An Assessment and Comparison of PLT and LWD Tests Results for Evaluating of High Speed Railway Embankment Modulus

According to essence of providing suitable subgrade and embankment for railway tracks, in-situ tests have been attained the considerable importance for controlling the allowable bearing capacity and settlement of the earth works. Usually, earthwork in under construction passenger and freight railways is controlled by means of simple tests such as CBR and Compaction. But in the case of high speed railways, determining the subgrade and embankment layers modulus using Plate Loading Test (PLT) is necessary to ensure adequate bearing capacity and limited embankment settlement. In this regard, the UIC-719R code is stipulated that all the embankment layers including subgrade, bearing part of embankment, sub ballast and ballast must provide a minimum static modulus which is introduced as EV2 (the modulus in second cycle of loading in PLT). Since the experimental process of the PLT is so expensive and time consuming, so controlling the mentioned requirements through the length and width of track, encounters with major difficulties in practice. Recently using the Light Weight Deflectometer test (LWD), the dynamic modulus of the earth works is measured in a very simple and fast manner. As the static modulus has been adopted as a practical criterion for approving the earth works quality in the jobsite, so, a reliable relation between the static and dynamic modulus should be established. The main goal of the present study is to introduce many practical correlation equations between the field tests results including LWD, PLT, and CBR. For this purpose the available data of under construction Qom - Esfahan high speed railway were proceeded in an accurate manner and consequently the best possible correlation equations were presented.