Iran (

Transcription

1 An Investigation of Structural Design Effect on Sewer System Defects Using Sewer Inspection Robot N. Mehrdadi 1, S. M. Tafazoli 2, S. M. Ghaneeizad 3 1 Faculty of Environment, University of Tehran, Tehran, Iran ( mehrdadi@ut.ac.ir) 2 Faculty of Environment, University of Tehran, Tehran, Iran ( smtafazoli@yahoo.com) 3 Department of Civil Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran ( s.m.ghanei@gmail.com) Abstract As construction of sewer system in Iran is increasing, selecting of a proper structural design which has fewer defects in future is very important. In addition, defects have a severe environmental impact on aquifers because they cause sewage leakage to soil. Sewage leakage is one significant source of ground water pollution which can put lives at risk. At first glance, numerous problems in present sewer system of Iran which has built in cities recently and are about only 31% of future system show the importance of attention to operation problems. A new technology which is used to detect sewer systems defect is sewer inspection robots. This research using this robot examines different types of defects in sewer system of Mashhad. This paper studies eleven different structural details, seven structural details used on trench design and four structural details used on tunnel design. About 35 km pipes of Mashhad sewer system is scanned by the robot. The study shows that there are nine types of defects in sewer system of Mashhad that are related to structural design. All defects are classified according to structural details which are designed and used to construct sewer system. Finally, the best structural design on two methods, trench and tunnel, which has the minimum defect in comparison with others is presented. Keywords: Defect; Pollution; Robot; Structural Design; Sewer System. INTRODUCTION Supply and the use of safe water are essential for all countries. Limitation of water resources and increase of population have reduced the amount of per capita renewable water. This figure in the year 1956 was about 7000 cubic metres, and it was about 2000 cubic metres in the year In the horizon year, 2036, it will approach to about 800 cubic metres that is less than dehydration threshold that is 1000 cubic metres. So, according to the United Nations Statistics, the condition in Iran in 2036 will be severe water scarcity. Thus, proper implementation of sewerage system and increase useful life of the network can prevent leakage in sewage pipes that will pollute groundwater. DIN, BS and ASTM Standard have provided structural design method for sewage pipes. Code 303 of President Deputy Strategic planning and Control of Iran has been included information about bedding in sewer system. Recently, numerous related researches on sewerage system are done. Davies investigated the structural condition of rigid sewer pipes (Davies, 2001a). Davies determined factors influencing the structural deterioration and collapse of rigid sewer pipes (Davies, 2001b). Hasseli have examined the effects of sewerage system on groundwater pollution in coastal areas (Hasseli, 2004). Rajabizade determined distribution of sewer diameters in wastewater collection in IRAN (Rajabizade, 2004). Gokhale developed a new method for locating leaks in sanitary sewers (Gokhale, 2004). Rutsch reviewed various methods used for the estimation of exfiltration and discuss data needs and applicability for rehabilitation planning (Rutsch, 2005). Sinha proposed neuro-fuzzy projection network classifiers for buried pipe defects (Sinha, 2006). Rieckermann estimated sewer leakage from continuous tracer experiments (Rieckermann, 2007). Guo sought to enable automated detection of defects in sewer pipelines from inspection videos and images (Guo, 2009).

2 CASE STUDY EXPLANATION First International Conference on Advances in Wastewater Treatment and Reuse This paper is based on a case study which is done in Mashhad. Different sewer defects are detected in various structural details of sewer lines using sewer inspection robot. Different structural defects Structural defects based on the EN13508 and WRc standard are longitudinally displaced joint/open joint, radially displaced, surface crack, cracked, fractured, broken, hole, collapsed, spalling, wear, intruding sealing ring, defective repair, weld failure for steel, weld failure for plastic and deformation. These 15 standard defects are summarized to 9 overall structural defects in order to better adaptation to robot condition. These 9 structural defects are water remaining, sediment deposit, improper slope, improper connection, settlement, deformation, fractured, root because of fractured, and broken/cracked. Sewer inspection robot The most important properties of the robot is automatically camera height change, pan-and-tilt camera (360 degrees in horizontal direction and 120 degrees in vertical direction), passing pipes with different diameters, passing length up to 300 metres, the ability to float in water. The robot could measure temperature, slope, and pressure by special installed sensors. The robot could present various report types such as error report, picture report, graphic report, data project report and data robot report. Structural details Since in Mashhad sewer system is designed by different consulting engineers companies, they proposed different structural design according to their reasons and experiences. Between different structural types, authors have selected 7 structural details on trench lines and 4 structural details on tunnel lines. Fig. 1 and 2 show structural details respectively in trench and tunnel system. Asphalt Final Backfill Initial Backfill (30 cm on Top of the Pipe) Bedding (7 cm) Structural Detail No. 1 Bedding Material 2 Screened Soil Initial Backfill Mareial Screened Soil Sand and Soil Concrete 3 Screened Soil Sand 4 Lime Concrete 5 Screened Soil Gravel 6 Gravel 7 Screened Soil Screened Soil Figure 1. Structural details description in trench system.

3 Final Backfill Initial Backfill (30 cm on the Pipe) Bedding (7 cm) Structural Detail No Bedding Material Initial Backfill Mareial Lime Concrete Sand and Gravel Screened Soil Gravel Figure 2. Structural details description in tunnel system. Pipe types Overall in the last 20 years, asbestos cement, concrete, polyethylene and polye vinyl chloride (PVC) pipes have used in sewerage system. It can be concluded from Water and Waste Water Engineering Co. report that using plastic pipes type, especially polyethylene type, is the most, and the most diameter of pipes that is used is less than 300 mm. Thus, in this research, 250 mm diameter pipes have studied more than others, and all pipes type that are examined is dual wall polyethylene. Data collection In Mashhad, 1400 km of sewer pipes is done by the end of 2008, and in this network about 64 percent of pipe diameter is less than 300 mm in size. Since 2006 to 2009, Mashhad sewer system, about 35 kilometres length of pipes, is examined by robot. Data is classified according to pipe type, diameter pipe size, execution method (trench or tunnel) and structural design. RESULTS After data collection that lasts about 3 years, data is classified according important parameters. Because of most uses, about 27 km length of 35 km length that studied is in 250 mm diameter pipes. Here, results are mentioned briefly, and the comparison is done. Three types of diagrams are drawn for detected defects for each system, trench or tunnel system. Minimum recommended cover based on vehicle loading conditions is varied in ASTM D2321 according to pipe diameters, so because of this different condition and different executive method of collection and transmission lines data are divided to two sections. One diagram is drawn for pipes that their diameter is equal and less than 340 mm. The other diagram shows defects for pipes that their diameter is more than 340 mm. Finally, the third diagram is an overall diagram that shows defects for all pipe sizes. The trench system In trench system, metres length of pipes is studied. Use of some Structural details is not common in some pipe diameters, so the blanks in some figures show this matter. Inspection length and detected defects in this system are cited in table 1.

4 Table 1. Examined length pipe and brief result for each structural detail in trench system. Detail No. Studied Length (m) Detected Defects The Number of Defects per 100 metres Sum Fig. 3 (A) and (B) show the number of detected defects in 7 structural details respectively for pipes with diameter equal or less than 340 mm and more than 340 mm. Figure 3. (A) The number of defects per 100 metres length of pipe in trench system for pipes with diameter equal or less than 340 mm. (B) The number of defects per 100 metres length of pipe in trench system for pipes with diameter more than 340 mm. Fig. 5 (A) shows the number of detected defects in 7 structural details for all pipe sizes. The tunnel system In tunnel system, metres length of pipes is studied. Use of some Structural details is not common in some pipe diameters, so the blanks in some figures show this matter. Inspection length and detected defects in this system are cited in table 2. Table 2. Examined length pipe and brief result for each structural detail in tunnel system. Detail No. Studied Length (m) Detected Defects The Number of Defects per 100 metres Sum

5 Fig. 4 (A) and (B) show the number of detected defects in 4 structural details respectively for pipes with diameter equal or less than 340 mm and more than 340 mm. Figure 4. (A) The number of defects per 100 metres length of pipe in tunnel system for pipes with diameter equal or less than 340 mm. (B) The number of defects per 100 metres length of pipe in tunnel system for pipes with diameter more than 340 mm. Fig. 5 (B) shows the number of detected defects in 4 structural details for all pipe sizes. Figure 5. (A) The number of defects per 100 metres length of pipe in trench system for all pipe sizes.(b) The number of defects per 100 metres length of pipe in tunnel system for all pipe sizes. DISCUSSION According to fig. 3, it can be concluded that the fourth detail in trench system is the best detail for pipes with diameter equal or less than 340 mm. Also, fig. 3 shows that the best detail for pipes with diameter more than 340 mm is detail No. 1. Finally, if all pipe sizes are considered together, the best detail is detail No. 4. Table 3 shows estimated cost for each detail in trench system. It is clear that the most economical detail is detail No. 7. Table 3. Estimated costs for each detail which is normalized according to minimum price in trench system. Detail No Normalized Cost

6 According to fig. 4, it can be concluded that the third detail in tunnel system is the best detail for pipes with diameter equal or less than 340 mm. Also, fig. 4 shows that the best detail for pipes with diameter more than 340 mm is detail No. 3. Finally, if all pipe sizes are considered together, the best detail is detail No. 3. Table 4 shows estimated cost for each detail in tunnel system. It is clear that the most economical detail is detail No. 3. Interestingly, the economical detail has the least defects in tunnel system, so third detail is the best technical and economical detail. Table 4. Estimated costs for each detail which is normalized according to minimum price in tunnel system. Detail No Normalized Cost Since fourth detail, lime concrete initial backfill, in comparison with seventh detail has more cost and building connections could not be installed on fourth detail, authors suggest detail No. 7 for pipes with diameter less than 600 mm. This result agrees with ASTM D2321 that suggests a similar detail. For pipes with diameter more than 600 mm that have no building connection, as fourth detail defects are about 70 percent less than detail No. 7 it is the best detail in that condition. COCLUSION This case study examines sewer defects using sewer inspection robot in order to compare different structural details which are common in sewer networks. Results of about 35 km length inspection of pipes show that the best detail in trench system is detail No. 4. The next detail in trench system that is better for collection lines is detail No. 7. In tunnel system, the best detail from an economical and technical point of view is detail No. 3. REFERENCES 1. Davies J. P., Clarke B. A., Whiter J. T., Cunningham R. J. (2001a). Factors influencing the structural deterioration and collapse of rigid sewer pipes. Urban Water, 3(1-2), Davies J. P., Clarke B. A., Whiter J. T., Cunningham R. J., Leidi A. (2001b). The structural condition of rigid sewer pipes: a statistical investigation. Urban Water, 3(4), Dini M., Alavimoghadam S. M. R., Torabian A. (2006). A review on performed studies about underground water pollutant in Iran. Second International Conference of Water Resources Management, Iran. 4. Gokhale S., Graham J. A. (2004). A new development in locating leaks in sanitary sewers. Tunnelling and Underground Space Technology, 19(1), Guo W., Soibelman L., Garrett Jr. J. H. (2009). Automated defect detection for sewer pipeline inspection and condition assessment. Automation in Construction, 18(5), Hasseli S., Masoudifar B. (2004). Effects of sewer collection network on underground water pollutant in coastal areas. 14th Civil engineering Student's Conference, Iran. 7. Rajabizadeh A., Afsari nejad M. R., (2004). Distriution of sewer diameters in wastewater collection based on population size for urban areas in Iran. Isfahan water and wastewater, 50, Rieckermann J., Bares V., Kracht O., Braun D., Gujer W. (2007). Estimating sewer leakage from continuous tracer experiments. Water Research, 41(9), Rutsch M., Rieckermann J., Krebs P. (2005). Quantification of sewer leakage - a review. 10th International Conference on Urban Drainage, Denmark. 10. Sinha S. K., Fieguth P. W. (2006). Neuro-fuzzy network for the classification of buried pipe defects. Automation in Construction, 15(1),