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GLASS REINFORCED PLASTIC (GRP) SEWERS REHABILITATION (A CASE STUDY): INVESTIGATION AND PERFORMANCE ANALYSIS

Sewer rehabilitation is defined as all aspect of upgrading the performance of sewerage system, it includes renewal of a sewer by new construction, reinforcement with duplicate sewers, attenuation of storm flows, and renovation where the existing structure is retained and improved. The present study concerns Helwan sewers network which were constructed of GRP sewers, in 1991. The sewer diameters range from 800 to 1800 mm with wall stiffness of 1250 KN/m 2 . Ground sinking and failure are happening at different location within the contract zone. A sophisticated investigation program has been carried out to identify the present conditions and to choose the proper rehabilitation technique. The investigations done included Closed Circuit Televising (CCTV) inspection for the entire sewer network. In addition, a detailed geotechnical investigation was carried out using the Electric Cone Penetration Test (ECPT) at different locations of the sewer network. The ECPT tests results revealed the stratification and geotechnical characteristics of the fill around and below the sewers were not properly constructed. This paper presents and analyzes the results of the CCTV inspection of the sewers and also inspects the bedding conditions around the sewer. In addition, the paper highlights the effects of rehabilitation on sewer capacity. Usually rehabilitation decreases the sewer carrying capacity due to reduction of the sewer cross-section area. The degree of sewer flow reduction due to rehabilitation depends upon many factors, include the percentage of deformation, and the rehabilitation material thickness. In the present study although the rehabilitation will decreases the sewer caring capacity due to the reduction of the cross-sectional area by lining it does not decrease the required sewer capacity in many locations.