This study investigates the performance of bentonite components of geosynthetic clay liners (GCLs) when exposed to aggressive leachates using the fluid loss test and provides a possible quick method for estimating the effect of acidic conditions on hydraulic conductivity. Fluid loss generally increases with increasing acid concentrations. Hydraulic conductivity values back-calculated from the fluid loss tests (k_FL) are compared with the values measured using a flexible-wall permeameter (k_Tri). Generally, the predicted hydraulic conductivity values are conservative (k_FL/k_Tri > 1) under water and low acid concentrations (≤0.015 mol/L). However, the back-calculated hydraulic conductivity is shown to be nonconservative (k_FL/k_Tri < 1) at high acid concentrations (≥0.125 mol/L).

This study reports supportive evidence, from scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (TEM) of bentonite cakes, of the textural effects caused by reaction of concentrated sulfuric acid on the bentonite component of geosynthetic clay liners (GCLs) and how these effects may influence observed bentonite hydraulic performance. SEM images revealed that changes to the natural micro-textures of bentonite were due to interaction with acidic leachate, the effects being greater with increased concentration. It was observed from high resolution TEM images that most of the effects detrimental to hydraulic performance were related to re-arrangement of smectite quasi-crystals, as expected for textural responses to increased ionic strength. Significant bentonite dissolution was also observed in both SEM and TEM images after reaction at room temperature for as much as 48 h with sulfuric acid. The observed changes in the microtexture of the bentonite component by both SEM and TEM provide a physical explanation to the bulk experimental results as well as a benchmark for the application of GCLs under acidic conditions.

When the pipe jacking technology is applied in expansive formation, the soil around the pipe will easily absorb water from the slurry and expand to wrap up the pipe, producing an excessive pipe jacking force. A water‐based slurry formula suitable for pipe jacking in expansive soil layer was proposed in this paper. Firstly, the key design points of pipe jacking slurry in expansive soil were put forward. Secondly, plant glue, potassium humate, Na‐CMC, and graphite powder were chosen as treating agents to improve the slurry performance. The effect of addition levels of different treating agents on the funnel viscosity, filter loss, expansion ratio, friction coefficient and water dissociation rate of the slurry were tested. Thirdly, based on the results of single‐factor tests, a water‐based slurry formula suitable for pipe jacking in expansive soil was obtained. Finally, the slurry formula was applied in a practical pipe jacking project in expansive formation, and the jacking force was controlled well in the whole jacking process. The new water‐based slurry is cheap and practical and has no pollution to environment. Furthermore, a simple and practical calculating method of the pipe jacking force was presented. The comparison of the calculated and measured pipe jacking force shows that the simple calculating method can estimate the jacking force well. Improving slurry performance to reduce jacking force in pipe jacking and predicting pipe jacking force accurately can help reducing the investment for counterforce wall and jacking system in pipe jacking engineering.