Ensuring a Subway expansion that last for generations to come.
If you’ve found yourself visiting the Northeast portions of Warsaw, you have likely found extreme congestion and large construction holes around the region.
In the Targowek area, entire intersections are incised by deep trenches: the foundation for the Metro expansion. This area has almost entirely been served by bus routes and rails that have limited routes and capacity. While the expansion is well behind schedule – it was assumed to be done by 2016 – the new development will finally be able to accommodate the recent population growth.
This corner of Warsaw has seen over 20,000 new condo units in the last decade and over 100,000 are expected to be added in the area before 2030. Coinciding with the Metro expansion, the increasing capacity is causing the outskirts of the city to grow tremendously.
There are many questions as to why the Metro expansion is taking so much longer than expected. The reason for the delay is quite simple: the engineers and builders involved want to ensure a structure that will last well into the next century. Using deliberate measures and ensuring that all portions of the construction are “error-free” the first time is a top priority for those managing the project.
I spoke with an on-site engineer named Grzegorz and uncovered a few reasons why the process is being conducted in such a meticulous manner.
“We had some initial problems with the older structures of the original Metro and our supervisors want to ensure that we only have to build this one once” Grzegorz said. He later explained that “the problem is that when it was first built, they did not conduct strong testing since their teams had to use destructive measures to pull test samples”.
Traditionally, the samples would be core-drilled directly from structural walls and foundations and then sent off site for analysis. Since this process took so long, construction would often continue without knowledge of material failures. When test results would come back, areas already completed would either have to be redone, or worse, require frequent maintenance.
Three simple and portable tools have completely changed the testing phase to ensure that pours and structural builds are completed correctly on the first attempt. Even while this may cause for a longer initial build time, it ensures that the Metro won’t have to shut down for maintenance due to poor construction.
The tools being championed by the engineer I spoke with are:
· Ultrasonic Testing Equipment
· Rebound Hammers
· Ground Penetrating Radar
While other testing devises pertaining to electrical and piping installations were mentioned, these three tools were the most regarded to ensure that the building will stay strong for generations.
Ultrasonic Testing Equipment, especially in a portable form, was the tool most lauded over by the team. I’ll admit, it wasn’t the one I was expecting. The team said they are using an ultrasonic tester now on every completed concrete wall that offers any form of structural integrity.
The reason for it?
While taking core samples in the past, they found the most common issue to be bubbles that had formed in the concrete pour. When the concrete hardened, these bubbles would later undermine concrete strength.
Using ultrasonic testing equipment, the team can now precisely pinpoint any potential voids or pockets and fix them individually without needing to take down an entire wall as they did before. Instead of removing a large section of concrete and replacing it, they simply drill into the detected voids and inject them with a crack filler. Fixes made during the initial build of the structure ensure that there won’t be years of erosion and cracking leading to premature failure in the future.
Another tool the team use on every load bearing and foundation slab is the Rebound Hammer. This tool is an industry standard for hardness testing of concrete pours and ensures that the concrete has cured to a proper consistency.
Grzegorz told me that, “while the Rebound Hammer is an absolutely vital tool for ensuring that the concrete has cured properly, it cannot tell us about the voids in a way that Ultrasonic Testing Equipment can. That said, it must be used in structural tests during the initial building and maintenance cycles to ensure the concrete will stay strong over time”.
The Ground Penetrating Radar is another one of team’s favorite. “We have to see what we cannot see to know everything is correct” Grzegorz explains. In a city with the vast history that Warsaw has, you have to be aware of underground intrusions that can hamper or even halt construction completely.
“Our records of buried lines, sewers and natural gas pipes aren’t the most complete but with GPR, we can ensure that we aren’t cutting important infrastructure or encasing it in large concrete pads that make them inaccessible”. This is an important detail since sections of the first Metro line cut and entombed portions of the city’s utilities. Some were so damaged or trapped that they had to be replaced with parallel installations. “No one wants to do the same job twice when once is hard enough” said Grzegorz.
Although the public is anxious for the streets to flow freely once more, they understand the reasons behind the delays. I spoke to a driver named Kasia who was waiting for flagmen to let her pass the construction. “I just want to drive my car without having to take five kilometers of detours to get downtown” she said.
That said, she recognizes that the proper construction will prevent the routine cycle of maintenance that the city’s original Metro line is currently experiencing. “I just want them to get it right” Kasia said.