3D Modelling of Discontinuity Sets using Xlog3D

 



3D Modelling of Discontinuity Sets for Varying Tunnel Orientations

Engineering geologists need to upgrade standard stereographic projections of discontinuities to identify and analyse their influence on the engineering requirements during the design and construction of tunnels.

This is where Xlog3D adds the third dimension.

Consider a hydropower project comprising a 4 km long headrace tunnel with two bends, resulting in three tunnel orientations:

  • Intake section: N070
  • Middle section: N100
  • Surge shaft section: N110

The project area contains three ruling discontinuity sets:

  • J1 (Foliation): N035/65
  • J2: N220/35
  • J3: N110/80

In addition, significant shear zones are known to be aligned along sets J1 and J3.

The stereographic plot of these discontinuity sets given below provides the conventional structural framework.




Using Xlog3D, schematic 3D discontinuity traces are generated for each tunnel orientation. The resulting models illustrate the changing behaviour of the same discontinuity sets as the tunnel direction changes.

1.       For tunnel orientation N100:

2.       For tunnel orientation N070:

 

 

3.       For tunnel orientation N110:

What Does Xlog3D Provide?

For any specified tunnel orientation, Xlog3D computes:

  • Schematic 3D traces of discontinuities within the tunnel profile
  • Angle between discontinuity strike and tunnel direction
  • Apparent dip along the tunnel axis
  • Chainages of discontinuity intersections
  • Crown radius and crown circumference
  • Most importantly, the total span of a discontinuity along the tunnel

The last parameter is particularly valuable because it directly relates to the potential length of rock mass influenced by a discontinuity or a shear zone.

Influence of Tunnel Orientation

The analysis yielded the following spans of discontinuities along the tunnel:

 

Tunnel Direction

J1 (N035/65)

J2 (N220/35)

J3 (N110/80)

N100

23.3 m

28.7 m

2.1 m

N070

8.2 m

15.0 m

6.2 m

N110

47.5 m

42.8 m

1.4 m

The results reveal a striking relationship between tunnel orientation and discontinuity persistence within the excavation.

For the N110 tunnel alignment, sets J1 and J2 produce exceptionally long tunnel spans of approximately 48 m and 43 m, respectively. In contrast, set J3 remains confined to a span of less than 7 m irrespective of tunnel orientation.

Engineering Significance

Since the known shear zones are aligned along discontinuity sets J1 and J3, the implications for tunnelling are immediate.

A persistent shear zone associated with J1 may influence nearly 50 m of tunnel length and could therefore require extensive support and stabilisation measures. Conversely, a shear zone aligned with J3 would affect only a limited tunnel length and would typically demand localised treatment.

Such insights are possible using Xlog3D.

Looking Beyond Visualisation

This example demonstrates that Xlog3D is not merely a tool for plotting discontinuity traces on tunnel surfaces. Rather, it serves as an engineering interpretation platform that helps geologists and designers visualise, quantify, and assess the influence of geological structures for any tunnel orientation.

Comments

  1. Devendra SinghJune 10, 2026 at 12:16 PM

    This tool is truly practical and highly useful for our work. Thank you, Deva Sir.
    You are a great source of inspiration for us.

    ReplyDelete
  2. Sidrah IramJune 15, 2026 at 11:28 AM

    Excellent product by Yogendra Deva Sir for understanding discontinuity traces in tunnels. The interface is simple and provides valuable insights in an easy to understand way.

    ReplyDelete
  3. amuluckyJune 15, 2026 at 9:46 PM

    Good and practical product, but it needs more advanced functionality. Currently, it focuses mainly on planar features. Adding the ability to predict and analyze faults, folds, and other structural features from input structural data would greatly improve its usefulness, especially for professionals working in structurally complex regions such as the Himalayas.

    Additionally, the software appears to have limitations when dealing with curved tunnel alignments, such as those commonly encountered in railway tunnels. For tunnels with significant curvature (e.g., curves extending over 100 m or more), the predictions may become less accurate. Addressing this limitation would enhance the reliability.

    The software would also benefit from comprehensive user guidelines and documentation. Clear instructions should be provided on how to use the tool for different tunnel geometries and conditions, such as outward-inclined tunnels, curved alignments, and kinked sections. Detailed guidance on data input requirements, parameter selection, assumptions, and interpretation of results would help users apply the software correctly and consistently, reducing the risk of errors and improving confidence in the outputs. overall nice approach by Deva sir.

    ReplyDelete
  4. Santosh Kumar PandeyJune 17, 2026 at 5:52 AM

    Very good product for understanding and cross checking the traces of discontinuities and predicting tunneling conditions ahead. Great efforts from Deva Sir..which illustrates inclusion of his vast field knowledge into software skills

    ReplyDelete

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