Trencher Method vs. Slurry Trenching: A Pros & Cons Comparison of Case Studies-PPT Presentation

PPT Presentation

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The presentation compares trencher-based soil mixing with excavator-based slurry trenching, using five project examples.

<strong>Trencher advantages</strong> include safer operation in tight spaces, reduced open-trench hazards, independence from groundwater conditions, potentially lower cost, improved vertical mixing, and less handling of contaminated material. Limitations include a roughly 20-foot headroom requirement, difficulty ensuring contact between adjacent elements, poor suitability for rock or boulders, limited depth (about 50 feet), no key verification, challenges with underground utilities, and inability to segregate soils.

Project choices reflected site conditions:

- A 7,000-foot, 25-foot-deep soil-bentonite wall in silty sand, with groundwater at 6 feet and no key requirement, used a trencher to improve schedule.
- A 3,300-foot, 20-foot-deep soil-cement-bentonite wall in sand and gravel required a key and had boulder obstructions, so an excavator was selected.
- A 100-foot emergency repair in tight space, 16 feet deep, used a trencher for speed and limited workspace.
- A 1,275-foot, 16-foot-deep trench in sand and boulders, with groundwater at 3–4 feet, used a trencher after boulders were pre-excavated.
- A 75-foot, 20-foot-deep trench in tight space used an excavator because the soil contaminant could react with the in-place mix.

Overall, the cases suggest trenchers can be advantageous when speed, groundwater, or restricted workspace drives the decision; excavators may be preferable where boulders, key requirements, or soil compatibility pose challenges.

Keywords

trencher-based soil mixing

excavator-based slurry trenching

soil-bentonite wall

soil-cement-bentonite wall

groundwater conditions

restricted workspace

boulder obstructions

contaminated soil handling

vertical mixing

key requirement