Mixing uniformity effect on hydraulic conductivity of cement-based stabilized soft clay

Mixing uniformity plays an important role in the quality control of the deep diaphragm wall in anti-seepage projects. However, there is a lack of quantitative evaluation of mixing uniformity and its effect on the hydraulic conductivity in geotechnical engineering. This study proposed a method to quantificationally characterize the mixing uniformity of the cement-based stabilized soft clay (CBSC) through the X-ray computed tomography. Note that, the phase with the grayscale value (i.e., the mode of the grayscale value of the sample closest to the uniform state) was tracked to obtain its layer-by-layer volume fraction, followed by quantitative analysis with the proposed equation. Additionally, the relationship between the CBSC’s mixing uniformity and the hydraulic conductivity was discussed. The results indicate that the characterization parameters of the hypertonic zone are related to the mixing uniformity, including the volume fraction, equivalent radius, channel length and coordination number of the connected hypertonic zone. With a low uniformity, plenty of hypertonic zones with high porosity provide continuous channels for percolation. Hence, a small volumetric and isolated hypertonic zones prevent the connectivity of the seepage channels resulting in the overall low permeability. The hydraulic conductivity decreases sharply, when mixing uniformity more than 81.1% in this study. These findings provide a guidance for the control of the mixing uniformity for the anti-seepage project construction.