THEORY EXAMINATION (SEM–VIII) 2016-17 GROUND IMPROVEMENT TECHNIQUES

SECTION – A

Explain the following (Short Answer Type)

Soil stabilization is the process of improving the engineering properties of soil by adding stabilizing materials such as lime, cement, or chemicals. It is used to increase soil strength and reduce compressibility.

Field methods of compaction include rolling, tamping, vibration, and dynamic compaction, which increase soil density and stability.

Vibro compaction is mainly applied to loose granular soils such as sand and gravel to improve their load-bearing capacity.

In-situ densification means improving soil density at the site without removing the soil. It is commonly used in foundation construction.

Factors affecting densification in cohesive soil include moisture content, soil type, compaction effort, and soil plasticity.

Dewatering removes groundwater to improve soil strength. Advantages include increased stability, while disadvantages include possible soil settlement and high cost.

Grouting is the process of injecting fluid material into soil to fill voids and increase strength. It is used in foundation repair and leak control.

Preloading is adopted when soil needs consolidation before construction to reduce future settlement.

Suspension grouts contain solid particles like cement, while solution grouts are chemical solutions that harden after injection.

Geotextiles act as filters by allowing water flow while preventing soil particle movement.

Questions (Section A)

What is soil stabilization?

List field compaction methods.

Define grouting.

What is preloading?

What is the function of geotextiles?

SECTION – B

Attempt any five (Long Answer Type)

Soil-lime stabilization improves soil strength by reducing plasticity and increasing durability. It is widely used in road construction.

Dynamic compaction uses heavy weights dropped from height to densify soil layers deeply.

Vibro-flotation densifies granular soils using vibrating probes, improving load-bearing capacity.

Vertical drains with preloading speed up consolidation by allowing water to escape from soil faster.

Thermal stabilization improves soil strength by heating to remove moisture.

Grouts include cement grout, chemical grout, and bitumen grout. They help improve soil strength and reduce permeability.

Granular piles replace weak soil with compacted granular material to increase load capacity.

Geosynthetics protect soil from contamination and improve stability by acting as filters and separators.

Questions (Section B)

Explain soil-lime stabilization.

What is dynamic compaction?

What is vibro-flotation technique?

What are types of grouts?

What is the role of geosynthetics?

SECTION – C

Attempt any two (Detailed Explanation)

Soil-cement stabilization involves mixing cement with soil to improve strength and reduce permeability. Factors affecting strength include cement content, moisture, and curing conditions.

Terra probe compaction improves deep soil density using vibrating probes that rearrange soil particles.

Soil nailing stabilizes slopes by inserting steel bars into soil and anchoring them for reinforcement.

Geosynthetics are used as separators to prevent mixing of different soil layers and improve stability.

Dewatering techniques for cohesive soils include well points, deep wells, and vacuum dewatering methods.

Questions (Section C)

What is soil-cement stabilization?

Explain soil nailing technique.

What are dewatering methods?