Geotechnics

Introduction

Geotechnics encompasses the application of scientific methods and engineering principles to the acquisition, interpretation, and use of knowledge about the Earth’s surface and subsurface.
This field is vital to many aspects of civil engineering, environmental engineering, petroleum engineering, and mining engineering.
Geotechnics can help in understanding and mitigating geohazards such as landslides, sinkholes, and ground subsidence.

Soil Properties

Soil is a blend of minerals, organic matter, gases, liquids, and countless organisms. Its properties determine its texture, structure, and porosity.
The type and arrangement of soil particles (grain size) play a role in its permeability and fluid transportation.
Differentiation is made between coarse-grained soil (sand and gravel) and fine-grained soil (silt and clay).
Understanding these properties helps in predicting how the soil will behave under different circumstances, and this behaviour is critical during construction and excavation activities.

Site Investigation

A thorough geotechnical site investigation is necessary before starting any construction. It includes soil exploration, drilling, sampling, testing, and profiling.
Soil profiles give valuable information about the types of soil layers present and their sequence.
Knowledge about the groundwater level is also necessary as it significantly impacts soil stability.
The data acquired during site investigation helps engineers design safe and effective structures.

Soil Mechanics

Soil mechanics involves understanding and predicting how soils will react under different types of stresses.
Two key parameters considered in soil mechanics are shear strength and compressibility.
Shear strength is a measure of soil’s ability to resist structural failure along internal surfaces, whereas compressibility describes the decrease in volume a soil goes through when under stress.
These parameters are essential when considering load-bearing capabilities, foundation design, slope stability, and retaining wall design.

Foundation Design

Geotechnics plays a significant role in foundation design by evaluating soil properties and determining soil’s ability to bear loads.
Different foundation types (shallow versus deep foundations) might be employed based on the soil conditions and expected loads.
This understanding is crucial to prevent failures, structural damage, or even complete collapse of buildings.

Mitigation of Geohazards

Geotechnical knowledge allows engineers to identify and predict geohazards like subsidence, slope failure, and soil liquefaction.
Assessing ground conditions can lead to suggestions for suitable mitigation measures. These can encompass ground improvement techniques such as compaction, grouting, or the use of geosynthetics.
Soil stabilisation and reinforcement techniques may also be implemented to enhance soil strength and decrease its deformability.
In the case of slope instability, corrective actions may include building retaining walls, shotcrete, ground anchors, or slope draining.

Geotechnical Monitoring

Regular monitoring of site conditions, particularly during and after construction, is key to ensure safety and stability.
Monitoring techniques may include tensiometers, piezometers, inclinometers, and extensometers.
The recorded data can lead to early detection of developing hazards, enabling timely intervention and risk reduction.