Underground Survey Planning Around Access Windows

Underground survey planning works best when it starts from the mine's cycle, not from the surveyor's diary. On underground development, the crew can usually reach the face only between other activities, and the plan has to make that window count.

This article is the planning procedure. The wider decisions that belong in the appointment are covered in our underground survey brief.

A procedure for underground survey planning

The procedure below separates face work from everything else, so the access window is not spent on tasks that could have been done before it opened.

Step 1: list the work that needs the face

Write down the tasks that can only be done at the active end. On most development, that means marking the next round, measuring the advance and recording the face position. Agree this list with the mine's survey department, because they know which tasks their own procedures require at the face.

Step 2: move everything else outside the window

Computation, data checks, plan updates and the record of the previous visit do not need the face. Nor, usually, does work on stations away from the active end, where the mine permits access at other times. Move all of it before or after the window.

Step 3: prepare the visit before the window opens

The marks for the next round should be computed, and the drawing revision confirmed, before the crew goes underground. A crew that prepares data at the waiting place is using the window for work that belongs in the office.

Step 4: close the visit with a record

Before the crew leaves the level, record what was done, which stations were used and what could not be done in the window. The record is short, but it is what tells the next shift which marks are current. It also shows the mine where the window was too short for the face list, which is the evidence needed to change the window rather than argue about it.

Step 5: review the lists as the cycle changes

The face list and the outside list are not fixed. When the development method, the number of ends or the shift pattern changes, review both. Underground survey planning that was right for one heading can be wrong for three, because the crew now competes with itself for the same windows.

Five things the mine confirms before each visit

Most lost windows trace back to something that was assumed rather than confirmed, so the mine should confirm five items the day before each visit.

A short call against this list the day before is usually enough. Where several crews or contractors share the same ends, a written confirmation per visit works better, because it records what was confirmed and by whom. Good underground survey planning puts the list in the hands of one person at the mine, so the confirmation does not depend on whoever happens to answer the phone.

The crew works under the mine's own entry and re-entry procedures. The Mine Health and Safety Council is a useful starting point for the wider framework those procedures sit in.

What to agree when a window is lost

Windows will sometimes be lost to the cycle, and the time to decide what happens next is before it occurs, not at the face.

Agree the next available window, and who decides whether a round may proceed without fresh marks. Agree how the decision is recorded. On a mine where several contractors share the same ends, agree who has priority when windows clash. These are planning decisions, and they belong in the plan rather than in a conversation on the day.

Where the mine depends on orientation brought down a shaft, plan the gyroscopic observations and shaft survey work around the same windows. Those visits are usually longer, and benefit most from the face list being clear.

Where survey cannot help you

Good underground survey planning protects the window, but some causes of delay sit outside what any survey plan can control.

A plan cannot create access the cycle does not allow. It cannot make a station usable once it has been disturbed, and it cannot replace the mine's own decision on whether a round proceeds. What it can do is make sure the window is ready, used for face work only, and recorded. The record of each visit belongs in the evidence covered by our survey handover checklist, and where results are questioned later, an independent check can test them.