Introduction
Anchors are essential in slope stabilization, landslide mitigation, excavation support, and retaining structures. Fully threaded anchors, cable anchors, and smooth bar anchors are commonly used. Selecting the appropriate anchor depends on ground conditions, load requirements, and installation constraints.
Anchor Types Overview
| Anchor Type | Description |
| Fully Thread Anchor | Continuous threaded steel bar, grouted in borehole; load transferred via threads and grout bond. |
| Cable Anchor | High-strength multi-strand steel cable, grouted; flexible and tensionable after installation. |
| Bar Anchor (Smooth Bar) | Smooth steel rod, grouted in borehole; load transferred through bond along bar surface. |
Load Transfer Mechanisms
| Anchor Type | Load Transfer | Key Feature |
| Fully Thread | Threads + grout + ground adhesion | Uniform stress along length; high bond efficiency |
| Cable | Friction along cable–grout interface | Flexible, staged tensioning possible |
| Bar | Grout–bar adhesion + ground bond | Stress concentrated near anchor head; less efficient in weak soils |
Installation Considerations
| Anchor Type | Installation Characteristics |
| Fully Thread | Requires proper drilling, grouting, centralization; compatible with shotcrete and retaining systems |
| Cable | Flexible alignment; suitable for deep or curved slopes; requires staged tensioning and monitoring |
| Bar | Simple drilling and grouting; less flexible; suitable for shallow competent rock/soil |
Load Capacity and Suitability
| Anchor Type | Performance in Soil | Performance in Rock | Maximum Length |
| Fully Thread | Good | Excellent | Moderate to Long |
| Cable | Good (with proper grouting) | Excellent | Very Long |
| Bar | Limited | Good | Moderate |
Advantages and Limitations
| Anchor Type | Advantages | Limitations |
| Fully Thread | Uniform load transfer; easy tensioning; reliable in heterogeneous ground | Moderate length; requires proper grouting |
| Cable | Very high load capacity; flexible; long anchors possible | Complex installation; requires monitoring |
| Bar | Simple and economical | Stress concentration; limited in weak soils; less bond efficiency |
Typical Applications
- Fully Thread: Steep slopes, shallow to moderate slip surfaces, integration with shotcrete.
- Cable: Deep-seated landslides, tunnel portals, long slip surfaces.
- Bar: Shallow, competent slopes; temporary stabilization; low-cost projects.
Summary Table
| Feature | Fully Thread | Cable | Bar |
| Load Transfer | Mechanical interlock + grout | Friction along strand | Bond along bar surface |
| Stress Distribution | Uniform | Gradual along strand | Concentrated near head |
| Installation Flexibility | Moderate | High | Low |
| Ground Suitability | Soil & rock | Soil & rock | Rock / strong soil |
| Tensioning | Easy | Staged | Limited |
| Cost | Moderate | High | Low |
Conclusion
- Fully threaded anchors: Best for uniform load distribution and moderate slopes; compatible with shotcrete and facing systems.
- Cable anchors: Ideal for deep, inaccessible, or long slip surfaces; high tensile capacity.
- Bar anchors: Simple and economical for shallow, competent ground; limited performance in weak or fractured soils.
Choosing the appropriate anchor type depends on slope geometry, ground conditions, load requirements, and project constraints.
