Reinforced Earth India Pvt. Ltd used TerraNail for long-term stability of the slope at Secondary Crusher House and JNT-3 of the Tata Steel plant in Joda, Odisha.
Joda Iron Ore Mines is a Tata Steel Ltd owned property, which is the largest private sector steel company in India.
Tata Steel, in order to expand its mining activities at Joda, engaged Larsen & Toubro Ltd for the construction of its Secondary Crusher House and JNT-3 on a slope of 12m high. Subsequently, it was observed that at a later stage the earlier constructed units were endangered due to severe erosion and failure of slope at different heights. The risk was identified and L&T consulted Reinforced Earth India Pvt. Ltd for an appropriate solution. After detailed analysis of the nature of the slope and its implication, Reinforced Earth India proposed the use of TerraNail for a long-term stability purpose.
Challenges
The Secondary Crusher House and JNT-3 were already constructed on the top of slope. The slope suffered heavy local failure at different locations during the monsoon of 2011. It was decided to adopt the stability techniques proposed by Reinforced Earth India to avoid any further danger to the existing structures.
The months of May to September, being monsoon period in most parts of the country, Reinforced Earth India had to encounter severe weather conditions at every stage of its operations. Because of inclement weather, the safety of the workers was of prime importance. To avoid any untoward and unsafe incidents, all corrective safety measures were taken against any local instability or erosion of the slope.
Initially, the surface preparation was carried out by L&T and subsequently the staging was also done by them. The process of drilling the slope surface to a desired depth for inserting the TerraNail and grouting around the TerraNail for strengthening purpose needs highly skilled expertise for slope stabilisation. Subsequently, the outer surface was shotcreted to provide permanent and stable facing surface. Grouting was done to serve as a prime function of transferring the stress from soil to TerraNail. The length of the nail was 9m & 7m as per design specifications. The design principle was based on the classical theory of ‘Bishop’s Stability’ analysis.
The design was carried out for stabilisation of existing slope using in-situ soil reinforcing nails, which was considered in two parts.
The first part is the external stability. The lateral earth pressure acting on the back of the soil nail structure is derived by using the coulomb’s active earth pressure coefficient, K, a passive earth pressure on the foot of the structure is always ignored when considering any stabilising forces. The nailed portion of the soil is considered to behave as mass gravity structure and is designed to prevent the following external failures from occurring and forward sliding of the structure on the foundation soil.
The second part is the internal stability analysis to check tensile rupture at any point along the length of the reinforcement and loss of frictional bond.
Unique features
- The system adopted for the stabilisation of the slope using TerraNail has greatly reduced the working time and project risk.
- The technology has proved to be a permanent solution to the slope destabilisation problem and also considered as a faster process which is the long-run saves time and money.
- The reinforced earth technology is sustainable and therefore is the ideal solution for such high and unstable slope. This method does not need any excavation during the process.
- The unique TerraNail technology is also an environment friendly since it requires less steel and cement which reduces carbon dioxide emission in the environment substantially.
Advantages
- TerraNail has been proved to be the unique and undisputed solution for soil stabilisation.
- It is the only time saving alternative for slope stabilisation in comparison to the conventional system.
- It requires minimum manpower which not only saves money but motivates to adapt the TerraNail technology in future project.
- TerraNail technology is the ideal solution when the time is of prime concern and quality of work is important.
- The system is highly adaptive in cases where the working space is a constraint.
