Project Inputs
Formula Used
S_base = 2 × R × (1 − overlap)
S_pattern = S_base × F
F ≈ 1.07457 to match square-grid point density.
S_safe = S_pattern ÷ safety, then clamp within [S_min, S_max].
How to Use This Calculator
- Measure the treatment footprint length and width, or enter area only.
- Set influence radius from trial injection data or experience.
- Choose overlap based on continuity and permeability requirements.
- Select a grid pattern, then apply a safety factor.
- Add spacing limits from specifications or constructability constraints.
- Submit to see spacing, offsets, and hole counts above.
Example Data Table
| Length (m) | Width (m) | R (m) | Overlap (%) | Pattern | Safety | Recommended S (m) | Estimated holes |
|---|---|---|---|---|---|---|---|
| 20 | 10 | 1.25 | 20 | Square | 1.10 | 1.818 | 30 |
| 25 | 12 | 1.40 | 25 | Staggered | 1.15 | 1.962 | 39 |
| 15 | 15 | 1.10 | 15 | Square | 1.05 | 1.782 | 64 |
Injection radius selection and validation
Influence radius is the controlling input for spacing. It should come from trial injections, packer pressure logs, take rates, and observed refusal behavior. Where ground conditions vary, use the lower bound radius to avoid untreated zones. The calculator converts the radius to an influence diameter and applies overlap to target continuity between bulbs.
Overlap targets and continuity control
Overlap is a planning tool, not a guarantee. Higher overlap reduces the risk of isolated voids and helps connect treatment columns, but it increases hole count, drilling time, and material use. A practical approach is to start with moderate overlap, then refine based on verification holes, permeability tests, or uplift response. The achieved overlap shown in results highlights how limits and safety factors change the final plan.
Grid pattern choice and constructability
Square grids are simple to set out and survey, making them common in confined work areas. Staggered grids provide improved packing and can reduce directional bias in coverage, especially for circular influence zones. Field constraints may dictate pattern choice, including access, utilities, and sequencing. When using a staggered plan, mark alternating rows clearly to prevent cumulative layout drift.
Edge offsets, boundaries, and service corridors
Treatment boundaries rarely match perfect rectangles. Edge offsets help keep the influence zone inside the footprint and prevent under-treatment near perimeters. Use the offset factor to reserve space for trenches, wall lines, or exclusion zones around sensitive assets. If boundaries are irregular, apply the recommended spacing to a gridded drawing and adjust locally while keeping average density consistent.
Using results for quantities and supervision
The total hole estimate supports drilling schedules, material forecasting, and crew planning. Combine the hole count with expected stage length and average take to estimate grout volume ranges. During execution, compare real-time take rates against assumptions and update spacing limits if ground response diverges. Always document layout revisions, test results, and as-built coordinates for handover and quality records. Coordinate checks help confirm offsets, spacing, and alignment daily.
FAQs
What is influence radius in injection work?
It is the estimated distance grout effectively improves ground from a hole. It depends on soil, grout viscosity, pressure, and staging. Use trials for reliable values.
Why does higher overlap increase hole count?
Overlap reduces spacing between holes so influence zones intersect more. Smaller spacing means more grid points across the same footprint, increasing drilling and injection locations.
When should I use a staggered grid?
Use it when you want more uniform coverage and reduced alignment gaps. It is helpful for circular influence zones, but it needs careful set-out and row control.
How do spacing limits affect the recommendation?
Limits clamp the computed spacing to what is practical or specified. If limits dominate, the achieved overlap may differ from the target, so validate with checks.
What does the edge offset factor do?
It reserves boundary space as a fraction of spacing. This helps keep influence zones inside the treatment area and supports corridors for utilities or exclusions.
Can I use area-only mode for irregular shapes?
Area-only mode assumes a square to estimate sides, so it is a quick approximation. For irregular areas, use measured dimensions and adjust the grid on drawings.