Bentonite and polymeric support fluids used for stabilization in excavations

Abstract

Bentonite is a natural and finite mineral resource. Dilute suspensions of sodium montmorillonite clay in water represents bentonite slurries. Suspension and orientation of colloidal clay particles define rheological properties in bentonite slurry (BS). The BS has been used about seventy years to temporarily support the excavations. More recently, polymer support fluids (PSF) gained much popularity and are widely used compared to bentonite support fluids. The PSF are categorized into natural (pure) and synthetic polymers. Physico-chemical properties of PSF are different than BS irrespective of the quite similarity in the mode of action. Synthetic polymer fluids are molecularly engineered fluids that can be a popular alternative of conventional BS deployed as excavation support fluids in different foundation applications such as diaphragm wall panels and pile bores. The synthetically engineered fluids of polymers (water-soluble) are different from conventional BS. The PSF offer additional benefits because their use is cost effective, eco-friendly, and these polymers need smaller site footprint as well as easy preparation, mixing, handling, management and ultimately the final disposal. Nevertheless, synthetic polymers have advantage over bentonite, however, foundation engineers and scientists have also certain concerns about their use because of their performance related issues. For an efficient use of polymers, specific properties and in situ behavior of polymers as well as their sorption onto the soils must be recognized because the polymer concentration in the solution is decreased with time during their use. The present manuscript reviewed the relative performance of excavation support fluids and displayed an arranged marriage of physicochemical and rhelogical properties of natural and synthetic excavation support fluids used in the foundation industry. This information will be highly useful to scientific community for their future ventures and will lay a foundation to understand the mechanisms of stabilization in open and deep excavations.

Synthesis and characterization of a novel functionalized silica/polyacrylamide composite for advanced water‐based drilling design

“…It is usually used as a flocculant and thickener in industrial sites, such as enhanced oil recovery, wastewater treatment and construction fields. Besides, its viscosity is usually higher than water, but its density is similar to water 4,13 . PAM is encouraged to be utilized in the drilling operation because synthetic polymer usually offers excellent viscosity at lower concentrations.…”

“…It can be elucidated that traditional bentonite has a concentration order of 25–50 times greater than PAM. In weight basis in technical usage in drilling sites, the concentration of bentonite is usually 2.5%–5%, while the concentration of PAM is 0.05%–0.2% 4,10 . Besides, bentonite slurries preparation is more complex than PAM operations due to the hydration stage requirement with high concentration, and longer mixing rate in the preparation of bentonite slurries.…”

“…[1][2][3] Meanwhile, the concept of "green chemistry" has been employed in the foundation field to minimize the environmental footprint and costeffectiveness. For instance, polyacrylamide (PAM) has been widely used due to its advantages such as a lower environmental footprint, 1,4,5 easy accessibility, 2,3,6 and resistance improvement when used with concrete sand in a foundation. [1][2][3]7 Polyacrylamide is also helpful in environmental footprint reduction.…”

“…In weight basis in technical usage in drilling sites, the concentration of bentonite is usually 2.5%-5%, while the concentration of PAM is 0.05%-0.2%. 4,10 Besides, bentonite slurries preparation is more complex than PAM operations due to the hydration stage requirement with high concentration, and longer mixing rate in the preparation of bentonite slurries. The bentonite slurries need a larger space for operation sites than PAM slurries.…”

“…Besides, its viscosity is usually higher than water, but its density is similar to water. 4,13 PAM is encouraged to be utilized in the drilling operation because synthetic polymer usually offers excellent viscosity at lower concentrations. The cluttered PAM dispersion in the mud triggers better bridge linking effect and surface adsorption in the drilling operation.…”