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The Hoa Binh Group, chaired by Nguyen Huu Duong, has unveiled a 70-meter test model of an underground metro tunnel and an autonomous train gilded in gold, valued at VND 9 billion, in Hanoi’s Hoang Mai District. The demonstration is intended to support a proposal to build the entire Van Cao–Hoa Lac metro line—nearly 40 km—using open-cut tunneling, while maximizing above-ground space over the bored tunnel and two large depots for a low-cost retail center and social housing (NOXH).
Hoa Binh says the model is designed to generate counterparty revenue through the sale or lease of apartments and commercial space, helping offset construction costs, reduce pressure on the city’s debt, and create a stable resident base by locating housing for primary public-transport users near station areas. The approach also aims to provide affordable housing connected to the city center to help spread population outward.
Despite the potential economic benefits, the company faces several technical issues that it must assess carefully.
Traffic disruption from open-cut construction. The shallow open-cut method and prefabricated panel assembly may require closing all street axes, raising the risk of prolonged traffic paralysis.
Structural load transfer and settlement risk. The proposed tunnel is about 8 meters deep. Hoa Binh’s panelized tunnel structure, designed for high-rise loads, may not be able to sustain vertical loads from adjacent towers if those loads are transmitted directly to the tunnel crown. This could lead to differential settlement, cracks, and deformation. The company’s suggested solutions include using a pile system entirely outside the tunnel perimeter and transferring loads through beams or a large steel framework spanning the tunnel crown to push loads to the sides. Implementing this would require extremely precise geotechnical engineering and rigorous location surveys.
Noise and vibration control. A major bottleneck in the model is noise and vibration. When trains run, friction between steel wheels and rails in a shallow tunnel generates vibration waves. While these vibrations may not harm the concrete shell, they could be amplified when transmitted through piles to walls and floors, creating loud surfaces. Hoa Binh’s mitigation approach includes multi-layer natural rubber bearings or steel-spring systems with dampers under footings, and designing rails inside the tunnel as floating slabs on rubber cushions.
Cost trade-offs versus NOXH affordability. Advanced vibration-control and foundation-transfer systems are described as extremely expensive. If such specialized components are included, structural investment costs could rise sharply, eroding NOXH’s price advantage. If costs are cut to maintain low prices, the company would need to address concerns about residents’ living quality and long-term structural safety.
Long-term dynamic effects and health. The proposal also raises questions about long-term dynamic effects on human health. With metro trains operating at 80–120 km/h, impact forces can excite ground waves that propagate to above-ground neighborhoods. Living spaces directly above a rail corridor and high-speed transport could become persistent low-frequency noise hotspots, and micro-vibrations could affect structural integrity over time.
Emergency response and safety. Placing a densely populated residential area on top of a high-speed transport corridor also introduces catastrophic-risk concerns. While Vietnamese standards require strict isolation and emergency egress, the proposal could face unpredictable rescue challenges.
Internationally, building civil works directly above shallow train tunnels is not new, particularly in mega-cities facing land constraints since the 1960s. However, the experience suggests that architectural solutions above tunnel crowns typically come with substantial technical costs and strict control. The content notes that no country has constructed NOXH directly on top of a shallow metro tunnel; projects above tunnel crowns are generally office towers or luxury residential towers, such as the 270 Park Avenue tower in New York.
Examples cited include:
These cases are presented as evidence that technical complexity and cost are high, which may undermine affordability and safety objectives.
Compared with Hoa Binh’s proposal, the content describes NOXH built in this manner as facing a potential economic dilemma.
Hoa Binh is therefore expected to study long-term dynamic effects on health and ensure emergency planning accounts for evacuation under potential incidents. While Vietnamese standards require strict isolation and exit routes, the proposal could still present unpredictable rescue challenges.
The content concludes that although the concept aligns with a circular economy approach and local technology independence, safe and feasible implementation would require rigorous scientific substantiation.
Source: MarketTimes (original article)
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