What Is the Geotextile Filter Apparent Opening Size (AOS) Calculator?
Geotextiles used in subsurface drainage and erosion control must satisfy conflicting requirements: retain base soil particles while allowing unrestricted water passage without clogging.
Piping occurs if pore openings are too large, while clogging or blinding occurs if pore openings are too fine relative to soil particles.
This calculator evaluates AASHTO M 288 and FHWA filtration criteria to determine the allowable Apparent Opening Size (AOS / O95) and minimum permeability.
How Does the Geotextile Filter Apparent Opening Size (AOS) Calculator Work?
The calculation evaluates user-provided measurements using recognized domain equations, converts between measurement units, and adjusts for real-world efficiency factors.
Geotextile Filter Apparent Opening Size (AOS) Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
O95 (AOS) is geotextile apparent opening size, B is coefficient based on Cu (0.5 to 1.5), and k is hydraulic conductivity.
How to Use the Geotextile Filter Apparent Opening Size (AOS) 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
Highway Edge Drain Trench Filter
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
- AASHTO M 288 Standard Specification for Geotextiles in Subsurface Drainage.
- Retention criterion limits maximum opening: O95 ≤ B · d85 to prevent soil loss.
- Permeability requirement dictates k_geotextile ≥ 10 · k_soil to prevent head buildup.
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.