Geotechnical and Foundation Engineering Flashcards

What is the primary purpose of a soil compaction test in geotechnical engineering?

Answer: Ensure proper density to support structural loads.

A soil compaction test is crucial in geotechnical engineering to determine the optimal moisture content and maximum dry density achievable for a given soil. Achieving proper compaction increases the soil's shear strength, reduces settlement, and improves its ability to support the weight of structures built upon it. This prevents future structural instability and damage by creating a stable foundation.

Which foundation type is best suited for areas with weak surface soil but strong deeper layers?

Answer: Pile foundation

Pile foundations are best suited for sites with weak surface soil layers overlying stronger, deeper strata. Piles are long, slender elements driven or drilled into the ground to transfer structural loads through the weak soil down to the more competent bearing layers. This bypasses the unsuitable shallow soil, providing stable and reliable support for the structure.

What is the main factor influencing soil bearing capacity?

Answer: Soil type

Soil type is the main factor influencing soil bearing capacity because different soil compositions have varying strengths and compressibilities. Cohesive soils like clay behave differently from granular soils like sand, affecting how much load they can safely support before shear failure or excessive settlement occurs. Engineers must analyze the specific soil type to determine appropriate foundation designs and ensure structural stability.

What is the primary function of a retaining wall in geotechnical engineering?

Answer: Prevent soil movement and erosion.

The primary function of a retaining wall is to hold back soil or rock mass, preventing lateral movement and erosion on slopes or at changes in ground elevation. These structures are designed to resist the lateral pressure exerted by the retained earth, creating stable, level areas for construction or landscaping. They are essential for managing grade changes and ensuring the stability of adjacent structures and land.

Which geotechnical investigation method is commonly used to determine subsurface soil conditions?

Answer: Borehole drilling

Borehole drilling is a common geotechnical investigation method used to obtain detailed information about subsurface soil and rock conditions. It involves drilling a hole into the ground, allowing engineers to collect soil samples at various depths and perform in-situ tests. This provides critical data on soil stratification, strength, and groundwater levels, which is essential for informed foundation design and construction planning.

Why is soil permeability an important factor in foundation engineering?

Answer: Influences drainage and stability of structures.

Soil permeability is crucial in foundation engineering because it dictates how easily water can flow through the soil. High permeability can lead to rapid drainage, potentially causing erosion or loss of fine particles, while low permeability can result in poor drainage, leading to water accumulation and increased hydrostatic pressure. Both extremes can significantly impact the stability and performance of foundations, making proper assessment vital.