Petra: Building Underground Utility Infrastructure Robotically
What led you to enter the business of utility infrastructure?
For years, I watched my home state of California crumble under the pressure of natural disasters. After running air purifiers 24/7 for months at a time to keep my home’s air breathable in the face of unprecedented wildfires, and watching hurricanes tear through the eastern seaboard, enough was enough. We had to do something. My goal in founding Petra was to reduce the impact of wildfires and storms on lives and property.
With Petra, I founded my second robotics company and created a solution to set up grids below the earth’s surface – keeping the lights on in communities across the country. After initially backing Petra as an investor at Lemnos Labs, Shivani Torres joined me as CTO and co-founder to help Petra build the future of utility infrastructure.
Please elaborate on Petra’s rock boring robotic tunneling innovation - the world’s first non-contact tunneling technology.
Petra developed the first robotics company capable of undergrounding critical utilities through the hardest geologies on earth. Petra’s semi-autonomous non-contact tunneling robot utilizes a non-contact thermal drilling method that minimizes surface disruption while promoting efficient drilling. By leveraging machine vision, Petra’s tunneling robot micro-tunnels through the hardest geologies faster and more reliably than conventional methods and can bore through rocks that are considered too challenging for other tunneling machines.
What are the advantages of Petra’s robotic technology over conventional micro tunneling methods and methods like HDD?
Petra’s semi-autonomous robot can tunnel faster and cheaper than conventional undergrounding methods, including through geologies previously thought to be impenetrable. By contrast, the traditional micro Tunnel Boring Machines (mTBM), the Horizontal Directional Drilling (HDD), and other conventional ‘trenchless’ methods have cutter heads which easily break when drilling through hard rock, and thereby increasing the project cost and complexity.
What is the time and cost incurred in this non-contact thermal drilling method?
Petra is making undergrounding feasible and affordable—and to do that, we have to solve the ‘hard rock’ problem in tunneling first. Traditional drilling methods rely on physical cutterheads and brute force to grind against and break rock. Unfortunately, when drilling in bedrock, these cutterheads break easily and must be replaced frequently, often every 12 inches. As you can imagine, the time and cost involved in replacing cutterheads can really add up—significantly driving up the cost of a project.
Petra’s non-contact thermal method more efficiently pulverizes rock and does not require swapping cutterheads. This means projects can be completed much faster, and with fewer material costs required, as compared to traditional methods.
What are the application areas and strata where this boring technology will work most successfully?
Petra’s new type of tunneling method works for a variety of applications. Our focus to date is boring utility tunnels less than 60” in diameter in geologies that give construction companies nightmares, for example, in hard bedrock.
Right now, we’re boring utility tunnels in the types of bedrock that, until now, were considered un-drillable: like granite, quartzite, and basalt. In the past, when underground utility construction companies used to encounter these types of geologies, they would either abandon the project, reroute the project to avoid the geology, or upsize the micro-tunneling machine to a larger diameter. All of this adds considerable cost to utility pipeline projects.
Oftentimes, the geotechnical baseline reports you get for projects get the geology wrong. That’s because out in the wild, geologies change and the underground environment is hard to analyze. When you have conventional methods that rely on thrust force and mechanical advantage to excavate rock, you better hope that your bore-hole analysis and geotechnical baseline reports are correct! Because if they aren’t, your project could be doomed.
We’ve seen hundreds of millions of dollars wasted because a construction team chooses the tunneling machine based on an incorrect report. At Petra, our non-contact method changes these economics because we take thrust force and mechanical advantage out of the excavation equation. We don’t care how hard or abrasive your rock is; in fact, the harder and more abrasive, the better it is for our non-contact method.
What tests and projects has Petra undertaken successfully?
Petra has successfully tested the following lithologies in the lab: Dolostone, Sandstone, Granite, Diorite, Syenite, Quartz-monzonite, Gabbro, Basalt, Diabase, Gneiss, and Quartzite.
We recently bored a 20-ft demonstration tunnel through the hardest rock on earth, Sioux Quartzite, at 1-inch per minute. This is the type of geology that is so hard, you have to dynamite it to excavate it. When we got the rock tested by the Colorado School of Mines, it had the following characteristics: (i)44,285 PSI; 305.3 mPA (ii) 4.2 Cerchar Abrasivity
In March 2022, Petra will take the robot out to a granite quarry for its second field test. And in April, we will take the robot to a dolostone quarry for its third field test. In fact, we are continually testing and updating our rock penetration rates and the latest information can be found on our website petra.cc.
Do you plan to take this technology to other parts of the world, especially India, where a lot of underground Infra projects like tunneling, pipelines for gas, crude oil, CNG, LPG, water, and sewerage, etc are being constructed?
We anticipate bringing Petra’s unique value to all corners of the globe, making utility undergrounding possible for more communities. Right now, we are conducting R&D, and making progress in the U.S. market.
We are about to announce a major partnership with a multinational construction company that specializes in utility infrastructure, and we have many other ongoing conversations, which we cannot disclose at this point of time.
What do you think will be the next level of advancement in this technology?
Ultimately, we’ll have a robot that can bore a variety of small diameters through all strata—hard rock and soft soils—with a single integrated solution that is both agnostic to rock hardness, can handle transition zones, and will know when it encounters soft geologies and can adjust its cutterhead accordingly. Having a single integrated solution that can go through soft geologies and the >30K PSI geologies has never been done before at the sub-60-inch diameter tunnel size.
It would revolutionize how we construct underground utilities, how we estimate trenchless projects, and how we assess risk on projects. Imagine how great it will be when we have a single solution that can mitigate the risks associated with changing ground conditions!
NBM&CW April 2022
