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Constant-Head Soil Conductivity Record

Reconcile one constant-head specimen calculation with a laboratory-reported saturated hydraulic conductivity while retaining method and specimen boundaries.

Use this result well

Inputs that matter
Collected flow volume, specimen length/area, defined hydraulic-head difference, elapsed interval and same-specimen laboratory conductivity
Output to expect
Calculated constant-head conductivity in cm/s and cm/day plus signed laboratory difference
How it works
Reconciles one documented saturated constant-head specimen/interval; it is not a universal field permeability or design value
  • Verify specimen/sample identity, orientation/structure, saturation/preconditioning, dimensions, steady flow, head definition, elapsed interval, temperature/correction and method.
  • Review cracks, smearing, sidewall/boundary effects, stratification, anisotropy and replication; use qualified geotechnical/soil guidance for infiltration, drainage, septic or design decisions.

Choose your path

Built around the job you need to finish

Reconcile one documented constant-head specimen calculation with a laboratory-reported saturated hydraulic conductivity.

Laboratory technician checking a permeameter sheet

Reproduce conductivity from the recorded volume, dimensions, head and elapsed time.

Enter the six matched specimen/test values and compare with the laboratory report.

Sees cm/s, cm/day and the signed report difference.

Geotechnical reviewer checking method conditions

Keep saturation, specimen preparation, temperature and boundary conditions attached.

Review those records outside the calculator before accepting the arithmetic comparison.

Does not compare incompatible method or correction bases.

Designer seeking a field infiltration value

Avoid using one laboratory specimen as a universal site design parameter.

Use field investigation, stratification, cracks/macropores, replication and governing design procedures separately.

Does not authorize drainage or earthwork design from this result alone.

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Reference & details

How it works

Use One Matched Constant-Head Run

Enter collected flow volume, specimen length and area, applied head difference and elapsed time from the same stabilized test interval. Every denominator must be positive.

Apply the Recorded Geometry

The worksheet calculates K = QL divided by A times delta-h times t in cm/s, then reports the equivalent cm/day. It does not substitute a texture class or typical value.

Compare Like Reporting Bases

The signed result compares calculated K with an entered laboratory K. Saturation, specimen preparation, temperature correction, flow direction and boundary conditions must match before interpreting a discrepancy.

Updated: August 2026

Example Scenarios

Reproduce a constant-head result from the original volume, time, head and specimen geometry records.

Compare the worksheet with a reported conductivity only after checking units, corrections, saturation and specimen condition.

Use the specimen record alongside replication, soil layers, cracks, macropores and field evidence; do not promote it to a universal site value.

Common Mistakes to Avoid

Using total head instead of the documented head difference

Enter the hydraulic head difference across the specimen for the same collection interval and retain the apparatus datum and reading record.

Treating one specimen as field or design permeability

Review sampling disturbance, saturation, anisotropy, stratification, cracks, boundaries, replication and the governing field/design procedure separately.

FAQ

For the entered constant-head run, K equals collected volume times specimen length divided by specimen area, head difference and elapsed time.

They are two unit expressions of the same calculated specimen result. The conversion does not add field representativeness or certainty.

Differences may reflect units, rounding, corrections, test interval, specimen dimensions, saturation or method conditions. Reconcile those records before accepting either value.

Not by itself. Field decisions require representative investigation, variability and stratification, macropores or cracks, applicable test methods and governing criteria.

Keep sample and horizon IDs, orientation, preparation and saturation, apparatus/head readings, temperature and corrections, interval data, replication and the signed report.

About Constant-Head Soil Conductivity Record

This tool checks constant-head arithmetic for one documented specimen and test interval. It does not assign a soil class, predict infiltration or provide a drainage, septic or earthwork design value.