Fluidos de sostenimiento

Bentonite slurries
Bentonite slurries consist of a mix of bentonite and water that has thixotropic properties, which means that whilst it is being mixed it behaves as a fluid, but whilst stable it becomes cohesive. It acts on the walls of the excavation by forming a mixture with the ground known as “cake”, reducing the permeability of the walls. This produces a membrane effect that can transmit the hydrostatic pressure of fluid to the excavation walls.

Bentonite slurries are considered toxic waste, and under current regulations must be disposed of at an authorised landfill site after use.

A viable alternative to bentonite slurries exists; the use of synthetic polymers, of which two groups can be distinguished:

Acrylic polymers
Consists of a fluid that contains polymers formed by a positively charged carbon chain. These react with the negatively charged particles found in the natural terrain, creating a cohesive effect on it.

Third generation system
Consists of a fluid containing several types of synthetic polymers. They consist of bipolar carbon chains (containing both types of charges) and therefore are capable f generating membranes that interact with the ground, forming a “cake”. The support of the walls of the excavation is achieved both because of the cohesive effect of the soil particles and by transmitting hydrostatic pressure to the walls of the excavation.

Their primary advantage is that they are biodegradable and it is not necessary to transport them to a landfill site.

The use of polymers reduces the amount of solids in the liquid and decreases their settlement in the base of the excavation.