Journal of Transportation Technologies, 2011, 1, 54-57
doi:10.4236/jtts.2011.13008 Published Online July 2011 (http://www.scirp.org/journal/jtts)
Ecological Tunnel for the 21st Century: A New Conception
and Methodology
Zixin Zh ang1*, Qinghua Lei1, Qiang Xue2
1Department of Ge ot echnical Engi neeri ng, School of Civil Engineering, Tongji University, Sha ngha i, China
2State Key Laboratory of Geomechanics and Ge o t ech n i cal En gi n eeri ng, Institute of Rock and Soil Mechanics, Chinese
Academy of Sciences, Wuhan, China
Received April 25, 2011; revised May 20, 2011; accepted May 30, 2011
Abstract
This paper presents a new conception—ecological tunnel, which is contrived to meet increasingly tough
challenges in the 21st century. Ecological tunnel refers to integrating ecological principles into tunnel design,
construction and operation in order to create a balanced and sustainable tunnel-nature system. It consists of
four elements: green tunneling, green lighting, green lining, and green recycling of excavated material. The
conception, function and implementation of each part are elaborated in the paper. In addition, computer
visualization technique is applied to simulate complicated internal conditions of an ecological tunnel.
Keywords: Ecological Tunnel, Green Tunneling, Green Lighting, Green Lining, Green Recycling,
Computer Visualization
1. Introduction
Currently, human needs, activities and communications
have increasingly stressed traffic systems and conse-
quently produced countless artificial tunnels. The tradi-
tional modes of tunneling and measures of disposing
excavated soils have yet gained unsatisfactory results.
Although tunnels have brought with them numerous
economic benefits to the society, they should also take
responsibility for a large share of material and energy
consumption, and generation of environmental emissions,
both nationally and globally. In details, these adverse
effects can be categorized as: consumption of electricity
and other energy, cost of human resources, emission of
carbon dioxide (CO2), abandonment of excavated soils
and other solid waste, and disturbance of ecological
equilibrium. Especially, the current tunneling activities
have often been merely focusing on the excavation proc-
ess rather than the balance between tunnels and nature.
These phenomena, combined with the advent of scien-
tific knowledge on ecosystems, make a request for new
strategies to construct tu nn els, and then the co n cep tion of
ecological tunnel is put forward.
During the past several decades, ecologists have pro-
posed a new method of urban planning and construction,
based on the con cep t of ecosyste m [1]. By the late 1980 s,
this ecosystem-based approach has been advocated by
many scientists, engineers, managers and organizations,
such as Agee and John son (1988), Kibert (2005) an d US
Department of Energy (USDE, 2009) [2-5]. Increasing
awareness of environmental issues and negative effects
from tunnel construction and operation coupled with
pressures from society has led us to establish a new con-
cept which is named as “ecological tunnel” or “eco-tun-
nel”. The eco-tunnel system would be a potential guid-
ance for implementing green design and construction
strategies of 21st century tunnels.
2. Definitions and Conceptions
2.1. What is an Ecological Tunnel?
Since 1935, when the term “ecosystem” was first pre-
sented by Sir Arthur Tansley (Tansley, 1935), many re-
searchers have been trying to use this concept in various
fields. The application of the ecosystem concept to tun-
nel is a subject concerned with studying the relationships
between human groups, tunneling processes, tunnel
structures and surrounding environments. Based on our
imagination, ecosystem-based tunnels should have the
following main characteristics:
· Eco-tunnel system is subjected to a continuous

Z. X. ZHANG ET AL.
55
change in space and time.
· Eco-tunnel system is constructed by efficient tun-
neling and soils/rocks removing, rational installing of
green linings, and pollution-free recycling of excavated
soils/rocks.
· Eco-tunnel system is operated with low-carbon emi-
ssion, energy-saving illumination and harmonious coexis-
tence with the nature.
There is an organized network combining different
parts of an ecological tunnel system, and each part per-
forms in close connections with all others.
2.2. Definition of Ecological Tunnel
Based on the aforementioned characteristics of an eco-
logical tunnel, its definition can be given as following:
Ecological tunnel is the integrating scientific knowl-
edge of ecology and energy-conservation within tunnel
design, construction and operation towards the major
goal of striking a careful balance between human beings,
tunnels and nature, which is achieved by the collabora-
tion of green tunneling, green lighting, green lining and
green recycling of excavated material.
The realization of an eco-tunnel system should be
based on the comprehensive usage of ecological concep-
tions, economic and political knowledge, power-saving
technologies, geotechnical theories, and even botanical
techniques.
3. Ecological Tunnel System
Ecological tunnel system is composed of four parts:
green tunneling, green lighting, green lining, and green
recycling of excavated material.
3.1. Green Tunneling
Tunneling is an art. Over time, numerous advanced
methodologies and techniques of tunneling have been
deliberately devised and developed. These techniques
have served well in meeting demands of desired progress
and limited time with low acciden t rates and few tunnel-
ing problems. Chinese designers, scien tists and engineers,
who have successfully accomplished a large number of
tunneling projects, are currently concentrating on new
challenging projects and also attempting several innova-
tive ideas to satisfy future requirements.
In response to rapid pace of national and global de-
velopment, there has been a pressing need of new tunnels
for congested traffic systems and massive underground
facilities. Tunneling, in virtue of its numerous excellent
qualities, has gradually been proved to be an attractive
approach in creating underground spaces for transport
and utility networks. However, the modern tunneling
modes still inevitably cause a variety of problems, in-
cluding third party impact, environmental disruption and
energy wastage. For instance, tunnel construction by a
slurry shield beneath groundwater table will inevitably
cause the drawdown of groundwater level, the pollution
of surrounding soils and even the influence to residents
nearby.
The concept of g reen tunneling is just pr oposed to set-
tle these matters and the mode consists of three features:
· The decision of green tunneling method should be
concerned with not only economic and technological
feasibility, but also political, ethical, sociological and
environmental effects.
· Green tunneling should technically achieve: low
power dissipation, low emission of greenhouse gas, low
noise pollution, low material consumption, low eco-
nomic expenditure, low environmental disturbance and
low manpower cost.
Green tunneling should be accomplished under effec-
tive management for the sake of reducing material, en-
ergy and hum an re so u rce c on su mption.
3.2. Green Lighting
Green lighting system comprises collecting, converting,
transmitting, storing and illuminating parts. In this sys-
tem, the input is natural light including all visible wave-
lengths, and the output is the redistributed sunlight which,
however, must comply with traffic regulations. The
functions and collaborations of these subsystems are il-
lustrated in Figure1.
· The collecting subsystem is in charge of gaining
sunlight that will be transmitted into the converting sub-
system.
· The converting subsystem is a device of photo-
electric conversion which can transfer the collected
sunlight into electric energy.
Figure 1. Green Lighting System.

56 Z. X. ZHANG ET AL.
· The collecting subsystem is in charge of gaining
sunlight that will be transmitted into the converting sub-
system.
· The converting subsystem is a device of photo-
electric conversion which can transfer the collected
sunlight into electric energy.
· The storing subsystem, just as its name implies, is
responsible for storing and supplying electric energy.
· The illuminating subsystem will reproduce the
sunlight using optical fibers to provide an agreeable en-
vironment for driving and plants growing.
In addition, it is the transmitting subsystem that con-
nects all other subsystems closely and efficiently
3.3. Green Lining
Designing and constructing the green lining system
should overcome the following main and difficult points:
· Appropriate growth mediums for green plants being
cultivated in tunnels should be selected, and the tech-
nique of fixing mediums on linings should also be mas-
tered;
· Green plants with good quality of living in tunnels
must be chosen fr om thousan ds ki n ds of plants;
· Requirements of the selected plant, including light
intensity, wave lengths, temperature and humidity,
should be tested systemically;
· The approach of creating such environment and
guaranteeing nutrient supply should also be devised;
A dynamic adjusting function of the system should be
additionally embodied in order to provide an optimal
natural circumstance timely and efficiently for plants and
human beings.
3.4. Green Recycling of Excavated Material
Soils/Rocks produced by industrial practice can be de-
scribed as a sink of pollutants and a source of pollution
with the quality of delivering po llutants in to groundwater,
into food chains and into human bodies, which would
undoubtedly risk people’s health. Green recycling in
tunnel construction is the very solution for this issue and
is achieved with three main steps, successively.
· Assessment of excavated soils/rocks
The concentration and distribution of major pollutants
contained in excavated samples, such as heavy metals
and some organic substances, are tested comprehensively
in the laboratory. Then results are compared with the
standard criteria in order to determine the contaminated
state of excavated soils/rocks.
· Washing of contaminated soils/rocks
If the experimental report of samples indicates that
excavated soils/rocks have been contaminated, a series of
effective separation and cleaning measures would be
necessary before recycling. A variety of pollution treat-
ments that use physical and/or chemical techniques have
been invented and devised by many environmental ex-
perts. These measures have been widely used in different
regions and demonstrated their amazing superiorities.
· Ruse of washed soils/rocks
Treated soils or rocks would be of great av ailability in
many aspects, such as agricultural planting, embankment
fill, urban greening, land reclamation and so forth; how-
ever, the decision on applications should be made flexi-
bly. Furthermore, a multidisciplinary app roach involving
geotechnical, environmental and computer database tech-
niques is necessary to ensure the excavated material
could be well understood and managed in order to opti-
mize their values.
The detailed procedure of green recycling is illutrated
in Figure 2.
4. Simulation and visualization
The driving conditions, lighting effects and plants
growth can be simulated meticulously using computer
visualization techniques. Figure 3 shows the resu lt of an
initial 3D-model of an ecological tunnel which is com-
pleted on the platform of Auto CAD 2009. In this model,
the tunnel structure, optical fibers, green plants, and
Figure 2. Green recycling of excavated soils/rocks.
Figure 3. Visualization of an ecological tunnel.

Z. X. ZHANG ET AL. 57
driving condition are visualized viv idly.
5. Conclusions
Ecological tunnel, a new tunnel mode involving green
tunneling, green lining, green lighting and green recy-
cling of excavated soils/rocks, is created in the paper.
The implementation of the eco-tunnel system, which
should be based on the combination of geotechnical, en-
vironmental, botanical and computer techniques, is un-
doubtedly endowed with promising future in facing in-
creasing demands and challenges of the 21st century.
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