CASE HISTORY Rev: 00, Issue Data 25.10.07 GABION& NETTING APPLICATIONS KONKAN RAILWAY (KRCL) ROUTE,INDIA ENVIRONMENTAL/ SLOPE PROTECTION/BALLAST RETENTION Product: Gabions,Baby Gabions & Rockfall Netting Problem: Konkan Railway Project can be considered as one of the most prestigeous projects in the Construction Industry of India.The project was launched in 1989 and the track became operational in the year 1998.The 760 km line passes through complex terrains.In many of the stretches, the available space was restricted and the side slopes were very steep.This formidable terrain and the short construction period necessitated the use of several technological innovations.

The construction and widening of the track called for large quantities of cutting in rocks of lateritic and basaltic origin.The exposed lateritic terrains were subjected to heavy rainfall and in the presence of water, the laterite loses all of its cohesiveness,strength and become very vulnerable to cause heavy slides and slips.This problem necessitated the provision of several landslide mitigation techniques like construction of proper retaining walls and rockfall prevention measures.

The ballast which is laid below the tracks primarily serves the purpose of load dispersion apart from giving added resiliance.Conventionally, a ballast layer of depth 250 mm is adopted below the sleepers with a depth of 500mm on the sides,sloping outwards.This requires a greater utilisation of space on the sides, with sufficient width for embankment.Further over a period of time,due to the repeated use of track,the ballast has a tendency to roll out of tracks.The Fig 1.A typical KRCL stretch with narrow tracks & steep side slope Solution Maccaferri Gabion walls with stepped rear face were adopted in many vulnerable stretches of hill cuttings of Konkan Railway. Backfill soil was carefully selected ensuring the omission of clayey soil. Additional arrangements included provision of transverse drainage system, comprising of 2.9mm dia heavy duty PVC pipes per metre laid at a slope of about 1:20.to carry water away from the foundation. The foundation com- prised basically of lateritic soil. Owing to the relatively high level of water table, the foundation depth was restricted to a minimum of 0.5m. At places where the foundation comprises of very fine clayey soil, Terram 1000 Geotextile was placed at the bottom of the Gabion Wall in addition to the backside in order to prevent the ingress of fines. Gabion walls were selected due to its flexibility, speed in construction and fine draining nature. Client name: KONKAN RAILWAY CORPORATION LIMITED Main contractor name: A NUMBER OF SMALL CONTRACTORS Consultant: ENGINEERING DIVISION OF KRCL,MUMBAI IIT,MACCAFERRI Product used: 50,000 CUM OF GABIONS,10000 SQM OF NETTING Fig 2 .Gabions for landslide mitigation constructed in 2001 Construction info Construction Start: FEBRUARY 2000 Construction end: MARCH 2005 Fig 3,4.Gabions for Platform construction at Ratnagiri & Kudal Railway Stations respectively

Along the Konkan Railway Route, instead of using the conventional methods, Gabion boxes were used for the construction of about 12 railway platforms. This innovative step resulted in easy and speedy construc- tion of railway platforms. After successful installation at one platform, they found it a very cost effective solu- tion. The cost was reduced to around 50% as compared to traditional construction methods.

Fig 5.Gabion Structure for abutment protection during con- Fig 6 Structure completed in 2004 for abutment protection struction

Project section drawing TYPICAL SECTION OF RAILWAY TRACK WITH BABYGA- BION BALLAST RETAINERS

Fig 7. Baby Gabions for ballast retention

. For the retention of ballast and reduce periodical maintenance, an entire new size of Gabions were adopted in Konkan Railway tracks. These Gabions are referred as baby Gabions and are of much smaller size, say 4mx.3mx.3m and 2mx0.5mx0.5m with a mesh opening size of 60 mmx80 mm, and 2.2mm wire diameter. Apart from less maintenance and retention of ballast, Baby Gabions, it was possible to reduce the width of embankment and thus to reduce the quantity of earthwork to a great extent by the adoption of Baby Gabions. Fig 8. Bottom anchoring of DT Mesh Fig 9 Slope after vegetation has grown

To prevent rock fall from the side hill slopes, double twist hexagonal PVC Coated Maccaferii netting of type 10x12 was laid along the slope and then anchored into the trench using suitable anchoring techniques. Double twist Mesh was selected over chain link mesh as it is not prone to unraveling. Their high tensile strength, punching resis- tance and low installation costs also helped the adoption of this system.

Fig 9 Rockfall Protection Netting using Maccaferri’s DT

Project section

Maccaferri Environmental Solutions Pvt. Ltd. 1003,10 th 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