Crest and Toe: The Two Edges That Define a Slope
Crest and toe are the simplest terms in pit design and two of the easiest to get wrong in practice. The crest is the top edge of a slope, the toe is the bottom edge, and almost every geometric check, blast measurement and safety distance on a bench is stated relative to one of them. This guide explains what they are, why their position is a computed result rather than a drawn line, and where the usual mistakes come from.
The definitions
The toe is the bottom edge of a slope, where the sloping face meets the level below it. On a bench, that is where the face meets the floor.
The crest is the top edge, where the face meets the level above — the berm, or the ground surface at the top of the wall.
Between them is the bench face, and its inclination from horizontal is the face angle, or batter angle. Everything else about the bench — height, berm width, overall angle — is expressed in terms of these three.
Why their position is computed, not drawn
In a design, the slope is a template: an angle, a height, a berm width. Where that template actually stops is where it intersects the existing ground, and that is the daylight line.
This matters because ground is not a plane. A design slope pushed into a rising hillside daylights further out; the same slope against falling ground daylights closer in. Computing the intersection against the surveyed surface gives toe and crest positions you can set out; assuming a plane gives positions that are wrong by however much the ground deviates from that assumption.
It is also why toe and crest positions change when the survey is updated. The design did not move — the ground did.
Crest distance in plan is not crest distance in rock
The most consequential mistake with these two terms happens in blasting. Distance from a blasthole to the crest is easy to measure in plan view, and it is not the burden.
Burden is the rock a hole actually has to break, measured perpendicular to the nearest free face. On a battered face, an inclined hole has progressively more rock in front of it as it goes deeper — so the plan distance to the crest understates the burden at the toe, which is exactly where a pattern goes tight and where a hard toe is left standing.
The practical consequence is that a pattern that looks correct on a plan drawing can be under-designed at floor level. Measuring relief along the hole axis at every elevation, rather than once in plan, is what exposes it.
Crest and toe in safety and access
Berm width is measured from crest to toe of the adjacent faces, and it is a safety parameter: it catches material that falls from above and gives machines somewhere to stand. A design that shaves berm width to steepen the overall angle is trading a geotechnical margin for volume.
Standoff distances for equipment near a crest, and exclusion zones near a toe, are both stated relative to these edges. When the edges are in the wrong place on the plan, so are the distances.
Overall angle versus face angle
A wall does not stand or fail one face at a time. The overall slope angle runs from the toe of the lowest bench to the crest of the highest and includes every berm along the way, which makes it always flatter than the individual face angles.
Two designs with identical face angles can have very different overall angles if their berm widths differ. That is why the geotechnical check belongs on the overall angle: it is easy to satisfy the face angle on paper and still exceed the limit that actually governs stability.
Frequently asked questions
What is the difference between crest and toe?
The crest is the top edge of a slope, where the face meets the level above it. The toe is the bottom edge, where the face meets the level below. On a bench, the toe is at the floor and the crest is at the berm above.
What is the daylight line?
The line where a design slope intersects the existing ground and therefore stops. Because it depends on the real surface rather than an assumed plane, it is what determines the true position of the toe and crest.
Why does the distance to the crest underestimate burden?
Because it is measured in plan while the rock is in three dimensions. On a battered face an inclined hole has more rock in front of it with depth, so the burden at the toe is greater than the plan distance to the crest suggests — which is where patterns go tight.
Why is the overall slope angle flatter than the face angle?
Because it includes the berms. Measured from the lowest toe to the highest crest, the horizontal contribution of every berm reduces the average angle, so the overall angle is always flatter than the individual bench faces.
STREAM computes the daylight line as the intersection of the slope profile with your surveyed terrain.
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