Interface (geology)
In geology and especially in engineering geology, a dividing surface denotes the area of a discontinuity within the mountain range . Separation surfaces therefore interrupt the continuity of the rock body and are an essential feature for its description. It is a collective term for different types of discontinuity surfaces, as shown in the table below. The totality of the interfaces in the mountain structure is called the interface structure . A group of dividing surfaces that are identical in type and orientation is called a group of dividing surfaces .
Types of parting surfaces
| Parting surface type | Discontinuity | Icon 1 | Mark | Emergence |
|---|---|---|---|---|
| Fissures | gap | K | without dislocation | by tectonics or otherwise caused stresses in the rock |
| Interference surfaces | Disorder | S t | with dislocation | through tectonics |
| Layer surfaces | Layering | S s | often parallel, marked by a change of material | by sedimentation |
| Foliage surfaces | Foliation | S f | parallel, close, sometimes with dislocation, crossing of a primary stratification possible | through tectonics |
1 Several joint families / generations of a joint type are distinguished by numerical indices (e.g. K 1 , K 2 etc.)
Properties of parting surfaces
The properties of the dividing surfaces together with the rock properties characterize the rock properties.
distance
The distance between the separating surfaces is measured perpendicular to the separating surface with the same spatial position, i.e. mutually parallel separating surfaces. One also speaks of the true separating surface distances, whereby differently measured separating surface distances - mostly in the horizontal - can be converted into these through angular relationships. The latter is also known as the apparent separating surface distances. The reciprocal of the apparent horizontal separation surface distance is the fracture factor . It is determined by counting the dividing surfaces along a characteristic measuring line of the rock formation and then dividing by the length of this measuring line. All the main groups of interfaces are counted, which is why they are also referred to as the average fracture index, in contrast to the specific fracture index of the respective dividing surfaces (only these are counted along the same measuring section). The sum of all specific fracture rates in turn results in the average fracture rate.
| code | Mean distance in cm tolerance ± 20% |
designation | |
|---|---|---|---|
| Fissure | Foliation / stratification | ||
| A01 | <1 | - | paging rig |
| A05 | 1 - 5 | very fissured | thin-plate |
| A10 | 5 - 10 | strongly fissured | thick-clad |
| A30 | 10-30 | cleft | thin banky |
| A60 | 30-60 | weakly fissured | thick banked |
| A61 | > 60 | compact | moderate |
literature
- Research company for road construction and transport, working group earthworks and foundation engineering : leaflet on rock group description and structural purposes in road construction. Edition 1980.