Geogrid Stabilization of Railway Ballast under Varying Moisture Conditions Evaluated Using Bender Element Shear Wave Technology

Ballast serves a critical role in railway track stability by supporting rails and crossties, distributing loads, and facilitating drainage. However, its structural integrity can be compromised due to fouling and moisture infiltration, leading to reduced shear strength and stiffness. While geogrid stabilization has been widely recognized for improving ballast performance, its effectiveness under different moisture conditions remains less understood. The objective of this study is to evaluate the effect of moisture content and geogrid stabilization on the dynamic characteristics of fouled railway ballast using Bender Element (BE) sensor technology. Laboratory box tests were performed on ballast specimens with a fouling index (FI) of 25.3, incorporating gravimetric moisture contents ranging from 0% to 12% by weight of fines smaller than 9.5 mm (3/8 in.). Shear wave velocities (Vs) were measured using BE sensors embedded within the ballast layer to estimate small-strain shear modulus (Gmax) characteristics. Geogrid-stabilized specimens were compared to non-stabilized control cases under both dry and wet states. The test results showed that (Vs) and (Gmax) increased for up to 6% moisture and then decreased at higher moisture levels, indicating a transition from stabilizing to lubricating effects of added moisture on the ballast fines. Under both dry and wet conditions, geogrid-stabilized ballast samples exhibited higher shear wave velocities and stiffness values than the control. These findings demonstrate the value of field-installed BE sensors for evaluating ballast layer stiffness and monitoring the performance improvement provided by geogrid stabilization of track substructure under varying moisture conditions.