The Basics of Geotechnical Engineering: An Introduction

The name of the profession offers some hints to its function, but what is the significance of geotechnical engineering? And what does a geotechnical engineer do on a day-to-day basis?

The purpose of this guide is to offer up an overview of geotechnical engineering: what it is, why it's important, where it's employed, and for those investigating a potential career path, how to get into it.

Geotechnical engineering is a branch of civil engineering that focuses on how earth materials like soil, rock and groundwater impact and interact with man-made structures.

Geotechnical engineers analyse a site, then design and construct foundations, slopes, retaining walls, tunnels, levees and embankments that enable the construction of man-made structures like buildings, roads, bridges and dams.

The goal is to ensure that the natural geological materials of a site are capable of supporting any man-made structures built on top.

What exactly does a geotechnical engineer look at when analysing and developing a site? There are a few areas of focus, so let's take a (very basic) look at the discipline's key principles:

Soil and rock characterisation: Understanding the soil mechanics, rock mechanics, physical and chemical behaviours of earth materials through site investigations and lab testing.

Stress and strain analysis: Predicting the settlement, deformation and stability of earth materials by analysing how they respond to external loads.

Bearing capacity: The ability of soil or rock to support loads without shear failure.

Settlement analysis: Predicting and controlling how earth materials settle over time due to factors such as soil compression.

Slope stability: Assessing the risk of landslides and working to prevent them through earthworks and stabilisation measures.

Lateral earth pressure: Evaluating the forces exerted by soil on retaining structures.

Foundation design: Safely and efficiently transferring loads from structures to the ground.

Ground improvement techniques: Enhancing soil properties like load-bearing capacity through methods like compaction, grouting, stabilisation, excavation and geosynthetics.

Seepage and drainage control: Analysing and managing water flow through soil and rock, and designing drainage systems to prevent issues.

Soil-structure interaction: Analysing how ground materials and man-made structures interact, and how that affects load distribution and deformation.

Environmental considerations: Mitigating the potential environmental impacts of a project through soil and groundwater protection, waste containment and site remediation.

Geotechnical engineering is one of the very first steps in any civil engineering project. Without a geotechnical engineer to analyse the geology of a site, a project is put at serious risk from hazards including:

• Landslides and slope stability issues.
• Soil erosion leading to foundations being undermined.
• Flooding, seepage and groundwater control issues.
• Seismic activity leading to structural damage and possible collapses.
• Soil liquefaction from earthquakes (when saturated soil temporarily behaves like a liquid).
• Ground subsidence/sinking.
• Retaining wall failures leading to landslides or collapses.
• Excessive structural settlement reducing the longevity and stability of structures.
• Shortened infrastructure lifespans.
• Negative environmental impacts such water and soil contamination, waste issues and habitat loss.

Geotechnical engineering therefore forms a critical part of any civil project. Without it the project could at best face cost blowouts and severely shortened infrastructure lifespans, and at worst could do active harm to the workers and users of that infrastructure and the surrounding environment.

This is why the use of geotechnical engineers on New Zealand civil projects isn't just a practical necessity, but a regulatory responsibility.

What is an example of geotechnical engineering in the real world? At Eliot Sinclair we have a wealth of case studies that outline exactly how the discipline is used to identify problems and develop solutions, from residential developments to conservation projects to land damage assessments.

But one example that most Kiwis will be familiar with is in the aftermath of the Christchurch earthquakes.

Geotechnical engineers were initially brought in to analyse the ongoing seismic hazards and the effects of liquefaction across the Canterbury area. Once the seismic activity died down, the engineers were then tasked with analysing how soil conditions had changed, and identifying and developing a range of solutions, including:

• Ground improvement techniques like soil compaction and strengthening.
• Foundational improvements like the use of deep pile foundations.
• Seismic resilience measures like base isolation and flexible utility connections.
• Improving slope stability through reinforcement and the use of retaining structures.

Are you considering becoming a geotechnical engineer or engineering geologist? Geotechnical engineering is a rewarding field to work in, and is one of those professions that will always be in demand.

While it is possible to enter the field armed with experience alone, the far more common and efficient route to becoming a geotechnical engineer is to enrol in a Bachelor of Engineering, Bachelor of Geology, ideally followed by a Master in Soil Mechanics or Master in Engineering Geology.

These are programs that are offered by most major universities, including the University of Auckland, University of Canterbury, and Victoria University of Wellington. You'll want to choose a program accredited by Engineering New Zealand (Te Ao Rangahau), the professional body for engineers. While a Bachelor's degree is enough to gain a foothold in the industry, you can also choose to complete a Master's degree.

From there you'll want to gain relevant work experience, whether on work placements or as an intern during your degree, or in a graduate role. You should become a member of Engineering New Zealand, and work towards becoming a Chartered Professional Engineer over the next five years.

Do you have a geotechnical engineering question that isn't answered here? Whether you're looking to work with a professional or become one yourself, at Eliot Sinclair we're more than happy to share our expertise. Get in touch with our team today.