Geo Hazard Management

1. Geo Hazard ManagementESH 31261 S.M.K Wijesinghe SEU/IS/18/BS/053

2. Land Subsidence and Liquefaction

3. Outline • Definition • How it should be a hazard • Mechanism • How Predict • Prevention • Mitigation • Early signs • What we should do before the hazard, during the hazard,andafter the hazard • Management system

4. Definition • Land subsidence is a gradual settling or sudden sinking of the Earth's surface owing to subsurface movement of earth materials.. Ground Subsidence - Colorado

6. Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading Liquefaction in switzerland

8. How it should be a hazard? • Subsidence causes infrastructure damage and ultimately leads to increased risk to society and the economy.. Joshimath Land Subsidence-India

9. Liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes  liquefaction cause damage in taiwan

10. Mechanism • land subsidence can be caused by the consolidation of sediments, the compaction of soil, or the withdrawal of underground fluids such as groundwater.

11. liquefaction mechanism as follows, • Saturation, Loose, granular soil,Shaking

12. How to predict? For forecast land subsidence, • Monitoring of groundwater levels • Geotechnical studies • Utilizing satellite data • InSAR

13. forecast liquefaction, • Geotechnical investigations • Standard Penetration Test (SPT) • Cone Penetration Test (CPT) • Shear wave velocity profiling

14. Prevention Here are some steps that can be taken to stop land subsidence, • Reduce groundwater extraction • Implementing sustainable groundwater management • Utilize other water sources • Implement land-use planning

15. Here are some actions that can be taken to stop liquefaction, • Choosing a location that is less prone to liquefaction • Ground improvement methods • Designing the foundations • Drainage systems • Retrofitting for seismic activity

16. Mitigation Here are several strategies commonly employed for land subsidence mitigation, • Land Reclamation and Compaction Control • Public Awareness and Education • Aquifer Recharge • Monitoring and Early Warning Systems

17. Here are some commonly used mitigation measures, • Drains and Dewatering • Public Awareness and Education • Building Codes and Regulations • Site Investigations and Engineering Studies

18. Early signs some indicators of land subsidence, • Cracks in the ground or in buildings • Elevation changes • Structures may tilt or sink unevenly • Water levels can change

19. some indicators of liquefaction, • Existence of loose, saturated soil • Sand boils or sand volcanoes • Water behavior changes • Tilting or leaning in structures

20. What we should do Before the hazard, during the hazard,and after the hazard Before, • Understand the risks • Evaluate your property • Implement mitigation measures • Develop an emergency plan: • Stay informed

21. During, It is important to take immediate action to protect public safety and minimize damage, • Evacuate the area • Secure the area • Contact emergency services

22. After To ensure affected area and the people who live or work there, • Assess the damage • Address immediate safety concerns • Plan for long-term solutions • Monitor the area • Communicate with the public

23. Management system Essential elements of a management system for land liquefaction and subsidence, • Hazard assessment • Risk evaluation • Planning for emergency responses • Monitoring and surveillance • Public outreach and education

24. Land subsidence in Sri Lanka Atchuweli,Jaffna Mathale

25. Thank You.