Impact of joints and discontinuities on the blast-response of responding tunnels studied under physical modeling at 1-g (original) (raw)
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Open Journal of Geology, 2016
Effect of Explosion on underground structures where drilled on the stony materials can be affected by explosive strength and rock mass properties of tunnel. In this paper, it has been studied on effect of explosion of 10 tons TNT on the round tunnel (diameter: 10 m) in 25 m depth in the mass rocks (RMR > 90) to estimate stability of tunnel to construct underground structure. Regarding to the studied stones, geo-mechanical indices of rock mass have been found to use as strength criteria in UDEC. In the next step, tunnel in real dimensions and founded indices is modeled with UDEC and analyzed stably. Explosion wave indices are found by UFC Instruction and other experimental relations to administer force from explosion wave on the model. Finally, on the base of FISH, indices of explosion wave are administrated in UDEC and tunnel is analyzed dynamically. According to modeling in depth of 25 m, amount of displacement of drilled tunnel in mass rocks (RMR < 90) is very lower than standard criterion and the tunnel is very stable. Development of plastic zone, vertical and horizontal displacement of rock mass around the tunnel, speed variations and stress from explosion wave are modeled and recorded as the graphs and figures.
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Engineering Reports, 2020
In the past few decade tunnels were targeted to explosives and that resulted in sizeable structural damage. The increase in the strategic importance of tunnel construction has increased the demand for the blast-resistant design approach. The present paper considered an internal blast loading on a rock tunnel constructed in Quartzite rock. A three-dimensional finite element model of the tunnel has been developed in Abaqus. The diameter of the tunnel has been kept constant to a two-lane transportation tunnel. However, the thickness of the concrete liner, depth of overburden, and mass of explosive charge has been varied to understand the response in different possible conditions. The Jones-Wilkins-Lee, Concrete Damage Plasticity, and Mohr-Coulomb material models have been used for the modeling of trinitrotoluene, concrete, and rock respectively. Blast has been formulated through Coupled-Eulerian-Lagrangian technique. The tunnel at 12.5 of the depth of overburden has been found 2.7-times more blast resistant than 5 m. Moreover, the extent of damage in shallow depth tunnels found to be more than the tunnels at higher depth of overburden. K E Y W O R D S Abaqus, blast, coupled-Eulerian-Lagrangian, rock, tunnel 1 INTRODUCTION Underground structures have become an essential part of the metro cities. Construction of the underground structures, especially tunnels for the efficient movement of humans and goods has resulted in the investment of a massive amount of money in the underground space. Therefore, underground structures, especially rock tunnel, have been an active area of research since the mid-19th century. 1-4 Tunnels are considered as high-risk zones due to the presence of numerous patronage in confined space at a single location. 5 Some of the manmade hazards in the tunnels that have caused severe loss of life and property are Bayrampasa metro tunnel attack, London underground metro attack, Moscow metro tunnel attack, Minsk metro bombing, and Saint Petersburg metro attack. 6 Therefore, the blast resistant design of tunnels and other underground utility structures is required. Scientists and researchers have carried out blast-related studies using different approaches. 7-12 Wu et al, 13 carried out the study for the blast wave-induced shock wave propagation in jointed rockmass. They concluded that the characteristics This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
2010
Considerations on the explosion resistant design of special infrastructures have increased in the recent years. Amongst the various types of infrastructures, road and railway tunnels have a unique importance due to their vital role in connection routes in emergency conditions. In this study, the explosion effects of a projectile impacting on a railway tunnel located in a jointed rock medium has been simulated using 2D DEM code. Primarily, a GP2000 projectile has been considered as a usual projectile and its penetration depth plus its crater diameter were calculated in rock mass. The blast pressure was, then, calculated via empirical formula and applied on the boundary of crater as input load. Finally, the wave pressure propagation through the jointed rock medium was investigated. In part of the study a sensitivity analysis has been carried out on jointed rock parameters such as joint orientation, dynamic modulus and damping ratio. Their effects on tunnel lining axial force as well a...
Evaluating the Effect of Underground Explosions on Structures
Mecánica Computacional, 2008
During the last decades, research activity related to underground explosions and their effect on buried structures and structures located on or above ground level have progressively increased. The correct evaluation of the effect of this type of explosion is very important for the design of protection structures. The action of buried explosions on soils and the resulting effect on structures is a strongly complex physical problem. The results are significantly dependent on many parameters that include the amount of explosive, the shape of the load, the explosion depth, soil type and properties, among others. Recent advances in numerical simulation have allowed the modeling of underground explosions. Although there are some papers related to this problem, the knowledge of the effect on buried structures or structures located on the ground is limited to a few numerical results without experimental validation or some isolated experimental observations. The effect of underground explosions on buried structures or structures on or above soil surface is numerically studied in this paper. Numerical simulation is performed with a hydrocode. Different alternatives to model the soil are analyzed. The effect of soil model and parameters on blast wave propagation is particularly studied. In the case of structures located above the ground the capability of different numerical models to reproduce soil ejecta that impacts on structures is also studied. The paper also compares the present numerical results with numerical values obtained by other authors using different hypothesis. Numerical results are contrasted with experimental results available in the specialized literature.
Blast Response and Failure Analysis of a Segmented Buried Tunnel
Structural Engineering International, 2015
Underground tunnels are vulnerable to terrorist attacks which can cause collapse of the tunnel structures or at least extensive damage, requiring lengthy repairs. This paper treats the blast impact on a reinforced concrete segmental tunnel buried in soil under a number of parametric conditions; soil properties, soil cover, distance of explosive from the tunnel centreline and explosive weight and analyses the possible failure patterns. A fully coupled Fluid Structure Interaction (FSI) technique incorporating the Arbitrary Lagrangian-Eulerian (ALE) method is used in this study. Results indicate that the tunnel in saturated soil is more vulnerable to severe damage than that buried in either partially saturated soil or dry soil. The tunnel is also more vulnerable to surface explosions which occur directly above the centre of the tunnel than those that occur at any equivalent distances in the ground away from the tunnel centre. The research findings provide useful information on modeling, analysis, overall tunnel response and failure patterns of segmented tunnels subjected to blast loads. This information will guide future development and application of research in this field..
Numerical analysis of underground tunnels subjected to surface blast loads
Frattura ed Integrità Strutturale
The increased terrorist attacks on important public structures and utilities have raised the vital necessity for the investigation of performance of structures under blast loads to improve the design and enhance the behavior of structures subjected to such threats. In this study, 3-D finite element analysis is used to study the effect of surface explosions on the response of RC bored tunnels. The soil behavior is modelled using Drucker-Prager Cap model. Two types of soil are investigated, and the blast load is considered through various weights of TNT explosive charges at heights of 0.50 m and 1.0 m from ground surface. To study the effect of horizontal standoff distance, six different horizontal distances are considered. The results show that the soil type has a significance effect on tunnel response due to surface blasts. Also the weight and the location of charge have a great effect on the safety of the tunnel. Finally, a parametric study is established to define the borders of th...
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Underground Space, 2019
Much effort has been dedicated to the study of underground explosions because they pose a major threat to people and structures below or above the ground. In this regard, it is especially important to model the propagation of blast waves in soil and their effects on structures. The main phenomena caused by underground explosive detonation that must be addressed are crater or camouflet formation, shock wave and elastic-plastic wave propagation in soil, and soil-structure interaction. These phenomena can be numerically simulated using hydrocodes, but much care must be taken to obtain reliable results. The objective of this study is to analyze the ability of a hydrocode and simple soil models that do not require much calibration to approximately reproduce experimental and empirical results related to different buried blast events and to provide general guidelines for the simulation of this type of phenomena. In this regard, crater formation, soil ejecta, blast wave propagation in soil, and their effects on structures below and above the ground are numerically simulated using different soil models and parameters; the results are analyzed. The properties of soil have a significant effect on structures, the ejecta, and the propagation of shock waves in soil. Thus, the model of the soil to study these phenomena must be carefully selected. However their effect on the diameter of a crater is insignificant.
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Физика горения и взрыва, 2016
The analysis of the dynamic response of a circular tunnel in three types of soil at different depths under surface detonation of a 250-kg TNT charge reveals that the tunnel peak particle velocity and the failure zone length are sensitive to the soil type and material properties. The buried tunnel in silty clay sand has the least damage; the length of the failure zone is 5 m in the longitudinal direction and 0 to 60° at the top arch.
Comparison of Full Scale and Scaled-Model Klotz Tunnel Explosion Test Results
1996
: Under high loading density, explosion effects in underground storage structures are associated with (1) blast pressure, (2) primary and secondary fragments, (3) chemical hazards, (4) thermal hazards, and (5) ground shocks. Extensive studies have been performed in the past on the hazardous effects of blast pressure, induced thermal and chemical environments, and ground shocks. However, the degree and extent of fragment-induced hazards associated with accidental detonation of explosives stored in rock/soil structures (underground magazines) are still not fully verified. The empirical relationships used are too general and do not account for the site specific characteristics of geologic and engineered systems. The KLOTZ Tunnel explosion test which was conducted in 1988 at China Lake, California, demonstrated how rupturing of the storage magazine cover can create a serious debris hazardous environment. The site specific characteristic data on the geologic and engineered systems for th...
Behavior of Steel Lining of a Vertical Sidewall Tunnel in Rock Media under Explosion Loading
The International Conference on Civil and Architecture Engineering, 2006
Due to the progressive development of military destructive weapons such as conventional weapons, a consequence development of the fortified structures is essential. One of the most important types of the fortified structures is tunnel in rock media. The basic premise of this work is studying the response of tunnels in rock-media exposed to high explosion loads, which help tunnel designers and military engineers in estimating displacements, stresses and over all damage in the tunnels due to wave propagation generated by that explosion loads. In this study, the tunnel steel lining for a vertical sidewall crosssection tunnel is studied for different rock types. 2500 kg TNT was used as an explosive load. This charge was located at 3.25m-bellow ground surface. The distance between charge and tunnel crown was fixed to 10m for all models. With regard to finite element solution, an appropriate mesh is employed to represent the geometry of the problem. The rock and lining are simulated by solid elements (one quarter of the domain) in a three-dimensional finite formulation. Joint to joint are used to simulate rock-lining interaction. The steel lining thickness to arc radius (ts/R) ratio was considered 1/300, 1/150, 1/100, 1/75 and 1/30 for ts 1, ts 2, ts 3, ts 4, ts 5, and ts 6 respectively. Von-Mises material model is used to simulate the behavior of steel lining. Grade 50 of steel is used where yield stress is 360MPa and the strength is 468.4MPa, modulus of elasticity equal to 210000MPa, elongation equal to 12%. The response of displacements and stresses, for all rock types and tunnel spans are determined at different lining points.