Construction of a steep soil slope near rail road tracks

Construction of a steep soil slope near rail road tracks

Owner South Carolina, Department of Transportation
General Contractor C. Ray Miles Construction Co. Elgin, SC
Slope Contractor Eckhart Construction Fort Mill, SC
Geogrid Type StrataGridTM SG200
Structure Geometry 5,200 square feet, 26 foot high, 1H:1V bridge abutment

Project Overview

The South Carolina Department of Transportation (SCDOT) needed to provide a right-of-way for an access road adjacent to a CSX Railroad line. The Clemson Road Bridge project required construction of a steepened soil slope to accommodate right-of-way needs between the northern bridge abutment and the railroad tracks. Bridge bent #4, located between the CSX tracks and the northern bridge abutment (bent #5), and reduced the available clear space for the access road. The grade separation between the road and the bottom of the northern bridge abutment was 26foot.

The Conventional approach

The conventional approach would be to construct a concrete retaining wall at northern bridge abutment. Another way would be to lengthen the northern bridge span between the bridge pier and the approach embankment at the northern bridge abutment. However, these approaches were time-taking and expensive.

Strata's Innovative Solution

Strata's geotechnical experts suggested the StrataSlope system with two major elements: geogrid solid reinforcement (StrataGridTM SG200 (SGi 60) was the perfect match for it) and a slope facing system . The slope facing systems comprised of three components:

  • Prefabricated welded-wire form.
  • Geogrid facing wrap.
  • Seven oz/sy non-woven geotextile and sod with permanent erosion control blanket.

StrataSlope with 1H:1V met the geometric and structural requirements of the project. The StrataSlope was built on silty-sand foundation soils and utilized locally available embankment soils for the reinforced fill zone. The slope face was constructed using prefabricated welded-wire forms bent to the specified slope batter of 45˚ (1H:1V). The use of bent forms facilitated the construction of a 4 inch concrete slab under the bridge where vegetation cannot typically be maintained. The secondary reinforcement provided surficial slope stability and a minimum six foot top and bottom embedment which was specified and required by the South Caroline Department of Transportation (SCDOT).

The geotextile provided temporary erosion protection until the concrete slope protection was placed. Outside the limits of the bridge, sod backed with a permanent erosion blanket and the secondary reinforcement was placed adjacent to the welded-wire form. This facilitated immediate vegetation of the slope during construction and provided long-term surficial slope stability and erosion protection.

Strata's Value Addition

  • A structurally and economically sound solution
  • StrataGridTM satisfied the structural requirements for the steepened soil slope, which was one of the main requirements of the client
  • The bent, welded-wire form facing system accommodated both the concrete slope protection and vegetation