Preventing Tunnel Construction: Technological, Architectural, and Policy Solutions in Conflict Zones

Introduction

Tunnel construction in conflict zones presents a critical security challenge, particularly in regions where underground passageways are exploited for smuggling, terrorism, and circumventing border controls. These tunnels undermine national security, threaten infrastructure stability, and complicate urban planning efforts, making their detection and prevention a priority for both military and civilian authorities. Nowhere is this issue more pronounced than in Israel, where subterranean networks along the Gaza and Lebanese borders have been used for arms smuggling, surprise attacks, and the holding and slaughtering of hostages.

Case Study: Israel’s Anti-Tunnel Strategies

The Gaza Strip hosts an extensive and complex network of tunnels developed primarily by Hamas and other Palestinian factions. This subterranean infrastructure serves multiple strategic purposes, including military operations, smuggling, and concealment. The earliest tunnels were primarily smuggling tunnels connecting Gaza to Egypt in the early 1980s. These were hand-dug and used for moving consumer goods, fuel, and small arms. Tunnels soon became primarily for the transport of weapons and launching attacks. In 2006, Hamas used tunnels to infiltrate Israel and capture Gilad Shalit, an Israeli soldier, as well as killing two others, which significantly raised Israeli concerns about underground threats. Gilad Shalit was kept as a hostage for more than five years as a result, used as leverage to free over 1,000 people convicted of terror offenses and murder, including the most senior Hamas leadership.

This success led Palestinians to recognize the potential of tunnelling, and they developed extensive military tunnels, some stretching beyond Gaza into Israel and others into Egypt. They also had a significant network within Gaza itself, allowing terrorists to move underground, shielded by the civilian populations above them. This system became known as the Gaza Metro. During 2014’s Operation Protective Edge , the Israeli Defense Forces (IDF) discovered over 100 kilometers of tunnels, with about one-third extending into Israeli territory. These tunnels featured multiple entry and exit points, were reinforced with concrete, and equipped with electricity, ventilation systems and communication lines. The IDF deployed troops into the tunnels to clear them of people, then had engineers inspect and map the tunnels for destruction, either by flooding or high precision strike. Egypt was also concerned during the Sinai insurgency, when ISIS-affiliated groups like Ansar Beit al-Maqdis declared a caliphate in the Sinai Peninsula, smuggling weapons, fighters, and supplies through tunnels from Gaza.

Egypt launched a decisive response, pumping seawater and sewage into tunnel networks to collapse them and make reconstruction difficult, and neutralize all those inside them. The Egyptian military razed entire neighborhoods in Rafah, a Gazan city near the border with Egypt, to create a buffer zone and eliminate tunnel entrances. By 2015, Egypt had destroyed hundreds of tunnels, significantly reducing the flow of arms and fighters between Gaza and Sinai. This did not prevent rebuilding. Hamas began to reinforce the tunnels with concrete and advanced materials to make them more durable and difficult to detect. Concrete was porous, easing lateral pressure, and they installed draining systems to reduce the efficacy of future flooding attempts.

Within three years, Gaza had expanded the tunnel network by hundreds of kilometers, and the subterranean complex began to include command centers and heavy weaponry storage. These tunnels were more complex, reaching depths of more than 50 meters underground, requiring different weaponry to penetrate. Gaza had also adapted to the detection success of the Israeli government, employing a branching design in some sections of the tunnels, making it harder for detection systems to identify the full extent of the network. They hid entrances within civilian homes, hospitals and schools, to create operational and moral dilemmas in targeting decisions, used blast doors to protect tunnel segments, and reduced the size of each tunnel in favor of a greater quantity to increase the precision of underground travel and increase Israel’s costs if they sought to destroy them. The tunnels became a critical part of military doctrine in Gaza, spearheaded by Ahmed Jabari and Mohammed Deif, and cost an estimated $1 billion.

These innovations would prove devastating to Israel. On October 7th 2023, fighters emerged from the tunnels in waves, able to emerge near the border fence and infiltrate Israel. The ability to move fighters and weapons quickly through the tunnels without being detected by Israeli air surveillance gave Hamas a significant advantage. They then returned to Gaza with 251 people, a significant portion of whom were held in the tunnels themselves. Israel’s response to this attack featured extensive tunnel warfare.

By 2024, Israeli security officials conceded that they had underestimated the scale of Gaza’s tunnels.  The Israelis discovered more than 1,000 entrances out of an estimated 5,000. What’s more, they discovered 500 kilometers of tunneling (see Figure 1). Gazan fighters shifted to using the tunnels to fight an insurgency, booby-trapping tunnels or using those undetected as a base to ambush soldiers at hidden entrances.

Figure One: Map of Known, Publicly Released Tunnels in Gaza as of 2024

Israel was not unprepared to meet these challenges. Prior to October 7th, the Israelis had invested in a 65 kilometer underground barrier to deal with the threat of cross-border tunnels along the border with Gaza, which effectively limited direct incursion into Israel. This was ultimately what forced participants on October 7th to enter via the security fence. Seismic sensors were placed along the border to monitor ground movements, while cyber techniques were used offensively to disable electronic equipment used to monitor tunnel construction and jam signals used in tunnel operations.

The IDF is the only military in the world with a unit dedicated to underground warfare (Yahalom) and has special training for military dogs to operate effectively in subterranean space. This includes a complete suite of equipment to operate underground safely and successfully. The task, however, was huge.

The IDF began to train soldiers in all units in shaft identification, site securing, and initial investigations. This eased the pressure on Yahalom, who were then deployed with fewer false positives, reducing the wait time to enter and clear tunnels. This allowed Yahalom to develop a typology of tunnels, and recognize that the tunnels existed in a system of systems.

Each Hamas company—and those of other groups—operated its own tunnel networks, which shaped how fighters moved and conducted combat operations. Some tunnels were tactical, such as small-unit tunnels that ran from building to building giving insurgents the ability to hold specific terrain. Some were more operational, connecting different battalions to each other—like the mile-long tunnels running underneath the river basin of central Gaza to connect the region’s northern and southern portions. This allowed for predictive analysis of tunnels prior to entering, and discovery of tunnels that would previously have been missed. Eventually, sufficient knowledge was gained of the tunnels, including their defenses, that the IDF were able to enter tunnels covertly. This allowed for simultaneous ground and subterranean operations, leaving nowhere for insurgents to escape.

Israel then turned to the challenge of destroying tunnels. They determined a prioritization, given the resource intensity of war, and ranked tunnels based on strategic importance to the enemy. Tunnels which crossed the Egyptian border and allowed for weapons supplies, tunnels which connected different areas of Gaza and facilitated freedom of movement, and command and control tunnels are prioritized for destruction. Tactical tunnels between local buildings are not, and may never be, destroyed at all given the resources required and the potential to undermine the foundations of neighborhoods on top of them. Despite this prioritization system, destruction is resource intensive. The tunnel network size means that concrete fill is not a plausible solution to destroy them. There is simply not enough concrete. There are also not enough explosives. Where explosives have been used, the IDF has prioritized using explosives seized in Gaza, often within the tunnel itself, and placing them every 200m before detonation.

Architectural Solutions

Architecture has much to offer in the way of providing effective solutions to terror tunnelling, and these solutions can be considered under the categories of (1) Prevention, (2) Detection, and (3) Destruction.

Prevention

The ideal situation for most states is to prevent tunnels being dug altogether. Urban planning measures can play a crucial role in reducing tunnel construction, particularly in border areas or conflict zones. Requiring deeper foundations of up to 30 meters for new developments near sensitive areas or conflict zones can effectively hinder tunneling efforts, as constructing tunnels beneath structures with deep, reinforced foundations becomes far more challenging. Tunnels would need to be dug deeper or at more complex angles to avoid these foundations, which increases the difficulty of construction and the likelihood of detection. Deeper foundations are typically designed to withstand substantial vertical and horizontal pressures, making it harder for tunnelers to breach them without triggering significant structural failures, which would compromise the tunnel’s stability and integrity. Any tunnel that could surpass these foundations would be extremely costly and challenging to design for most non-state actors.

Incorporating bio-based systems into building designs could offer an innovative, sustainable method for deterring tunneling activities. By utilizing deep-rooted plants, such as trees or fast-growing grasses, around buildings, these natural structures can create an impenetrable barrier beneath foundations. Through strategic planting and minimal maintenance, these living root structures could provide an evolving and adaptable barrier against tunneling, blending security with environmental benefits. Buildings could be designed to employ a hybrid approach that combines reinforced structural elements with deep-rooted plants or trees. Initially, the building would rely on conventional materials, such as reinforced concrete pilings or steel beams, to support its weight. Over time, the roots, encouraged by growth stimulants and integrated with geotechnical supports like mesh or bio-concrete, would extend deep into the ground, gradually contributing to the load-bearing capacity. Root systems, particularly from trees like oak, mangrove, or certain types of bamboo, have the ability to grow deep into the earth, creating an expansive web that increases soil stability and strengthens the ground beneath the building. This hybrid system would create a complex, interwoven barrier that makes tunneling beneath the structure increasingly difficult, offering a sustainable, bio-engineered solution to prevent tunnel construction in sensitive areas.

Another soil-based solution to prevent tunnelling is to inject non-lethal chemical agents into the soil along key border areas that can effectively disrupt tunneling by destabilizing the ground, creating physical barriers that make tunnel construction difficult or dangerous. Chemicals such as sodium silicate, polymer gel solutions, or hydrophobic agents could be injected into the soil in controlled quantities. Sodium silicate, for example, reacts with the soil to form a hardened gel, making the earth more rigid and difficult to dig through. Polymer gel solutions can fill voids in the soil, preventing tunnelers from progressing by creating a viscous barrier. Hydrophobic agents would make the soil resistant to water, complicating tunneling efforts and destabilizing tunnels with moisture infiltration even at relatively low levels. These chemicals could be injected at strategic intervals to form a continuous barrier, with the amount of chemical tailored to the size and depth of the targeted tunneling areas, requiring a few hundred liters per square kilometer for effective coverage. These agents would have to be reapplied roughly every six months, requiring access to the area where tunnelling is a concern, but these chemicals are specifically suggested because hardy crops can continue to be grown without significant harm.

Finally, in scenarios where there is complete construction control at the foundation level throughout an area, chemically treated subterranean netting or mesh structures could be installed at the depth tunnels would pass through. As tunneling equipment begins digging through the soil, it would encounter the mesh, which could be designed to either entangle the machinery or obstruct the tunnel itself. The netting could be triggered by seismic sensors or vibration detectors that monitor ground movement. Once tunneling activity is detected, the polymerizing agent on the mesh would harden and form a solid, rigid barrier within seconds. The mesh would also be challenging for machinery to penetrate, as it would encounter a dense, obstructive network of interwoven fibers that are difficult to cut through, further slowing progress and making the operation more costly and time-consuming. This combination of chemical hardening and mechanical entanglement would dramatically increase the difficulty of tunnel construction, forcing operators to either abandon the project or face a considerable increase in the cost and time required to complete their work.

Detection

While prevention is ideal, it’s not always feasible or infallible. Detection plays a vital role because it allows authorities to identify tunnels that manage to bypass prevention efforts, ensuring swift response and mitigation at an early stage. Building on existing seismic and acoustic detection methods, we can incorporate machine learning (ML) systems to enhance the prediction of tunnel construction. Yahalom were able to increasingly predict tunnel extensions due to the networked design because tunnels are designed by people, and people behave predictably. As more data is gathered, algorithms would become more adept at distinguishing between natural seismic events and the unique signatures of tunnel construction. This predictive capability allows for early identification of tunnel construction activities, even before the tunnel is fully completed, enabling authorities to target potential tunnel sites for interception or mitigation.

The underground nature of tunneling makes direct observation difficult. However, buildings can be designed as passive indicators by incorporating strategically weakened components into their foundations. These sections would collapse if the underlying soil is disturbed—yet remain safe for regular use. Weakening methods could include selectively reducing polymer fibers, glass fibers, or steel rebar, or introducing intentionally thin areas, voids, or pre-cut lines near foundation columns. Concrete panels might include grooves or notches that act as stress concentrators. When tunneling machinery creates vibrations and pressure, these weak points would absorb the force, causing localized collapse and visibly disrupting the structure above—making it nearly impossible for tunneling to proceed undetected.

Destruction

In the case study, tunnel destruction stands out as a critical challenge for the Israeli government. Effective solutions must be low-cost and plentiful, easily transportable and rapidly deployable. One plentiful substance is fungi, or mold spores. Deploying aggressive fungal spores into the tunnel environment, where their natural growth in dark, damp conditions could be harnessed to undermine the tunnel’s structural integrity. A fungi such as Penicillium chrysogenum would be an ideal candidate because of their rapid growth rates and their ability to secrete enzymes and organic acids that break down organic materials, adhesives, and even some mineral components found in tunnel linings and concrete. These spores can be introduced into the tunnel via aerosol dispersal systems or liquid injection ports, ensuring that they reach every crevice of the structure. Once established, the fungi germinate and proliferate, colonizing surfaces and progressively degrading the support materials. As the fungal colony expands, it weakens the tunnel walls and support structures until they eventually collapse. Moreover, the persistent presence of these fungi creates an inhospitable environment for future tunneling activities by continuously degrading new structural reinforcements and preventing the establishment of stable excavation conditions. For reference, a state with existing industrial biotechnology infrastructure could produce sufficient spores to deploy across 500 kilometer of tunnels within weeks, and it is possible to freeze-dry the spores for stability and ease of transport to ease military operations.

An alternative to this, that doesn’t require ongoing detection methods, would be the use of bioengineered microbes to create an autonomous, self-propagating system that destroys tunnels. Produced using industrial fermentation processes, they can be optimized to secrete powerful enzymes that break down concrete, steel reinforcements, adhesives, and other structural materials found in tunnel construction. This is achieved by selecting a resilient host organism, and modifying the DNA of the selected microbe to secrete the appropriate enzymes for the tunnel construction materials in the target area. By using inducible promoters like intelligent genetic circuits, the organisms can sense environmental cues—such as pH or the presence of specific tunnel materials—and ramp up enzyme production as needed. Once tested, these microbes can then be produced on a huge scale, in fermentation tanks, and injected into the soil. This self-sustaining, adaptive system not only rapidly compromises tunnel integrity but also prevents future tunneling by maintaining an inhospitable environment for structural stabilization. The fermentation process for microbial production is already widely used in industries like pharmaceuticals, food production, and biofuels, so this innovation would have low operational costs.

Conclusion

Architects and experts in warfare must work together to confront the evolving threat of subterranean conflict. Tunnel warfare exploits the blind spots between disciplines: engineers focus on buildings, strategists on battlefields. But tunnels collapse both. The future of counter-tunnel efforts lies not just in better materials or smarter sensors, but in bridging these fields—merging spatial design with military strategy. We must never forget that the struggle against tunnels is marked by profound human tragedy. The children slaughtered in the tunnels serve as a stark and devastating reminder of what is at stake. The pursuit of more effective tunnel prevention is not just a matter of security infrastructure—it is a moral imperative to ensure that subterranean warfare is no longer a tool of terror.

The post Preventing Tunnel Construction: Technological, Architectural, and Policy Solutions in Conflict Zones appeared first on Small Wars Journal by Arizona State University.