Roadways

For construction of approaches to flyovers and Road Over Bridge’s, Reinforced earth technology has almost completely replaced conventional retaining structures. Geogrid Reinforced earth wall retaining structures have gained wide acceptance in India as a technically proven and cost effective alternative to conventional concrete retaining wall. The ongoing and planned initiatives of central and state governments for improving the road infrastructures in the country are likely to give a major boost for the demand for Geogrid reinforced wall systems. Geosynthetics have become well established construction material for geotechnical and environmental applications in most parts of the world. Results from recent research and from monitoring of instrumented structures throughout the years have led to new design methods for different applications of geosynthetics. The geosynthetic reinforced soil has emerged in the last few decades as a technically attractive and cost effective solution to many geotechnical problems. This concept was used for the construction of vertical wall in the Outer Ring Road of Hyderabad

So a research work was carried out to study about the material required for the construction of reinforced earth wall and its specifications and also the construction methodology adopted. A cost and time comparison study was also carried out between reinforced earthen wall and conventional retaining wall, and it was found that the cost for the construction of reinforced earthen walls was approximately 20% less than the cost of conventional retaining wall. From the time comparison study it was observed that the time required for construction of reinforced earthen walls was more when compared to the construction of retaining walls. But if the wall height is more the reinforced earth walls can be preferred in the context of their stability, and also in its capacity to reduce the future settlement of pavement by controlling the erosion of soil fill with the help of geotextile placed between the soil fill and drainage aggregate.

Introduction

A retaining structure is used for maintaining the ground surface at different elevations on either side of it. Geo grid reinforced earth technology has almost completely replaced conventional retaining structures with the help of geosynthetics. Over the years, these products have helped designers and contractors to solve several types of engineering problems where the use of conventional construction materials would be restricted or considerably more expensive. There are a significant number of geosynthetic types and geosynthetic applications in geotechnical and environmental engineering. Common types of geosynthetics used for soil reinforcement include geotextiles (particularly woven geotextiles), geogrids and geocells. The combination of improved materials and design methods has made possible engineers to face challenges and to build structures under conditions that would be unthinkable in the past

The foundation on which the gabions are to be placed shall be cut or filled and graded to the lines and grades shown on the drawings. Surface irregularities, loose material, vegetation, and all foreign matter shall be removed from foundation surface area. When fill is required, it shall consist of materials conforming to the specified requirements. Gabions and bedding or specified geotextiles shall not be placed until the foundation preparation is completed, and the subgrade surfaces have been inspected and approved by the engineer or the engineer’s representative. Compaction of bedding or filter material will be required per plans and specifications. The surface of the finished material shall be to grade and free of mounds, dips or windrows. Extra care should be taken with foundation preparations in order to ensure a level and smooth surface. Geotextile shall be installed in accordance with the requirements of the plans and specifications.

2) ASSEMBLY AND PLACEMENT

The assembly and placement of gabions shall be in accordance with the following procedures:

Assembly

Rotate the gabion panels into position and join the vertical edges with fasteners for gabion assembly. Where lacing wire is used, wrap the wire with alternating single and double half hitches at intervals between 100) to 130 mm. Where spiral fasteners are used, crimp the ends to secure the spirals in place. Where ring type alternate fasteners are used for basket assembly, install the fasteners at a maximum spacing of 150 mm.

Gabions are manufactured with all components mechanically connected at the production facility. Units are delivered to site folded and compressed in bundles weighing approximately 800kg, and measuring approximately 2m x 1m plan and 0,5m in height. Type and size determine the number of units per bundle. The correct size and type of units should be delivered to the site. Ensure that the correct sizes are selected for the different structures. For easy identification, bundles are coded with coloured stripes, in different positions and orientations, to identify the sizes.

A barrier comprising:

a barrier having a thickened foot portion buried in ground supporting pavement for a roadway, an upstanding portion projecting above the surface of said pavement, and a tapered intermediate portion integrally interconnecting said foot portion to said upstanding portion; said foot portion provided with an open-ended duct below said pavement and at least one passageway connecting the surface of said pavement to said duct whereby said duct is in communication exteriorly of said foot portion; and a second open-ended duct provided in said intermediate portion in fixed parallel relationship with respect to said first mentioned duct.

2. The invention as defined in claim 1 including interlocking means comprising a pair of elements outwardly projecting from one end of said barrier and a pair of depressions provided in the other end of said barrier.

3. The invention as defined in claim 2 including guide means comprising tapering each of said elements and conforming said depressions to align and receive said tapered elements.

4. The invention as defined in claim 3 wherein said passage ways are open from opposite sides of said barrier and downwardly converge to as to conduct drainage from the surface of said pavement to said first mentioned duct via gravity.

5. The invention as defined in claim 4 including an additional pair of passageways provided at the other end of said barrier.

6. A positive barrier for blocking passage of a vehicle separating lanes on a roadway comprising: a unitary, integrally constructed barrier having a foot portion buried in a ground supporting pavement for a roadway, a tapered upstanding rail portion projecting above the surface of said pavement, and a tapered intermediate portion integrally interconnecting said foot portion to said upstanding rail portion; and said foot portion provided with an open-ended duct below said pavement extending longitudinally along the length of said barrier having a central axis lying on a central vertical plane of said upstanding portion and at least a pair of transverse passageways opening from opposite sides of said tapered intermediate portion at substantially pavement level and downwardly converging so as to conduct drainage from the surface of said pavement to said duct via gravity and connecting the surface of said pavement to said duct whereby said duct is in communication exteriorly of said foot portion.

7. A barrier section forming a section in combination with a plurality of identical sections to provide a continuous and co-extensive barrier separating lanes on a roadway, the combination comprising: