Why Soil Type Changes the Plan
Excavation estimates start with the measured cut, but the soil type determines what happens after the bucket breaks it loose. Some soils bulk up only slightly, some turn into heavy wet material that reaches truck payload limits early, and some compact or reuse poorly because of moisture, organics, or mixed debris.
Use the excavation calculator for basic dig volume, then use soil behavior to decide whether the controlling planning number is bank volume, loose volume, compacted volume, or haul weight. The values below are planning defaults, not a substitute for site sampling or a geotechnical recommendation.
Excavation Soil Planning Table
The table uses the shared soil data behind the excavation tools so the guide stays consistent with calculator defaults. Bank density is the in-place soil density. Loose density is the excavated material density used for hauling and truckload checks.
| Soil Type | Swell | Shrink | Bank Density | Loose Density | Planning Concerns |
|---|---|---|---|---|---|
| Clay (Heavy) | 35% | 15% | 1,900 kg/m3 | 1,185 kg/m3 | Sticky when wet, higher haul weight, slower drying, and more selective reuse as compacted fill. |
| Clay (Light/Sandy) | 30% | 12% | 1,600 kg/m3 | 1,070 kg/m3 | Moderate swell with moisture-sensitive workability; verify compaction moisture before reuse. |
| Sand (Dry) | 15% | 10% | 1,600 kg/m3 | 1,280 kg/m3 | Easy to dig but prone to raveling and sloughing; loose density drives truck payload checks. |
| Sand (Wet) | 20% | 12% | 1,900 kg/m3 | 1,425 kg/m3 | Heavier to haul and less stable at open faces; water control can change volume assumptions quickly. |
| Gravel | 15% | 8% | 1,800 kg/m3 | 1,480 kg/m3 | Usually free-draining and reusable, but voids and segregation affect compaction assumptions. |
| Gravel/Sand Mix | 18% | 10% | 1,700 kg/m3 | 1,350 kg/m3 | Often workable structural fill when clean, with moderate weight and compaction sensitivity. |
| Topsoil/Loam | 25% | 10% | 1,250 kg/m3 | 950 kg/m3 | Organic content and roots make it poor structural fill; strip and stockpile separately for reuse. |
| Rock (Blasted/Broken) | 60% | 20% | 2,700 kg/m3 | 1,600 kg/m3 | High swell and variable fragment size; volume capacity can control before fine grading is possible. |
| Mixed Fill | 25% | 12% | 1,500 kg/m3 | 1,120 kg/m3 | Unpredictable composition; use conservative swell, shrink, and density assumptions until verified. |
Swell, Shrink, and Which Volume to Use
Soil swell is the increase from bank volume to loose volume after excavation. It matters for stockpile space, truck bed volume, and how much material is available to move around the site. Shrink is the reduction from bank volume to compacted volume, which matters when deciding whether excavated soil can satisfy a compacted fill need.
A dense clay cut may produce much more loose material than the hole volume, but less compacted fill than expected after moisture conditioning and compaction. Sand may be easier to dig, yet it can ravel at trench faces and require a more conservative open-cut geometry. Rock and broken hard material can swell sharply because large fragments create voids that do not pack efficiently in a truck bed.
Use the soil swell and shrink factors guide to review the bank, loose, and compacted volume relationship, and use the swell and shrink calculator when you need to convert between bank, loose, and compacted states without reapplying factors by hand.
Moisture and Haul Weight
Moisture changes both workability and haul planning. Wet clay can be sticky, difficult to place, and heavy enough that payload limits control before truck bed volume is full. Wet sand may dig cleanly in one pass and start sloughing as water drains or vibration changes the face. Topsoil and loam can hold moisture and organic matter, which makes them useful for landscape reuse but unsuitable for structural fill unless the project allows it.
For hauling, compare loose volume and loose density with the actual truck inputs in the truckload estimator. Dense or wet soils often need more trips because weight, not volume, becomes the limiting condition.
Sloughing and Open-Cut Assumptions
Diggability is not the same as stability. Granular soils such as dry sand and gravel may excavate quickly, but they can ravel into the opening and increase the actual cut volume. Clay can stand more steeply when stiff and dry, then lose strength after rain, seepage, vibration, or repeated disturbance. Mixed fill is especially uncertain because pockets of debris, organics, sand, and clay can behave differently within the same excavation.
If an excavation needs sloped sides, use the trench sloping calculator to model the additional top width and cut volume. Treat calculator dimensions as planning geometry only; field stability still needs competent site judgment.
Reuse as Fill
Clean granular soil and gravel-sand mixtures are often easier to reuse because they drain and compact predictably. Clay can be reusable when moisture is close to the workable range, but wet clay may pump, rut, or fail compaction checks. Topsoil should normally be kept separate from structural fill because roots, organics, and variable moisture make it compressible. Mixed fill should be treated cautiously until debris, contamination, and particle size are known.
Conservative planning means separating unsuitable material early, keeping bank, loose, and compacted volumes distinct, and updating factors when field conditions differ from the default soil type.
Safety Handoff
This page uses soil type for volume, weight, handling, and reuse planning. OSHA soil classification is a separate safety decision that affects protective systems, sloping, benching, shoring, and trench entry. For that workflow, see the OSHA trench safety guide.
Calculator Handoff
Start with the excavation calculator to calculate bank volume from the planned cut dimensions. Then use the swell and shrink calculator to translate that bank volume into loose hauling volume and compacted reuse volume using soil-specific factors.