Submerged floating tunnel is an innovative tunnel infrastructure passing through the deep sea independent of wave and wind so that high speed vehicle or train can run. It doesn't depend on water depth and is cost effective due to modular construction on land. The construction period can be reduced drastically. In this paper, a concept design of submerged floating tunnel is introduced and a method to analyze structural behavior of the body in case of collision with ships or submarines is proposed for securing safety. In this study, the local damage and global behavior of submerged tunnel in collision with submerged moving body are simulated via commercial hydrocode ANSYS LS-DYNA. In simulations, a conceptual tunnel section prepared in Korea is considered and various penetration and deformation responses with respect to impact velocity, applied materials and collision scenarios are obtained. Finally, for a conceptual design of submerged floating tunnel, maximum deformation, bending moment and impact forces are analyzed based on force and energy equilibrium

Han, S.H.

Kim, D.M.

Lee, Y.

Park, W.S.

Hasanuddin University Repository

 214 
 
 
Proceedings of the 7th International Conference on Asian and Pacific Coasts  
(APAC 2013) Bali, Indonesia, September 24-26, 2013 
 
 
 
IMPACT ANALYSIS OF SUBMERGED FLOATING TUNNEL 
FOR EXTERNAL COLLISION 
 
Y. Lee1, D.-M. Kim1, S.-H. Han2 and W.-S. Park2 
 
 
ABSTRACT: Submerged floating tunnel is an innovative tunnel infrastructure passing through the deep sea 
independent of wave and wind so that high speed vehicle or train can run. It doesn't depend on water depth and is cost 
effective due to modular construction on land. The construction period can be reduced drastically. In this paper, a 
concept design of submerged floating tunnel is introduced and a method to analyze structural behavior of the body in 
case of collision with ships or submarines is proposed for securing safety. In this study, the local damage and global 
behavior of submerged tunnel in collision with submerged moving body are simulated via commercial hydrocode 
ANSYS LS-DYNA. In simulations, a conceptual tunnel section prepared in Korea is considered and various penetration 
and deformation responses with respect to impact velocity, applied materials and collision scenarios are obtained. 
Finally, for a conceptual design of submerged floating tunnel, maximum deformation, bending moment and impact 
forces are analyzed based on force and energy equilibrium.  
 
Keywords: Collision, submerged floating tunnel, penetration, impact analysis, hydrocode 
. 
 
                                                 
1  Department of Civil Engineering, Daejeon University, 96-3,Yongun-dong, Dong-gu, E-mail :yunis@dju.ac.kr, Daejeon 300-716, 
SOUTH KOREA,  
2 Coastal Engineering and Ocean Energy Research Department, Korea Institute of Ocean Science and Technology, Sa-2-dong, Ansan, 
   Gyeonggi, SOUTH KOREA 
INTRODUCTION 
Recently, many submerged floating tunnel projects 
connecting inter-continents have seen the increase, 
especially those between Korea & China and Korea & 
Japan. The submerged floating tunnel technology can be 
used when developed to accommodate drive ways for 
vehicle and rails for train for 3 nations.   
Submerged floating tunnel can maximize the use of 
undersea space and if a part of tunnel can be built 
transparent, it can be environment-friendly world class 
tourist attractions. Bridge is very difficult to build over 
the deep waters and is not easy to secure the safety over 
the sea lanes where there are heavy vessel traffics, 
floating debris or ices. However, submerged floating 
tunnel will be free from all those obstacles. There have 
been significant progresses made and technologies 
accumulated on the development of submerged floating 
tunnel technology from 1960s through 1970s, however, 
no such commercially operating tunnels are yet built. 
The technical gaps between domestic and foreign 
technology can be quickly reduced considering the level 
of construction technology sophistication of domestic 
firms. It is noted that time is rife for the domestic 
development of the technology over the technical 
licensing from overseas. Furthermore, it is desirable to 
develop those technologies employed in submerged 
floating tunnel within country which are also applicable 
to the building of offshore construction as gigantic sea 
platform construction. 
This research to analyze the impact load and its 
characteristics was undertaken given consideration to 
those domestic industrial considerations. The existing 
structures for impact loads, except few cases, are not 
designed for with such details, and thus this study is 
done with consideration given to excess pressure loads. 
Ideally, tests are warranted for the   performance and for 
movement of structures for impact loads, but due to its 
restrictions in both testing sites and measurements and 
for the lack of accuracy, movement analysis and its 
design are mostly conducted utilizing analytical tools.   
This analysis was conducted using LS-DYNA, a 
commercial structure analysis program to analyze the 
impact loads for submerged floating tunnel. 
Impact load is different from existing static analysis 
and dynamic analysis in that it takes place in a very short 
instance with big pressure loads, its response time is 
within the range of shock. 
It thereby needs a new approach for other than 
existing analytical approaches. The study performed to 
design and for movement of structures when submarine 
collides with submerged floating tunnel and when the 
submarine sunk due to collision. This analysis was 
conducted under those realistic impact scenarios of 
submerged floating tunnel applying non-linear concrete 
material models. 
Y. Lee, et al. 
215 
 
IMPACT ANALYSIS OF SUBMARINE 
COLLISION IN OPERATION 
 
Overview 
  This analysis has performed mesh modeling with 
specification of submerged floating tunnel described in 
Fig. 1. Partition wall has little effect in this analysis 
when it comes to resisting against actual impact loads. It 
is expected that when partition wall are built, it will have 
many configurations and therefore did not consider 
partition wall in this analysis as in Fig.2 and instead gave 
considerations to outer walls. In order to take into 
consideration of elliptical impact objects as submarines, 
the elliptical objects as in Fig.2 was modeled. And to 
take into consideration of elliptical objects as vessels and 
submarines for collision, the elliptical objects as 1,860 
tons SON WON-IL class submarine (in Korea) with 50m 
length and 10m width has been selected shown in Fig.2 
and was modeled with rigid solid elements. The impact 
velocity in operation was assumed to 5 m/s. The 
submarine was considered as a rigid body which did not 
permit any deformation. Considering the hydrodynamic 
behavior of submerged body, the added mass of both 
submarine and tunnel with approximate spherical shape 
was increased by 50%, respectively. Outer walls of 
tunnel are reinforced by rebar with 100mm cover depth 
on top and bottom and a reinforcement ratio of 0.2% was 
applied. 8 Node solid elements was used in modeling for 
impact structure and for tunnel and 2 Node Truss 
element was used for rebar modeling. Analysis used LS-
DYNA v.971 and 72(*MAT_CONCRETE_DAMAGE) 
was used for concretes. The diameter of tunnel is 20m 
and thickness of wall is 1m and 100m for the length of 
tunnel. This analysis has performed mesh modeling with 
specification of submerged floating tunnel described in 
Fig. 1. Since partition wall is factored in the conceptual 
design phases for submerged floating tunnel, this 
modeling is attempted to model its typical cross section 
of tunnel’s outer wall and partition wall in order to 
simulate as close as actual movements.  
 
Fig. 1  Trader submerged floating tunnel specification 
and planned tunnel modeling 
 
 
Fig. 2  Submerged floating tunnel impact structure, 
tunnel (concrete) and rebar modeling 
 
Analysis Results  
 Collision scenarios are categorized into 4 cases 
labeled to scenario A, B, C and D. Each scenario A, B, C 
and D is assigned to head-on impact, impact on middle 
of hemisphere, impact on top of hemisphere and sinking 
impact, respectively. 
 Fig. 4 and 5 show distribution of cracks and strains 
on tunnel when collided head-on with impact structures. 
It is indicated that the penetration failure of the 
submerged tunnel will take place in the event the tunnel 
is impacted with head-on collisions.  
 
Fig. 3  Submerged floating tunnel impact scenario A 
(head-on collision) 
 
Impact Analysis of Submerged Floating Tunnel for External Collision 
 
216 
 
 
Fig. 4  Crack strain distribution after 1 sec impact 
 
Fig. 5  Principal stress distribution after 1 sec impact 
 
 Fig.6 shows the reduction of movement energy from 
its impact structure as it is progressing to the energy 
history of each impact scenario A~D. 
 
 
 
Fig. 6  Energy history of each impact scenario (A~D) 
  Fig 8 and 9 indicate the distribution of cracks and 
strains on tunnel when collided with a structure on its 
sides. It is indicated that the penetration failure of the 
submerged tunnel will take place in the event the tunnel 
is impacted on middle of hemisphere. Fig.9 shows 
distribution of principal stress when impacted on its 
sides. On the whole, the stress when impacted shows that 
it does not exceeds the concrete pressure strength of 
45MPa. Fig. B shows the reduction of movement energy 
from its impact structure as it is progressing to the 
energy history of impact scenario B. 
 
Fig. 7  Submerged floating tunnel impact scenario B 
(impact on middle of hemisphere) 
 
Fig. 8  Crack strain distribution after 1 sec impact 
 
Fig. 9  Principal stress distribution after 1 sec impact 
 
  Fig 11 and 12 indicate the distribution of cracks and 
strains on tunnel when impacted with structure on its 
sides. It is indicated that the penetration failure of the 
submerged tunnel will take place in the event the tunnel 
is impacted on top of hemisphere. Fig.13 shows 
distribution of principal stress when impacted on its 
sides. On the whole, the stress when collided shows that 
it does not exceeds concrete pressure strength of 45MPa.  
 
Y. Lee, et al. 
217 
 
 
Fig. 10  Submerged floating tunnel scenario C (impact 
on top of hemisphere) 
 
Fig. 11  Crack strain distribution after 1 sec impact 
 
Fig. 12  Principal stress distribution after 1 sec impact 
 
  Fig 14 and 15 indicate the distribution of cracks and 
strains on tunnel when collided with sinking vessel 
structure. It is indicated that the penetration failure of the 
submerged tunnel will take place in the event tunnel is 
collided with such sinking vessel. Fig.17 shows 
distribution of principal stress when collided on its sides. 
On the whole, the stress when collided shows that it does 
not exceeds concrete pressure strength of 45MPa. Fig.6 
shows the reduction of movement energy from its impact 
structure as it is progressing to the energy history of 
impact scenario D. 
 
Fig. 13  Submerged floating tunnel scenario D (sinking 
impact) 
 
Fig. 14  Crack strain distribution after 1 sec impact 
 
Fig. 15  Principal stress distribution after 1 sec impact 
 
IMPACT ANALYSIS OF SUBMARINE 
COLLISION WHILE SINKING 
 
Overview 
This analysis has performed mesh modeling with 
specification of submerged floating tunnel described in 
Fig. 1. Since Partition wall is factored in the conceptual 
design phases for submerged floating tunnel, this 
modeling is attempted to model its typical cross section 
of tunnel’s outer wall and partition wall in order to 
simulate as close as actual movements. And to take into 
consideration of elliptical objects as vessels and 
submarines for collision, the elliptical objects as 18,750 
tons Ohio class submarine with 100m length and 20m 
width has been selected shown in Fig.16 and was 
modeled with rigid solid elements. Outer walls of tunnel 
are reinforced by rebar with 100mm cover depth on top 
and bottom with collision speed of 0.463m/s and a rebar 
ratio of 0.2% was given consideration. 8 Node Solid 
elements was used in modeling for impact structure and 
tunnel and 2 Node truss element was used for rebar 
modeling. Analysis used LS-DYNA v.971(LSTC, 2007) 
and 72(*MAT_CONCRETE_DAMAGE, LSTC, 2007) 
was used for concretes. The external diameter of tunnel 
is 23m and thickness of wall is 1m and the length of 
100m, 300m, 500m, 1000m tunnels were considered. 
 
Impact Analysis of Submerged Floating Tunnel for External Collision 
 
218 
 
 
Fig. 16  Impactor and tunnel mesh modelling 
 
Analysis Results 
Fig. 17 show deformations at impact in 1000m 
tunnels and indicates direction and the movement from 
its perpendicular, skew and parallel collision when a 
colliding object sinks. As were the cases in the 
aforementioned lengths, for 1000m tunnels, pressure 
deformation rate occurs all over central cross section 
Partition wall and over the surface of top colliding plane 
toward tunnel due to its bending moment. No damage 
movements penetrating tunnel from collision from 
perpendicular, skew and parallel collision resulted and 
showed colliding structure bouncing back in reverse 
direction from its colliding direction. Out of 3 impact 
scenarios, as it were for 100m and 300m cases, the 
collision impacted areas varied in accordance with the 
shape of colliding objects, however, since the length of 
tunnels used for testing were longer as the colliding 
objects get bigger, the relative scope and difference in 
area of collision were not significant. 
 
  
 
 
 
  
 
 
 
  
 
 
 
Fig. 17  Deformations at impact (Tunnel length : 1000m) 
Y. Lee, et al. 
219 
 
Table 1, 2, and 3 show maximum impact forces on 
the contact surface, when the impact forces are 
longitudinal, transverse, or sinking direction, 
respectively. The longitudinal and transverse impact 
forces demonstrated very little destruction, within 8% of 
the downward impact load, which could have resulted 
from the change of contact surface at the time of 
collision of the crashing object and the concrete part of 
tunnel. As seen in Table 1, the colliding force was the 
biggest when the crashing object was perpendicular to 
the longitude of the tunnel and the least when the 
crashing object was parallel to the longitude of the 
tunnel. It seemed the collision force is transferred less as 
the longitudinal contact surface is relatively less when 
collision is parallel than when it is perpendicular to the 
longitude of the tunnel. 
 
Table. 1  Comparisons of longitudinal forces(X-force) 
X-force (UNIT: MN) 
 100(m) 300(m) 500(m) 1000(m) 
X-force(perpendicular) 1.9 2.4 2.1 2.2 
X -force(skew) 0.9 0.8 0.75 1.15 
X -force(parallel) 0.31 0.39 0.22 0.23 
 
Table. 2  Comparisons of transverse forces(Y-force) 
Y-force (UNIT: MN) 
 100(m) 300(m) 500(m) 1000(m) 
Y-force(perpendicular) 0.35 0.3 0.35 0.36 
Y -force(skew) 1.3 1.2 1.18 1.1 
Y -force(parallel) 1.4 1.3 1.2 1.42 
 
Table. 3  Comparisons of sinking direction forces(Z-
force) 
Z-force (UNIT: MN) 
 100(m) 300(m) 500(m) 1000(m) 
Z-force(perpendicular) 24 25 23.8 25.8 
Z -force(skew) 20.5 24 22 25.7 
Z -force(parallel) 46 19.5 20 26 
 
As shown in Table 2, the collision force to the 
tunnel's vertical axis is the biggest when the impact of 
the crashing object is parallel and the least when the 
impact of the crashing object is vertical to the tunnel axis. 
It seemed the collision force is transferred most as the 
longitudinal contact surface is formed relatively larger 
when impact is parallel to the tunnel axis.    
As shown in Table 3, except when the crashing 
object is longitudinally collided on 100 meters long 
tunnel, the maximum impact force appears to be  
 
 
 
approximately 20 to 25 MN. It is estimated that impact 
surface is formed momentarily wider throughout the 
short length of the tunnel in case of the horizontal impact 
of the 100 meters long tunnel, and the result would be 
similar of the submerged floating tunnel longer than 1 
km in length.  
 
CONCLUSION 
This research performed analyses of collisions to 
design submerged floating tunnel against possible impact 
loads from anticipated colliding submerged objects and 
concludes as follows:  
The loads vertical to the tunnel-axis were found to be 
less than 8% of loads along the direction of collision. 
This is due to the deformation occurring on the colliding 
surface against concrete surface of tunnel. And the 
maximum loads along the direction of tunnel occurred 
when impact object crashed vertical to the tunnel. This is 
due the minimum impact surface results perpendicular to 
the tunnel-axis direction when collision occurs along the 
direction of tunnel-axis. This impact in turn minimizes 
the loads from collision in comparison. The collision 
force to the tunnel's vertical axis is the biggest when the 
impact of the crashing object is parallel to the tunnel.  It 
seemed the collision force is transferred most as the 
longitudinal contact surface is formed relatively larger 
when impact is parallel to the tunnel axis. When 
designing the structure for submerged floating tunnel 
against possible collision, the impact loads from crashing 
objects along its colliding direction is the most critical 
aspect in design. The study shows that maximum load 
lies in the range of 20 ~ 25 MN when the length of 
tunnel is 500m and 1000m.  
  This maximum loads should be carefully examined 
when designing the submerged floating tunnel in future, 
since the submarines operating in Korean waters are 10 
times lighter than the one being considered for this 
analysis, U. S Ohio class submarine with 18,750 ton. 
 
ACKNOWLEDGEMENTS 
This research was supported by the project 
‘Development of core techniques for submerged floating 
tunnels (PE98941)’ funded by Korea Institute of Ocean 
Science and Technology. 
 
REFERENCES 
LSTC (2007) LS-DYNA Keyword User’s Manual. 
Version 971., Livermore Software Technology 
Corporation (LSTC), Livermore, May, 2007 
 
 


Impact analysis of submerged floating tunnel for external collision

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Impact analysis of submerged floating tunnel for external collision

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