Modelling of blast-induced damage in tunnels using a hybrid finite-discrete numerical approach (original) (raw)
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Stavební obzor - Civil Engineering Journal, 2017
A hybrid finite-discrete element method (FEM/DEM) is introduced to model the excavation damage zone induced by blast in a deep tunnel. The key components of the hybrid finite-discrete element method, i.e. transition from continuum to discontinuum through fracture and fragmentation, and detonation-induced gas expansion and flow through fracturing rock, are introduced in detail. The stress and crack initiation and propagation of an uniaxial compression test is then modelled by the proposed method and compared with those well documented in literature to calibrate the hybrid FEM/DEM. The modelled stress-loading displacement curve presents a typical failure process of brittle materials. The calibrated method is then used to model the stress and crack initiation and propagation induced by blast for the last step of excavation in a deep tunnel. A separation contour, which connects the borehole through the radial cracks from each borehole, is observed during the excavation process. The newl...
The response of rock tunnel when subjected to blast loading: Finite element analysis
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.
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...
Dynamic Analysis of Underground Tunnels Subjected to Internal Blast Loading
2013
In the recent decades, explosion incidents caused by terrorist activities have become a growing threat to the human civilization and civil infrastructure. Underground tunnels used for roadway and railway, utility lines and water pipe lines are an indivisible part of the modern civil infrastructure. Blast loading inside tunnel may cause numerous lives and severe damage of properties. Internal explosion in tunnel may lead to multiple reflections of the blast induced shock wave and the result in channeling of the shock wave. The underground tunnels are seldom designed adequately for sustaining the blast loading. Hence, in order to safeguard the tunnels from blast loading, it is necessary to understand the response of these structures when subjected to blast. Experimental determination of the response of underground tunnels under blast loading often becomes difficult due to socio-political issues. Hence, advanced numerical analysis of tunnels subjected to blast loading is of utmost impo...
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..
3D Finite element model of a blast load in a tunnel
2021
This paper presents a 3D finite element analysis of the effect caused by a blast inside a reinforced concrete tunnel. The simulated explosion was caused by the crash of a heavy vehicle transporting inflammable material (LPG). The finite element technique was used to analyze the structural problems on the tunnel reinforced concrete structure considering the fire action and the subsequent explosion (blast) effect, incorporating appropriate material models. Through FEM software the tunnel behavior was described with regard to structural safety. Indeed, tunnels must be designed to withstand damage factors, so it is desirable that if such an explosion did occur, the tunnel should be able to return to service in safety as soon as possible with minor repairs. Therefore, following the presented analysis, the most important factors influencing the dynamic response and the damage of the structure could be identified. The simulation involved aspects of thermal analysis and structural problems ...
International Journal of Rock Mechanics and Mining Sciences, 1997
Sub-surface structures provide attractive alternatives for storage of explosives and other military hardware. These facilities are commonly constructed at shallow depths where rocks have undergone extensive weathering and the geologic system contains joints and discontinuities. For underground munitions storage structures, risk and performance assessment studies have to be conducted to qualify the site and establish the "clear zone" in case of accidental detonation. At high loading densities, accidental detonation of a munitions storage facility can lead to rupturing of the overburden cover and creation of a hazardous fragment environment. The degree and extent of the "clear zone" is controlled by the overall characteristics of the geologic and engineered systems. Rock joint spacing is considered to be important in prediction of the hazardous range of blast-induced fragments and associated impact energy. A full scale tunnel explosion test was conducted in 1988 in the desert of California. The tunnel was constructed in a weathered, jointed, igneous rock mass with several well defined discontinuities. The information from the overall characteristics of this tunnel was used to construct five scaled model tunnels, with simulated joints and discontinuities, under physical modeling at 1-g. The loading densities used in two of the model tests were equivalent to that of the full scale event. For the other three tests, loading densities were changed in order to determine the effects of the explosive weight on the jointed rockmass response. The tests reported in this paper are unique in terms of size and simulation method. Five large test beds were constructed in trenches filled with model material simulating the full scale jointed rockmass with through-going discontinuities at 20:1 scale. Geometric and strength related properties were scaled, whereas the density scale factors were maintained at unity. The model materials were formulated in such a way that similitude conditions between the properties of the full scale rock mass were maintained. Test beds were constructed by step-by-step casting of the model materials into the excavated trenches. Impedance characteristics of the model materials were matched with those of the host-ground for realistic simulation of the ground shock propagation. This paper provides a brief discussion on the tests performed and elaborates on the applicability and the economics of the physical modeling for studies related to explosives-underground-structures interaction.
Blast induced rock mass damage around tunnels
2018
Drilling and blasting is a preferred method of rock excavation world-wide due to low initial investment, cheap explosive energy, easy acceptability among the blasting engineers and, possibility to deal with different shapes and sizes of openings. Although, drill and blast method has witnessed significant technological advancements, it has inherent disadvantage of deteriorating surrounding rock mass due to development of network of fine cracks in it leading to safety and stability problems. The damage in the peripheral rock mass culminates in the form of overbreak and damaged zone beyond overbreak. In some cases the projects cost has increased more than 15% because of overbreak. Although significant efforts have been made to assess damage to the surrounding rock mass using different methods, the solution based on easily available site parameters is still lacking. Authors have carried out field investigations at five different tunnels located in Himalaya, India to study blast induced ...
Development of Predictive Models for controlling Blast Induced Overbreak in Tunnels
Drilling and blasting continues to be the predominant rock excavation technique in driving horizontal openings and tunnels for underground construction purpose. Faster drivages, attempted these days for reducing the long gestation periods of projects, have often resulted in large overbreak. This is due to the unacceptable levels of ground vibration to which the rock is subjected. Factors contributing to this include longer pulls; burn cuts, higher explosive per hole and per delay etc. Blast-induced rock damage (BIRD) assessment based on far-field peak particle velocity (PPV) measurement, when extrapolated near the face, has often resulted in suggesting higher PPV threshold levels. Apart from this the geological and structural features play a dominant role in masking the intensity of blast waves. Therefore, near-filed monitoring using accelerometers has been attempted in one of the metal mines to study the blast damage in faces excavated by burn cut. Present seismographs available have limited range (2540mm/s) and are not suitable for near-field monitoring. This paper reports the investigations carried out for measuring acceleration, PPV and overbreak in a development heading for arriving at a suitable method of predicting blast-induced rock damage. The analysis of both acceleration and PPV measured against overbreak has revealed that rock damage is found to depend more on acceleration than PPV.