Applicability of pipeline materials under specific complex geological conditions

In irrigation projects, complex geological conditions such as high drop in mountainous areas, distribution of rock layers, and soft soil foundations and highly corrosive soils in some areas pose challenges to the selection of irrigation pipeline materials. Different irrigation pipeline materials have their own characteristics, which determine their applicability under specific complex geological conditions. Studying the applicability of different irrigation pipeline materials under specific complex geological conditions is of great significance for ensuring the long-term stable operation of the irrigation system, reducing engineering costs, and improving the efficiency of water resource utilization.

Analysis of common irrigation pipeline material characteristics

1. Polyvinyl chloride (PVC) pipe

• Physical properties: PVC pipe has good corrosion resistance and can resist erosion by a variety of chemical substances. Its inner wall is smooth, the water flow resistance is small, and the head loss can be effectively reduced. For example, in some areas where the water quality contains a certain pH, PVC pipe can maintain stable performance.

• Mechanical properties: moderate strength, can withstand a certain internal pressure and external load. However, at low temperatures, the pipe will become brittle, the toughness will decrease, and it is easy to break. In cold areas in the north in winter, if there is water in the pipe and it is not emptied in time, the pipe may rupture due to the expansion of water freezing.

• Cost characteristics: relatively low price, easy installation, various connection methods, such as adhesive connection, rubber ring connection, etc., can reduce construction costs. In some small-scale farmland water conservancy facilities projects, PVC pipes are widely used to reduce the overall project cost.

2. Polyethylene (PE) pipe

• Physical properties: good flexibility, can adapt to a certain degree of foundation deformation. High chemical stability, resistant to most chemicals. In some areas with slight foundation settlement, PE pipes can reduce pipeline damage caused by foundation changes with their flexibility.

• Mechanical properties: good impact resistance, can withstand certain external force impact. Its strength increases with density, and PE pipes of different densities are suitable for irrigation systems with different pressure requirements.

• Cost characteristics: mature production technology and relatively low cost. Especially in large-diameter pipe applications, its cost-effectiveness advantage is obvious. PE pipes are often used in the laying of main pipelines in some large-scale irrigation projects.

3. Steel-plastic composite pipe

• Physical properties: It combines the high strength of steel and the corrosion resistance of plastic. The inner layer of plastic can prevent water from contacting steel, avoid rusting of steel, and ensure that the water quality is not polluted.

• Mechanical properties: It has high strength and rigidity, and can withstand large internal pressure and external load. It is suitable for some occasions with high requirements for pipeline strength, such as crossing roads, rivers and other areas.

• Cost characteristics: Due to its composite structure, the price is relatively high, and the installation process is relatively complicated. It requires professional equipment and technicians for connection and installation, which increases the construction cost.

4. Concrete pipe

• Physical properties: Good durability, long service life, and can operate stably for a long time in harsh natural environments. It is generally suitable for permanent irrigation projects with high requirements for pipeline service life.

• Mechanical properties: High compressive strength, can withstand large external pressure, such as lateral pressure of soil. However, the concrete pipe has a large self-weight and requires a high bearing capacity of the foundation.

• Cost characteristics: When it is used on a large scale and the pipe diameter is large, the cost is relatively low. However, larger mechanical equipment is required during transportation and installation, which increases the difficulty and cost of construction. In areas with relatively flat terrain and high requirements for pipeline durability, such as irrigation mains in large farms, concrete pipes have certain applications.

The impact of specific complex geological conditions on the applicability of irrigation pipe materials

1. Soft soil foundation

• PVC pipe: Since soft soil foundations are prone to settlement, the brittleness of PVC pipes may cause them to break easily when the foundation settles. Although its stability can be improved by strengthening foundation treatment, such as laying sand cushion layers, in general, its applicability on soft soil foundations is relatively limited.

• PE pipe: Its good flexibility gives it certain advantages on soft soil foundations. It can adapt to a certain degree of uneven settlement of the foundation without breaking. However, if the settlement is too large, it may also cause excessive deformation of the pipeline and affect the water delivery capacity.

• Steel-plastic composite pipe: It has high strength and can resist the pressure caused by the settlement of soft soil foundations to a certain extent. However, its large dead weight may exert greater pressure on the soft soil foundation, further aggravating the settlement of the foundation. The foundation needs to be specially treated, such as piling, which increases the project cost.

• Concrete pipe: It has a large weight and requires high bearing capacity for soft soil foundation. When used on soft soil foundation, sufficient foundation treatment must be carried out, such as deep mixing pile reinforcement, otherwise the pipe is very likely to rupture due to foundation settlement. Generally, it is not recommended to use concrete pipes on soft soil foundations that have not been fully treated.

2. Rock formation

• PVC pipe: The hardness is relatively low. When laid in rock formation, it is easy to be scratched and punctured by the edges and corners of the rock, causing damage to the pipe. If it must be used in rock formation, special treatment of the pipe trench is required, such as laying a sand cushion layer or using casing protection.

• PE pipe: It also has the problem of being easily scratched by rocks. However, its flexibility can buffer the local pressure of rocks on the pipe to a certain extent. When laid in rock formations, protective measures are also needed to extend the service life of the pipe.

• Steel-plastic composite pipe: The steel part provides higher strength and can better resist the wear and extrusion of rocks. In rock formations, its applicability is relatively good. However, during the installation process, care should be taken to avoid damage to the internal plastic layer due to construction operations such as welding.

• Concrete pipe: It has high compressive strength and can withstand external pressure well in rock formations. However, due to the difficulty of excavating rock formations, the transportation and installation of concrete pipes are inconvenient, which increases the construction cost. When used in rock formations, construction conditions and cost factors must be considered comprehensively.

3. Strongly corrosive soil areas

• PVC pipe: It has good corrosion resistance and can be used normally in strongly corrosive soils. No additional anti-corrosion measures are required, which can reduce the cost of engineering maintenance.

• PE pipe: It has high chemical stability and can also resist erosion by strongly corrosive soils. In such areas, PE pipe is one of the more ideal choices.

• Steel-plastic composite pipe: Although the inner layer of plastic can prevent water from corroding steel, if the outer layer of steel is not properly protected, it may still be corroded by corrosive substances in the soil. Special anti-corrosion treatment is required for the steel surface, such as coating with anti-corrosion coating, which increases the cost and maintenance workload.

• Concrete pipe: In general, concrete pipes have a certain resistance to corrosive substances in the soil. However, in highly corrosive soils, problems such as concrete carbonization and steel bar corrosion may occur, affecting the service life of the pipe. Special anti-corrosion concrete or anti-corrosion treatment of the pipe is required.

Case analysis

1. A mountain irrigation project: The mountain has a large terrain undulation and complex geological conditions. Some areas are rock formations and some areas have soft soil foundations. In the early stage of the project, PVC pipes were selected as irrigation pipe materials. During the laying process of the rock formation, it was found that a large number of pipes were scratched by rocks, resulting in water leakage. Later, the trench was treated with sand cushion layer, and some pipes were protected by casing, but it was still impossible to completely avoid pipe damage. In the soft soil foundation area, some PVC pipes broke due to foundation settlement. Subsequently, steel-plastic composite pipes were replaced in the rock formation area, PE pipes were replaced in the soft soil foundation area, and sand pile reinforcement was carried out on the soft soil foundation. After adjustment, the irrigation system operated stably and the pipe damage was significantly reduced.

2. A coastal saline-alkali irrigation project: The soil in this area is highly corrosive. The project initially selected ordinary concrete pipes as irrigation pipes. After a period of operation, it was found that the concrete pipes were carbonized, the internal steel bars were corroded, and the strength of the pipes decreased. Later, they were replaced with PVC pipes, which effectively solved the problem of pipe corrosion and ensured the normal operation of the irrigation system.

There are differences in the applicability of different irrigation pipe materials under specific complex geological conditions. In soft soil foundations, PE pipes have certain advantages due to their flexibility; in rock formations, steel-plastic composite pipes are relatively more adaptable; in highly corrosive soil areas, PVC pipes and PE pipes are better choices. In actual projects, geological conditions, project costs, construction difficulties and other factors should be fully considered, and the most suitable irrigation pipe materials should be selected after comprehensive evaluation to ensure the long-term stable operation of the irrigation system, improve the efficiency of water resource utilization, and promote the sustainable development of agricultural production. At the same time, with the continuous development of materials science and engineering technology, new irrigation pipe materials that are more adaptable to complex geological conditions are expected to appear in the future, providing more options for irrigation projects.