A column system for modeling bentonite slurry infiltration in sands

Abstract

Abstract:Pressurized bentonite slurry is applied on a tunnel face to form a filter cake to stabilize the tunnel face when the slurry shield excavates through the sandy soil. Failure of the tunnel face may be caused by a high permeable filter cake, which commonly has a long penetration distance of slurry in sands. A column system with a height of 680 mm and a diameter of 300 mm was developed to model pressurized slurry infiltration in sands. Pressure transducers were installed to estimate the hydraulic conductivity of the filter cake during slurry infiltration. The electrical conductivity of the leachate of collected samples was measured. Results show that the majority of fine particles in slurry are within the range 100-300 mm into the sand specimen. The time for forming an impermeable filter cake is about 300 s, which indicates the impermeable filter cake is hard to form during the excavation.

On the morphology and pressure-filtration characteristics of filter cake formation: Insight from coupled CFD–DEM simulations

“…The friction coefficient of slurry particles matches the value chosen by Smuts [28] and other parameters used are consistent with our previous work [20]. The chosen applied pressure is within the range of values typically chosen for laboratory slurry filtration tests [5,8,10].…”

“…A common approach to investigate the slurry filtration process is the slurry filtration column test [3][4][5]. During the test, a sand column is firstly prepared and saturated in a Perspex cylinder.…”

Upper bound analysis for estimation of the influence of seepage on tunnel face stability in layered soils

“…Usually, a mixture of foam and bentonite is used in conditioning to reduce the permeability of the excavated material in the chamber. The effect of conditioning has been discussed in previous studies (Maidl and Cordes, 2003;Babendererde et al, 2004;Borghi and Mair, 2006;Gugliemetti et al, 2008;Liu and Yuan, 2014;Yin et al, 2016). In this work, two types of excavated soils in the chamber are considered.…”

Experimental Study on Electrical Resistivity Characteristics of Saturated Sand Mixes with Bentonite Slurry

“…Xu et al [26] eventually demonstrated the relationships between the bentonite concentration of slurry, slurry penetration velocity, and the range of slurry penetration depth. Yin et al [27] also employed filtration column tests to explore the distribution of bentonite concentration along the soil column and the range of slurry penetration depth by measuring the electrical conductivity of leachate and scanning electron microscope (SEM) qualitatively. However, it is difficult to observe the process of slurry penetration directly in all of the above tests.…”