RE-INFORCED EARTH RETAINING STRUCTURES DESIGN OF LAI EXPRESSWAY FROM AMMAR CHOWK TO IJP ROAD, RAWALPINDI PAKISTAN

Abstract

This document will present brief information on “Re-inforced Earth Retaining Structures”, which will include the types of re-inforcement, facing panels, backfill, fasteners between face panels and reinforcement; and drainage system to reduce pore pressure. The technique of reinforced earth retaining structures or mechanically stabilized earth walls is quite new in Pakistan. The structure is easy to erect and require less man power than that required in other retaining structures. The MSE wall structure is economical. Huge damages to property and lives of the nearby residents of Rawalpindi have been caused by Lai Nullah during flood season. The area surrounding the Nullah is heavily populated and requires special attention. An expressway along both sides of Lai Nullah using MSE walls will not only provide a signal free corridor for the residents of Rawalpindi but also prevent the huge damages that had been caused by the flooding in Lai Nullah. Side slopes are to be straightened by providing reinforced earth wall or MSE wall box structure for roadway space. The purpose of this project is to provide a signal free corridor from Rawalpindi to Islamabad. Extensive field surveys, by using modern tools such as GPS, have been conducted. Data collected from various sources include existing past data concerning geology, topography and hydrology of the area. The whole project is designed in 12 sections. For the design of the reinforced wall, site investigation is performed and load combinations are taken into account. Static Equilibrium Method is used to calculate the internal and external stability of system. Seismic forces and water level variations are also taken into account while designing. There are 14 existing bridges over Lai Nullah, 12 bridges are in our area of project. A total of 3 interchanges (one at Ammar Chowk, second at Murree Road Bridge and the third at Kattarian Bridge) and 9 Flyovers have been designed. To dissipate excessive pore water pressure, geo-composite sheet drains are provided. The different sections are modeled using Autodesk AutoCAD. Analysis of these sections is done using Rocscience Slide 6.0. 3D modeling of the project is done using Google Sketchup. At the last quantity surveying and cost estimation is carried out to judge the cost and economy of the whole project.