What Is the Terzaghi Critical Hydraulic Gradient & Quicksand Safety Calculator?
Upward seepage flow in sandy soils reduces intergranular effective stress by exerting an upward hydrodynamic drag force.
When the upward seepage force exactly balances buoyant soil self-weight, effective stress drops to zero, triggering quicksand conditions, sand boiling, and catastrophic base heave.
This calculator computes the Terzaghi critical gradient (i_cr) from specific gravity and void ratio, and evaluates safety factors against seepage failure per USACE and Eurocode 7 standards.
How Does the Terzaghi Critical Hydraulic Gradient & Quicksand Safety Calculator Work?
The calculation evaluates user-provided measurements using recognized domain equations, converts between measurement units, and adjusts for real-world efficiency factors.
Terzaghi Critical Hydraulic Gradient & Quicksand Safety Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Terzaghi equilibrium formulation equating upward seepage drag force to downward buoyant effective weight.
How to Use the Terzaghi Critical Hydraulic Gradient & Quicksand Safety Calculator
- Enter your primary measurements in the input fields above.
- Select your preferred units (e.g. metric or imperial) if applicable.
- Review or adjust operational assumptions such as field efficiency.
- Click Calculate to instantly generate the full results breakdown and visual chart.
- Use the Reset button at any time to clear the form and test a new scenario.
Step-by-Step Example Calculation
Deep Excavation Dewatering in Medium Sand
Input Values:
Understanding Your Result
Your calculated result represents the realistic operational capacity or baseline output under the specified conditions. Comparing theoretical and effective outputs reveals the direct impact of turns, overlap, and practical downtime.
Factors That Affect the Result
Field terrain, operator experience, equipment maintenance, overlap margin, and weather conditions can significantly influence real-world output.
When Should You Use This Calculator?
Use this calculator whenever you need quick, verified estimates for job planning, budgeting, equipment sizing, or project timelines.
Assumptions & Limitations
- Terzaghi Critical Gradient: i_cr = (G_s - 1) / (1 + e).
- Submerged Unit Weight: γ' = [(G_s - 1) / (1 + e)] · γ_w.
- Factor of Safety: FS = i_cr / i_exit. Standard USACE and Eurocode 7 engineering practice requires FS ≥ 3.0 to prevent boiling.
Frequently Asked Questions
Calculation Accuracy & Reference Note
This calculator implements verified, deterministic mathematical equations based on published standards. Results should be treated as professional engineering estimates; always verify critical operations with local equipment manuals and site inspections.