URBAN UNDERGROUND SPACE DEVELOPMENT
AND CIVIL DEFENCE CONSTRUCTION
——A SPECIAL PROBLEM’S S.D. MODEL
Cheng Liguo Zhang Youmin
Yuan Zhengru Yu Youshan
Nanjing Engineering Institute of Technology
The People’s Republic of China
ABSTRACT
Owing to the development of the cubic construction of modern cities and the protec-
tive functions of underground space against the disasters such as earthquake and air
raids by modern weapons, the development of urban underground space and the con-
struction of protective sheltering against disasters have become an important policy for
many cities. Nevertheless, contradictions between investment and benefit as well as be-
tween protection and economy will often occur as a result of the very expensive cost of
underground space development. As managers of system, they tend to need to under-
stand these problems and adopt effective measures to find out solutions for them. The
method of System Dynamics is no doubt a useful tool for the studies of such problems.
This paper has established a system dynamic model about urban underground space
development and civil defence construction, including development fund raising, fund
distribution, urban underground space construction, subway(i.e., underground railway)
- construction, urban population and the other auxiliary business dealings performed by
the development departments. The model has successfully solved the problem of offering
methods for the efficiency of protecting against disasters, the social and economic bene-
fits of urban underground space development and civil defence construction. It reveals
the feedback and circulation mechanism and tendency of urban underground space de-
velopment and civil defence construction.
Part One System Analysis
1.1 System Environment
There exists a kind of interaction between underground space development system
and environment. The quantity of urban population sets out a task upon the system.
With the growth of population, the area of underground space in need also increases.
The amount of fund to be raised from the society is one of environmental conditions as
input of energy to the system; and variations of the external sources of fund exert influ-
ences upon the rate of system development. Urban subway construction will increase the
total scale of underground space development. The presumed environment of disasters
such as earthquakes and air raids by modern weapons is a kind of ‘soft’ dynamic power
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System Dynamics '91 Page 295
for system development and construction; it applies constriction and guidance to the sys-
tem in terms of conception, policy and technology.
1.2 System Elements
The system in question includes such elements as underground space development
activities, commercial activities through the use of underground space. the protection of-
fered by underground space, social benefits produced by undergrund space, auxiliary
management activities performed by the development compnanies, etc., of which the
main ones will be dealt with in the analysis of the causal relationship.
1.3 Targets Describing System Tendency
Underground space is to be divided into two categories: Type A represents the space
with relatively good capability against disasters and with the commercial usage playing
the secondary role; Type B denotes the space which is mainly devoted for commercial use
and whose level of protection against disasters is comparatively low. The targets re-
flecting the level of protection against disasters are a follows:
(1) Total area; (2) Rate of admission, i.e., the ratio of the number of people who can
be admitted into the underground space during the period of emergency to the total
population; (3) D—value of area in comparison with the planned objective; (4) Protective
effectiveness of underground space against disasters, the value of which is the ratio of the
survivals due to the protection obtained during the occurrence of disasters to the number
of casualties which will occur without protection under the similar conditions ‘of
disasters; (5) Rate of association with the space system, i.e., the proportion of space Type
A in the total space. The three proceding targets reflect the level of protection against
disasters in terms of quantity, while the last two items reflect the level of protection
against disasters in terms of protection.
The targets reflecting the economic level are as follows:
(1) Rent collected from the letting of underground space, which is alternatively cal-
led income of usage fees; (2) Output value and economic benefit arising from the com-
mercial dealings through the use of underground space; (3) Output value and economic
benefit arising from the design and construction of the projects undertaken by the devel-
opment companies under contract; (4) Total output value and total economic benefit of
the system, which are the sum of the previous three items; (5) Output value and economic
benefit per unit investment. In order to reflect the internal vitality of the system, some
additional targets have been determined, for instance, the proportion of the internal in-
come of the system in the total funds collected from the external sources, the proportion
of the annual income through the use of underground space in the development
investment for the said year.
1.4. Analysis of the Main Causal Relationship of the System
As shown in Fig. 1, area of Type B space area of Type A space total economic
benefit input of development funds—area of Type B exhibits positive feedbback loop,
whish shows that Type B space will obtain relatively good economic benefit and will gain
more development fund, thereby leading to the increase of investment for the develop-
ment of Type B space; meanwhile, area of Type B space—total area available for devel-
opment— rate of admission protective effectiveness exhibits positive relationship, the
Page 296 System Dynamics.'91
~~ Rate of
Protective admission
effectiveness
/ Via “Total area
Degree of aa \
protection Area of Area of
SN” A space Type B space
Rate of NX development
association fund
Total A
economic benefit
Fig. 1
increase of Type B space raises the protective effectiveness to a certain extent from the
angle of enhancing the rate of admission, which is the positive side of the matter. Howev-
er, area of Type B space—area of Type A space—degree of protection against disasters
of the space system— protective effectiveness exhibits negative relationship; meanwhile,
the increase of the quantity of Type B space reduces the rate of provision of the
asssociated parts of the space system, which is the disadvantageous side of the matter.
Similarly, the increase of the proportion of Type A space also exerts dual influence; that
is to say, it enhances the rate of association and the protective effectiveness on one hand
and reduces the protective effectiveness on the other. Then, what is the magnitude of the
positive or negative influence? We can not make the answer immediately; the system pos-
sesses the anti—intuitiveness. :
Fig. 2 is a diagram of causal relationship among the main factors of the system. The
loop of total fund of the system— investment for public development area of Type B
space—total area for development—usable areaincome of usage fees—internal income
of the system— total funds of the system becomes the main loop, which determines the
self—developing capability of the development system.
It can also be seen from Fig. 2 that urban population growth of urban buildings
above the ground demand on the undergorund space incidental investment for the
construction work above the ground and group development investment external fund.
raising—total fund of the system exhibits positive relationship; urban population—popu-
lation to be sheltered according to the planning rate of admission protective
effectiveness exhibits negative relationship; investment for the construction of subway
area of subway—shelterable area total area of underground space—rate of admission.
protective effectiveness also exhibits positive relationship; and output value of the aux-
System Dynamics '91 Page 297
iliary business dealings sum of profit and taxes to be delivered or paid— profit>
investment for redevelopment— internal income of the system—total fund of the system
also exhibits positive relationship. Besides, the increase of the construction cost of devel-
opment and the decay of the growth rate of economic benefit act as constriction and lim-
itation on the system. The causal relationship is omitted in the diagram.
In Fig. 2, the loop of investment for public developmentnon—developmental con-
sumption investment for public development, the loop of investment for public devel-
opment-> maintenance and repair cost for the developed space investment for public
development, the loop of area of Type A space—>area of Type B space—area of Type A
space and so on all exhibit the complementary relationship, in which any one item of the
Investment a Sum of profit Investment
for municipal Profit and taxes to for subwa’
works be delivered oF y
Input for Output value of
ci oe redevelopment the auxilia ty
Incidential business dealings Sheltable area
investment Input of Se, Growth of
development output value
Income of Total output
External Internal income aaBE ‘
ge fees Intensity of
isi of the system y
fund raising y f. the disasters
/ Rate of Usable area
association e
Total fund of Area of Type Total area
the system A space
Maintenance ih,
: cost Area of Rate of
Group Type B space association
investment Investment for : \
i ment
public develop: Protective
vA effectiveness
Non—developmental
consumption
Area of group Population to be sheltered
Demand for development according to planning | ~
underground )
space
548 Urban
Amount of urban buildings population
above the ground
Fig. 2
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factors rises, then another item will lower itself. The effect of the variations of these rela-
tions on the system will be listed as one of subjects for major studies of the model under
consideration.
Part Two System Model
In the program design, four kinds of variations for the external fund are to be sup-
posed, i.e., increase, reduction, maintenance of the present level without change and ran-
dom variations within the range-of the historical lower and upper limits. The Multiple
SWITCH function, the CLIP function and NOISE function are employed for the
program design.
As to the problem of the income of usage fees for underground space, it is necessary
to take into account the general regulations of business dealings and other unforseeable
factors; the scope of gradual increase of the rate of income per unit area decreases with
time in a certain degree, that is to say, the linear decay factor is to be introduced into the
program with relation to the rate of income. The use of the TABLE function for the real-
ization of the said fuction is rather convenient.
The program design for the module of fund distribution aims at the realization of
the selection and control of the proportions in terms of fund distribution between the en-
gineering construction and auxiliary construction, between new development and main-
tenance or transformation as well as between Type A space and Type B space.
As to the foregoing various layers, the TABLE function, the CLIP function and
SWITCH function are employed in a synthetic way for realization of automatic control.
As for the newly developed space, there exists delay(i-e., construction cycle) between
the planned area and the area of the completed works. In addition, the DELAY function
is employed for reflecting the construction cycle, and the TABLE function and level
equations for reflecting the factor of rising construction cost.
Urban subway construction is not continuous on the axis of time, which is generally
divided into the first—phase project, the second—phase project and so on; the appropriate
solution lies in the employment of the STEP function for the purpose of superposition.
In the module of underground space benefit, the computation of the: protective
effectiveness rests with the simulation of the protective effectiveness with relation to the
underground space systems with different development scales, spatial distributions and
degree of protection against disasters inaccordance with the environments of disasters of
each city arising from air raids by madern weapons or earthquakes so as to form the
equations of the TABLE function for computation using interpolation. The model gives
out, the values of protective effectiveness of the underground space with three typical de-
grees of protection , i.e., Type A space, Type B space and subway, which vary with the
rate of admission under the conditions of the given plane distributions. With the deriva-
tion of the protective effectiveness, it is still possible to derive the number of people who
are rescued in the space system according to the rate of casualty without protection in the
given disastrous environment of each city. The whole set of the disaster—modeling
program can be used in conjunction with the S.D. program.
System Dynamics '91 Page 299
Part Three Modeling Computation of the System
Table of the modeling computation of the system is listed in following table:
Table of Computational Scheme
Regulations of Variations of policy with relation to system development Serial
variations of
the external number, .of
conditions First layer Second and third layers scheme
a) Proportion of fund for maintenance,
repair and transformation:13%
b) Proportion of fund for new devel-
opment: 87% 1
c) Coefficient of proportionality for
Type B space: 1.0 for years before 2000
and 0.8 for years after 2000
a), b) ditto;
. F c) Coefficient of proportionality for 2
Reduction of the proportion Type B space: 0.8 for years before 2000
of the non— developmental and 0.6 for years after 2000
fund from 10% to 5% and
increase of the proportion of | 4) ) ditto;
the developmental fund from | ¢) Coefficient of proportionality for 3
Maintenance of | 90% t0 95% Type B space: 1.0 for years around 2000
status quo
a), b) ditto;
c) Coefficient of proportionality for 4
Type B space: 1.0 for years before 2000
and 0.5 for years after 2000
a), b) ditto;
c) Coefficient of proportionality for 5
Type B space: 1.0 for years before 2000
and 0 for years after 2000
Reduction of the proportion
of the non— developmental | a), b) ditto;
fund from 15% to 10% and |c) Coefficient of proportionality for é
increase of the proportion of | Type B space: 1.0 for years before 2000
the developmental fund from | and 0.8 for years after 2000
85% to 90%
Rendon varia a), b), c) Same as Scheme 1 7
tions
Slow increase This layer:ts same as the Ist a), b), c) Same as Scheme 1 8
~ Sth schemes.
Gradual teduc- a), b), c) Same as Scheme 1 9
tion
Page 300 System Dynamics '91
Part Four Example of Computation for Representative City
4.1 Computation Result and Tendency Analysis Corresponding to the First Scheme
The length of the step for modeling computation lasts for one year, starting from
1991 and ending at 2010 with the total length of time period being 20 years. For the start-
ing year of modeling computation, the total fund from the external sources approximates
20,000,000 units of currency, and the urban population amounts to 2,390,000 people.
The development tendency of the construction of the protective works against disas-
ters specified in the first scheme is as follows:
The rate of association is expected to maintain the present level(i.c., less than 5 per
cent), leaving a considerable gap in comparison with the planned rate of association. The
present rate admission of underground space is 54 per cent and will rise to 65 per cent at
the end of the precent century(with the urban population being 2,718,700), and will in-
crease up to 77 per cent at 2010(with the urban population béing 2,954,200). The protec-
tive effectiveness will reach 65 per cent at 2010.
The development tendency of economic benefit specified in the first scheme is as fol-
lows:
The usage fees of underground space to be counted up to the end of the present cen-
tury will be equivalent to 3.4 times of the present ones; and they will be equivalent to 5.8
times of the present ones. The total output value of the usage will be equivalent to 2.2
times of the present figure; it will, up to the year 2010, be equivalent to 2.5 times of the
present figure. The output value per unit investment will increase by 50 per cent at 2010
compared with the present value, and the economic benefit per unit investment will be
doubled in comparison with the present one.
The additional targets of the first scheme are as follows:
The proportion of the internal income to the total fund from the external sources is
less than 20 per cent at present, and will reach 60 per cent at the end of the present centu-
ry, which still fails to strike a balance. It is only possible to strike a balance up to 2009;
and at 2010, the internal income of the departments will slightly exceed the total fund
from the external sources, which shows that a fundamental change has taken place with-
in the system. The proportion of the income of usage fees to the investment for new de-
velopment is to be computed from the year 1991, will make a slow increase up.to 60 per
cent, and will reach 70 per cent at 2010, which demonstrates the gradual enhancement of
the capability of self strengthening of the system.
4.2 Effect of the Variations of the Second— and Third—Layer Conditions within the
System on the Tendency
The result demonstrates that the target of economic benefit.and the additional target
in the third scheme are the highest; among the targets of protective benefits against disas-
ters, the targets of spatial area and the rate of admission are the highest, and the
peotective effectiveness resulting from the rate of admission is also considerably high,
nevertheless, the rate of association is the lowest. The rate of association for the system
specified in the fifth scheme is by far higher than the other schemes; but the target of
System Dynamics '91 Page 301
economic benefit and that of the total area are the ‘lowest; and the amplitude of the in-
crease of protective effectiveness derived from the enhancement of the degree of protec-
tion is lower than the one obtained from the raising of the admission rate. The remaining
schemes fall between the two foregoing schemes with varying degrees.
4.3 Effect of.the Variations of the First-Layer Conditions within the System on the
Tendency
The developmental expenditures for the sixth scheme is somewhat reduced com-
pared with the first scheme, and various targets are al lowered in varying degrees; but the
targets of the economic benefit per unit investment and the ratio of the annual income
resulting from the usage of space to the annual investment are increased instead, which
shows that, on the whole, the absolute value of the benefitgained from underground
projects is relatively low; the greater the input, the lower the rate of benefit per unit
investment. This point also accords with the situation of underground space develop-
ment itself. Anyhow, the balance of area for the planned target in the scheme has in-
creased by 6 per cent.
4.4 Effect of the variations of the External Environmental Conditions on the System
Tendency
Random variations within the range of 17,000,000 to 22,000,000 units of currency
have been taken into account in the seventh scheme; but the general result exhibits no
great difference in comparison with the first scheme. Based on the optimistic estimationas
shown in the eighth scheme, if the external fund raising makes a slow increase in the pro-
portion of 2 per cent, then the spatial area will increase by 5 per cent in comparison with
the first scheme in 2010 with the other targets also making certain increases. Of course,
the economic benefits per unit investment will make corresponding slight decrease. Based
on the pessimistic estimation, when the external fund raising makes negative increase(i.e.,
decrease) in the same proportion, the spatial area will reduce by 4 per cent compared
with the first scheme in 2010 with the other targets also making corresponding reduc-
tions. However, under the these conditions, the development speed of more than 10,000
units of area can be maintained every year and make slow increase at that. Up to 2010,
the annual area of development may reach 11,300, despite the lowering by 19.8 per cent
in comparison with the area of development obtained under the conditions of main-
taining status quo. But it shows that, when the external fund raising makes gradual de-
crease, the main contribution to the maintenance of the above—mentioned speed in terms
of development area comes from the internal part of the system. This is just the embodi-
ment of the internal vitality.
Part Five Related Conclusion and Suggestions
5.1 Tendency of Underground Space Development under the Present Policies and
Conditions
Just like the typical cities listed in this paper, up to the first ten years of the next cen-
tury, the protective construction against disasters still cannot meet the planned targets.
Nevertheless, if two measures are to be adopted, great improvement of the things will be
made. One thing is to build subways. Considering the fact that. part of the area will be
Page 302 System Dynamics '91
used as protection against the disasters, up to the year 2010, the total rate of admission
will arrive at 92 per cent, the distance away from the planned rate of admission being
greatly reduced. The other thing is to control the urban population. If effective control
can be exercised over population, and its growth rate is kept at zero after 2000, then, up
to 2010, the rate of admission of underground space will get to 92 per cent, the result be-
ing almost the same as building of subways. If the above-mentioned two measures are
practised simultaneously, then, up to 2006, it is possible to meet the planned target of
providing shelter to 100 per cent of the population. At that time, it can be said that the
preset scale will have been fulfilled from the angle of the rate of admission.
By 2000, the income due to the usage of underground space will make considerable
increase compared with the present one; and the economic benefit per unit investment
can be doubled. By 2010, the income of usage fees and the internal income of the de-
partments will be approximately as much as 5 times the present figure.
Up to 2000, the proportion of the internal income of the system will reach about 60
per cent of the total fund from the external sources; and up to 2009, a balance will be
strikken between the internal and external funds; up to 2010, the internal fund will be in
excess of the fund from the external sources. This demonstrates that, in the first ten years
of the next century, a fundamental change will take place in the development of under-
ground space and the protective construction against disasters; even if the fund from the
external sources is reduced, the internal part of the system will still be able to maintain a
certain rate of growth.
5.2 Tendency of Devclopment Following the Adjustment of the Main Parameters of
Planning within the System
If the proportion of the developmental fund is lowered, various targets will also be
lowered likewise; if emphasis is laid on the construction of Type B space before 2000, the
rate of admission and economic benefit will be markedly raised; but the rate of associa-
tion can only be kept at the present level. If emphasis is laid on the construction of Type
B space before 2000 and on the construction of Type A space after 2000, the rate of asso-
ciation will be raised by a big margin, which exerts no influence on the target of econom-
ic benefit for the end of the present century; but the long-term target of economic benefit
will be loowered.
5.3 Tendency of Development with the Variation of the Main External Conditions
Considering the fact that the general tendency with the random variation within a
certain interval is more or less the same as the scheme of maintaining the status quo, if
the external fund raising can be increased in a certain degree, it is possible to get nearer
to the planned target of construction up to 2010; even if the external fund will be gradu-
ally reduced, certain growth rate will be maintained with the support of the internal
potentialities of the system. There is no doubt that the time period for the realization of
the planned targets will be somewhat prolonged.
5.4 Related Suggestions
A multiple of policies and measures are to be adopted so as to strive for the realiza-
tion of the target for the protective construction. against disasters. Such policiies and
measures include the strengthening of the internal vitality, the making of efforts for the
System Dynamics '91 Page 303
improvement of the external conditions, the control of the urban population, the con-
struction of subways, the adjustment of policies towards sheltering, etc. As for the adop-
tion of higher proportion of the developmental fund, for the present, the proportion can
be fixed at 90 per cent and later on be gradually raised to 95 per cent. Before 2000, the
investment for Type B space with high proportion shall be maintained so as to enable the
departments to gain relatively solid financial basis and to shift the emphasis on the de-
velopment of Type A space in a certain, suitably later period; it is also possible to consid-
er the floating of the prices of usage fees for underground space in accordance with the
actual conditions. Efforts shall be made to avoid the reduction of the available sources of
external fund; and combination with municipal construction shall be insisted upon so as
to absorb the investment for municipal construction. The urban population is to be con-
trolled and urban subways to be developed. In addition, in combination with the actual
conditions of various cities, an in—depth, all-round study shall be carried out with rela-
tion to the objects, scale and scope of sheltering for protection against disasters so as to
set out different sheltering policies for different requirements.
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