What Is Shoring in Excavation?
Shoring serves as a protective system in trenching operations that actively reinforces excavation walls to prevent soil collapse. It differs from sloping (angled cuts) or shielding (trench boxes), as shoring specifically supports unstable ground.
Why Shoring Is Essential
- Prevents fatalities and injuries from soil collapse
- Meets OSHA excavation standards (29 CFR 1926 Subpart P)
- Protects underground utilities during hydro excavation
- Ensures structural stability near roads, foundations, or equipment
The Different Types of Shoring Systems
1. Hydraulic Shoring
Uses prefabricated aluminum hydraulic cylinders with steel or aluminum plates. Cylinders are pressurized with fluid to hold trench walls in place. The system is easily adjustable and reusable.
Best For: Quick installation and flexibility across multiple soil types.
2. Pneumatic Shoring
Operates on air pressure instead of fluid, using pneumatic cylinders. Requires an on-site air compressor. Lighter than hydraulic systems for easier transport.
Best For: Projects with available compressed air or where lightweight systems are preferred.
3. Timber Shoring
A traditional system using timber uprights, cross braces, and sheathing to support trench walls. Labor-intensive and slower to install than hydraulic alternatives. Requires careful spacing based on soil classification.
Best For: Remote areas or irregular excavation sites where prefabricated systems aren't available.
4. Aluminum Hydraulic Shoring with Sheeting
Combines aluminum cylinders with plywood or steel sheeting for added stability in unstable soils. Lightweight and reusable, allowing wider, deeper trench protection.
Best For: Utility projects in extremely unstable soil conditions.
5. Screw Jack Shoring
A manual system using adjustable screw jacks instead of hydraulic pumps. Workers adjust threads to press uprights against trench walls. More labor-intensive but requires no pumps or compressors.
Best For: Smaller-scale projects prioritizing simplicity and cost savings over speed.
6. Soldier Pile and Lagging
For deep excavations near roads, structures, or urban areas. Steel H-piles are driven into the ground with wood or concrete lagging inserted between them. Often used with tiebacks or bracing.
Best For: Large infrastructure projects or deep excavations near highways and buildings.
7. Sheet Piling Shoring
A permanent or semi-permanent method for deep, long-term excavations. Steel sheets are driven vertically to create retaining walls. Highly durable and reusable.
Best For: Projects near water sources, harbors, or where soil retention must be exceptionally strong.
How to Choose the Right Shoring System
Consider these factors:
- Soil type (Type A = stable, Type C = very unstable)
- Depth of excavation
- Project duration
- Equipment availability
- Proximity to roads, utilities, or structures
Always ensure a competent person evaluates soil conditions and selects the appropriate system.
OSHA Requirements for Shoring
OSHA mandates:
- Protective systems in trenches 5 feet or deeper (unless in stable rock)
- Designs approved by a registered professional engineer for trenches exceeding 20 feet
- Regular inspections by a competent person, especially after rain, vibrations, or soil changes
Frequently Asked Questions (FAQ)
Q1: What is the most common type of shoring?
Hydraulic shoring is most widely used due to speed, adjustability, and safety features.
Q2: How deep can shoring systems go?
Systems support trenches up to 20 feet deep without engineering approval; deeper systems require professional design.
Q3: Is shoring always required?
Shoring is required for trenches 5 feet or deeper, unless cut in stable rock or alternative protections are used.
Q4: Which shoring system works best for Type C soils?
Aluminum hydraulic shoring with sheeting or sheet piling suit very unstable soil conditions.
Q5: Can trench boxes replace shoring?
Trench boxes protect workers but do not support soil—they represent a different protective approach.
