Line a hand-dug well as you dig, not afterwards: dig no more than one metre below the last lining, build or sink the next section of lining before digging on, and never leave an unlined wall taller than the 1.2 m depth at which excavations need support. The lining holds the soil back while people work, then seals the upper 3 m of the finished well against surface water, with the lower part left open to admit groundwater.
Part of Deep Wells
Lining as you go is the practice of supporting the wall of a shaft in sections during excavation, so that people never work beneath unsupported ground. The same lining then becomes the permanent wall of the well.
An Unlined Wall Is An Unsupported Excavation
The strictest regulatory figure this guide uses is that an excavation deeper than 1.2 m needs sloped or shored walls. A well shaft cannot be sloped back, so its walls are supported by a lining. If you dig deeper than one section before lining, a person is working below an unsupported wall taller than that. A cave-in buries the digger faster than a rope can pull them out (Safety Protocol).
The Phase 0 guides give the same sequence: dig in 1 m steps and line each step before the next (Well Lining). A 1 m step keeps the exposed wall under the 1.2 m figure.
Three Ways To Support The Wall
| Method | How it works | Suits | Limits |
|---|---|---|---|
| Dig-and-line | Dig 1 m, then build the lining section from the bottom of the cut up, packed behind with gravel or clay | Stable ground; brick or stone (Brick Lining) | Needs a stable face for the 1 m that is open |
| Sinking | Build or place a complete ring at the surface, dig beneath it, and let it sink under its own weight; add rings on top | Soft, uniform ground; concrete rings (Concrete Rings) | Fails in boulders or mixed ground, where a ring jams |
| Temporary shoring | Upright boards or split poles held by rings, then replaced by permanent lining | Loose ground while lining is made | Needs more labour and must be checked each shift |
The Deep Wells guide calls sinking rings the safest method, because the digger works inside the lining.
What You Need
- Lining material — rings, brick with lime mortar, or stone
- Gravel and clay — gravel backfill for the permeable lower zone, clay or grout for the sealed upper zone
- A plumb line — a stone on a string, to check each course is vertical
- The hoist and safety kit — see Hand Digging
Method: One Section At A Time
Step 1: Dig one section. Dig the next 1 m below the last lining, keeping the wall vertical and trimmed. Do not leave overhangs.
Step 2: Line before you dig on. Lay the new lining on a firm base, check it is plumb, and pack the gap behind it. Do this before anyone digs deeper.
Step 3: Backfill by zone. In the water-bearing lower zone, pack gravel behind the lining and leave the lining open to admit water. In the top 3 m, the lining and the space behind it are sealed with clay or grout so that surface water cannot run down behind it. Plaster the inside of the top 3 m watertight with cement mortar.
Step 4: Continue to the water. Repeat to the water table and then 2-3 m into the saturated zone, with the sump bailed as you go (Dewatering).
Step 5: Extend above ground. Carry the lining above ground level, so it forms the collar that keeps runoff and animals out (Well Protection).
Worked Example: The Gap Behind A Ring
Take the Deep Wells figures: a concrete ring 1.0 m across in a shaft marked out 1.2 m across. The gap on each side is (1.2 − 1.0) ÷ 2 = 0.1 m. The ring is 0.5 m tall, so the annulus behind each ring holds π × (0.6² − 0.5²) × 0.5 = π × 0.11 × 0.5 = 0.17 m³, or 173 L, of gravel or clay. Ten rings leave 1.7 m³ to place. Leaving that gap unfilled in the top 3 m would let surface water run down the outside of the lining into the aquifer.
Common Mistakes
- Letting the open section grow. “Just one more metre” is how cave-ins happen. Fix the section height and keep to it.
- Lining on a soft base. A lining bedded on loose soil settles unevenly and cracks.
- Sealing the lower zone. The aquifer part must admit water; sealing it closes the well.
- Forgetting the outside. A sealed lining with an open gap behind it still lets surface water in.
Safety
People work under the lining, and above it
Line every section before going deeper and do not enter a section whose lining is unfinished. Nobody is below when a ring or a load of brick is lowered. Ventilate and use a harness and line on every entry (Safety Protocol). A ring or stack of bricks dropped down a shaft kills.
What’s Next
- Learn next: Brick Lining and Concrete Rings — the two permanent linings
- Combine with: Surface Seal — sealing the top of the lining