Abstract: Plastic pipes are widely used in municipal engineering due to their numerous advantages, including high flexibility, excellent hydraulic performance, ease of installation, and strong corrosion resistance. Their application significantly enhances the quality and safety of municipal projects. Currently, various types of plastic pipes, such as PVC-U, HDPE, and PE pipes, are employed in municipal construction. This article analyzes the advantages of plastic pipes in municipal engineering and explores common connection methods, aiming to provide a reference for their broader application in the field.

In recent years, the scale of municipal engineering projects in China has continued to expand, with government investment increasing year by year and construction technology steadily improving. As a result, the materials used in municipal infrastructure have also undergone notable changes. For instance, plastic pipes are gradually replacing traditional steel and concrete pipes. Compared with conventional materials, plastic pipes offer significantly improved performance and can effectively address issues such as poor sealing. They offer high load-bearing capacity, simplified installation, and excellent overall performance, helping to ensure both the progress and quality of municipal construction projects.

Plastic pipes offer excellent flexibility, high tensile strength, and good wear resistance. Although their strength is lower compared to concrete pipes and they lack significant rigidity, their flexibility is a major advantage. When buried underground and subjected to external pressure, the load-bearing behavior of plastic pipes differs from that of concrete pipes. Plastic pipes generally undergo significant deformation before failure, whereas rigid concrete pipes tend to break without much deformation. As a result, flexible plastic pipes are less prone to damage under external loads.

Plastic pipes also exhibit outstanding hydraulic performance. Their inner walls are extremely smooth, resulting in minimal resistance to fluid flow. Studies have shown that the head loss in plastic pipes is approximately 30% lower than that in metal or concrete pipes. Additionally, for the same flow capacity, the required pipe diameter can be reduced by about 20% when using plastic pipes.

Plastic pipes are lightweight and come in long lengths, making them easier to install. During the laying and installation process, they do not require strict conditions for pipe trenches or foundation structures. Additionally, fewer joints are needed during connection. This reduction in the number of joints not only enhances the operational stability of the pipeline but also lowers the workload for future maintenance.

Plastic pipes offer excellent resistance to corrosion and can maintain their quality over long periods. In municipal engineering, this advantage is particularly evident. Thanks to their excellent corrosion resistance, plastic pipes are suitable for transporting domestic sewage, rainwater, and even highly corrosive industrial wastewater.

In recent years, the use of plastic pipes in municipal engineering has steadily increased, with notable improvements in both quality and performance. Compared to pipes made from other materials, plastic pipes are equally competitive. In China's municipal engineering sector, a wide variety of plastic pipes are used, including HDPE pipes, UPVC pipes, PE pipes, PVC-U pipes, RPM pipes, and FRP pipes. Each type of pipe serves a different purpose and is applied in specific areas of municipal engineering (see Table 1).

Table 1 Scope of Application of Plastic Pipes

PVC-U pipes, HDPE pipes, PE pipes, and fiberglass-reinforced plastic (FRP) pipes are selected as the focus of this study and the key aspects of their application in municipal engineering are examined.

PVC-U pipes effectively prevent scaling during liquid transportation and inhibit bacterial growth, reducing the risk of secondary pollution to water resources. Due to their lightweight properties, PVC-U pipes help lower transportation, labor, and equipment costs, reduce handling difficulties, shorten the project construction period, and enhance construction safety. PVC-U pipes are typically connected using elastic sealing rings, and they offer a reliable flange connection. Workers can install them directly in trenches without the need to excavate work pits or use expansion materials like cement. During installation, workers first place a rubber ring in the socket and then use a manual hoist to insert the spigot end of the PVC-U pipe into the socket. Make sure the insertion depth is accurate so the alignment marks on the socket and spigot match up.

According to relevant data, when applying PVC-U pipes, construction teams must consider the actual conditions of the municipal project and place a strong emphasis on design to ensure the service life of the pipes meets standard requirements. This improves overall project quality. PVC-U pipes play an important role in urban sewage systems, providing effective low-pressure water delivery. At present, they have been widely adopted in various types of municipal engineering and have demonstrated excellent performance.

HDPE pipes are large-diameter reinforced pipes manufactured using a winding forming process with high-density polyethylene as the raw material in a molten state. The inner and outer walls of the pipe are formed through synchronous winding, resulting in a pipe body without any welds. During the natural cooling and forming process, internal heat is evenly dissipated, effectively preventing stratification or cracking caused by internal stress. Additionally, HDPE pipes are produced using a cold demolding process, which requires only cooling to room temperature for shrinkage and demolding. This process helps prevent pipe deformation. HDPE pipes have a high moment of inertia and strong ring stiffness. For example, a pipe with a nominal diameter of 1500 mm typically has a ring stiffness of 16 kN/m². Although the production process places high demands on the quality of raw materials, it has relatively low requirements for other materials, resulting in a low overall production cost. HDPE pipes also offer high safety and are often used in major national infrastructure projects. Their internal I-shaped structure offers high ring stiffness, superior load-bearing performance, excellent overall strength, and good toughness. These properties make HDPE pipes suitable for use in municipal stormwater and sewage systems. In construction, HDPE pipes are typically joined using socket-type electrofusion connections. After this process, the pipe joints exhibit high load-bearing and sealing performance. Field results have shown that HDPE pipes can tolerate uneven settlement well, and construction workers can choose from various installation methods. Once the pipes are laid, the trench can be backfilled quickly.

PE pipes are made from polyethylene and offer numerous advantages, including high strength, non-toxicity, excellent corrosion resistance, long service life, good flexibility, and strong scratch resistance. In municipal engineering, PE pipes are commonly used for water supply and drainage. Their unique flexibility enables them to effectively absorb end loads. Before installation, designers must carefully evaluate the construction and laying conditions to ensure that the PE pipe and the surrounding soil share the load once buried, thereby minimizing the risk of damage.

PE pipes exhibit excellent resistance to low temperatures, with a brittleness point as low as –70°C. Compared to other types of pipes, PE pipes are especially suitable for use in northern regions of China, as they do not become brittle or damaged in cold environments. In practical engineering applications, PE pipes are widely used. Their high comonomer content enhances resistance to environmental stress cracking and significantly reduces the risk of brittle failure.

Glass pipes offer excellent thermal insulation and anti-fouling performance after curing. With fewer joints, simplified installation procedures, strong mechanical properties, and superior insulation, glass pipes have shown outstanding performance in municipal engineering applications. Although their tensile strength is lower than that of steel pipes, it is higher than that of ductile iron or concrete pipes. The thermal conductivity of glass pipes is about 1% that of steel pipes, making them significantly better insulators. As a result, glass pipes are often used in municipal projects where dense power transmission and communication lines are present.

In addition to their good hydraulic performance and corrosion resistance, glass pipes are highly durable, allowing engineers to design systems based on specific project requirements. These pipes are adaptable, require minimal maintenance, and do not need cathodic protection when used as buried pipelines. Due to these advantages, glass pipes have broad application prospects in municipal engineering.

In recent years, the performance and quality of plastic pipes in China have significantly improved, leading to an increasing number of municipal projects adopting plastic pipes. During the construction process, it is crucial for construction units to adhere strictly to relevant national policies when selecting appropriate plastic pipes to ensure the quality of municipal pipelines and enhance the overall standard of municipal engineering. This paper analyzes the advantages of plastic pipes and explores their application in municipal engineering, aiming to provide valuable insights for the advancement of municipal construction projects.