A geotechnical report is a critical step in a project but doesn’t get much of the limelight. However, get it wrong and you’re at risk of a house or development that sinks, slides or cracks wide open.
We asked our resident ‘rockman’, engineering geologist Joe Hepper, to give us an insight into how he covers this critical step for building designers, architects, homeowners and builders to confidently move forward to the design and construction phases.
What is a geotechnical report?
Whilst most people generally understand structural engineering, geotechnical engineering is less well-known. Geotechnical is the analysis of the ground and site conditions where any building will be situated, otherwise known as a site investigation or soil testing. In Tasmania, that means determining the reactivity of clay soil that will affect material and design choices, along with conditions above ground that may impact design possibilities.
Joe says, “My job is to look at the ground before anything is built – in fact even designed. When you’ve found a site, the next step is finding out what is possible for the type of footings, what constraints exist and possible strategies for any issues that arise from the soil and site testing. This gives you cost implications at the start to plan out your project, understanding the realities of your site.”
How do you arrange a geotechnical report?
Arranging a geotechnical report for the site can happen in a number of ways. If you’re the landowner, you can go directly to a geotechnical service such as HED’s engineering team. We’ll work directly with you on your site to help navigate the conditions and costs early in your planning.
We understand that architects and building designers need trusted experts to provide the geotechnical parameters for design. We provide the report you need with the pertinent information succinctly prepared to keep your client’s project moving.
What is the geotechnical report process?
If the land has been earmarked or purchased, then the geotechnical process can begin. Allowing 2-3 weeks for the process is a reasonable timeframe to conduct the investigations and deliver the report.
Each project begins as a desktop study where we look at aerial data, land information, site topography or overlays that are applicable.
At HED Consulting, Joe follows the process from start to finish for a comprehensive understanding of the site and insights from the combination of field and laboratory data. Getting out of the office, Joe says,
“I like to head out to the site once the preliminary desktop study is done and perform a thorough inspection. There’s so much to notice on and above ground, more than what is simply captured through samples. I also like to ensure the boreholes and test pits for the soil samples are not just done sporadically across the site but located where the building will actually be. Getting as accurate a picture as possible is important.”
Joe Hepper, Engineering Geologist
With samples and data captured, the soil may be sent to a laboratory for analysis to ascertain its reactivity and give it the classification required based on its shrink and swell data. When this data comes back to the office, the final geotechnical report is prepared. This brings together Joe’s experience and knowledge for interpretations and recommendations, giving engineers and designers the information they need to create the foundations and building design.
Breaking ground in Tasmania
In Tasmania, we predominantly have two types of soil – clay and sand and it’s the reactivity of this clay that determines its classification along with the depth to bedrock or water table. With Tasmania needing more housing, it’s pushing development into land that is perhaps not as favourable for building and therefore needs more in-depth analysis.
Joe notes, “We have different bedrocks that impact how we build. If it’s sandstone, then that’s quite easy to manage. However, if it’s hard rock such as Jurassic dolerite, then excavation can prove expensive with rock breaking required. We need to know at what depth this base is. For soils with low-bearing capacity, foundations can easily move so getting footings into a solid base is important.”
What is included in the geotechnical report
Whilst reporting varies from different services, at HED Consulting, we focus on providing the information succinctly with the essentials:
- Client information
- Site location
- Overlays
- Site visit summary
- Soil profile
- Site stability
- Classification
- Recommendations
- Wind classification
- Borehole logs
- Site plan
- Site Photos
- Form 55
The engineer, client and surveyor should all have copies to take this information into the next project phase.
As the lead engineering geologist, Joe does the site investigation, boreholes, reporting and liaising with the engineers and designers within the HED team. Importantly, it’s not simply the data and the report that holds value but his expert interpretation as it relates to each project.
With the designers and engineers by his side, Joe says, “Once I’ve classified a site, I can liaise directly with them to find workable solutions for footings that will ensure a stable foundation base and also help to keep costs down for clients, which is particularly pertinent right now. No one wants to spend more money on foundations and forego some much-desired design choices.”
This is a clear advantage of having the pre-construction engineers, engineering geologists and building designers in the same office. Each has the full project knowledge to get to outcomes quickly without missing important input, delaying timelines or creating budget surprises.
It’s about finding a working team doing what is best for every client. Where it’s more collaborative, requiring fewer steps and people to move essential information between them wherever possible.
That is what every client wants – an efficient, cost-sensitive and stable base that gives their creative vision a path out of the ground to become a reality.
Contact Joe Hepper at in**@****************om.au to discuss geotechnical reporting, soil tests and site investigations for your projects.
