What is the primary purpose of soil sampling in construction?
A To determine bearing capacity
B To obtain a representative soil sample for analysis
C To measure soil moisture
D To check soil color
Soil sampling is done to collect a representative sample from a specific area. This sample is analyzed to determine the soil’s properties, such as composition, strength, and permeability, which are crucial for construction and design decisions.
What does “effective stress” in soil mechanics refer to?
A Total stress minus pore water pressure
B Total stress
C Shear strength
D Pore water pressure
Effective stress is the stress that influences the soil’s strength and stability. It is calculated by subtracting the pore water pressure from the total stress. Effective stress plays a crucial role in soil’s ability to resist deformation and failure.
Which of the following tests is used to determine the shear strength of soil?
A CBR test
B Triaxial test
C Proctor test
D Triaxial test
The triaxial test is commonly used to determine the shear strength of soils. It measures the soil’s ability to resist shear stress under various loading conditions, providing essential data for understanding soil behavior under applied stresses.
What is the main characteristic of cohesive soils?
A They are easily compacted
B They are permeable
C They can hold together under stress
D They do not retain water
Cohesive soils, like clays, have fine particles that attract each other due to molecular forces, allowing them to hold together under stress. This property makes them more suitable for compacting and supporting structures.
What is the main cause of slope instability?
A Low plasticity
B Excessive water content
C High permeability
D Low shear strength
Excessive water content can lead to slope instability by reducing the cohesion between soil particles and increasing the pore water pressure. This can cause the slope to weaken and potentially result in landslides or soil slippage.
What does soil stabilization generally aim to improve?
A Soil strength and durability
B Soil moisture content
C Soil permeability
D Soil color
Soil stabilization aims to improve the physical properties of soil, especially its strength and durability. Techniques like adding lime, cement, or other stabilizers reduce soil’s susceptibility to environmental factors and enhance its load-bearing capacity.
What is the primary factor that affects bearing capacity of soil?
A Moisture content
B Soil depth
C Soil compaction
D Soil texture
Bearing capacity is the maximum load per unit area that the soil can support. Compaction is crucial in this process as it reduces voids, increasing soil density and, consequently, its capacity to support structures or loads without failure.
What is the typical effect of consolidation on soil?
A Increases water content
B Increases permeability
C Increases soil volume
D Decreases soil volume
Consolidation is the gradual decrease in soil volume due to the expulsion of pore water under a sustained load. This process helps in the settlement of structures and is particularly important for clayey soils, which consolidate slowly over time.
What does seepage analysis primarily measure?
A Water movement through soil
B Soil consolidation
C Soil permeability
D Shear strength
Seepage analysis involves studying the movement of water through soil, particularly in relation to flow under pressure. It is essential for understanding drainage, foundation stability, and erosion control in civil engineering projects.
What is the primary goal of earth pressure theories?
A Calculate soil compaction
B Measure soil strength
C Estimate the pressure exerted by soil on structures
D Determine soil composition
Earth pressure theories, such as Rankine’s and Coulomb’s theories, are used to estimate the pressure exerted by soil on retaining walls or other structures. These pressures are crucial for designing stable structures that can withstand the forces applied by surrounding soil.
What happens to soil shear strength as the water content increases in cohesive soils?
A Shear strength remains the same
B Shear strength decreases
C Shear strength increases
D Shear strength doubles
As water content increases in cohesive soils, the soil particles become lubricated, which reduces friction and cohesion. This leads to a decrease in shear strength, making the soil more susceptible to failure under load.
What is the main cause of soil erosion?
A Excessive moisture content
B High plasticity
C Low compaction
D Water and wind
Water and wind are the primary forces causing soil erosion. They remove the topsoil, which is rich in nutrients and essential for vegetation growth. Erosion can significantly degrade land quality and reduce agricultural productivity.
What does soil permeability indicate?
A Soil’s ability to transmit water
B Soil’s ability to compact
C Soil’s ability to resist water movement
D Soil’s ability to retain moisture
Permeability refers to the ability of soil to allow water to pass through its pores. It varies according to soil type, with sandy soils having high permeability and clayey soils having low permeability, affecting drainage and water retention.
What does the term “capillarity” in soils refer to?
A Soil shrinkage
B Water movement in soil against gravity
C Water evaporation from soil
D Water absorption by soil
Capillarity is the upward movement of water through the small pores of soil against gravity. This phenomenon occurs due to surface tension between water molecules and soil particles, particularly in fine-grained soils like clays and silts.
What is the primary characteristic of a soil with high plasticity?
A It has high permeability
B It is easily compacted
C It can be molded and retains its shape
D It has low moisture content
Soils with high plasticity, such as clays, can be easily molded and retain their shape when wet. This property is critical for construction and engineering purposes, as it influences the soil’s workability and stability in various conditions.