Mitigation strategies of underground tunnels against blast loading

2021 ◽  
pp. 204141962110380
Author(s):  
Senthil Kasilingam ◽  
Muskaan Sethi ◽  
Loizos Pelecanos ◽  
Narinder K Gupta
Keyword(s):  
Blast Loading ◽  
Plain Concrete ◽  
Fiber Reinforced Concrete ◽  
Mitigation Strategies ◽  
Critical Parameters ◽  
Small Scale ◽  
Burial Depth ◽  
Inelastic Behavior ◽  
Steel Fiber Reinforced Concrete ◽  
Finite Element Software

An evaluation of mitigation strategies of underground tunnels against explosions is important to the society. Therefore, a small scale tunnel was modeled against blast loading using finite element software ABAQUS. The inelastic behavior of concrete and steel bar has been incorporated through concrete damage plasticity model and Johnson-cook models respectively, available in ABAQUS. The Drucker-Prager model as well as acoustic infinite medium have been used to model the damage behavior of soil and tunnel respectively. The simulated results thus obtained from the present study were compared with the experimental results available in the literature and found in good agreement. Further, the simulations were carried to predict the damage intensity in tunnel in terms of acceleration, impulse velocity, displacement, and Mises stresses. There are many parameters which were taken into consideration to assess the mitigation strategies for the underground tunnels. The critical parameters include the influence of tunnel shapes, lining materials, lining thickness, burial depth of the tunnels, inclusion of a barrier in between the blast source-the tunnel and layered configuration of tunnel lining, and were considered to evaluate the mitigation strategy. It was concluded that the square shape of tunnel was most vulnerable as compared to circular and U-shaped tunnels. It was also concluded that plain concrete monolithic lining as well as layered configuration consisting of Dytherm foam layer between Steel Fiber reinforced Concrete layers, was found to be more vulnerable among the chosen lining materials. Also, the thickness of lining and burial depth of the tunnel found to be a significant role against blast loading.

scholarly journals Vulnerability analysis of tunnel linings under blast loading

2018 ◽  
Vol 10 (1) ◽  
pp. 73-94 ◽  
Author(s):  
Ranjit Kumar Chaudhary ◽  
Sunita Mishra ◽  
Tanusree Chakraborty ◽  
Vasant Matsagar
Keyword(s):  
Syntactic Foam ◽  
Blast Loading ◽  
Plain Concrete ◽  
Tunnel Lining ◽  
Fiber Reinforced Concrete ◽  
Steel Fiber Reinforced Concrete ◽  
Cement Concrete ◽  
Element Analysis ◽  
Suitable Material ◽  
Reinforced Cement

In the present study, a comparative assessment on the performance of conventional and advanced tunnel lining materials subjected to blast loading is done using a three-dimensional non-linear finite element analysis procedure. The conventional tunnel lining materials analyzed herein are plain concrete, steel, reinforced cement concrete, and steel fiber–reinforced concrete. The advanced tunnel lining materials analyzed herein are dytherm, polyurethane, and aluminum syntactic foam sandwich panels with steel–foam–steel composites. The pressure generated by 10 kg Trinitrotoluene (TNT) is applied to each element on the inner wall of the tunnel which has an effect equal to the scaled distance Z = 1.16 m/kg1/3. Analyses are conducted by varying the thickness of lining materials for a tunnel built in rock domain. The response of the tunnel lining materials, for example, deformation, stresses, and strains generated at different interfaces, is compared with each other to assess the best suitable material for the present blast scenario discussed herein. It is observed from the simulations that the reinforced cement concrete and steel–aluminum syntactic foam (90 µm)–steel are found to be the suitable tunnel lining materials for the present blasting scenario described herein. Moreover, a set of probabilistic analysis is also performed for the suitable tunnel lining materials decided through deterministic analyses using Monte Carlo simulations. The results obtained are normal random distribution curves depicting the extent of deformation in lining materials. A probability failure curve is also proposed for the suitable lining materials.

scholarly journals Effect of the Notch-to-Depth Ratio on the Post-Cracking Behavior of Steel-Fiber-Reinforced Concrete

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 445
Author(s):  
José Valdez Aguilar ◽  
César A. Juárez-Alvarado ◽  
José M. Mendoza-Rangel ◽  
Bernardo T. Terán-Torres
Keyword(s):  
Reinforced Concrete ◽  
Plain Concrete ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Cracking Behavior ◽  
Bending Tests ◽  
Depth Ratio ◽  
Residual Performance ◽  
Concrete Control

Concrete barely possesses tensile strength, and it is susceptible to cracking, which leads to a reduction of its service life. Consequently, it is significant to find a complementary material that helps alleviate these drawbacks. The aim of this research was to determine analytically and experimentally the effect of the addition of the steel fibers on the performance of the post-cracking stage on fiber-reinforced concrete, by studying four notch-to-depth ratios of 0, 0.08, 0.16, and 0.33. This was evaluated through 72 bending tests, using plain concrete (control) and fiber-reinforced concrete with volume fibers of 0.25% and 0.50%. Results showed that the specimens with a notch-to-depth ratio up to 0.33 are capable of attaining a hardening behavior. The study concludes that the increase in the dosage leads to an improvement in the residual performance, even though an increase in the notch-to-depth ratio has also occurred.

scholarly journals Blast-Resistant Performance of Hybrid Fiber-Reinforced Concrete (HFRC) Panels Subjected to Contact Detonation

2019 ◽  
Vol 10 (1) ◽  
pp. 241
Author(s):  
Wenjin Yao ◽  
Weiwei Sun ◽  
Ze Shi ◽  
Bingcheng Chen ◽  
Le Chen ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Blast Resistance ◽  
Plain Concrete ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Hybrid Fiber ◽  
Hybrid Effect ◽  
Pva Fiber ◽  
Resistance Performance

This paper experimentally investigates the blast-resistant characteristics of hybrid fiber-reinforced concrete (HFRC) panels by contact detonation tests. The control specimen of plain concrete, polypropylene (PP), polyvinyl alcohol (PVA) and steel fiber-reinforced concrete were prepared and tested for characterization in contrast with PP-Steel HFRC and PVA-Steel HFRC. The sequent contact detonation tests were conducted with panel damage recorded and measured. Damaged HFRC panels were further comparatively analyzed whereby the blast-resistance performance was quantitively assessed via damage coefficient and blast-resistant coefficient. For both PP-Steel and PVA-Steel HFRC, the best blast-resistant performance was achieved at around 1.5% steel + 0.5% PP-fiber hybrid. Finally, the fiber-hybrid effect index was introduced to evaluate the hybrid effect on the explosion-resistance performance of HFRC panels. It revealed that neither PP-fiber or PVA-fiber provide positive hybrid effect on blast-resistant improvement of HFRC panels.

scholarly journals Fasteners in Steel Fiber Reinforced Concrete Subjected to Increased Loading Rates

Fibers ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 93 ◽  
Author(s):  
Boglárka Bokor ◽  
Máté Tóth ◽  
Akanshu Sharma
Keyword(s):  
Reinforced Concrete ◽  
Static Loading ◽  
Steel Fiber ◽  
Plain Concrete ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Loading Rates ◽  
Rate Dependent ◽  
Ultimate Resistance

Increased loading rates on fasteners may be caused by high ground accelerations as a consequence of e.g., nuclear explosions, earthquakes or car collisions. It was concluded by Hoehler et al. (2006) that fasteners under rapid loading rates show an increased ultimate resistance in the concrete dominant failure modes or the ultimate resistance is at least as large as under quasi-static loading. Due to the increased demand on using fasteners in steel fiber reinforced concrete (SFRC), it is intended to show how the ultimate concrete cone capacity of fasteners changes under higher than quasi-static loading rate in normal plain concrete (PC) and in SFRC. This paper presents the results of an extensive experimental program carried out on single fasteners loaded in tension in normal plain concrete and in SFRC. The test series were conducted using a servo-hydraulic loading cylinder. The tests were performed in displacement control with a programmed ramp speed of 1, 100, 1000, and 3500 mm/min. This corresponded to calculated initial loading rates ranging between 0.4 and 1600 kN/s. The results of the tension tests clearly show that the rate-dependent behavior of fasteners in SFRC with 30 and 50 kg/m3 hooked-end-type fibers fits well to the previously reported rate-dependent concrete cone behavior in normal plain concrete. Additionally, a positive influence of the fibers on the concrete cone capacity is clearly visible.

scholarly journals Performance of Hybrid Steel Fibers Reinforced Concrete Subjected to Air Blast Loading

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Mohammed Alias Yusof ◽  
Norazman Mohamad Nor ◽  
Ariffin Ismail ◽  
Ng Choy Peng ◽  
Risby Mohd Sohaimi ◽  
...  
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Steel Fiber ◽  
Volume Fraction ◽  
Blast Loading ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Air Blast ◽  
Air Blast Loading

This paper presents the results of the experimental data and simulation on the performance of hybrid steel fiber reinforced concrete (HSFRC) and also normal reinforced concrete (NRC) subjected to air blast loading. HSFRC concrete mix consists of a combination of 70% long steel hook end fibre and also 30% of short steel hook end fibre with a volume fraction of 1.5% mix. A total of six concrete panels were subjected to air blast using plastic explosive (PE4) weighing 1 kg each at standoff distance of 0.3 meter. The parameters measured are mode of failure under static and blast loading and also peak overpressure that resulted from detonation using high speed data acquisition system. In addition to this simulation work using AUTODYN was carried out and validated using experimental data. The experimental results indicate that hybrid steel fiber reinforced concrete panel (HSFRC) possesses excellent resistance to air blast loading as compared to normal reinforced concrete (NRC) panel. The simulation results were also found to be close with experimental data. Therefore the results have been validated using experimental data.

The Numerical Study on Load-Transferring Model for SFRC Double-Column Combined Six-Pile Caps

2008 ◽  
Vol 400-402 ◽  
pp. 321-327
Author(s):  
Yuan Yuan Zhang ◽  
Li Hua Xu ◽  
Yin Chi
Keyword(s):  
Large Scale ◽  
Steel Fiber ◽  
Numerical Study ◽  
Limit Load ◽  
Fiber Reinforced Concrete ◽  
Steel Fiber Reinforced Concrete ◽  
Finite Element Software ◽  
Pile Caps ◽  
Reinforced Steel ◽  
Distribution Of Stress

For discussing the mechanism of load-transferring for reinforced steel fiber reinforced concrete (SFRC) double-column combined six-pile caps, the large-scale general finite element software-ABAQUS is used for the tested SFRC caps with computing in the aspects of modeling, cracking load, limit load, load-deformation curve, distribution of stress in caps and cracks and etc. The results of computing is compared with the result of experiments and the comparison is indicated: The results of computing and experiments are coincided well; The destroy pattern of SFRC double-column combined six-pile caps is sheared damage or punched damage and the model of load-transferring accords with spatial strut-and-tie method (STM); The mixture of steel fiber can improve cracking load and limit load for RC caps, delay the crack for caps, block the cracks’ expansion, and enhance the cap’s ductility.

Numerical Experiment on Size Effect for SFRC Splitting Fracture

2011 ◽  
Vol 250-253 ◽  
pp. 335-339
Author(s):  
Chuan Qing Fu ◽  
Xian Yu Jin ◽  
Ye Tian ◽  
Nan Guo Jin
Keyword(s):  
Numerical Model ◽  
Size Effect ◽  
Plain Concrete ◽  
Fiber Reinforced Concrete ◽  
Test Method ◽  
Test Results ◽  
Steel Fiber Reinforced Concrete ◽  
Calculation Results ◽  
Different Dimensions ◽  
Wedge Splitting

Based on the MFPA2D software system and test method of the wedge splitting fracture in the Lab., a numerical model was established. The numerical experiments on wedge splitting fracture with plain concrete and SFRC (steel fiber reinforced concrete) were carried on. The calculation results about plain concrete with different dimensions and ligament length proved the numerical model is effectively on numerical calculation, and have a good agreement with the results of the test results. Then, the process of crack initiation, propagation of SFRC specimens with different dimensions and fitting formula about size effect were given. The results indicated that the size effect existed in the splitting fracture energy of SFRC.

scholarly journals Volume changes of concrete in interaction with sliding joint

2019 ◽  
Author(s):  
Michal Kropacek ◽  
Radim Cajka ◽  
Petr Mynarcik
Keyword(s):  
Significant Influence ◽  
Plain Concrete ◽  
Fiber Reinforced Concrete ◽  
Outdoor Environment ◽  
Steel Fiber Reinforced Concrete ◽  
Volume Changes ◽  
Comparison Results ◽  
Sliding Joint ◽  
Sliding Joints ◽  
Calculation Models

The paper describes volume changes of cement plain concrete and steel fiber reinforced concrete with strength class C 30/37 in interaction with sliding joints. In the research experiment was performed large-dimensional specimens, on which volume changes were measured using string strain gauges. Below the large-dimensional specimens were designed sliding joints. The specimens were placed in a controlled laboratory environment and in an outdoor environment to simulate real conditions during construction and the measurements were carried out for several months. Volume changes of the concrete were compared to each other and significant influence of the sliding joints was observed. Significant influence on the development of volume changes also has dispersed reinforcement. Another part of the article is a comparison of experimental results with calculation models that allow to calculate the final shrinkage of concrete. Comparison results of volume changes with calculation models is important for demonstrating the effect of sliding joint, as currently valid calculation models do not consider the influence of subsoil and sliding joints, and the results are different as expected. For comparison model B4 (Bazant, 2015), model from technical standard EN 1992-1-1 (CSN EN 1992-1-1, 2006), model from fib model code 2010 (FIB, 2010) and model ACI (ACI, 2008) are used. The paper describes a unique experiment dealing with the influence of sliding joint on the development of volume changes of concrete from beginning of setting and hardening of concrete under precisely defined conditions, that allow comparison with calculation models and thus points to the shortcomings of the building practice.

Anchorage Capacity and Performance in Plain and Steel-Fibre-Reinforced Concrete

2020 ◽  
Author(s):  
R. Nilforoush ◽  
G. Pia ◽  
M. Nilsson ◽  
L. Elfgren
Keyword(s):  
Reinforced Concrete ◽  
Current Knowledge ◽  
Plain Concrete ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Structural Elements ◽  
Steel Fiber Reinforced Concrete ◽  
Steel Fibre Reinforced Concrete ◽  
Current Design ◽  
And Performance

<p>Nowadays, prefabricated concrete components made from Steel-Fiber-Reinforced Concrete (SFRC) are widely used in the construction industry. These components are often connected to existing or new structural elements through various fastening systems. Previous studies have shown that the addition of steel fibers to concrete mixture substantially improves the fracture properties of concrete. To date, however, rather limited research is available on the behavior of fastening systems in SFRC. To improve the current knowledge of fastening systems to SFRC structures, a pilot experimental study is carried out on cast-in-place anchor bolts embedded in Plain Concrete (PC) and SFRC members. In this study, the influence of the presence of steel fibers and concrete compressive strength on the anchorage capacity and performance is evaluated. Furthermore, the applicability of current design methods is evaluated for anchorage systems in SFRC.</p>

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