I. Research BackgroundIn the construction of smart cities, PVC-U seven-hole pipe (Figure 1) has become the mainstream choice for small and medium-sized communication pipes because of its **“1 big 6 small” honeycomb structure** (1 Φ50mm main hole + 6 Φ32mm sub-holes). Its space utilization rate is 37% higher than that of single-hole pipe, and its cost is 15%-20% lower than that of nine-hole pipe. However, the deformation of the pipe caused by insufficient compressive resistance of the overburden (accounting for 61% of the failure cases) restricts its in-depth application in municipal engineering.Second, the core problem: cellular...

1. Research Background Steel-belt corrugated pipes, with a "steel reinforcement + HDPE composite" structure (Figure 1), occupy 35% of the market for municipal drainage projects with burial depth >4m (2024 China Plastic Pipe Industry Report). While their ring stiffness reaches SN16, steel corrosion causes 41% of failures, especially in coastal saline-alkali soil (Cl⁻ >500mg/L) and industrial wastewater areas (pH <4). 2. Core Issue: Steel-Plastic Interface Failure Mechanism 2.1 Three-Stage Corrosion Process Through salt spray testing (GB/T 10125-2021) and electrochemical analysis, steel corrosion proceeds as: Initial Stage (0-6 months): Localized corrosion at HDPE coating pinholes Medium Stage (6-24 months): Coating delamination due to rust expansion Final Stage (>24 months): Structural collapse with >30% steel...

1. Research Background MPP (Modified Polypropylene) power pipes play a critical role in urban power grid upgrades due to their Vicat Softening Temperature (VST) ≥ 120℃, outperforming ordinary PE pipes. However, State Grid testing reveals: When cable current exceeds 600A, long-term operating temperature reaches 85-95℃ Traditional MPP pipes exhibit 3.2% creep strain at 80℃/10MPa after 5000 hours (close to failure threshold 3.5%) 2. Core Issue: Thermo-Mechanical Coupling Failure Mechanism 2.1 Three-Stage Creep Process Through Dynamic Mechanical Analysis (DMA) and long-term hydrostatic tests (GB/T 6111-2018), MPP pipe creep behavior is divided into:  Instantaneous Elastic Deformation (0-100h): Strain <0.5% Steady-State Creep (100-5000h): Strain rate 0.002%/h Accelerated Failure (>5000h): Plastic...