PVC sheet piles can be used underground for certain applications and in specific conditions, but there are considerations to keep in mind due to the material's properties and limitations. The decision to use PVC sheet piles underground for an extended period of time should be based on factors such as soil conditions, water levels, load-bearing requirements, and potential chemical interactions. Here are some points to consider:

Soil Conditions: The type of soil and its properties play a significant role in determining the suitability of PVC sheet piles for underground use. PVC sheet piles might be suitable for cohesive soils with low to moderate groundwater levels, where their corrosion resistance can be advantageous.

Water Levels: PVC sheet piles are often used in water-related applications due to their resistance to corrosion. In underground applications, the water table and groundwater conditions should be evaluated. PVC sheet piles could be used in scenarios where the water table is relatively stable and not subject to extreme fluctuations.

Chemical Compatibility: Some soils or underground environments may contain chemicals, minerals, or contaminants that could potentially interact with PVC and affect its structural integrity. Before using PVC sheet piles underground, it's important to assess the chemical compatibility of the material with the surrounding environment.

Load-Bearing Capacity: PVC sheet piles have different load-bearing characteristics compared to traditional materials like steel or concrete. If the project requires significant structural support or if there will be heavy loads above the PVC sheet piles, a thorough engineering analysis is necessary to ensure they can handle the loads without deformation or failure.

Long-Term Performance: The long-term performance of PVC sheet piles underground depends on various factors, including UV resistance (if exposed to sunlight during installation), resistance to soil and water interactions, and potential deformation or settling over time.

Installation Considerations: Proper installation techniques are crucial for the success of underground PVC sheet pile applications. This includes ensuring proper interlocking of the sheet piles, providing adequate drainage to prevent water buildup, and considering soil compaction around the sheet piles.

Maintenance and Inspections: Regular inspections and maintenance are important to monitor the condition of PVC sheet piles over time. If used underground, periodic assessments should be conducted to ensure there's no degradation, deformation, or other issues affecting their performance.

Consultation with Experts: Before using PVC sheet piles underground, it's advisable to consult with engineers, geotechnical experts, and manufacturers familiar with PVC materials. They can provide insights based on the specific project requirements and conditions.