CASE HISTORY Rev: 00, Issue Data 25.10.07 R.E.WALL FOR MANGALORE REFINERIES, PVT, LTD KARNATAKA,INDIA ENVIRONMENTAL/ SLOPE PROTECTION/ Product: Gabions & Geogrids Problem Mangalore Refineries and Petrochemicals Limited are situated in Mangalore which is one of the places existing along the west coastal belts of India. The region receives high amount of rain- fall during the monsoon. Since the terrain is hilly and because of the high rainfall, the slopes are highly unstable. M/s Manga- lore Refinery and Petrochemicals Limited proposed to carry out slope stabilization and restoration work. The in-situ soil is red laterite. There were three different locations where the slopes had failed in the year 2003. The height of the slope that had to be re-constructed varied between 15 to 35 meters. The client insisted for a solution which is cost-effective and speedy since the project had to be finished in a very short span of time. Solution For this project, the main cause of the slope failure was devel- opment of pore water pressure due to poor draining character- istic of backfill soil which was initiating the slips and surface erosion due to storm water. The in-situ soil was non seasoned Lateritic soil (red soil). Gen- erally the Lateritic soil is hard when dry and becomes soft Fig 1: Before construction when wet. In wet condition it can be cut with knife. The respective site is prone to very heavy rainfall. Hence the surface erosion and slope failure take place in almost every stretch. There were different stretches with gentle and steep slope incli- nation. To prevent the surface erosion, the gentle slopes were protected by Geonet (Erosion Control Mat). The steep slopes with greater heights were stabilized by pro- viding the reinforced soil walls with intermediate berms. While selecting the type of reinforced soil system substantial attention had been given to the system which can dissipate the pore water pressure. The free draining characteristics of Gabion had attracted the attention of consultant and client. The adopted system was Gabion as facia and Geogrid as reinforcement (Refer drawing). Client name: MRPL,KARNATAKA Main contractor name: M/s PRABHU CONSTRUCTION Consultant: IIT MADRAS— GEOTECHNICAL DEPT Product used: Gabion Construction info Construction date: JUNE 2005 Construction info: AUGUST 2005 Fig 2: During construction Fig 3: During Construction TOP WALL STRUCTURAL FILL 500 MM HIGH GABION INTERMEDIATE WALL 1 STRUCTURAL FILL REINFORCEMENT-GEOGRID GEOTEXTILE BOTTOM WALL STRUCTURAL FILL Fig 4: Standard section Fig 5: During Construction Fig 6: Construction of Intermediate Berm High strength Geogrid is used in the bottom most layers of reinforced soil wall. The strength of the reinforcement was varied ac- cording to design requirement. The use of flexible Gabion as facia and Geogrid as reinforcement provides a complete solution to both the environmental needs and structural requirements. The vegetation has appeared on the gentle slopes treated with Geonet. The Geonet in sequence with Gabion facia with vegetation gives a very pleasant appearance. There were no separate arrangements for drainage due to the draining characteristic of Gabions. As expected the Ga- bion acted as completely free draining facia to dissipate the pore water pressure. The system provides greater cost effectiveness especially for higher structures and the construction was having good speed and they were able to finish the work before the mon- soon started. Stone facia gave a very harmonious balance with the envi- ronment. Mangalore Refineries and Petrochemicals Limited had cer- tain environmental policy, in which they sustain and promote the green belt. Hence they got impressed by the aesthetics of the structure and especially the environmental balance of the structure. The client requested the consultant Dr. Gandhi of IIT Madras to design for the completely flexible system with Gabion as facia for the stretches which were failed in next monsoon (i.e. 2005). Dr. Gandhi recommended the Maccaferri Ter- ramesh system and included its specification in the tender for the stabilization of these slopes which proved the suc- cess of the Maccaferri Gabion provided for the pilot project. Fig 7: After Completion Gabion Geogrid Height Width Length m 1.00 Fig 8: After Completion Maccaferri Environmental Solutions Pvt. Ltd. 1003,10th Floor,Casablanca,Plot No.45,Sector-11,CBD Belapur,Navi Mumbai-400614 Tel. 91-22– 27580475/27565451/ 27565906/27580931/ 27580932 - Fax (022) 27580488 E-mail: [email protected], [email protected] - Web site: www.maccaferri.com .