This tunnel is being constructed for two-track lines which is normally not made on Indian Railways.
- The tunnel lies in the Ratapani wildlife sanctuary area where only daytime working is allowed Rail Vikas Nigam Limited successfully achieved the breakthrough of Tunnel 4 out of the 5 tunnels on the Budni- Barkhera 3rd line Project on 16.03.2022.
- This is a part of the Bina – Bhopal – Itarsi 3rd line, where the construction lies in the ghat section. The Project is being executed by RVNL’s Project Implementation Unit, Bhopal. There are 05 Tunnels, 13 Major Bridges, and 49 Minor Bridges in this ghat section. Out of the five tunnels, three have been completely excavated and breakthrough of the fourth one was achieved on 16.03.2022.
- Tunnel-4 is the fourth tunnel in Barkhera – Budni section located near CHOKA station with a total length of 133.4m and 13.2m excavated dia. The alignment of the tunnel is in the curvature of 2500m. This tunnel is being constructed for two-track lines which is normally not made in Indian Railways.
- Tunnel excavation was started in the month of July-2021 and breakthrough was achieved on 16.03.2022 i.e., completed within 09 months. Both ends met in perfect alignment with an accuracy of 4mm. This tunnel lies in the Ratapani wildlife sanctuary area where only daytime working is allowed.
- The tunnel is excavated in very close vicinity of more than 70 years old existing CHOKA tunnel. Wall to wall distance between two tunnels is approx. 3m which makes the construction of a new tunnel is very difficult due to safety concerns of existing trains running tunnel a part of important North-South corridor.
- After the repair work of the existing tunnel excavation of the new tunnel started. A new methodology for tunneling was designed and was proof checked from the Council of Scientific and Industrial Research (CSIR) Roorkee.
- The tunnel lies in the Ratapani sanctuary area. This alignment was selected as per the direction of the National Board of Wild Life to maintain the course of Gadariya nalla intact, new alignment track should be as close as possible to the existing down rail track to avoid extra land for construction.
- Ratapani Wild Life Reserve is a major governing criterion in selecting the alignment which has the least impact on wildlife and is technically suitable for railway operations and at the same time being constructible with the least wildlife impact. No crossing of Gadariya Nalla was allowed. Hence, alignment kept close to the existing tunnel.
Challenges:
- The downline track is very busy. During the passing of trains vibration amplitude in the existing tunnel increases, therefore, excavation work had to be stopped during trains movement which affected the pace of work.
- Tunnel lies in the ghat section and progress affected badly approx. three months due to heavy monsoon. This area is susceptible to cloud bursts. In monsoon, all roads got washed.
- Blasting is not permitted.
- This tunnel lies in the Ratapani sanctuary area where only daytime working is allowed, which also affected work progress badly. There were several restrictions by the Forest organization.
- Despite the above challenges, the breakthrough is achieved within 09 months, hence it is a major achievement for Rail Vikas Nigam, Project Implementation Unit, Bhopal.
For the safety of the existing tunnel following Safety measures were taken:
- 3D monitoring targets were installed at every 5-meter interval to check the movement in the horizontal, vertical, and longitudinal directions. During excavation, the maximum recorded deformation was only 8mm while the permissible limit was 25mm.
- Crack meters were installed to monitor the width and every crack. No cracks were found alive after epoxy grouting treatment.
- Ground settlement markers (GSM) were also installed at the top of the existing tunnel to monitor the settlement. The total recorded settlement was only 4mm.
- Vibrations during breaking were recorded at every 10m on daily basis and kept below 5mm/sec. For that breaking with two breakers was done in an unsynchronized manner.
- RVNL is committed to targeted completion of the Barkhera-Budni 3rd Line Project, which is a major capacity-addition project on the high-density Bhopal-Itarsi section of the North-South busy rail corridor.
Source: RVNL- Update
