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Modernization of underground pipes in towns in Poland
INFRASTRUCTURE S0886-7798(96)00013-2
Modernization of Underground Pipes in Towns in Poland Andrzej Kolonko and Cezary Madryas A b s t r a c t - - R e n o v a t i o n of the existing, worn-out network infrastructure in Polish towns is one of the basic elements necessary to make those towns confbrm to European standards. This problem has gained significance, especially in light of Poland's efforts tojoin the European Union. Re,~abilitation ofpipes is necessary as a result of the poor technical co~lition of pipes, their inefficiency, or the location of the pipes (e.g.. in a location that interferes with planned development of underground space in towns). Trenchless technologies for renovation of underground network infrastructure are discussed, from technologies used tim single pipes to rnultieonduit tunnels as a method for achieving complex modernization of infrastructure. Economic, technical, and legislative problems connected with the use of these solutions are also presented.
Introduction " ew economic principles adopted in Poland and the nation's consequent transition to a market economy have given new value to urban development, due to changes in the livin[[ conditions and labour conditions of city dwellers, in addition to their varied expectations and demands. Poland has witnessed a growing demand for high-quality services, fast and comfortable transport, and improved or expanded parking facilities and network services for communication, energy and water supply, and sewage systems. It is also expected that those areas of cities that have been mode]Tfized will be characterized by greater utility, and will conform to ecological, safety and aesthetic standards. In order to satisfy the above requirements, it is necessary to intensify the use of space in towns by developing underground structures that integrate comfort and safety while observing principles of ecology. In Poland, rehabilitation of network infrastructure and development of underground communication infrastructure are matters of great urgency that can be accomplished either simultaneously or with the latter following the completion of network rehabilitation. Some network renovation work is necessary because of the bad technical state of the pipes, resulting in increased frequency of network failures and poor efficiency of the pipes. Network renovation also includes cases where it is necessary to change the location of pipes to accompany development of other underground structures. The poor technical condition of pipes may result from construction errors, flawed materials and errors in technol-
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P r e s e n t address: Andrzej Kolonko a n d Cezary M a d r y a s , Technical U n i v e r s i t y of W r o c h w , I n s t . of Civil E n g i n e e r i n g , Wybrze~e Wyspiafiskiego 27, 53-370 W r o d a w , Poland.
Tunndlingand UndergroundSpaceTechnology,Vol. 11, No. 2, pp. 215-220, 1996 Copyright © 1996 ElsevierScienceLtd Printed in Great Britain. All rights reserved 0886-7798/96 $15.00 + 0.00
ogy, and/or errors in operation, as well as from environmental impacts and normal aging processes. In such cases, rehabilitation of pipes can be carried out by open-cut or trenchless methods, without any significant changes in the dimensions or locations of the pipes. One example of renovation of sewage ductwork undertaken because of the poor technical condition of the pipes involved work carried out in Tarn6w [5]. The duct was made of reinforced concrete with diameters of 300, 400 and 500 ram. A TV camera was used to assess the technical stateof the pipes. The examination revealed the following faults and damage in the construction of the duct: • Scratches and longitudinal cracks in the upper part of the cross-section. • Horizontal and vertical displacements. • Significant losses at pipe connections. • Corrosion of the inner surface of the duct. The technical state of the construction in sections where longitudinal cracks occurred was considered to be a failure condition. The length of the duct cracked in this way was 558 m. It was decided to apply the relining method in renovation works because, according to structural analysis, a new polyethylene (PEHD) pipe placed inside the damaged duct was capable of taking over the total load exerted on the duct. A scheme of the renovation is presented in Figure 1. Following the principles of this technology, 0.50-m-long segments of PEHD pipe were pushed through control shafts to the inside of the damaged duct with the use of a servomotor. Free space between the old and new pipes was filled with a special mortar of foamed concrete. Such a solution, on the one hand, protected the old duct against collapse; and on the other hand, increased its load capacity (a new "pipe" was formed with three-layer wall construction). In addition, pressure-forced mortar filled empty spaces that appeared in the surrounding soil as a result of the penetration
Pergamon
of grains to the inside of the leaky duct, together with infiltrating groundwater. As a result of the renovation, loads acting on the construction were more uniformly--and, therefore, more advantageously--distributed [4]. Inadequate efficiency of pipes in cities is associated with increased consumption of water and the resulting growing volumes of sewage. This is one effect of setting higher standards for urban facilities. In Polish towns destroyed during World War II, this problem is particularly noticeable. Although fii~y years have passed since the war, large areas of urban development are still being reconstructed. Present regulations in Poland provide for equipping residential buildings with sanitary fittings of an incomparably higher standard than those applied in prewar houses (i.e., basic running water, bathrooms, w.c. in each flat). Consequently, the amount of sanitary sewage has increased considerably; and old pipes, with diameters established well before the war, are not able to dispose of it. In this case, renovation of the system may consist of building a new larger-diameter duct to replace the old one; increasing the dimensions of the existing pipes; or building an additional parallel duct so that the modernized system can dispose of greater volumes of sewage. Building a new duct causes inconvenience because it requires putting some sections of the network out of operation during construction and, consequently, pumping sewage over a longer period. Such solutions were used earlier in Poland, when no other methods were available. In most cases, it is impossible, or nearly so, to build additional ducts in parallel because of the great concentration of underground conduits that already exists in towns in Poland. An additional disadvantage of this solution is that the old duct, although quite worn out, is still in operation. A technology that offers a feasible solution to this problem is the trenchless method of replacing the old pipe, which has too small a diameter, with a new pipe that has a larger diameter. The technology known in Europe as berstlining (pipe-bursting) involves destroying the old pipe and replacing it with a new one. This method has gained in popularity as the headers used to burst old pipes have been improved, thus diminishing the intensity of the shocks they cause. Consequently, it is possible to use such headers in cases involving a great concentration of technical infrastructure conduits. An example of renovating a duct of insufficient flow capacity with the use of this technology is the renovation of a sewage duct in D~bica. In this case, a concrete sanitary duct 200 mm in diameter was replaced with polyethylene (PEHD) pipe 315 mm in diameter [5]. Figure 2 shows a scheme of the course of this renovation. The bursting header was placed inside the existing duct through cleanout shafts. Then, by expanding circumferentially and moving forward, the header destroyed the old duct, while simultaneously pulling in 0.50-m-long segments of a new PEHD duct. Similar renovations of ducts
using the relining and pipe-bursting technologies have been performed in recent years and are still being carried out in many towns (e.g., Krak6w, Katowice, Warszawa, Wroc~aw). When the existing system interferes with a planned underground installation, it becomes necessary to change the location of the pipes. This frequently happens in the construction of new underground pedestrian walkways. The tunnels for such underpasses are usually located at the same depth as the conduits of the technical infrastructure. In such situations, open-cut techniques are generally used; and if sewers happen to be located there, it is often necessary to build a local sewage pumping plant. Therefore, these cases should not be considered as network renovation, but rather as examples of rebuilding, necessitated by the improvement of other elements of the urban underground infrastructure. It follows from the above considerations that the scope of rehabilitation may be confined to either repair works, repair and modernization (as in the first and the second cases described above); or to rebuilding (the third case). Repair works and repair and modernization are usually performed by trenchless techniques, and rebuilding by open-cuttechniques (in open excavations). An influx of imported technologies has resulted in the increased use of trenchless techniques for repair works and repair and modernization in Poland. It is expected that the demand for modernization works will further increase in the near future because of the above-mentioned necessity to develop integrated urban space---first of all, by rebuilding communication systems.
Trenchless Technologies for Rehabilitation of Underground Pipelines Leakage of underground networks may cause discomfort in the daily life of inhabitants, as well as increase the degree of environmental pollution. The term ~ecological bomb" graphically describes the disastrous effects of sewage exfiltration to soil, if it is not quickly halted. In Germany alone, the present volume of exfiltration is estimated at about 300 million m 3 [1]. A failure of gas piping may even be life-threatening to inhabitants. Another consequence of such a situation is the economic losses stemming from uncontrolled outflow of gas ifa failure of pressure pipelines (e.g., water mains or gas piping) occurs. In the case of leakage into sewage duct laid below the groundwater level, sewage carried off to a treatment plant is diluted, thereby increasing the operational costs to a sometimes considerable degree. Legal regulations that impose tough sanctions against polluting the natural environment appear to be the most effective means of speeding up action taken to improve the technical state of underground pipes. Introduction of such regulations in western Europe was a turning point that led to the development of research, development of new technologies, and establishment of numerous firms offering such services.
Classification of Rehabilitation Methods for Underground Pipelines
Figure 1. Scheme o f renovation o f sewage ducts using the relining method [B] 1 - segments o f P E H D pipes, 2 - shaft, 3 - old duct, 4 - servomotor.
216 TUNNELLING ANDUNDERGROUND SPACETECHNOLOGY
Underground utilities that have been in operation for 100 years or more are, for the most part, worn out and in poor condition. In Germany, nearly 80% of cast-iron piping ranges from 66 to 144 years in age [2]. In Poland, the percentage of old pipelines is even higher, as a result of neglect of underground infrastructure maintenance and construction during the post-war period. As indicated in [9], the most frequent causes of pipeline failures are: • Ground settlement. • Chemical and biological corrosion. • Aging of construction materials. • Inadequate load capacity of pipelines, compared to the increasing traffic loads.
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Figure 2. Scheme of renovation of sewage ducts with the use of the pipe-bursting method 1 - hydraulic header, 2 - old duct, 3- shaft, 4 - segments of polyethylene pipes. Damaged underground pipelines can be restored to an adequate technicalstate through rehabilitation,which can be performed using the technicalstrategiesdescribed below.
with a new one having the same or larger diameter, and the old pipe m a y eitherbe moved or itsfragments m a y be leftin the ground.
a) Repair
Renovation Experiences in Wroctaw
Repairs apply to single, local faults. In the case of pipes having diameters smaller than 60 cm, all sorts of robots, packers, and other similar appliances may be used. Repairs, carried out from the outside and inside, consist of: • Mending. • Injection. • Sealing.
In recent years, modern Western technologies of trenchless renovation of underground pipeline have become available on the home market in Poland. Prior to implementing any of those methods, an economic analysis should be performed. Because labour is still relatively cheap in Poland, it is often more cost-effective to replace the old pipeline with a new one using traditional methods in open excavation, instead of employing trenchless technologies that are widely applied in western countries. However, investors sometimes are compelled to use trenchless methods, especially in centres of Polish towns, for the following reasons: • A desire to avoid disruption to traffic organization due to underground works. • Numerous points of intersection with other networks of underground infrastructure. • The possibility of damaging underground infrastructure network not being repaired at the time. • Costly pavement along the pipeline route. • The need to carry out the works quickly. • The need to avoid lowering the groundwater level. In choosing a method, both technical and economic aspects should be taken into consideration. It is important to estimate how long the service life of the pipe can be extended aRer renovation using a particular technology. Such an analysis may show that using the least costly technology is not economically feasible. The situation in Wroc~aw with regard to the application of trenchless technologies is reviewed, by network, below.
b)
Renovation
Renovation involves restoring the damaged pipeline to its original technical state by applying suitable technical procedures and preserving the old structure. The following categories of renovation methods may be used: • Methods of spreading special sealing coatings o n t h e i n s i d e o f t h e p i p e . The coatings, which may be
composed of various materials, are spread by techniques such as spraying. • R e l i n i n g m e t h o d s (rigidinserts). These methods involve placing a P E or P V C tube, with an outer diameter smaller than the inside diameter, insidethe damaged duct. This operation m a y be performed in short sections,from the shaft (shortrelining);or in long sections,covering as m u c h as several hundred meters, from some suitableexcavation (longrelining).Ifitisimportant that reduction ofthe cresssection be limited,renovation of damaged pipeline can be carried out using a "close fit~ technique of the relining method. • Relining met]hods (elasticinserts). Here, elastic coating, usually ha~.ing a multi-layer structure, is introduced in a reversible process to the inside of damaged pipe (afterthe latterhas been previously cleaned), and is then stuck to the inner surface of the pipe. While the adhesive hardens, the coating is held tight by water vapor, air or water pressure. • Fitting methe~Is. Fittingmethods involve covering the insidesurface oftlhedamaged duct with suitablyformed elements made of materials that ensure complete tightness and resistance to chemical corrosion and abrasive wear. This method is commonly used to repair the damaged bottoms of small-diameter ducts. For ducts with diameters greater than 60 cm, a complete inside liningis made, using suitably formed segments of dimensions that permit their transport.
c) R e p l a c e m e n t Replacement involves laying a new section of underground pipeline to take over the function of the old pipe, when the latter is in bad technical condition or its capacity is insufficient. Replacement can be carried out by means of traditionalmethods in an open excavationor usingtrenchless methods. In the lattercase, the old pipe m a y be replaced
Volume 11, Number 2, 1996
a) Gas piping With respect to underground gas piping in Wrodaw, there is an urgent need for cast-iron pipes to be tightened. This work must be performed quickly because of factors related to the city's conversion to natural high-methane gas, which is more effective as fuel and which causes the least environmental pollution when burned. A sudden increase in the number of leaks occurring in bell joints is expected after conversion to natural gas because of its unfavourable action on the sealing material. Consequent gas losses may amount to 20% [3]. Therefore, in Wroclaw priority is given to the task of sealing cast-iron sections of gas pipelines. This is done by: • Gluing thin, polyethylene sheeting to the inside of pipe in a reverse process (polyurethane glue). • Gluing thin sheeting and needled cloth in a two-stage reverse process (polyurethane glue). • Renovation by means of a relining method using Ulinear technology (close fit). • Replacement ofold, cast-iron pipes with new PE pipes in open excavations.
TUNNELLINGANDUNDERGROUNDSPACETECHNOLOGY217
b) Water main In the case of the water-pipe network, progressive corrosion causes a loss of tightness and a decrease in crosssections of cast-iron and steel pipes due to formation of incrustations. In Wrocbaw, these problems are dealt with
by: • Gluing the sheeting reinforced with needled cloth to the inside of pipe in a single-step reversible process (epoxy glue). • Renovation by means of the relining method, using Ulinear (close fit) technology. • Cementing the inside surface of pipe by the spraying method (pipe dia. < 60 cm). • Trenchless replacement of damaged pipes with new ones using a pipe-bursting method. • Open-cut replacement of damaged pipes with new ones.
c) Sewage system In the case of Wroc]~aw'ssewerage network, basic technical problems, apart from leakage, include construction damage, which may be caused by: • Increasing traffic loads of dynamic character. • Chemical and biological corrosion. • Friction of solid particles contained in sewage against the sewer bottom. • Military operations during war. These problems are being solved by: • Repairing damaged and leaking ducts ( dia. > 60 cm), using mortar. • Trenchless replacement of damaged sewers with new ones, using the pipe-bursting method. • Open-cut replacement of damaged sewers with new ones.
Multiconduit Tunnels in Network Rebuilding The rebuilding of networks that cross newly developed structures can be carried out by systematically replacing particular pipes and laying them back in the ground. This method of modernizing operating networks has the following disadvantages: • The possibilities of inspecting the state of the pipes, providing current maintenance and removing failed pipes, without tearing up the street, are limited to TV techniques and trenchless methods of renovation. • The pipe failure rate is increased, because of their direct contact with the environment. These factors make it difficult to operate the network and increase the costs of operating it, while simultaneously lowering the functioning quality of the system. Taking into account the above arguments, in cases where pipes of particular networks have been worn out to much the same degree, as often happens in Polish towns, it should become a rule to consider the possibility of replacing pipes of all networks simultaneously and laying them down in multiconduit tunnels or in technical passages. The idea of using multiconduit tunnels and technical passages as technologies for network rebuilding [6] is also justified by the need to integrate the systems of underground infrastructure, thereby raising the possibility of control and, as a result, increasing their reliability and safety of operation. Moving in this direction also stems from the need to "compress" the network in order to save underground space for other purposes--first of all, communication. Multiconduit tunnels are usually created by open-cut methods as shallow underground structures situated at various places in the cross-section of a street. Because of the construction loading, it is best to lay out the route of the
218 TUNNELLING ANDUNDERGROUND SPACETECHNOLOGY
tunnel under the sidewalk or, if there are two traffic lanes, along the division line of the lanes. It is important to plan connections from buildings to tunnels. Connections that are laid directly in soil constitute the most unreliable element of the whole system, because they render it impossible to control pipes along a stretch of multiconduit tunnel-building. Therefore, whenever possible, connections should be planned as tunnels at least 60 cm in diameter or as a bundle of circuits laid in protective linings, permitting their disassembly and assembly, and thus avoiding the need to tear up a street to make repairs. It is especially advantageous to locate multiconduit tunnels in constructions used for other purposes as well (e.g., communication tunnels) or to join them with technical passages. In the latter category are multiconduit tunnel-technical passage "chains, ~ in which the length of connections is reduced to a minimum, on the condition that there are two separate "chains" of buildings situated on both sides of a street. In constructing a technical passage, it is necessary to adapt the basements of buildings adjacent to the street. This may prove impossible to carry out legally if property owners do not consent to allow the conduits to be driven through the basements of their premises, or if they charge too high a rental fee. That is why economic and legal issues should be settled at the beginning of the planning process, so as to ensure that it is technically possible and economically feasible to carry out the project. Putting the networks in technical passages creates optimal conditions for underground space to be used for other purposes, because it eliminates the need for a considerable number of circuits. Sewerage networks may be located in tunnels when longitudinal slopes of the bottom of the tunnel are suited to the required sewer slopes. The sewers are separated from other grids by laying them under the tunnel floor in a bottom plate fitted for that purpose, or by enclosing them by a tight construction that protects the tunnel against being flooded with sewage and against the action of gases escaping from sewage. Laying the network in multiconduit tunnels implies an increase in capital costs, stemming from the costs of both construction and tunnel fittings (lighting, ventilation, communication, signalling, drainage), and including dispatcher and personnel rooms. The relation between these costs and the costs of networks laid directly in soil depends upon local conditions and technological solutions and materials used. Naturally, the investment costs in such a case are higher by several dozen percent than the costs of placing the network directly in soft. Cost-effectiveness in laying networks in multiconduit tunnels will be achieved only if the operational costs over a predicted period of tunnel amortization are included in the costs analysis. If the account is based on annual costs, considering the discount account, then the costs can be expressed by the equation K =K+Ke=rKo+K , (1) where: Kr~ = annual costs of capital and future replacement; K = annual operational costs; Ko = capital costs reduced to zero year; and r = coefficient of costs ofcapital and future replacement. The annual costs method is applied in order to identify the solutions that ensure the maximum production effect [7]. In investigating the costs of networks, elements of decision occur that are seemingly not connected with the production sphere. These include decisions about improving the technical quality of pipelines and the ability to operate them, in order to increase the operational reliability of the network. Therefore, it is necessary to extend the annual costs K over the costs of system unreliability K [8]: K z=Kr+K =rKo+K+K, (2)
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The unreliability costs introduced into the costs account have a character of economic reproduction of the effects of unreliable network operation, and equal K = K + K~m, (3)
After algebraic transformations, the effectiveness index el,2 of transition from a more unreliable variant (with pipes laid in soil) to a less unreliable one (pipes laid in a multiconduit tunnel) is defined by the relation
where:
(ILl Ka) (Ka ILl) a -
K
= annual costs of recipients losses due to network unreliability; and K m = annual cost~s of repairs a l ~ r failure, extended over losses of suppliers, caused by not levying charges for cut-offperiods due to unreliability of the network. Thus, optimization is achieved by seeking the set of admissible solutions, in view of minimizing their annual costs K . If the analysed solution suggests laying pipes in multiconduit tunnel to minimize the costs of their unreliability K , then this also implies changes of other components of equation (2), since the investment costs Ko will increase and the operational costs K will probably diminish. This explains why optimization does not merely consist of seeking solutions of extremely high reliability, which may appear to be economically unjustified due to too large an increase in investment costs. In such a case, seeking a minimum resolves itself in comparing the sums of costs of the solutions considered. In practice, we deal with a discrete model of costs, which allows formulation of differential criteria fi)r variants being compared, e.g.: I: low-cost variant, with greater unreliability (laying pipes in soil) II: high-cost variant, with less unreliability (laying pipes in multiconduit tunnel). The more expensh,e solution will be cost-effective if the following condition is satisfied: K z l - - Kz2 > K~ - K, (4) This inequality correspends to the assumption that the high-cost variant (II) is considered advantageous if reduction of unreliability costs covers increased annual costs caused by the rise in investment costs due to the building of a multiconduit tunnel. Taking the difference K 1- Ks to be a profit resulting from the improvement of reliability, implied by additional annual costs K 2 - Krl , we can determine the effectiveness index e, illustrating economic effectiveness of means earmarked for decreasing the unreliability of analysed variants E = (Kzl
--
Kz2) -- (Kr2 (I~1 K$2 )
--
Krl) > 0
(5)
--
The effectiveness index is mainly of benefit in analyzing the effectiveness of transitions between variants of increasing reliability, which consists of determining the"profitabili t f ' o f m e a n s u s e d for rehabilityimprovement. The problem to be solved in the above costs account model involves comparing the quantities that have been determined (annual costs) with random quantities (unreliability costs). According to decision-making theory, such a procedure is correct on condition that unreliability costs should be determined on the basis of known distributions of random variables, or some representative statistical material. Unfortunately, there are no such data from investigations available in Poland that would allow any of the above-mentioned conditions to be satisfied. This means that for the time being, decisions can be made merely on the basis of approximate determination of costs, using the strategic decisionmaking model. In this model, the unreliability costs should be assigned the weight 1 - a < 1, where a is the measure of the lack of confidence in the values K being introduced. For the weight thus form~alated, the annual costs are expressed by the equality K= := rK= + K + (1-a)K, (6) and the differential criterion takes the form ( l - - a ) (K1-K2)_> K 2 - K ~ (7)
Volume 11, Number 2, 1996
ei,2 =
-
(ILl
-
-
(8)
>
IL~)
-
The unreliability costs cannot be analysed without taking account of the time factor, since its functions are the changes in intensity of pipe failures and in the market prices ofmatex*ials, equipment and labour. Taking the time factor into consideration requires that the mean discount values be included in the calculus, and thus equation (8) takes the form ar ~[(I El,2
-
a) (Kzl i Kz2i) (Ke2i -
-
-
K e l i ]
]
(I + p)T-i (Kilo2 Knol)r
l=L
_
_
~a
a r ~ ( K z l i - Kz2i) (1 + p)T 1--1
(9) where: a = coefficient of progressive amortization, T = amortization time in years; p = accumulation rate; and i = successive years of operation. The difficulties and limitations presented above render it impossible to carry out an analysis of the real costs of multiconduit tunnels, thus reducing it to comparisons of capital expenditures, the results of which are decisive in rejecting solutions of this type. Because there are few multiconduit tunnels in Poland, it is difficult to carry out the research on pipeline operation that would be needed to establish the necessary data bases, making it impossible to show the technical and economic advantages of tunnels. In the face of those limiting circumstances, researchers today have at their disposal only heuristically directed, intuitive methods. This reluctance to use multiconduit tunnels is also connected with an absence of laws regulating the operation of networks located in tunnels. Pipes laid in soil are run by owners of particular networks. However, if pipes are placed in a multiconduit tunnel, there arises the question of who should run them or coordinate the operation of particular network owners. This problem can be overcome by: 1. Establishing one-person companies in districts, in order to build tunnels and to operate pipes laid there, in return for a rent charged from particular owners; or 2. Establishing companies that are assigned the same tasks, and whose members would be the owners of pipes laid in tunnels. According to principles of market economy, companies cannot operate at a loss in either case. Once the multiconduit tunnels are seen as a source of potential income, the problem of their effectiveness will have to be solved by companies undertaking the risk of building and running them, which until now has practically been nobody's problem. Such enterprises might stimulate development of multiconduit tunnels as a technology of the network infrastructure rebuilding in the case of considerable wear of a majority of grids, their inadequate efficiency, or their interference with planned development of underground space. C o n c l u s i o n s
In view of the fact that the poor technical state of pipelines is quite a serious problem in Poland, it is necessary to balance needs and possibilities in determining how to improve them. In order to intensify technical activities, appropriate legal regulations should be established and put into force, compelling the owners of pipelines to keep them in a condition that would not create environmental and safety hazards. A number of firms on the domestic market
TUNNELLINGANDUNDERGROUNDSPACETECHNOLOGY219
now offer various technologies for renovating u n d e r g r o u n d pipelines. In o r d e r to i m p l e m e n t t h e m rationally, it is n e c e s s a r y to m a k e thorough economic and e n v i r o n m e n t a l a n a l y s e s to compare trenchless methods with open-cut methods. In s i t u a t i o n s w h e r e p i p e s a r e inefficient, w h e r e t h e pipes of more t h a n one n e t w o r k a r e in poor condition, or w h e r e t h e p r e s e n t location of t h e pipes r e n d e r s it impossible to c a r r y out o t h e r u n d e r g r o u n d projects, it is advisable to use m u l t i c o n d u i t t u n n e l s a s a technique for rebuilding t h e n e t w o r k i n f r a s t r u c t u r e . However, before such a technique can be a d v a n c e d , laws m u s t be p a s s e d to authorize p o t e n t i a l owners of t u n n e l s , for whom m u l t i c o n d u i t t u n n e l s can provide a source of income.
References [I] Engelmann, H. 1990. NeubauoderInstandsetzungvonKanalisationen. Tiefbau Ingenieurbau Stra~nbau, Heft 10. (In German)
220 TUNNELLINGAND UNDERGROUNDSPACE TECHNOLOGY
[2] Hofer, P. 1994. Planung der langiiistigen Emeuerung yon Wasserrohrnetzen. 3 R International, Heft 1-2. (In German) [3] Kolonko, A. 1994. Problemy techniczne przy renowacji sieci gazowej metod~ Process Phoenix. GW i TS Nr 8. (In Polish) [4] Kolonko, A. 1995. Rheologishe Eigenschaften eingebetteter starrer Rohrleitung im Baugrund. Strassen und Thiefbau Nr. 12. (In German) [5] Kuliczkowski, A.; Pluta, R.; and Zwierzchowski, D. 1995. Diagnostyka i odnowa kanalow. Conference Papers; Trenchless Tech Warsaw '95. (In Polish) [6] Kuliczkowski, A. and Madryas, C. 1989. Tunele wieloprzewodowe, Skrypt nr 189, Politechnika Swi~tokrzyska, Kielce, 1989. (In Polish) [7] Lange, O. 1975. Teoria reprodukcji i akumulacji, PWN, Warszawa, 1975. (In Polish) [8] Sozariski,J. 1982. Niezawodnoddzasilaniaurz~dzefiiuldaddw elektroenergetycznych,P W N , Warszawa, 1982. (In Polish) [9]Stein,D. and Kaufman, O. 1992. Schadensanalyse anAbwasserkan~ilen aus Beton- und Steinzeugrohren der BRD-West. Korrespondenz Abwasser 2/92. (In German)
Volume 11, N u m b e r 2, 1996
Modernization of Underground Pipes in Towns in Poland Andrzej Kolonko and Cezary Madryas A b s t r a c t - - R e n o v a t i o n of the existing, worn-out network infrastructure in Polish towns is one of the basic elements necessary to make those towns confbrm to European standards. This problem has gained significance, especially in light of Poland's efforts tojoin the European Union. Re,~abilitation ofpipes is necessary as a result of the poor technical co~lition of pipes, their inefficiency, or the location of the pipes (e.g.. in a location that interferes with planned development of underground space in towns). Trenchless technologies for renovation of underground network infrastructure are discussed, from technologies used tim single pipes to rnultieonduit tunnels as a method for achieving complex modernization of infrastructure. Economic, technical, and legislative problems connected with the use of these solutions are also presented.
Introduction " ew economic principles adopted in Poland and the nation's consequent transition to a market economy have given new value to urban development, due to changes in the livin[[ conditions and labour conditions of city dwellers, in addition to their varied expectations and demands. Poland has witnessed a growing demand for high-quality services, fast and comfortable transport, and improved or expanded parking facilities and network services for communication, energy and water supply, and sewage systems. It is also expected that those areas of cities that have been mode]Tfized will be characterized by greater utility, and will conform to ecological, safety and aesthetic standards. In order to satisfy the above requirements, it is necessary to intensify the use of space in towns by developing underground structures that integrate comfort and safety while observing principles of ecology. In Poland, rehabilitation of network infrastructure and development of underground communication infrastructure are matters of great urgency that can be accomplished either simultaneously or with the latter following the completion of network rehabilitation. Some network renovation work is necessary because of the bad technical state of the pipes, resulting in increased frequency of network failures and poor efficiency of the pipes. Network renovation also includes cases where it is necessary to change the location of pipes to accompany development of other underground structures. The poor technical condition of pipes may result from construction errors, flawed materials and errors in technol-
N
P r e s e n t address: Andrzej Kolonko a n d Cezary M a d r y a s , Technical U n i v e r s i t y of W r o c h w , I n s t . of Civil E n g i n e e r i n g , Wybrze~e Wyspiafiskiego 27, 53-370 W r o d a w , Poland.
Tunndlingand UndergroundSpaceTechnology,Vol. 11, No. 2, pp. 215-220, 1996 Copyright © 1996 ElsevierScienceLtd Printed in Great Britain. All rights reserved 0886-7798/96 $15.00 + 0.00
ogy, and/or errors in operation, as well as from environmental impacts and normal aging processes. In such cases, rehabilitation of pipes can be carried out by open-cut or trenchless methods, without any significant changes in the dimensions or locations of the pipes. One example of renovation of sewage ductwork undertaken because of the poor technical condition of the pipes involved work carried out in Tarn6w [5]. The duct was made of reinforced concrete with diameters of 300, 400 and 500 ram. A TV camera was used to assess the technical stateof the pipes. The examination revealed the following faults and damage in the construction of the duct: • Scratches and longitudinal cracks in the upper part of the cross-section. • Horizontal and vertical displacements. • Significant losses at pipe connections. • Corrosion of the inner surface of the duct. The technical state of the construction in sections where longitudinal cracks occurred was considered to be a failure condition. The length of the duct cracked in this way was 558 m. It was decided to apply the relining method in renovation works because, according to structural analysis, a new polyethylene (PEHD) pipe placed inside the damaged duct was capable of taking over the total load exerted on the duct. A scheme of the renovation is presented in Figure 1. Following the principles of this technology, 0.50-m-long segments of PEHD pipe were pushed through control shafts to the inside of the damaged duct with the use of a servomotor. Free space between the old and new pipes was filled with a special mortar of foamed concrete. Such a solution, on the one hand, protected the old duct against collapse; and on the other hand, increased its load capacity (a new "pipe" was formed with three-layer wall construction). In addition, pressure-forced mortar filled empty spaces that appeared in the surrounding soil as a result of the penetration
Pergamon
of grains to the inside of the leaky duct, together with infiltrating groundwater. As a result of the renovation, loads acting on the construction were more uniformly--and, therefore, more advantageously--distributed [4]. Inadequate efficiency of pipes in cities is associated with increased consumption of water and the resulting growing volumes of sewage. This is one effect of setting higher standards for urban facilities. In Polish towns destroyed during World War II, this problem is particularly noticeable. Although fii~y years have passed since the war, large areas of urban development are still being reconstructed. Present regulations in Poland provide for equipping residential buildings with sanitary fittings of an incomparably higher standard than those applied in prewar houses (i.e., basic running water, bathrooms, w.c. in each flat). Consequently, the amount of sanitary sewage has increased considerably; and old pipes, with diameters established well before the war, are not able to dispose of it. In this case, renovation of the system may consist of building a new larger-diameter duct to replace the old one; increasing the dimensions of the existing pipes; or building an additional parallel duct so that the modernized system can dispose of greater volumes of sewage. Building a new duct causes inconvenience because it requires putting some sections of the network out of operation during construction and, consequently, pumping sewage over a longer period. Such solutions were used earlier in Poland, when no other methods were available. In most cases, it is impossible, or nearly so, to build additional ducts in parallel because of the great concentration of underground conduits that already exists in towns in Poland. An additional disadvantage of this solution is that the old duct, although quite worn out, is still in operation. A technology that offers a feasible solution to this problem is the trenchless method of replacing the old pipe, which has too small a diameter, with a new pipe that has a larger diameter. The technology known in Europe as berstlining (pipe-bursting) involves destroying the old pipe and replacing it with a new one. This method has gained in popularity as the headers used to burst old pipes have been improved, thus diminishing the intensity of the shocks they cause. Consequently, it is possible to use such headers in cases involving a great concentration of technical infrastructure conduits. An example of renovating a duct of insufficient flow capacity with the use of this technology is the renovation of a sewage duct in D~bica. In this case, a concrete sanitary duct 200 mm in diameter was replaced with polyethylene (PEHD) pipe 315 mm in diameter [5]. Figure 2 shows a scheme of the course of this renovation. The bursting header was placed inside the existing duct through cleanout shafts. Then, by expanding circumferentially and moving forward, the header destroyed the old duct, while simultaneously pulling in 0.50-m-long segments of a new PEHD duct. Similar renovations of ducts
using the relining and pipe-bursting technologies have been performed in recent years and are still being carried out in many towns (e.g., Krak6w, Katowice, Warszawa, Wroc~aw). When the existing system interferes with a planned underground installation, it becomes necessary to change the location of the pipes. This frequently happens in the construction of new underground pedestrian walkways. The tunnels for such underpasses are usually located at the same depth as the conduits of the technical infrastructure. In such situations, open-cut techniques are generally used; and if sewers happen to be located there, it is often necessary to build a local sewage pumping plant. Therefore, these cases should not be considered as network renovation, but rather as examples of rebuilding, necessitated by the improvement of other elements of the urban underground infrastructure. It follows from the above considerations that the scope of rehabilitation may be confined to either repair works, repair and modernization (as in the first and the second cases described above); or to rebuilding (the third case). Repair works and repair and modernization are usually performed by trenchless techniques, and rebuilding by open-cuttechniques (in open excavations). An influx of imported technologies has resulted in the increased use of trenchless techniques for repair works and repair and modernization in Poland. It is expected that the demand for modernization works will further increase in the near future because of the above-mentioned necessity to develop integrated urban space---first of all, by rebuilding communication systems.
Trenchless Technologies for Rehabilitation of Underground Pipelines Leakage of underground networks may cause discomfort in the daily life of inhabitants, as well as increase the degree of environmental pollution. The term ~ecological bomb" graphically describes the disastrous effects of sewage exfiltration to soil, if it is not quickly halted. In Germany alone, the present volume of exfiltration is estimated at about 300 million m 3 [1]. A failure of gas piping may even be life-threatening to inhabitants. Another consequence of such a situation is the economic losses stemming from uncontrolled outflow of gas ifa failure of pressure pipelines (e.g., water mains or gas piping) occurs. In the case of leakage into sewage duct laid below the groundwater level, sewage carried off to a treatment plant is diluted, thereby increasing the operational costs to a sometimes considerable degree. Legal regulations that impose tough sanctions against polluting the natural environment appear to be the most effective means of speeding up action taken to improve the technical state of underground pipes. Introduction of such regulations in western Europe was a turning point that led to the development of research, development of new technologies, and establishment of numerous firms offering such services.
Classification of Rehabilitation Methods for Underground Pipelines
Figure 1. Scheme o f renovation o f sewage ducts using the relining method [B] 1 - segments o f P E H D pipes, 2 - shaft, 3 - old duct, 4 - servomotor.
216 TUNNELLING ANDUNDERGROUND SPACETECHNOLOGY
Underground utilities that have been in operation for 100 years or more are, for the most part, worn out and in poor condition. In Germany, nearly 80% of cast-iron piping ranges from 66 to 144 years in age [2]. In Poland, the percentage of old pipelines is even higher, as a result of neglect of underground infrastructure maintenance and construction during the post-war period. As indicated in [9], the most frequent causes of pipeline failures are: • Ground settlement. • Chemical and biological corrosion. • Aging of construction materials. • Inadequate load capacity of pipelines, compared to the increasing traffic loads.
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Figure 2. Scheme of renovation of sewage ducts with the use of the pipe-bursting method 1 - hydraulic header, 2 - old duct, 3- shaft, 4 - segments of polyethylene pipes. Damaged underground pipelines can be restored to an adequate technicalstate through rehabilitation,which can be performed using the technicalstrategiesdescribed below.
with a new one having the same or larger diameter, and the old pipe m a y eitherbe moved or itsfragments m a y be leftin the ground.
a) Repair
Renovation Experiences in Wroctaw
Repairs apply to single, local faults. In the case of pipes having diameters smaller than 60 cm, all sorts of robots, packers, and other similar appliances may be used. Repairs, carried out from the outside and inside, consist of: • Mending. • Injection. • Sealing.
In recent years, modern Western technologies of trenchless renovation of underground pipeline have become available on the home market in Poland. Prior to implementing any of those methods, an economic analysis should be performed. Because labour is still relatively cheap in Poland, it is often more cost-effective to replace the old pipeline with a new one using traditional methods in open excavation, instead of employing trenchless technologies that are widely applied in western countries. However, investors sometimes are compelled to use trenchless methods, especially in centres of Polish towns, for the following reasons: • A desire to avoid disruption to traffic organization due to underground works. • Numerous points of intersection with other networks of underground infrastructure. • The possibility of damaging underground infrastructure network not being repaired at the time. • Costly pavement along the pipeline route. • The need to carry out the works quickly. • The need to avoid lowering the groundwater level. In choosing a method, both technical and economic aspects should be taken into consideration. It is important to estimate how long the service life of the pipe can be extended aRer renovation using a particular technology. Such an analysis may show that using the least costly technology is not economically feasible. The situation in Wroc~aw with regard to the application of trenchless technologies is reviewed, by network, below.
b)
Renovation
Renovation involves restoring the damaged pipeline to its original technical state by applying suitable technical procedures and preserving the old structure. The following categories of renovation methods may be used: • Methods of spreading special sealing coatings o n t h e i n s i d e o f t h e p i p e . The coatings, which may be
composed of various materials, are spread by techniques such as spraying. • R e l i n i n g m e t h o d s (rigidinserts). These methods involve placing a P E or P V C tube, with an outer diameter smaller than the inside diameter, insidethe damaged duct. This operation m a y be performed in short sections,from the shaft (shortrelining);or in long sections,covering as m u c h as several hundred meters, from some suitableexcavation (longrelining).Ifitisimportant that reduction ofthe cresssection be limited,renovation of damaged pipeline can be carried out using a "close fit~ technique of the relining method. • Relining met]hods (elasticinserts). Here, elastic coating, usually ha~.ing a multi-layer structure, is introduced in a reversible process to the inside of damaged pipe (afterthe latterhas been previously cleaned), and is then stuck to the inner surface of the pipe. While the adhesive hardens, the coating is held tight by water vapor, air or water pressure. • Fitting methe~Is. Fittingmethods involve covering the insidesurface oftlhedamaged duct with suitablyformed elements made of materials that ensure complete tightness and resistance to chemical corrosion and abrasive wear. This method is commonly used to repair the damaged bottoms of small-diameter ducts. For ducts with diameters greater than 60 cm, a complete inside liningis made, using suitably formed segments of dimensions that permit their transport.
c) R e p l a c e m e n t Replacement involves laying a new section of underground pipeline to take over the function of the old pipe, when the latter is in bad technical condition or its capacity is insufficient. Replacement can be carried out by means of traditionalmethods in an open excavationor usingtrenchless methods. In the lattercase, the old pipe m a y be replaced
Volume 11, Number 2, 1996
a) Gas piping With respect to underground gas piping in Wrodaw, there is an urgent need for cast-iron pipes to be tightened. This work must be performed quickly because of factors related to the city's conversion to natural high-methane gas, which is more effective as fuel and which causes the least environmental pollution when burned. A sudden increase in the number of leaks occurring in bell joints is expected after conversion to natural gas because of its unfavourable action on the sealing material. Consequent gas losses may amount to 20% [3]. Therefore, in Wroclaw priority is given to the task of sealing cast-iron sections of gas pipelines. This is done by: • Gluing thin, polyethylene sheeting to the inside of pipe in a reverse process (polyurethane glue). • Gluing thin sheeting and needled cloth in a two-stage reverse process (polyurethane glue). • Renovation by means of a relining method using Ulinear technology (close fit). • Replacement ofold, cast-iron pipes with new PE pipes in open excavations.
TUNNELLINGANDUNDERGROUNDSPACETECHNOLOGY217
b) Water main In the case of the water-pipe network, progressive corrosion causes a loss of tightness and a decrease in crosssections of cast-iron and steel pipes due to formation of incrustations. In Wrocbaw, these problems are dealt with
by: • Gluing the sheeting reinforced with needled cloth to the inside of pipe in a single-step reversible process (epoxy glue). • Renovation by means of the relining method, using Ulinear (close fit) technology. • Cementing the inside surface of pipe by the spraying method (pipe dia. < 60 cm). • Trenchless replacement of damaged pipes with new ones using a pipe-bursting method. • Open-cut replacement of damaged pipes with new ones.
c) Sewage system In the case of Wroc]~aw'ssewerage network, basic technical problems, apart from leakage, include construction damage, which may be caused by: • Increasing traffic loads of dynamic character. • Chemical and biological corrosion. • Friction of solid particles contained in sewage against the sewer bottom. • Military operations during war. These problems are being solved by: • Repairing damaged and leaking ducts ( dia. > 60 cm), using mortar. • Trenchless replacement of damaged sewers with new ones, using the pipe-bursting method. • Open-cut replacement of damaged sewers with new ones.
Multiconduit Tunnels in Network Rebuilding The rebuilding of networks that cross newly developed structures can be carried out by systematically replacing particular pipes and laying them back in the ground. This method of modernizing operating networks has the following disadvantages: • The possibilities of inspecting the state of the pipes, providing current maintenance and removing failed pipes, without tearing up the street, are limited to TV techniques and trenchless methods of renovation. • The pipe failure rate is increased, because of their direct contact with the environment. These factors make it difficult to operate the network and increase the costs of operating it, while simultaneously lowering the functioning quality of the system. Taking into account the above arguments, in cases where pipes of particular networks have been worn out to much the same degree, as often happens in Polish towns, it should become a rule to consider the possibility of replacing pipes of all networks simultaneously and laying them down in multiconduit tunnels or in technical passages. The idea of using multiconduit tunnels and technical passages as technologies for network rebuilding [6] is also justified by the need to integrate the systems of underground infrastructure, thereby raising the possibility of control and, as a result, increasing their reliability and safety of operation. Moving in this direction also stems from the need to "compress" the network in order to save underground space for other purposes--first of all, communication. Multiconduit tunnels are usually created by open-cut methods as shallow underground structures situated at various places in the cross-section of a street. Because of the construction loading, it is best to lay out the route of the
218 TUNNELLING ANDUNDERGROUND SPACETECHNOLOGY
tunnel under the sidewalk or, if there are two traffic lanes, along the division line of the lanes. It is important to plan connections from buildings to tunnels. Connections that are laid directly in soil constitute the most unreliable element of the whole system, because they render it impossible to control pipes along a stretch of multiconduit tunnel-building. Therefore, whenever possible, connections should be planned as tunnels at least 60 cm in diameter or as a bundle of circuits laid in protective linings, permitting their disassembly and assembly, and thus avoiding the need to tear up a street to make repairs. It is especially advantageous to locate multiconduit tunnels in constructions used for other purposes as well (e.g., communication tunnels) or to join them with technical passages. In the latter category are multiconduit tunnel-technical passage "chains, ~ in which the length of connections is reduced to a minimum, on the condition that there are two separate "chains" of buildings situated on both sides of a street. In constructing a technical passage, it is necessary to adapt the basements of buildings adjacent to the street. This may prove impossible to carry out legally if property owners do not consent to allow the conduits to be driven through the basements of their premises, or if they charge too high a rental fee. That is why economic and legal issues should be settled at the beginning of the planning process, so as to ensure that it is technically possible and economically feasible to carry out the project. Putting the networks in technical passages creates optimal conditions for underground space to be used for other purposes, because it eliminates the need for a considerable number of circuits. Sewerage networks may be located in tunnels when longitudinal slopes of the bottom of the tunnel are suited to the required sewer slopes. The sewers are separated from other grids by laying them under the tunnel floor in a bottom plate fitted for that purpose, or by enclosing them by a tight construction that protects the tunnel against being flooded with sewage and against the action of gases escaping from sewage. Laying the network in multiconduit tunnels implies an increase in capital costs, stemming from the costs of both construction and tunnel fittings (lighting, ventilation, communication, signalling, drainage), and including dispatcher and personnel rooms. The relation between these costs and the costs of networks laid directly in soil depends upon local conditions and technological solutions and materials used. Naturally, the investment costs in such a case are higher by several dozen percent than the costs of placing the network directly in soft. Cost-effectiveness in laying networks in multiconduit tunnels will be achieved only if the operational costs over a predicted period of tunnel amortization are included in the costs analysis. If the account is based on annual costs, considering the discount account, then the costs can be expressed by the equation K =K+Ke=rKo+K , (1) where: Kr~ = annual costs of capital and future replacement; K = annual operational costs; Ko = capital costs reduced to zero year; and r = coefficient of costs ofcapital and future replacement. The annual costs method is applied in order to identify the solutions that ensure the maximum production effect [7]. In investigating the costs of networks, elements of decision occur that are seemingly not connected with the production sphere. These include decisions about improving the technical quality of pipelines and the ability to operate them, in order to increase the operational reliability of the network. Therefore, it is necessary to extend the annual costs K over the costs of system unreliability K [8]: K z=Kr+K =rKo+K+K, (2)
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The unreliability costs introduced into the costs account have a character of economic reproduction of the effects of unreliable network operation, and equal K = K + K~m, (3)
After algebraic transformations, the effectiveness index el,2 of transition from a more unreliable variant (with pipes laid in soil) to a less unreliable one (pipes laid in a multiconduit tunnel) is defined by the relation
where:
(ILl Ka) (Ka ILl) a -
K
= annual costs of recipients losses due to network unreliability; and K m = annual cost~s of repairs a l ~ r failure, extended over losses of suppliers, caused by not levying charges for cut-offperiods due to unreliability of the network. Thus, optimization is achieved by seeking the set of admissible solutions, in view of minimizing their annual costs K . If the analysed solution suggests laying pipes in multiconduit tunnel to minimize the costs of their unreliability K , then this also implies changes of other components of equation (2), since the investment costs Ko will increase and the operational costs K will probably diminish. This explains why optimization does not merely consist of seeking solutions of extremely high reliability, which may appear to be economically unjustified due to too large an increase in investment costs. In such a case, seeking a minimum resolves itself in comparing the sums of costs of the solutions considered. In practice, we deal with a discrete model of costs, which allows formulation of differential criteria fi)r variants being compared, e.g.: I: low-cost variant, with greater unreliability (laying pipes in soil) II: high-cost variant, with less unreliability (laying pipes in multiconduit tunnel). The more expensh,e solution will be cost-effective if the following condition is satisfied: K z l - - Kz2 > K~ - K, (4) This inequality correspends to the assumption that the high-cost variant (II) is considered advantageous if reduction of unreliability costs covers increased annual costs caused by the rise in investment costs due to the building of a multiconduit tunnel. Taking the difference K 1- Ks to be a profit resulting from the improvement of reliability, implied by additional annual costs K 2 - Krl , we can determine the effectiveness index e, illustrating economic effectiveness of means earmarked for decreasing the unreliability of analysed variants E = (Kzl
--
Kz2) -- (Kr2 (I~1 K$2 )
--
Krl) > 0
(5)
--
The effectiveness index is mainly of benefit in analyzing the effectiveness of transitions between variants of increasing reliability, which consists of determining the"profitabili t f ' o f m e a n s u s e d for rehabilityimprovement. The problem to be solved in the above costs account model involves comparing the quantities that have been determined (annual costs) with random quantities (unreliability costs). According to decision-making theory, such a procedure is correct on condition that unreliability costs should be determined on the basis of known distributions of random variables, or some representative statistical material. Unfortunately, there are no such data from investigations available in Poland that would allow any of the above-mentioned conditions to be satisfied. This means that for the time being, decisions can be made merely on the basis of approximate determination of costs, using the strategic decisionmaking model. In this model, the unreliability costs should be assigned the weight 1 - a < 1, where a is the measure of the lack of confidence in the values K being introduced. For the weight thus form~alated, the annual costs are expressed by the equality K= := rK= + K + (1-a)K, (6) and the differential criterion takes the form ( l - - a ) (K1-K2)_> K 2 - K ~ (7)
Volume 11, Number 2, 1996
ei,2 =
-
(ILl
-
-
(8)
>
IL~)
-
The unreliability costs cannot be analysed without taking account of the time factor, since its functions are the changes in intensity of pipe failures and in the market prices ofmatex*ials, equipment and labour. Taking the time factor into consideration requires that the mean discount values be included in the calculus, and thus equation (8) takes the form ar ~[(I El,2
-
a) (Kzl i Kz2i) (Ke2i -
-
-
K e l i ]
]
(I + p)T-i (Kilo2 Knol)r
l=L
_
_
~a
a r ~ ( K z l i - Kz2i) (1 + p)T 1--1
(9) where: a = coefficient of progressive amortization, T = amortization time in years; p = accumulation rate; and i = successive years of operation. The difficulties and limitations presented above render it impossible to carry out an analysis of the real costs of multiconduit tunnels, thus reducing it to comparisons of capital expenditures, the results of which are decisive in rejecting solutions of this type. Because there are few multiconduit tunnels in Poland, it is difficult to carry out the research on pipeline operation that would be needed to establish the necessary data bases, making it impossible to show the technical and economic advantages of tunnels. In the face of those limiting circumstances, researchers today have at their disposal only heuristically directed, intuitive methods. This reluctance to use multiconduit tunnels is also connected with an absence of laws regulating the operation of networks located in tunnels. Pipes laid in soil are run by owners of particular networks. However, if pipes are placed in a multiconduit tunnel, there arises the question of who should run them or coordinate the operation of particular network owners. This problem can be overcome by: 1. Establishing one-person companies in districts, in order to build tunnels and to operate pipes laid there, in return for a rent charged from particular owners; or 2. Establishing companies that are assigned the same tasks, and whose members would be the owners of pipes laid in tunnels. According to principles of market economy, companies cannot operate at a loss in either case. Once the multiconduit tunnels are seen as a source of potential income, the problem of their effectiveness will have to be solved by companies undertaking the risk of building and running them, which until now has practically been nobody's problem. Such enterprises might stimulate development of multiconduit tunnels as a technology of the network infrastructure rebuilding in the case of considerable wear of a majority of grids, their inadequate efficiency, or their interference with planned development of underground space. C o n c l u s i o n s
In view of the fact that the poor technical state of pipelines is quite a serious problem in Poland, it is necessary to balance needs and possibilities in determining how to improve them. In order to intensify technical activities, appropriate legal regulations should be established and put into force, compelling the owners of pipelines to keep them in a condition that would not create environmental and safety hazards. A number of firms on the domestic market
TUNNELLINGANDUNDERGROUNDSPACETECHNOLOGY219
now offer various technologies for renovating u n d e r g r o u n d pipelines. In o r d e r to i m p l e m e n t t h e m rationally, it is n e c e s s a r y to m a k e thorough economic and e n v i r o n m e n t a l a n a l y s e s to compare trenchless methods with open-cut methods. In s i t u a t i o n s w h e r e p i p e s a r e inefficient, w h e r e t h e pipes of more t h a n one n e t w o r k a r e in poor condition, or w h e r e t h e p r e s e n t location of t h e pipes r e n d e r s it impossible to c a r r y out o t h e r u n d e r g r o u n d projects, it is advisable to use m u l t i c o n d u i t t u n n e l s a s a technique for rebuilding t h e n e t w o r k i n f r a s t r u c t u r e . However, before such a technique can be a d v a n c e d , laws m u s t be p a s s e d to authorize p o t e n t i a l owners of t u n n e l s , for whom m u l t i c o n d u i t t u n n e l s can provide a source of income.
References [I] Engelmann, H. 1990. NeubauoderInstandsetzungvonKanalisationen. Tiefbau Ingenieurbau Stra~nbau, Heft 10. (In German)
220 TUNNELLINGAND UNDERGROUNDSPACE TECHNOLOGY
[2] Hofer, P. 1994. Planung der langiiistigen Emeuerung yon Wasserrohrnetzen. 3 R International, Heft 1-2. (In German) [3] Kolonko, A. 1994. Problemy techniczne przy renowacji sieci gazowej metod~ Process Phoenix. GW i TS Nr 8. (In Polish) [4] Kolonko, A. 1995. Rheologishe Eigenschaften eingebetteter starrer Rohrleitung im Baugrund. Strassen und Thiefbau Nr. 12. (In German) [5] Kuliczkowski, A.; Pluta, R.; and Zwierzchowski, D. 1995. Diagnostyka i odnowa kanalow. Conference Papers; Trenchless Tech Warsaw '95. (In Polish) [6] Kuliczkowski, A. and Madryas, C. 1989. Tunele wieloprzewodowe, Skrypt nr 189, Politechnika Swi~tokrzyska, Kielce, 1989. (In Polish) [7] Lange, O. 1975. Teoria reprodukcji i akumulacji, PWN, Warszawa, 1975. (In Polish) [8] Sozariski,J. 1982. Niezawodnoddzasilaniaurz~dzefiiuldaddw elektroenergetycznych,P W N , Warszawa, 1982. (In Polish) [9]Stein,D. and Kaufman, O. 1992. Schadensanalyse anAbwasserkan~ilen aus Beton- und Steinzeugrohren der BRD-West. Korrespondenz Abwasser 2/92. (In German)
Volume 11, N u m b e r 2, 1996