There is an underground powerhouse structure in the Himalayan region. In this structure, rockbolts and steel ribs were installed.
The rockbolts have load holding capacity of 57 tons but due to improper installation and poor rockmass condition, the final load-holding capacity of the rockbolt varies between 30 tons to 57 tons.
The load is increasing on the underground structure and at several locations, rockbolts are failing because the load reached 45 tons.
At the same time, steel rib has a compression capacity of 1.06 MN/m2 but at a few steel ribs, it has reached 1.33 MN/m2.
What are the geotechnical risks involved in such a situation in this underground rockmass structure?
What corrective measures would be necessary to handle such a situation in this underground rockmass structure?
You havent say anything about deformations. If the structure is stable right now and the support elements were overloaded in the past, is a different case then deformations occurs and squezing the support elements. In that case, you might need the reprofilation too.
The most obvious solution is more support, which means more bolts and steel ribs in this case, or something else, like sprayed concrete.
But such problems are difficult and expensive to solve, and the solutions depends of situation, so you dont take this for granted. best regards. J.
Dear Vikalp Kumar Please do recommend my answer if helpful
Choosing the wrong type of rock bolt in an underground structure can lead to failure and compromise the stability and safety of the structure. Corrective measures should be taken promptly to address such issues. Here are some recommended corrective measures:
1. **Site Assessment and Evaluation:**
- Conduct a thorough assessment of the site, including geological conditions, rock type, stress distribution, and other relevant factors.
- Reevaluate the load-bearing capacity and structural requirements to ensure that the selected rock bolts are appropriate for the specific conditions.
2. **Engineering Analysis:**
- Engage geotechnical and structural engineers to perform a detailed analysis of the failure and determine the root causes.
- Assess the load-carrying capacity of the original rock bolts and identify any design flaws or miscalculations.
3. **Selection of Appropriate Rock Bolts:**
- Choose rock bolts that are suitable for the geological and structural conditions of the underground environment.
- Consider factors such as rock type, stress levels, and the required load-bearing capacity when selecting new rock bolts.
4. **Implementation of Monitoring Systems:**
- Install monitoring systems to continuously assess the performance and behavior of the rock bolts.
- Implement instrumentation such as strain gauges, displacement sensors, or other relevant devices to detect any signs of stress or movement.
5. **Reinforcement and Redesign:**
- Reinforce the failed rock bolt locations with additional support or alternative reinforcement methods.
- Redesign the structural support system if necessary, incorporating lessons learned from the failure.
6. **Quality Control and Assurance:**
- Implement stringent quality control measures during the installation of new rock bolts to ensure proper installation and adherence to design specifications.
- Regularly inspect and maintain the rock bolts to identify any potential issues before they escalate.
7. **Training and Education:**
- Provide training to personnel involved in the selection, installation, and monitoring of rock bolts.
- Ensure that the engineering and maintenance teams are aware of best practices and lessons learned from the failure.
8. **Documentation and Reporting:**
- Document the failure incident, including the identified causes and implemented corrective measures.
- Share this information within the organization and with relevant stakeholders to prevent similar mistakes in future projects.
9. **Continuous Monitoring and Feedback:**
- Establish a continuous monitoring and feedback system to track the performance of the structure over time.
- Regularly review the effectiveness of corrective measures and make adjustments as needed.
By taking these corrective measures, it is possible to address the issues caused by the wrong choice of rock bolts and enhance the stability and safety of the underground structure.
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