Question

A fully saturated soil after a heavy rain in a watershed will undergo with following state in sequence if no further water is added.
• Solid state
• Semi Plastic state
• Liquid state
• Plastic state Choose the correct answer from the options given below:

• A. A, D, B, C
• B. A, C, D, B
• C. B, A, C, D
• D. C, D, B, A

Hint:

Remember the drying sequence of fine-grained soil: \[ \text{Liquid} \rightarrow \text{Plastic} \rightarrow \text{Semi-solid} \rightarrow \text{Solid} \] As water content decreases, soil gradually changes from flowing behavior to rigid behavior.

Answer 1

The Correct Option is D

Concept: The consistency states of fine-grained soil depend mainly upon the amount of water present in the soil mass. As the water content changes, the behavior and engineering properties of soil also change continuously. The four important consistency states of soil are:
• Liquid State: Soil behaves like a viscous liquid and flows easily due to very high water content.
• Plastic State: Soil can be molded into different shapes without cracking because the water content is moderate.
• Semi-plastic State: Soil begins to lose plasticity and starts becoming stiff.
• Solid State: Soil becomes hard and brittle due to very low moisture content. In soil mechanics, when water content gradually decreases after rainfall, soil transitions successively through these consistency states.

Step 1: Understanding the initial condition after heavy rainfall. The question states that the soil is fully saturated after heavy rain. Fully saturated soil contains maximum water in its void spaces. Under such conditions, the soil possesses extremely high moisture content and therefore behaves almost like a flowing mass. Hence, the soil initially exists in the: \[ \boxed{\text{Liquid State}} \] This corresponds to: \[ C \]

Step 2: Understanding what happens when no further water is added. When rainfall stops and no additional water enters the soil:
• Drainage begins,
• Evaporation starts,
• Moisture content gradually decreases. As the water content reduces, the soil progressively changes its consistency condition.

Step 3: Transition from liquid state to plastic state. After losing some water, the soil no longer flows like liquid. Instead, it becomes moldable and deformable without cracking. This stage is called the: \[ \boxed{\text{Plastic State}} \] This corresponds to: \[ D \]

Step 4: Transition from plastic state to semi-plastic state. As drying continues further:
• Soil stiffness increases,
• Plasticity decreases,
• Soil becomes tougher and less deformable. This intermediate stage is known as: \[ \boxed{\text{Semi Plastic State}} \] This corresponds to: \[ B \]

Step 5: Final transition into solid state. After substantial drying:
• Moisture content becomes very low,
• Soil becomes rigid,
• Cracks may develop,
• Soil behaves like a solid body. Thus, the final state becomes: \[ \boxed{\text{Solid State}} \] This corresponds to: \[ A \]

Step 6: Writing the complete sequence. Therefore, the complete sequence followed by the soil during drying is: \[ \boxed{\text{Liquid State} \rightarrow \text{Plastic State} \rightarrow \text{Semi Plastic State} \rightarrow \text{Solid State}} \] or, \[ \boxed{C \rightarrow D \rightarrow B \rightarrow A} \] Hence, the correct option is: \[ \boxed{(D)\ C, D, B, A} \]