Soil stabilization – a proven technology in India

Road construction in India faces the big challenge of having to complete huge projects in the shortest possible construction time. Thousands of new road kilometres are needed and will be built over the next years to expand the network of traffic arteries in the booming economy. This requires fast-paced, reliable and economical construction processes. Soil stabilization meets these requirements. It has become a standard construction method on largescale construction projects around the world. Application examples from Nagpur (NH7) and Angul provide an insight into the standard practice, supplemented by comprehensive background information.

Soil stabilization – dependable technology and high performance.

Soil stabilization – dependable technology and high performance.

India – a booming country: Soil stabilization in Nagpur (NH7)

The black cotton soils predominant in the Nagpur area have a CBR (California Bearing Ratio) value of less than 3% but maximum plasticity and swelling pressure values exceeding 0.65 kg/cm². In view of the highly plastic and compressible nature of the soil, the contractor decided to use locally available fly ash (pond ash) in the stabilizing process. Laboratory testing showed 15% by mass of fly ash to be the optimum quantity to be added for stabilization of this type of soil as it drastically reduced the free swell index from 0.65 kg/cm² to 0.33 kg/cm² while increasing the CBR value to more than 10% at the same time.

Stabilization was performed in three layers. The first and bottommost layer was stabilized at a depth of 200 mm, and the second and third layers were stabilized at a depth of 150 mm each, introducing 15% by mass of fly ash into each layer to increase the CBR value to exceed 10 %. In a first operational step, the soil was dumped on site, levelled with a motor grader and then compacted to a thickness of 200 mm using a vibratory roller. The fly ash was spread on top of the compacted layer in a second step, and the WR 2400 then stabilized the layer to the specified working depth. The required quantities of water were supplied by a water tanker. After completion of the stabilizing process, the layer was pre-compacted in one plain roller pass. Final compaction was effected in four vibratory passes to achieve the required minimum field density of 98% of the maximum dry density (MDD). The process was repeated for the second and third layers at a thickness of 150 mm each.

Special features of the Wirtgen WR 2400

The high-performance WR 2400 stabilizer from Wirtgen has a capacity of 400 m³ per hour and stabilizes up to 8,000 m² per day. These exceptional performance levels are ensured by the machine’s variable mixing chamber as well as the mixing and milling rotor with quick-change toolholder system.

The high-performance WR 2400 stabilizer from Wirtgen has a capacity of 400 m³ per hour and stabilizes up to 8,000 m² per day. These exceptional performance levels are ensured by the machine’s variable mixing chamber as well as the mixing and milling rotor with quick-change toolholder system.

The high-performance WR 2400 stabilizer from Wirtgen has a capacity of 400 m³ per hour and stabilizes up to 8,000 m² per day. These exceptional performance levels are ensured by the machine’s variable mixing chamber as well as the mixing and milling rotor with quick-change toolholder system.

Preliminary investigations produce economical solutions

Binding agents

Wirtgen soil stabilizers, such as the WR 2400, improve or stabilize soil by mixing in binding agents, thus producing high-quality construction material. The most frequently used binding agents include lime, cement and fly ash, as well as special binding agents specifically tailored to the soil to be treated. Introducing lime into the soil, for example, adjusts the optimal water content, which greatly improves the soil’s compactability. Adding cement stabilizes the soil and improves its bearing capacity. Soils treated in this way are eminently suitable for the construction of all types of roads.

Mix designs

Soil samples taken on site are subjected to mix design testing in road laboratories in order to determine the suitability of construction materials and construction material mixes for the intended application. Soil classification determines the type and quantity of binding agents to be used. Compressive strength is determined and documented in a final step.

Facts on the Nagpur (NH7) job site

  • Total area: 600,000 m²
  • Quantity removed: 300,000 m³
  • Completion time: 80 days
  • Milling width: 2.40 m
  • Advance rate: 12 m/min
  • Milling performance: 300 m³/h

High performance, reliability and economy are customer requirements

If site conditions require the addition of water or special liquid binding agents, tanker trucks coupled to the Wirtgen soil stabilizer deliver them to the machine’s injection system via hose connections. The injection systems are fitted with up to 16 spraying nozzles, which can be switched on or off separately to precisely adjust the spraying width to the specified mixing width. In addition, the spraying nozzles are cleaned automatically to ensure permanent operational readiness. The microprocessor-controlled injection system is operated and monitored from the operator’s cabin. Job parameters, such as advance rate, daily production rate and consumption rates, are also indicated and saved.

Tanker trucks supplying water or liquid binding agents can be directly connected to the soil stabilizer. The microprocessor-controlled injection system can be relied on to apply the binding agents in precisely metered quantities.

Tanker trucks supplying water or liquid binding agents can be directly connected to the soil stabilizer. The microprocessor-controlled injection system can be relied on to apply the binding agents in precisely metered quantities.

Facts on the Angul job site

  • Total area: 200,000 m²
  • Quantity removed: 70,000 m³
  • Completion time: 30 days
  • Milling width: 2.40 m
  • Advance rate: 10 m/min
  • Milling performance: 300 m³/h

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