Table 12 Environmental characteristics and risk assessment indicators: a statistical reference for industrial maintenance
From: Survival analysis framework for sewer failure time: evidence from Hong Kong
Categories | Subcategories | Types | Risk characteristics | Maintenance strategies |
|---|---|---|---|---|
Environmental factors | Land use | Industrial areas | Earliest warning threshold at 41 years Rapid risk increase over the next 20 years Accelerated risk for 60–70 years | Prioritize monitoring from age 41 Enhance inspections during the acceleration phase Age 60 with replacement, when necessary |
Commercial areas | Warning threshold at age 46 Slow growth 46–61 years Steady growth 61–76 years | Conduct regular monitoring until age 76 Significantly increase inspection frequency after age 76 | ||
Residential areas | Warning threshold at age 47 Steady growth by age 65 Slightly accelerated growth after 65 | Schedule regular periodic inspections after the warning level Moderately increase monitoring after age 65 | ||
Green open spaces | Warning threshold at age 48 Most stable risk pattern Uniform growth rate between ages 48 and 70 | Regular periodic inspection after the warning level Consistent maintenance intervals due to stable progression | ||
Humidity | High humidity | Earliest critical threshold at age 43 Accelerated risk between 60 and 70 years Moderate progression pattern | Provide consistent maintenance throughout the service life Pay particular attention after age 60 | |
Medium humidity | Critical threshold at 48 years Gradual growth 48–60 years Sharp acceleration after 60 years | Intensively monitor and prevent around age 60 Enhance measures during the risk acceleration phase | ||
Low humidity | Critical threshold at 45 years Rapid in early stages before stabilizing around age 63 Maintains a relatively low final risk level | Establish regular inspection schedules After stabilization, maintain standardized maintenance intervals | ||
District | New Territories | Earliest warning level at 42 years Steady risk increase until age 63 Lowest final risk among all regions | Conduct routine maintenance between the ages 42 and 63 Implement enhanced preventive measures after age 63 | |
Kowloon | Warning level at 47 years Moderate risk growth until age 59 Sharp upward trend after age 59 | Perform moderate maintenance between the ages 47 and 59 Significantly enhance interventions after age 59 Intensify maintenance after age 60 | ||
Hong Kong Island | Warning level at 48 years Steady, slow growth until age 68 Significant turning point at 68 | Standard maintenance before age 68 Reinforced measures after age 68 Renewal plans after age 76 | ||
Island | Latest warning period at 49 years Best early survival characteristics Most dramatic risk increase after age 59 | Apply moderate interventions before age 59 Intensify maintenance after age 60 Develop comprehensive renewal plans for the highest risk period | ||
Temperature | High temperature | Latest warning threshold at 49 years Better reliability until age 75 Rapid deterioration after age 75 | Enhance preventive maintenance from age 49 Prioritize replacement planning after age 75 Replacement after 75 years | |
Medium temperature | Warning threshold at 46 years Most stable risk progression | Schedule regular maintenance intervals from age 46 Consistent monitoring throughout the lifecycle | ||
Low temperature | Earliest warning threshold at 43 years Gradual risk increase between ages 43 and 61 Rapid risk ascent after age 61 | Initiate intensive early-stage monitoring from age 43 Sustain attention throughout the lifecycle Enhance monitoring during the acceleration phase | ||
Traffic load | Heavy traffic | Earliest warning threshold in 44 years Risk increases between the ages 44 and 60 Significant risk acceleration after age 60 | Commence rigorous monitoring from age 44 Prioritize for replacement after age 60 | |
Moderate traffic | Warning threshold at 48 years Most stable risk growth pattern | Scheduled inspections from age 48 Longer maintenance intervals permitted | ||
Light traffic | Warning threshold at 47 years Stable late-stage risk growth | Scheduled inspections from age 47 Longer maintenance intervals permitted | ||
No traffic | Warning threshold at 46 years Moderate risk growth | Regular maintenance from age 46 Standard inspection protocols Moderate maintenance frequency | ||
Rainfall | High rainfall | Latest warning threshold at 48 years Risk remains stable until age 64 Sharp increase between ages 65 and 79 | Maintain standard maintenance until age 64 Implement intensive preventive maintenance after age 65 with replacement consideration when necessary | |
Medium rainfall | Earliest warning threshold in 44 years Risk remains stable until age 64 Moderate, steady increase thereafter | Conduct moderate preventive maintenance Schedule regular inspection intervals | ||
Low rainfall | Warning threshold at 46 years Risk remains stable until age 64 Most gradual risk progression thereafter | Extend preventive maintenance cycles Optimize inspection frequencies | ||
Soil | Graphite-bearing | Earliest warning threshold at 33 years Minimal risk increase Remarkable long-term stability | Initiate basic monitoring from age 33 Conduct periodic structural integrity checks Implement preventive measures only when necessary | |
Backfilled areas | Warning threshold at 42 years Accelerated degradation 50–70 years | Begin preventive maintenance from age 42 Focus on compaction testing and soil improvement for 50–70 years Perform regular density assessments | ||
Tuff and lava | Warning threshold at 44 years Sharp risk increase between 55 and 70 years | Start monitoring from age 44 Implement weathering prevention measures during the 55–70 years Conduct regular strength assessments | ||
Granodiorite | Warning threshold at 45 years Rapid risk increase between 45 and 58 years Risk stabilizes after age 58 | Monitor from age 45 Intensify inspections between the ages 45 and 58 Reduce inspection frequency after age 65 | ||
Superficial deposits | Warning threshold at 47 years Sharp rise 72–75 years Late-stage deterioration | Monitoring from age 47 Implement ground stabilization before 72–75 years Perform regular settlement control | ||
Granite | Latest warning threshold at 49 years Moderate risk increase between 60-65 years | Begin monitoring from age 49 Monitor stress concentration after age 65 |
