MASTER OF TECHNOLOGY
NATIONAL INSTITUTE OF TECHNOLOGY
DEPARTMENT OF CIVIL ENGINEERING
This is our great pleasure & privilege to acknowledge Prof .S.K.DAS sir for his help and guidance during the preparation of this project report. We would also like to thank our teachers and my friends to give us moral support.
In October 2003, stormwater overflows from an intense, short-duration storm eroded approximately 20,000 yds.3 of soil from the bottom and side slopes of a ravine between the Tacoma Narrows Bridge and a subdivision near Tacoma, Wash. The erosion ruptured two storm drains and left undermined slopes that continued to ravel and retreat. Measures were implemented to help stabilize the eroded slopes and prevent further retreat that could affect the Tacoma Narrows Bridge expansion project and a residence above the opposite ravine slope. The measures also addressed regulatory agency concerns about sediment-laden water discharging from the ravine into the Narrows that could damage sensitive sand lance habitat on the beach at the mouth of the ravine.
Ravine restoration measures consisted of constructing unreinforced soil, flexible geocell-faced reinforced soil, and geocell-geogrid reinforced soil slopes that mimic the former steep ravine. After slope construction, a mixture of drought tolerant and native vegetation was planted to provide erosion protection and restore the natural ravine environment. The geocells had the flexibility to fit against, and transition between variable slopes and create steep slopes with planting benches for trees, pockets for smaller plants, and terraces that slow stormwater runoff. The perforated geocell walls allowed roots to spread. The geocell ravine repair design was an effective, economical solution that
References: Elias, V. and Christopher, B.R. (2000), Mechanically Stabilizeed Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines, U.S. Department of Transportation Federal Highway Administration, FHWA Demonstration Project 82, FHWA-NHI-00-043, 393 p. GeoProducts LLC. (2004), EGA 30P geocell product information, www.geoproducts.org Huesker Inc. (2004), Fortrac 80/30-20 geogrid product information,www.hueskerinc.com Washington State Department of Transportation (2002), Standard Specifications, M41-10.