2.5.7.2. 3D mode and vertical shafts

A normal alignment is a 2.5D model: the horizontal geometry defines the chainage (the horizontal length along the axis), the vertical profile gives the elevation at each chainage, and offsets are measured horizontally, square to the plan direction.

That model breaks for a vertical shaft or a steep incline. A shaft has no horizontal length at all, so every point would measure at chainage 0 and every setout would land on the shaft bottom. 3D mode treats the alignment as a true space curve instead:

  • Chainage is the 3D length along the axis (slope distance), measured from the start chainage of the vertical profile. On a vertical shaft the chainage is the depth along the shaft.

  • Sections are perpendicular to the 3D axis. On a vertical shaft a section is a horizontal disc; on an incline it is tilted with the axis.

  • Offsets are measured in the section plane, not horizontally.

3D mode is set per alignment and is stored in the .alm file (mode3D="true"). Alignments without it behave exactly as before.

2.5.7.2.1. Turning 3D mode on

Open Tools ▸ Alignment Settings… and tick Use 3D mode.

  • Section azimuth — orients the section axes of a (near) vertical shaft, where the axis itself has no plan direction. The box shows and accepts the current angular unit (the label beside it says grad, deg or rad). It is measured like the bearings shown elsewhere in the Alignment Solver: 0 = East, counter-clockwise. With azimuth 0 the section’s U axis points East. The azimuth is ignored on axes that are not within 1° of vertical. In the .alm and LandXML files the value is stored in radians.

3D mode needs a vertical profile; without one the alignment keeps working in 2D.

2.5.7.2.2. Defining a vertical shaft

A vertical shaft is defined by

  • a horizontal geometry that is a single point — the shaft collar (two PIs with the same coordinates, giving one zero-length element), and

  • a vertical profile whose chainage runs over the depth of the shaft: the profile rises (or falls) one metre per metre of chainage, so the profile chainage is the depth.

Example — a shaft at X = 278124.426, Y = 4305854.311 from H = 120 m to H = 250 m (vertical_shaft.alm):

<Alignment_1 mode3D="true" sectionRefAzimuth="0">  <!-- other attributes omitted -->
  <HorizontalAlignment HorizontalElementsCount="1" StartStation="0">
    <Elements>
      <HElement1 Type="1" StartX="278124.426" StartY="4305854.311"
                 EndX="278124.426" EndY="4305854.311" Chainage="0"/>
    </Elements>
    <!-- PiElements omitted -->
  </HorizontalAlignment>
  <VerticalAlignment VerticalElementsCount="1">
    <Elements>
      <VElement1 Type="1" Level="120" Chainage="0"
                 EndLevel="250" EndChainage="130"/>
    </Elements>
    <!-- PiElements omitted -->
  </VerticalAlignment>
</Alignment_1>

The alignment runs from chainage 0 (H = 120) to chainage 130 (H = 250).

Note

In IQCAD the same alignment is created with ALIGNFROMPOLYLINE from a plumb 3D polyline (all vertices on the same plan point). ALIGNFROMPOLYLINE switches 3D mode on by itself only for plumb polylines and for polylines with a segment steeper than 45°; ordinary graded roads stay 2D.

2.5.7.2.3. Section axes

At every chainage the section plane has two axes:

  • U — the lateral axis. On an incline it is horizontal and points to the left of the direction of travel. On a vertical shaft it is set by the section azimuth.

  • V — the in-plane “up” axis, square to the axis and to U. On an incline it tilts with the grade; on a vertical shaft it is horizontal. With azimuth 0 and a profile that rises with chainage, V points North. A profile that falls with chainage points V the other way, because V follows the direction of travel.

The position of a point in the section is also given in polar form: R = distance from the axis, Theta = angle from U towards V. On a shaft, R is the radial distance — e.g. the gunite or final-lining radius.

2.5.7.2.4. Setout and Measure in 3D mode

The Setout / Measure dialog and the batch tools work unchanged; only the meaning of the inputs and results changes.

Field

Meaning in 3D mode

Chainage

3D length along the axis (depth on a shaft)

Offset

Section-plane offset, positive = right of travel, i.e. along −U

Dh

Section-plane offset along V

Height

Setout: elevation (Z) of the computed point. Measure: the axis elevation (the measured Z is carried by the chainage and by V)

Elevation

Elevation (Z) of the axis at that chainage

Bearing

Plan direction of the axis (0 on a vertical shaft, which has no plan direction)

U / V

Section coordinates of the point (shown in place of Super L/R)

R / Theta

Polar section coordinates (shown in place of Turn)

Superelevation, widening and cant do not apply to a 3D axis and are ignored; Rail mode computes a plain section-plane setout.

Measure finds the nearest point on the 3D axis, so the Z of the measured point matters. A point above the top or below the bottom of the alignment is reported at the end chainage, and the chainage field says how far beyond the end it lies, e.g. 130.000 (10.000 beyond end).

Worked example (shaft above, section azimuth 0, so U = East, V = North):

Input

Result

Setout: Chainage 65, Offset −4.35, Dh 0

X 278128.776, Y 4305854.311, Z 185.000 (4.35 m East)

Setout: Chainage 100, Offset 0, Dh 3.35

X 278124.426, Y 4305857.661, Z 220.000 (3.35 m North)

Measure: X 278128.776, Y 4305854.311, Z 185

Chainage 65.000, Offset −4.350, U 4.350, V 0, R 4.350

Measure: 3 m East + 3 m North of the axis, Z 200

Chainage 80.000, R 4.243, Theta 45°

Measure: on the axis, Z 260

Chainage 130.000 (10.000 beyond end)

Tip

To check a shaft lining, measure the scanned or surveyed points from file (Measure from file) and compare R with the design radius at each chainage. To stake a ring, set out at the required chainage with Offset / Dh on the circle (e.g. Offset = −R·cos θ, Dh = R·sin θ).

2.5.7.2.5. Batch setout, Multi-offset and the chainage range

The default chainage range of Batch Setout and Multi-offset, and the range shown in the status bar, are the 3D range (0 – 130 for the example shaft). Station equations of the horizontal geometry do not apply to 3D chainage and are ignored.

2.5.7.2.6. Drawing tabs

  • Plan — a vertical shaft is a single point in plan, so no station ticks or labels are drawn. On an incline, ticks and labels are placed at the 3D chainage. The live cursor readout stations the cursor from its plan position.

  • Profile — the profile view is drawn in profile chainage (the chainage the vertical profile is defined in); the cursor readout shows the corresponding 3D chainage. On a vertical shaft both are the same.

2.5.7.2.7. Limitations

  • .alm and LandXML both store mode3D and sectionRefAzimuth (radians) and round-trip them. GSI, PSYMO and the other interchange exports write the horizontal and vertical geometry only, and drop the 3D flag.

  • GRD import and the TIN surface work on the horizontal geometry and are not meaningful for a vertical shaft.