Building on stronger grounds with geotechnical engineering

Building on stronger grounds with geotechnical engineering


With Bentley Systems‘ acquisition of Plaxis, the concept of geotechnical engineering gains more relevance. Keen to explore, we dig deeper through an engaging interaction with Jan-Willem Koutstaal, Managing Director, Plaxis and Raoul Karp, S.E., Vice President, Structural and BrIM Products, Bentley Systems, at YII 2018.

Simply defined

Geotechnical Engineering is the branch of engineering that merges geology and physics to model soil mechanics and rock behavior. It considers the effects of water from rain, rivers or tides on soil as well as other aspects of the physical site in which a AEC project might find itself. It uses principles of soil mechanics and rock mechanics to investigate subsurface conditions and materials, determine the relevant physical/mechanical and chemical properties of these materials, evaluate stability of natural slopes and man-made soil deposits, assess risks posed by site conditions, design earthworks and structure foundations, and monitor site conditions, earthwork and foundation construction.

“At the core of geotechnical engineering lies the engineer who engineers the behavior of the soil. It is necessary to do this since whatever you built or construct will always end up at the surface or sub surface. So a geotechnical engineer does reengineering of what happens underground with the soil,” says Jan.

What’s the need?

Without geotechnical engineering, the risk of a collapse rises. For instance, consider building on an area close to waterways. There is lot of sediment there, so it’s not rock, it’s not sand; just a big heap of sediments. If something is built on that, slowly it will become more and more heavy and the building will eventually sink.

Geotechnical engineers can prevent such a catastrophe by investigating and making calculations about the soil beforehand. Through investigation, they can find out whether there is sand, rock, heap or anything else inside. When you know that, you know which layers can carry the building or the bridge, that’s what a geotechnical engineer does. If we don’t carry out this kind of investigation and analysis, sometimes it would be okay, but in a lot of cases, the buildings will collapse.

With time the good soil to build on is becoming harder and harder to find. There is a lot of reclaimed land, there is a lot of congestion, there is building over previous buildings, all of that make the science of the foundation, the design and the soil, the geotechnical design lot more challenging. So that’s a trend that’s only going to increase as we become more and more urbanized.

What’s the problem with traditional methods of building?

In the early days, even today sometimes, people build on the basis of ‘basement experience’ or what you call the ‘rule of thumb’. So they look at the soil and sand and decide that they can do this. Sometimes they are right, most of the cases they are not. So the next stage after doing basement experience is that they use more conventional methods to calculate. The problem with these methods is that they don’t make use of real data and real knowledge of soil. So they are always knowingly or unknowingly riding too high on safety factors. Most of the older structures, which have been done with conventional methods, could have been build more easily in a cheaper and faster way using geotechnical engineering.

There are many examples to consider. Many a times our failures are attributed to natural events, be it flooding, or earthquake. However, if we had done geotechnical analysis, many of the collapses would have been avoided. For instance, 50 buildings turned over in Kobe earthquake. Agreed the earthquake was big, but had there been geotechnical analysis much of the damage would have been avoided. There are hundreds of such examples. Fundamentally, the point is that every building that uses conventional methods is by definition over-designed, so we are wasting a lot of money by not considering the traditional condition.

What exactly is this concept of ‘over design’?

Many of the traditional buildings are over-designed. They may look impressive, but what has been done there, from geotechnical or structural point of view, could have been achieved with half efforts, so it could have been cheaper and faster. A lot of times the foundation under the smaller buildings is rectangular or square, isolated footing, and the size of the building depends on how much capacity the soil has.

And in the past, we have always used very conservative values for the capacity. And that meant that the building came out to be twice as big as it really had to be. So every footing that many of us have ever designed is probably twice as big as it had to be. There are billions of dollars spent there unnecessarily on ‘over-design’ in the absence of geotechnical analysis.

How the collaboration of Bentley and Plaxis going to help the construction industry?

There are a lot of reasons why this is a good marriage, including the efficiencies of moving data between a geotechnical and a structural engineer. When you look at the direction of the company and the itwin announcement and the value of the itwin, it really is in long term operation of the assets. And fundamental to the operation is going to be ‘change’, and what is the most important piece of information you need in order to make a decision about whether you can make a change, whether you can add a floor, whether you can move some load or something from one area to another, it’s the foundation, and it’s a geotechnical information, it’s the strength of what you are sitting on.

So the collaboration of Bentley and Plaxis, not only does it help in the design efficiency, it adds value to this digital twin that overtime can be used and reused to improve that asset. So there are a number of different ways.

Then we have a great cultural match, we are both a set of engineers, Plaxis is a great name globally. We have a global presence; we have strong structural experience. Now we have a strong geotechnical base. The collaboration is a great marriage of efficiencies and improved performance for our users. There would be lot of benefits.

For instance, if you look at a region in Asia, the winds are getting stronger, and earthquakes and floods are getting stronger. So, it’s all about making things more resilient and this collaboration is a step towards achieving that.

Digital Twins are the talk of the town, especially at Bentley YII 2018

The concept of geotechnical engineering, even after being so good, lacks adoption. Is skilled workforce a constraint?

There is definitely not enough skilled workforce. There are just not enough people educated. One solution could be to make tools such that the limited number of resources can do more.

A big part of Plaxis’ mission is education. With some of the solutions, training is provided, and it’s not the training on the product, it’s training on the science of geotechnical engineering. Plaxis is the defacto standard globally when it comes to geotechnical engineering. So they are able to train and educate the workforce.

“We have technology at Bentley to deliver in-product learning. We just tie it to the product, figure out the right level and help users to help themselves to some extent. However, fundamentally it’s the education that’s required, which will have to be taken from Plaxis,” shares Raoul.

What’s next in the construction industry?

It’s like to be in a candy shop, what to choose, there is so much. Infrastructure is being digitized, so you have a digital copy of what is there out there. With sensor data you get nearly live calculation, and you can analyze whether my building is still strong, because there is new load or whatever. So you get to know things like the ongoing temperature of water. You know the situation, how my building is, how my road is, and that sounds strange for one year, but if you keep on doing that, since your assets need to be there for twenty years or thirty years, it becomes extremely valuable. That’s where the next step is and its starting now, getting these live sensor data and keeping them.

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