EARTHQUAKE EFFECTS ON INFRASTRUCTURE SYSTEMS

The properties of materials used in infrastructure lines are highly significant. Regardless of the type of pipe, various damages occur in underground pipelines due to external mechanical factors, soil movements, corrosive environments, and improper pipe connections. Long-term characteristics, such as oval deformation under vertical loads, resistance to point loads, and maintaining fluid purity, are also critical. Resistance to seismic movements and heavy/light traffic loads is especially vital. Damage to pipelines can sometimes result in losses far exceeding expectations in terms of goods and services.

Distribution and transmission networks, often referred to as lifelines, are critical systems spread across extensive geographical areas. Calculating the reliability (survival probability) of a lifeline network under earthquake risk is essential to ensure these systems function during and after a damaging earthquake.

The distribution of earthquake damage is particularly notable in certain regions of the country. Fault movements and soil liquefaction are two primary causes of earthquake damage. Post-earthquake water supply becomes significantly challenging, and emergencies, such as fires, cannot be addressed due to water shortages. For instance, in the 1906 San Francisco earthquake, the earthquake damage itself was minimal, but the breakdown of water lines led to greater fire damage. Design, installation, and performance must be tailored to withstand earthquakes. Flexible joint connections can minimize the movement caused by earthquakes and reduce adverse impacts. Both the system and materials must be selected based on their performance under seismic conditions.

Ground movements are the primary issue faced by urban pipelines. Therefore, the chosen material must have the flexibility to absorb these movements. Damage-resistant materials that can bend, flex, and endure impacts are necessary. Each pipe material has its own advantages and disadvantages under seismic conditions.

Factors such as pipe type, diameter, joint types, soil corrosion, and pipe age play significant roles in the potential damage to buried pipeline systems. The material used and the way pipes are connected affect their performance during earthquakes. Broadly, pipelines are categorized as either ductile or brittle.

The most common pipe materials used in water distribution systems to date include:

• Metals: Steel, ductile iron, cast iron

• Plastics: PVC, polyethylene (PE), glass fiber-reinforced polyethylene (CTP)

• Concretes: Reinforced concrete and asbestos cement (AÇB) pipes

In gas distribution systems, steel and PE pipes are commonly used, while sewer and stormwater systems often employ concrete and PE pipes.

Due to its geographical location and geological structure, Türkiye is frequently exposed to earthquakes, lying along active fault lines. Moreover, the rapid urbanization observed in cities has turned them into construction zones. Consequently, artificial ground movements often occur during excavation works, posing sudden localized load and damage risks. Regardless of the

cause, urban infrastructure is the most affected and damaged by ground movements. After an earthquake, damage to urban water supply networks can prevent access to one of the most basic human needs: water.

During earthquakes, two types of ground deformations are encountered:

1. Temporary Ground Deformations (GYD): Dynamic soil response during the passage of seismic waves.
2. Permanent Ground Deformations (KYD): Irreversible displacements in the ground occurring after the earthquake.

The relative magnitudes of GYD and KYD determine which has a dominant impact on the pipeline. GYD results in smaller elongation ratios and deformations in pipelines, while it affects a much larger area than KYD. Therefore, GYD can significantly impact pipelines weakened by corrosion. KYD, on the other hand, occurs more locally but causes extensive damage.

During the 1995 Kobe earthquake, areas with KYD experienced severe damage. Studies revealed that older pipes and joints sustained more damage than newer, more flexible and ductile pipes. Below are images of various damages to pipelines caused by earthquakes.

Environmental Effects of Earthquakes;

• Earthquakes can lead to hazardous material releases from industrial structures, pipeline ruptures, and fires, threatening human life and ecological systems.

• In water distribution networks, if water supply is not immediately cut off via local valves, water leaking from broken pipes and installations can endanger people trapped under debris and weaken structural elements due to water saturation.

• Damage to water supply and sewer systems results in water shortages and increases the risk of epidemics due to the use of unhealthy, contaminated water.

• Contaminated water infiltrating broken water pipelines compromises public health.

• Damaged wastewater collection systems (sewage) can result in the uncontrolled spread of pollutants, leading to health hazards.

• Inadequate resolution of post-earthquake water supply and wastewater disposal issues exacerbates disaster impacts, increasing casualties.

• A designated buffer zone, such as a 1 km-wide green belt, should be established along active fault lines where no construction is permitted.

• Roads, pipelines, and similar structures intersecting fault lines should be designed with flexible transitions capable of withstanding maximum fault displacements using current technologies.

• Brittle pipelines in water supply and wastewater systems should be replaced with flexible ones, especially in active seismic zones.

• Further research is needed on pipe materials, horizontal movement impacts, and appropriate joint designs.

• Wastewater systems, such as the large coastal collectors in Istanbul, must be reassessed for earthquake risks.

• Pump stations and water reservoirs in distribution and wastewater systems should be reinforced, with buried reservoirs preferred over elevated ones.

• A centralized computer control and data acquisition system should be established to quickly identify damaged infrastructure sections.

Precautions During and After an Earthquake;

• Hazardous material pipelines, as well as water, gas, and electricity lines, should automatically shut down under horizontal load conditions. Early warning systems should be implemented.

• Post-earthquake water needs should be estimated, and contingency plans devised.

• Water from damaged networks should not be consumed immediately; pipes should be flushed, and water initially treated with high disinfectant levels should be used only for non-drinking purposes.

The Turkish Society for Infrastructure and Trenchless Technologies is committed to advancing construction methods and infrastructure systems. Through national and international collaboration, the association seeks to provide optimal solutions to manufacturers, users, and researchers alike.