Mass Types for Trenches¶
Introduction¶
After retrieving predefined mass types in the SFI model, we can calculate masses and create mass reports. For mass calculation of trenches, the program uses the cross-section method. This is described in more detail in the Cross-Section Method section.
For the mass report in Excel, there are specific columns for masses, mass balance, and accumulated mass balance. The balance factor is only used for the Mass Balance and Accumulated Mass Balance columns. All other masses in the report are fixed masses.
Some quantities are calculated in the longitudinal profile (running meters of trench in given intervals). The mass types for these quantities require that we build a layer for the trench bottom in the longitudinal profile. We cannot use the Gemini Terrain surface generator for this, but must manually create the layer with the Add/Create function in the horizontal list field for layer names. For trench bottom layers, this function asks if we should add an offset value relative to the heights in the cross-sections or the vertical curvature/3D line.
Info
The program contains predefined mass types for both process code and NS3420.
The mass types described below are a starting point and will not necessarily cover all combinations you may encounter. It may therefore be necessary to edit standard mass types and/or create new user-defined mass types as needed.
Predefined Mass Types for Process Code¶
| Id | Process Code | Mass Type | Calculation Type | Balance Factor | Min. Thickness |
|---|---|---|---|---|---|
| 40 | 42.21 | Trench excavation | Volume | ||
| 41 | 42.22 | Trench blasting and excavation | Volume | 1.000 | |
| 42 | Trench rock cutting | Area oblique | 1.400 | ||
| 43 | 42.23 | Trench geotextile | Volume | ||
| 44 | 42.24 | Trench foundation and backfilling | Volume | ||
| 45 | 42.25 | Trench backfilling with local materials | Volume | -1.400 |
Below are sketches illustrating the mass types.
Excavation¶
Excavation, A = Trench bottom road/terrain, B = Rock
Blasting and Excavation¶
Blasting and excavation, A = Trench bottom road/terrain, B = Rock
Geotextile¶
Geotextile, A = Trench bottom road/terrain, B = Rock
Foundation and Backfilling¶
Foundation and backfilling, A = Trench bottom road/terrain, B = Rock
Backfilling with Local Materials¶
Backfilling with local materials, A = Trench bottom road/terrain, B = Rock
Predefined Mass Types for NS3420¶
The program also contains predefined mass types for the NS3420 standard. These are described below.
Mass Types in Longitudinal Profile¶
| Code | Description | Unit | Note |
|---|---|---|---|
| H11.11 | Trench excavation | Length horizontal | One mass type for each depth interval |
| H11.3 | Blasting and excavation of combined trench | Length horizontal | One mass type for each depth interval |
| H11.21 | Trench blasting | Length horizontal | One mass type for each depth interval |
| H14.11 | Foundations of imported materials | Length horizontal | |
| H16.12 | Backfilling above the pipe zone for pipeline | Length horizontal |
H11.11 Trench Excavation¶
Mass types have been created for each depth interval. The mass types assume a soil layer that covers the entire trench bottom layer.
Trench excavation, A = Soil, B = Trench
H11.21 Trench Blasting¶
Mass types have been created for each depth interval. The mass types assume a rock layer that covers the entire trench bottom layer.
Trench blasting, A = Rock, B = Trench
H11.3 Blasting and Excavation of Combined Trench¶
As we can see above, it is easy to calculate trench sections that are either excavation, blasting, or combined excavation and blasting. But how do we handle trench sections that contain multiple variants?
Blasting and excavation of combined trench
In these cases, we currently need to perform some manual operations.
Procedure
- Generate longitudinal profile for the trench section
- Create vertical help lines at the transition between trench variants
- Create three new user-defined trench bottom layers. Name them for example:
- 101: Trench-excavation
- 102: Trench-blasting
- 103: Trench-combined
- Construct the user-defined trench bottom layers by snapping to 1:Trench and intersections between 1:Trench and help lines
- Update standard mass types with new trench bottom layers
Mass Types in Cross-Sections¶
| Code | Description | Unit | Note |
|---|---|---|---|
| F11.01 | Vegetation clearing, complete | Area horizontal | |
| F12.01 | Complete stripping and relocation of topsoil | Area horizontal | |
| H11.12 | Trench excavation | Volume | |
| H11.22 | Trench blasting | Volume | |
| I43.1 | Geotextile as filter in trenches | Area oblique | Alternative solution is that geotextile follows the backfill layer |
| Gross side fill/protective layer | Helper mass, without deduction of pipe volume | ||
| WS pipeline | Helper mass for pipe volume. Calculated for pipes larger than value set in advanced mass type settings. Note that labeling for WS line definition data shows the pipes in the cross-section. | ||
| H15.16 | Side fill/protective layer for pipeline in trench with imported materials | Volume | With possible deductions of pipe volume. Without deduction for pipe volume, the mass equals gross mass. |
| H16.11 | Backfilling above the pipe zone for pipeline | Volume |
Below are sketches illustrating the mass types.
Vegetation Clearing¶
Vegetation clearing, A = Trench bottom road/terrain, B = Rock
Excavation¶
Excavation, A = Trench bottom road/terrain, B = Rock
Blasting¶
Blasting, A = Trench bottom road/terrain, B = Rock
Geotextile¶
Geotextile, A = Trench bottom road/terrain
Side Fill¶
Side fill, A = Trench bottom road/terrain, B = Rock
Backfilling¶
Backfilling, A = Trench bottom road/terrain, B = Rock
Trench Table¶
Many contracts also have an appendix with a dedicated trench table.
The table below shows an example of this.
Example of a trench table
We have created a specific template for contracts that are to be settled according to this type of table. The template contains mass types for all these combinations (a total of 54 mass types) and it is called Grøftetabell-kombinert-grøft.sfi.
Tip
Select Use template... in the dialog for SFI properties to retrieve the mass types in the template.
Examples of mass types in the template:
- H. total 0.5, H. rock 0.0
- H. total 0.5, H. rock 0.5
- H. total 1.0, H. rock 0.0
- H. total 1.0, H. rock 0.5
- etc.
Note
The following requirements must be met for the masses to be calculated correctly. The longitudinal profile must contain a continuous soil layer for the entire section. This is not necessary for the rock layer. In cases where you only have soil for parts of the trench, you must add the rest manually in the longitudinal profile. The solution is to snap the soil layer to the rock layer in these areas.