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Slurry Trenching Method


Since 1950, bentonite slurry has been used to stabilize trenches under excavation. This technique is referred to as the slurry trench method of excavation. This method allows for the excavation of  deep, narrow vertical trenches in soils, particularly for trenches extending beneath the groundwater table. Slurry trenching eliminates the need for shoring or dewatering of the area that could not stand unsupported otherwise.

As the excavation proceeds, the trench is  filled with bentonite slurry. The hydrostatic thrust of the slurry on the trench wall is the primary stabilizing force supporting the saturated soils. The penetration of the slurry in pervious soil layers adjacent to the trench, as well as the formation of a filter cake on the side walls, are also stabilizing factors. Slurries fabricated with biodegradable polymers, instead of bentonite, are now used for specific applications including deep drainage trenches and permeable reactive barriers.

The slurry trench method of excavation presents advantages over other seepage control methods.

Advantages of Slurry Trenching versus In-Situ Construction Methods

  • Visual determination of top elevation of the aquitard formation throughout the trench
    alignment. The trench can be deepened or raised as needed locally
    to ensure a continuous key embeddment of the seepage barrier into the aquitard
  • Sampling of the impermeable key material to verify its quality
  • The backfill can be engineered to meet a variety of field conditions. For instance,
    borrow material can be added to ensure that the backfill will meet the filter criteria
    required by the soil stratigraphy
  • Visual observations of soil cuttings and continuous logging of soil formations
  • Flexible construction sequencing
  • Excavation can proceed through hard soil formations, including cobbles, boulders, cemented soils, and rock formations
  • Formation of a low permeability filter cake on the trench sidewalls, improving the effectiveness of the cutoff

INQUIP is a global specialist in the application of the slurry trenching method with offices throughout North America. We work as a general contractor as well as a subcontractor.  We also provide technical expertise.