviour have been used to obtain the corresponding GRCs. The effects of the standard support and reinforcement are also assessed. 1 INTRODUCTION
- North America (0.47)
- Europe > Spain (0.28)
ABSTRACT An excavation slope in left abutment trough of Xiluodu arch dam has 380 meters or so. In order to ensure safety of the excavation slope, the designed excavation and reinforcement process of the slope is simulated systematically with self-developed 3D elasto-viscoplastic finite element method (FEM) analysis program based on the model of reinforced jointed rock masses. Distribution patterns of displacements, stresses and point safety factors of the rock slope and reinforcement effects under tectonic initial geostress field are analyzed and the slope stability is evaluated in each excavation step. The simulation results show that displacements of the excavated slope between 470 meter and 400 meter in elevation are relatively bigger and its yield zone extends deeper into the mountain body in the designed excavation and reinforcement scheme. Supplementary reinforcements with some pre-stress cables are suggested for strengthening the excavation slope from 470 meter to 400 meter in elevation. The numerical simulation results show that the new reinforcements help improve the stability of the excavation slope in left abutment trough and ensure the safety of the slope. 1 INTRODUCTION The Xiluodu Hydropower Project is an extreme project in China and its installed capacity is 12.6 MW, which locates on the upper reaches of the Yangtze River. The dam type is double-curvature arch dam and its maximum dam height is 278 meters. Its plan and section X-X in left bank are presented in Figure 1. Figure 1(b) shows lithological characteristics of rock masses and distributions of dominant texture planes in left bank. The rock masses mainly have four rock types according to weathering degrees: II, III1, III2, IV1. The dominant texture planes mainly include three strain-slipzoneinlayers and two joint sets. The strain-slipzoneinlayers are C7,C8,C9. Occurrences of such texture planes are presented in Table 1. After completion of excavations, the final excavation slope in left abutment trough of Xiluodu arch dam has more than 380 meters height, and its spatial shape is very complicated. Because the physical and mechanical parameters of rock masses are usually weakened for exploding construction, failures of the excavation slope are likely to occur. In order to ensure the stability and safety of the excavation slope, many supports should be utilized to reinforce the slope in a construction period, which are pre-stress cables, pre-stress bolts, systematic bolts, etc.. Which position should be reinforced, and how many bolts and cables should be adopted are focuses of engineering design and construction. Unsuitable reinforcement measures and reinforced locations will not prevent slope from instability effectively and only increase engineering investments. Consequently it has a great significance to study excavation slope stability and reinforced effects of corresponding reinforcement measures with computer aided simulation technologies before the slope excavation (FENG Xue-min, WANG Wei-ming, et al., 2004) Finite element method has gained popularity in analyzing geotechnical problems for fewer assumptions and more powerful functions (Chen, S.H., Egger, P.,1999; Chen Sheng-hong, Qing Wei-xin, Shahrour Isam, 2007). The excavation and reinforcement process of rock slope can be simulated conveniently by finite element method with suitable constitutive models of geomaterials.
- North America > Canada (0.28)
- Asia > China (0.24)
ABSTRACT A The responses of some lined underground openings under hydrostatic or biaxial stress field are examined numerically for original HB and equivalent MC strength parameters. The rock mass is assumed brittle and the horizontal to vertical stress ratio is varied. Selected tunnel responses of the openings for the original HB rock mass are compared to the responses computed using equivalent MC strength parameters. These include the displacement at the crown and the side walls of the opening, the yielded zone formed around the tunnel and the internal forces within the tunnel lining. Results indicate the cases where deviations in the tunnel performance are computed. 1 INTRODUCTION The non-linear Hoek-Brown (HB) strength criterion is widely employed in numerical analysis for tunnel design, as the failure criterion to simulate the triaxial behavior of the rock mass. However, many numerical codes, either of general purpose or specialized for geotechnical design, do not implement the HB criterion, while they may allow for the linear Mohr-Coulomb (MC) criterion. This necessitates the development of procedures for the evaluation of MC parameters from the prototype HB ones, which when used in numerical codes for the simulation of constructions in rock, would evaluate similar responses. Such MC parameters and corresponding rock masses are defined as equivalent to the prototype HB ones, respectively. Several methods have been developed for the evaluation of equivalent MC strength parameters for given HB ones. Traditionally, they are based on a linearization procedure of the HB strength envelope for a selected range of the minor principal stress. This range is either considered as independent of the in situ stress field (Hoek and Brown, 1997) or depends on it. In the latter case the internal pressure offered by the tunnel support may either be neglected (Hoek et. al., 2002), covering thus a wider range of rock mass responses, or taken into account (Sofianos and Halakatevakis 2002, Sofianos 2003, Sofianos and Nomikos 2006, Jimenez et. al. 2008), aiming to better approximate the final equilibrium condition of the tunnel. Most of the existing methods are concerned with the case of an elastic-perfectly plastic rock mass. However, rock mass may exhibit a strain-softening behavior after failure. The importance of post-peak behavior of rock mass for rock engineering design has already been recognized (Hoek & Brown 1997, Russo et. al. 1998, Ribacchi 2000) and recently emphasized (Cai et. al., 2007), since it may have a strong influence on the stability of the underground excavations. Sofianos & Nomikos (2006) presented two methods, BFe and EMR, to calculate the equivalent MC rock mass strength parameters for axisymmetric tunnels in plastic or brittle rock. These are shortly described in the following. 2 BACKGROUND Brittle behavior of the rock mass is represented with a sudden drop in its strength parameters after failure, corresponding to the two failure envelopes of Figure 1. For the HB criterion the rock mass strength is defined by two sets of parameters;σci, mb, s and a for the pre-failure behavior and σciR mbR, sR and αR for the post-failure behavior.
ABSTRACT One improved SVR algorithm was introduced into the field of elasto-plastic displacement back analysis in this paper. The strong nonlinear and uncertain relation between calculation parameters of rock mass and displacement of surrounding rock was described by the improved SVR algorithm. In order to find the optimal parameters of this improved SVR model during samples training course, the Genetic Algorithm (GA) was combined with it to form the improved GA-SVR algorithm. After the optimal non-linear mapping between the elasto-plastic mechanical parameters and displacement had been established, GA was used to identify these mechanical parameters within their search interval. By dint of MATLAB toolbox, GA also was integrated with BP neural network to form the GABP algorithm. Compared the back analysis results of the same elasto-plastic model parameters in BAOZHEN long and large railway tunnel by the two different algorithms, it can be concluded that the improved GA-SVR algorithm can obtain a more high inversion precision and calculation efficiency than that of GA-BP algorithm, so the improved GA-SVR can be applied in similar geotechnical engineering. 1 INTRODUCTION Artificial neural network (ANN) is characterized by self learning, self adapting and parallel computation, so it can be used to solve strong nonlinear, discontinuity and uncertain relation. The BP neural network was employed to estimate the mechanical parameters of rock mass of Three Gorges permanent shiplock(Feng,2000). However, ANN is a large sample learning machine and has the disadvantages in overfitting and local optimization, which set a bottleneck constraint in application of geotechnical engineering (Zhao, 2003). Support vector regression (SVR) algorithm has many merits such as small sample and global optimization etc. Compared with ANN, SVR algorithm based on the structure risk minimization principle can avoid the overfitting (Vapnik, 1995). So it is more appropriate to be applied into underground engineering than ANN algorithm (Zhao 2003, Liu 2004). During the process of BAOZHEN tunnel construction in Yichang-Wanzhou railway, SVR algorithm was introduced into the displacement back analysis in this paper. 2 BRIEF INTRODUCTION OF BAOZHEN LONG AND LARGE TUNNEL BAOZHEN tunnel, located between the HEJIAPING and LANGPING Town of CHANGYANG County, HUBEI province, is one long and large tunnel of railway from YICHANG to WANZHOU which is the national key engineering. The distance between the left and right line is 30M. The total length of left line is 11563M, and the other is 11595M. According to the initial design, the right line is a parallel pilot which severs as assistant function during left line construction period. The length of IV and V grade surrounding rock is about 60 percents of whole tunnel. The embedded depth of this tunnel is large, and local section reaches 630M. The section of left line from DK72+834 to DK79+887 and the section of right line from YDK72+248 to YDK79+995 belong to extreme high stress district and inclined to generate large deformation during construction process. The section from DK73+430 to DK73+480 of left line is the study part in this paper which possess high crustal stress and soft surrounding rock.
ABSTRACT Mountain tunnels are linear structures constructed in inner ground and geological data usually cannot be fully collected in the tunnel design stage. Therefore, standard support patterns are generally used in construction and modified according to measurements on cutting face during excavation. In recent years, the development of auxiliary methods like umbrella method facilitates the construction on severe ground conditions (unconsolidated ground, fracture zone, water inflow, neighboring construction etc.). However, reliable prediction method to the behaviors of ground ahead cutting face has not been established. In this study, two sites(Rittou Tunnel and Hirayama Tunnel) employing such auxiliary methods for stability of cutting face are depicted. In the future, more and more tunnels will be constructed under critical and severe conditions, such as construction beneath urban area with thin overburden, large cross section and unsymmetrical in-situ stresses. Therefore, applying appropriate tunnel support and auxiliary method is becoming more and more important. 1 INTRODUCTION Mountain tunnels are linear structures constructed in inner ground and geological data usually cannot be fully collected in the tunnel design stage. Therefore, standard support patterns are generally used in construction and are modified according to measurements on cutting face during excavation. In recent years, the development of auxiliary methods like umbrella method facilitates the construction on severe ground conditions (e.g. unconsolidated ground, fracture zone, water inflow, neighboring construction). However, reliable prediction method to the behaviors of ground ahead cutting face has not been established. In this study, two sites employing such auxiliary methods for stability of cutting face are depicted. Rittou tunnel has a cross section of 252m for dust collector using top heading & bench cutting NATM method. In Hirayama tunnel, ground estimation system based on behavior prediction to the ground ahead of cutting face using the mechanical data from tunnel jumbo was applied since this tunnel is located in complicated ground condition where geological characteristics vary remarkably. The images of survey process using borehole camera carried out during excavation are shown in Plate 1 and Plate 2. (Plate in full paper) 2 DECISION AND EXECUTION OF AUXILIARY METHODS 2.1 Commonly used auxiliary methods in Japan Safe and effective countermeasures (auxiliary method) should be adopted to solve the problems generating during construction. At the same time, cost considering the construction conditions (ground condition, restriction condition during construction and construction schedule etc.) is also an important factor. Characters of a few commonly used auxiliary methods are described as follows:Long steel pipe forepiling (L>5m) Preceding displacement in front of cutting surface could be inhibited by placing long steel pipe ahead of cutting surface. Recently, applying this method by general construction instruments in tunnel construction becomes possible. It has advantages in construction period and economy and is adopted increasingly. Injection forepoling (L<5m) This method is an extensively adopted forepoling method, which strengthens the necessary region of preceding ground by injection. In large-section cases, this method sometimes cannot inhibit the preceding displacement.
- Geology > Structural Geology (0.57)
- Geology > Geological Subdiscipline > Geomechanics (0.35)
ABSTRACT With the introduction of a new four-year degree program at The University of Hong Kong, a Centennial Campus is being developed at the western side of the existing Main Campus. The scope of this infrastructure project comprises the design, construction and commissioning of two new salt water and two new fresh water service reservoirs. Cavern was excavated in sandstone and tuff to accommodate the new salt water reservoir in a twin-cell tunnel system. The cavern was constructed inside a sloping ground due to the need to find adequate rock cover. Starting at the portal, an about 30 m long, 7.2 m span access tunnel was constructed and then separated into two reservoir tunnels. Two 10 m long transition zones were constructed and then the tunnels were enlarged from 7.2 m span to 17 m span to create the cavern for the new salt water reservoir. With the requirements of minimal damage and disturbance to the rock mass during the excavation, it provided an ample opportunity to study the convergence of the cavern as the excavation approached an undisturbed zone. This paper presents an evaluation of the magnitude of stresses acting on the crown of the large span tunnel at different stages of ground movement. Back analysis was carried out based on the observed stresses and deformation resulted from approximately 6 m high top heading tunnel excavation. Two-dimensional finite element analysis program was utilized for this back analysis. Different empirical equations such as Bieniawski, Serafim and Pereira, Barton and Hoek et al. have been used in the numerical analysis to simulate the rock mass behaviors. It revealed that the Serafim and Pereira estimation was generally applicable for this particular HKU cavern project with volcanic tuff bedrock of as-mapped Q-value higher than 2.3 or RMR value higher than 50. The observed monitoring records also demonstrated that approximately 2 mm of vertical deformation was mobilized to provide an efficient temporary support to the tunnel crown. Little stress relief and deformation was observed after the temporary rock support has been substantially mobilized. This paper presents a case-study of the rock behavior due to the underground opening. It also demonstrated the performance of immediate support to the tunnel crown in controlling the ground settlement and stress relaxation. 1 INTRODUCTION 1.1 Project Background In April 2007, Gammon Construction Limited was commissioned for the design and construction of re-provisioning of the Water Services Department (WSD) utilities and infrastructure works for the proposed Centennial Campus at The University of Hong Kong. The re-provisioning service reservoirs included the fresh water and salt water service reservoirs with a capacity of 26,500 m3 and 12,000 m3 respectively, in which the proposed salt water service reservoirs were located inside the 17 m span rock cavern in a complex geology (see Figure 1 for the site layout plan). In this project, drill and mechanical breaking was adopted rather than drill and blasting to excavate the caverns.
- Asia > China > Hong Kong (0.92)
- South America > Colombia > Risaralda Department > Pereira (0.46)
- Geology > Geological Subdiscipline > Geomechanics (0.69)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.34)
Study On the Flexible Lining of the Tunnel In the Active Faulted Zone
Zhengzheng, Wang (School of Civil Engineering, Southwest Jiaotong university) | Bo, Gao (School of Civil Engineering, Southwest Jiaotong university) | Yusheng, Shen (School of Civil Engineering, Southwest Jiaotong university) | Wanjun, Zang (SPCD, Yaxi Expressway Engineering Construction Directorate)
Abstract The tunnel may have to be constructed across a faulted zone as it is not always possible to avoid crossing active faults. In these situations, the tunnel lining must tolerate the expected fault displacements and seismic action, and allow only minor damages for the assumed life time. This paper presents a method of designing flexible lining for tunnels within the regions of active faults. The effects of the method are analyzed. The results show the tunnel lining with flexible joints allows the tunnel to distort into S-shape through the fault zone without rupture and thus it can provide reference to the design and construction of tunnels located in the active faulted zones. 1. Introduction The tunnel may have to be constructed across a fault zone as it is not always possible to avoid crossing active faults. In these situations, the fault movement may subject the tunnel to differential displacments and generate stress concentrations. Looking through the previous studies and relevant cases, it can be concluded that the current methods of designing the safe secitons for the cases of probable deflection along the longitudinal profile of tunnels can principally be classified into fourth kinds of approaches, i.e.:excavating a larger diameter section in order to provide enough space for the conditions of earthquake or faulting. The grouting reinforcement technique, which means grouting the ground in order to increase the strength and ductility of the faulted zones. The isolation technique, which means filling the space gap between the ground and the lining by some soft materials. the use of flexible joints, which may be considered to increase longitudinal flexibility of the tunnel. For the present study the fourth method is applied. 2. Theoretical analysis The main loading of tunnels is the deformation imposed by the surrounding ground. For design purpose, this deformation must be somehow predicted. This is a very difficult tast called seismic hazard analysis. Prediction can be attempted based on deterministic or probabilistic analysis. In either case the results are highly uncertain but possibly still the best achievable assumption. Assume now that the wave motion. We consider harmonic waves with the circular frequency w. Non-harmonic waves can be decomposed into harmonic ones. Let the unit vector I denote the direction of wave propagaion and let a be the amplitude of oscillation. Then the displacement u of a point with spatial coordinates x is given by the following expressions. Herein, up and us denotes the p-wave and s-wave displacement vectors, respectively. <> cp, cs, ap and as are the corresponding propagation speeds and amplitudes, respectively. Let t be the unit tangential vector at a particular point P of the tunnel axis. Then, the earthquake-induced longitudinal strain and the change of curvature of tunnel can be obtained as: <> With α being the angle between I and t. Thus, a joint between two rigid tunnel segments will suffer the elongation s and the rotation θ (see Figure 1) as follows: <>
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (1.00)
- Geology > Structural Geology > Fault (1.00)