LANDSLIDE MITIGATION BY USING SOIL NAILING TECHNIQUE
- 1. WELCOME 1
- 2. LANDSLIDE MITIGATION BY USING SOIL NAILING TECHNIQUE SEMINAR PRESENTATION Guided By Ms.Silpa Mohan K Lecture in CE GWPC Thrissur Presented By Anagha J P(2101013069) 2
- 3. INTRODUCTION ● A landslide is a geological phenomenon characterized by the movement of a mass of rock , soil and debris down a slope or incline. ● Landslide can be triggered by various factors , including heavy rainfall, earthquakes, volcanic activity , human activities such as mining or construction, and change in slope stability due to natural processes or erosion. ● Landslide can have significant environmental and societal impacts often leading to property damage , loss of life and disruption of infrastructure. 3
- 4. CAUSES OF LANDSLIDE IN KERALA ● Heavy rainfall ● Geological Factors ● Soil Erosion ● Human Activities ● Poor Drainage 4 ● Land Use Changes ● Earthquakes ● Poor Construction Practices ● Climate Change ● Vegetation Cover
- 5. IMPACTS OF LANDSLIDE ● Loss of Lives ● Property Damage ● Displacement of people ● Environmental Damage ● Economical Impact ● Disruption of Transportation ● Water Quality Issues ● Long term Consequence ● Psychological Impact 5
- 6. CONVENTIONAL METHODS FOR MITIGATING LANDSLIDES ● Slope gradient and Terracing ● Vegetation and Afforestation ● Retaining Walls ● Rock Bolting and Mesh 6 ● Drainage system ● Erosion Control Measure ● Early Warning Systems ● Land Use Planning and Zoning ● Education and Awareness
- 7. GROUND IMPROVEMENT TECHNIQUE ● Ground improvement techniques are methods employed in geotechnical engineering to enhance the engineering properties of soil and other geological materials for construction purposes. ● These techniques are applied to increase the bearing capacity, reduce settlement, and improve overall soil stability. 7
- 8. BENEFITS OF GROUND IMPROVEMENT ● Increased bearing capacity ● Cost savings ● Reduced settlement ● Control of ground water ● Improved stability ● sustainability 8
- 9. SOIL REINFORCEMENT ● Soil reinforcement is a ground improvement technique used to enhance stability, strength, load bearing capacity of soil structures. ● It involves reinforcing materials to improve its mechanical properties. ● The primary purpose of soil reinforcement is to prevent or reduce soil settlement , erosion and potential for failure. 9
- 10. TYPES OF SOIL REINFORCEMENT ● Geo-grids ● Geo- textiles ● Geo- cells ● Soil nail technique ● Ground anchors 10 ● Micropiles ● Reinforced soil ● Terra mesh ● Rock bolts ● Gabions
- 11. APPLICATIONS OF SOIL REINFORCEMENT IN GEOTECHNICAL ENGINEERING ● Retaining wall ● Slope stabilization ● Road and Pavement construction ● Foundation support 11 ● Erosion control ● Landfills ● Mining ● Bridge abutment ● Railway infrastructure
- 12. RELEVANCE OF SOIL REINFORCEMENT IN LANDSLIDE MITIGATION ❏ INCREASED SHEAR STRENGTH Soil reinforcement techniques, such as the use of geosynthetics ( geotextiles, geogrids etc.) can significantly increase the shear strength of soil. This added strength can help stabilize slopes and reduce the risk of landslides. ❏ ENHANCED SLOPE STABILITY The reinforced materials distribute loads more evenly and can withstand greater forces, making the slope less susceptible to failure. 12
- 13. ❏ RETAINING WALL REINFORCEMENT In areas prone to landslides, retaining walls are often used to support slopes. Soil reinforcement can be integrated into the design of these walls, providing additional stability and preventing wall failure due to excessive lateral forces. ❏ EROSION CONTROL Geo-synthetic materials can protect the soil surface from erosion by stabilizing it and preventing the loss of soil particles. 13
- 14. ❏ RAPID RESPONSE Some soil reinforcement techniques, like the installation of soil nails or anchors, can be implemented relatively quickly. This can be crucial for landslide mitigation in emergency situations or when rapid stabilization is needed to prevent further damage. ❏ FLEXIBILITY AND VERSATILITY Soil reinforcement methods are adaptable to various soil types, making them suitable for a wide range of geological conditions and landslide-prone areas. 14
- 15. ❏ LONG-TERM DURABILITY Properly designed and installed soil reinforcement measures can provide long-term stability and continue to mitigate landslide risks over an extended period. ❏ COST-EFFECTIVE SOLUTIONS In many cases, soil reinforcement can be a cost-effective alternative to extensive earthwork or other landslide mitigation measures, particularly for projects with budget constraints. 15
- 16. SOIL NAILING TECHNIQUE ● Soil nailing is a ground reinforcement technique used in geotechnical engineering to stabilize and strengthen slopes, excavations, and retaining walls. ● It involves the installation of passive reinforcement elements (nails) into the soil or rock to improve its stability 16
- 17. COMPONENTS OF SOIL NAILING TECHNIQUE ● Soil nail (tendons) ● Nail head ● Nail shaft ● Nail tip or grout body ● Face reinforcement ● Grout 17
- 18. KEY DESIGN PARAMETERS OF SOIL NAIL ● NAIL LENGTH Nail lengths are typically in the range of 0.8H to 1.2H, where H is the retained height of the wall. ● NAIL SPACING 5feet for both horizontal and vertical spacing 18
- 19. ● NAILANGLE Soil nails are typically installed at a slight downward angle (usually 10-20 degrees from horizontal) to improve stability ● GROUT TYPE AND MIX The choice of grout material, its strength, and mix design are critical to ensure proper bonding and anchorage of the soil nail within the drilled hole. The grouting materials like cement-based grout, chemical grout and bentonite grout. 19
- 20. ● LOAD TRANSFER MECHANISM ● FACE REINFORCEMENT ● SAFETY FACTORS 20
- 21. PRINCIPLE OF SOIL NAILING TECHNIQUE ● Shear strength enhancement ● Load transfer ● Slope stabilization ● Increased effective stress ● Flexibility and adaptability ● Rapid implementation ● Erosion control ● Long term durability 21
- 22. DESIGN AND ANALYSIS ❖ Site investigation ❖ Analysis of load ❖ Stability Analysis ❖ Nail Design ❖ Nail spacing and layout 22 ❖ Grouting design ❖ Load transfer mechanism ❖ Face reinforcement ❖ Construction details ❖ Monitoring plan ❖ Quality control and inspection
- 23. ❖ Construction ❖ Monitoring and maintenance ❖ Documentation and reporting ❖ Review and adaptation 23
- 24. KEY LOAD COMPONENTS TO ANALYZE ● Dead load ● Surcharge load ● Live load ● Seismic load ● Shear and pullout loads 24 ● Earth pressure ● Hydrostatic pressure ● Soil nail interaction ● External stability ● Internal stability ● Safety factor
- 25. FACTORS INFLUENCING DESIGN DECISIONS 1. SOIL PROPERTIES ● Soil types ● Soil shear strength ● Compaction and settlement 1. SLOPE GEOMETRY ● Slope angle ● 25
- 26. 3. ENVIRONMENTAL CONDITIONS ● Climate ● Vegetation ● Seismic activity ● Drainage 4. LOAD AND USAGE 26
- 27. SOIL NAILING CONSTRUCTION TECHNIQUE ● Excavation ● Drilling of nail holes ● Nail installation and grouting ● Installation of strip drain ● Construction of initial shortcrete facing ● Construction of final facing 27
- 28. 28
- 29. STEP 1 EXCAVATION ● Prevent surface water from infiltrating the excavation site. ● Serving as interceptors to redirect surface water away from the site. ● Initial cut is typically 3 to 5 feet deep ● Using back hoes or excavators. ● Important to ensure that the excavated face maintains a reasonably smooth profiles 29
- 30. STEP 2 DRILLING OF NAIL HOLES ● Nail holes are drilled using one of several available drilling methods, including rotary, percussion, auger, and rotary-percussion drilling. ● The choice of drilling technique may also be influenced by the equipment's local availability and the particular ground conditions to be encountered. 30
- 31. ● In unstable ground, these potentially harmful effects can be prevented by utilizing drill casings or Hollow Bar Soil Nails (HBSNs), or by restricting the air flush to keep the drill hole open and prevent pressure buildup. ● Duplex rotary and single tube drilling techniques are both used in cased drilling. 31
- 32. 32 DRILLING NAIL HOLES DUPLEX ROTARY DRILL
- 33. STEP 3 NAIL INSTALLATION AND GROUTING ● After the tendon is inserted in the drill hole, the drill hole is filled with grout using a tremie pipe. ● The grout pipe is inserted to the bottom of the drill hole and the grout is injected until it fills the hole. 33
- 34. STEP 4 INSTALLATION OF STRIP DRAIN ● Strip drains are positioned against the excavation face, with the geotextile filter side facing the soil. ● When strip drains come in rolls, they should be shielded during shotcrete application for each layer, and then rolled down continuously. 34
- 35. ● The bottom drainage cap and exit pipe connect to the strip drains and attach to the reinforcing steel of the facing. During shotcrete placement, the exit pipe must be adequately covered to prevent shotcrete from entering the system. After shotcrete is applied, the exit pipe can be connected to the under drain system if needed. 35
- 36. 36 STRIP DRAIN
- 37. STEP 5 CONSTRUCTION OF INITIAL SHORTCRETE FACING ● Shotcrete is a construction technique that involves spraying or shooting a mixture of concrete, onto the surface at high velocity. ● In soil nail wall applications, the initial facing is typically created using shotcrete, with a thickness ranging from 3 to 4 inches. ● In the realm of shotcrete mixtures, two opposing requirements must be balanced: "shoot ability" and "pump ability." ● Two primary methods are employed in shotcrete application: the dry mix method and the wet mix method. 37
- 38. STEP 6 CONSTRUCTION OF FINAL FACING A) Reinforced concrete ● The total thickness of a reinforced shotcrete final facing typically falls within the range of 6 to 12 inches, not including the initial facing. ● Headed studs, welded to bearing plates, are employed to connect the final facing to the soil nails. 38
- 39. B) Cast-in Place reinforced concrete ● CIP concrete, commonly employed as the ultimate surface layer, is typically strengthened with both vertical and horizontal bars ● In comparison to a shotcrete facing, a CIP reinforced concrete finished facing may offer potential advantages, such as the utilization of form liners for aesthetics, a consistent appearance, and a uniform quality. ● The maximum spacing for vertical contraction joints in permanent CIP facing is typically in the range of 90 to 100 feet, which is similar to that of shotcrete final facings. 39
- 40. 40
- 41. CASE STUDIES 1.Landslide Mitigation by Using Soil Nailing Technique in Maharashtra,India Soil Nailing Technique Overview: ● Soil nailing involves drilling holes for steel bars in a slope face, grouting them in place, and attaching mesh to hold the slope face. ● Derived from the New Austrian Tunnelling method (NATM), adapted for stabilizing slopes and excavations in soils. 41
- 42. ● Involves rigid bars driven into soil or pushed into boreholes, filled with grout, creating a structural body for excavation support or stabilizing unstable slopes. Feasibility Study at Gaganbawda Ghat: ● The study evaluates geological reviews and site surveys at Gaganbawda Ghat, Maharashtra, India. ● Considers physical and chemical specifications of soil and geotechnical landslide characterization. 42
- 43. Benefits of Soil Nailing Technique: ● Effective for preventing landslides in Gaganbawda Ghat area. ● Cost-effective method for land mitigation compared to traditional techniques like retaining walls. ● More efficient, consumes fewer materials, easy to implement, and economical. ● Applicable to specific soil types, ensuring suitability for execution 43
- 44. Application Examples: ● Based on a case study from Sorchen Bypass in Bhutan, demonstrating successful implementation of soil nailing technique. Conclusion: ● Soil nailing technique proves to be a viable, cost-effective, and efficient method for preventing landslides, especially in areas like Gaganbawda Ghat. ● Its implementation requires careful consideration of soil types and geological factors for optimal results. 44
- 45. 2. La Conchita Landslide Mitigation, California, US ● The community of La Conchita, California, faced a history of deadly landslides, leading to a comprehensive mitigation effort after a catastrophic landslide in 2005. ● The mitigation strategy included soil nails, retaining walls, slope terracing, and other stabilization measures to ensure the safety of the residents. ● Frequent landslides in the region posed a significant risk to the community, prompting a geotechnical investigation to assess slope conditions and identify suitable stabilization methods. ● Passive measures like retaining walls and slope terracing were implemented to provide stability, along with active measures such as soil nails and rock bolts to 45
- 46. ● A robust monitoring system was established to continuously track slope movements, groundwater levels, and rainfall patterns. ● The successful implementation of these measures demonstrated the effectiveness of combining passive and active techniques in mitigating landslide risks in La Conchita ● Soil nailing, when properly designed and executed, proved to be a cost-effective and long-lasting solution for stabilizing slopes and mitigating landslide risks in various geological and geographical contexts. 46
- 47. CHALLENGES FACED DURING THE SOIL NAILING TECHNIQUE ❖ Geotechnical challenges : Geotechnical challenges during soil nailing projects primarily revolve around the unpredictable nature of soil and the specific site conditions. The variability in soil properties, such as cohesion, angle of internal friction, and shear strength, can pose significant challenges in determining the design parameters for soil nails. ❖ Design challenges : . One key challenge is determining the optimal spacing and length of soil nails, which requires careful analysis of the geotechnical properties of the soil and the intended purpose of the reinforced structure. 47
- 48. ❖ Construction challenges : One of the primary challenges is drilling holes for soil nails, especially in hard or rocky soils, which often necessitates specialized equipment and techniques. Ensuring the proper installation of soil nails, including the quality of grouting and the bond between the nail and the soil, is essential for structural integrity. ❖ Quality control and monitoring :One of the primary challenges in this regard is the need for continuous monitoring of the nail installation, grouting, and structural performance. This often involves the use of instrumentation to measure factors like nail load, deformation, and settlement. 48
- 49. ❖ Weather conditions : Weather conditions can present significant challenges during soil nailing projects, particularly in regions with variable or extreme climates. Such as heavy rainfall, snow, or high winds, can disrupt construction schedules and increase project durations. ❖ Cost management : One of the primary challenges is the potential for cost overruns due to unforeseen issues such as difficult drilling conditions, changes in design, or unexpected soil conditions. 49
- 50. ADVANTAGES OF SOIL NAILING ● Cost effective ● Minimal disruption ● Adaptability ● Quick installation ● Reduced environmental impact 50
- 51. LIMITATIONS ● Soil suitability ● Maintenance ● Limited height reach ● Design complexity ● Potential for corrosion 51
- 52. COMPARISON OF SOIL NAILING WITH OTHER LANDSLIDE CONTROL METHODS 1.Retaining Walls ● Soil Nailing: Reinforced soil slopes by inserting steel bars, offering flexibility and suitability for limited spaces. ● Retaining Walls: Rigid structures made of concrete, suitable for areas with high vertical loads and visible erosion barriers. 52
- 53. 2. Slope Grading and Terracing ● Soil Nailing: Structural reinforcement using steel bars; effective for unstable slopes. ● Slope Grading: Alters slope angles, reducing erosion risk; focuses on topography modification. ● Terracing: Creates level platforms on slopes; primarily used in agriculture and landscaping. 3. Rockwall Protection System ● Soil Nailing: Strengthens soil slopes with steel bars. ● Rockwall Protection: Constructs barriers in rocky terrains to prevent rockfall and erosion. 53
- 54. 4.Vegetation Control ● Soil Nailing: Structural solution, reinforces unstable slopes. ● Vegetation Control: Uses plants to prevent erosion, environmentally friendly solution. 5.Drainage Control ● Soil Nailing: Reinforces soil slopes, preventing erosion and landslides. ● Drainage Control: Manages water flow with pipes, swales, or ditches; addresses hydraulic stability. 54
- 55. SAFETY MEASURES ● Safety of worker ● Excavation stability ● Equipment hazards ● Environmental protection ● Public safety 55 ● Emergency response ● Compliance with regulations ● Project success ● Cost savings ● Reputation
- 56. ENVIRONMENTAL CONCERNS AND MITIGATION MEASURES ● Soil erosion and sediment control ● Water quality protection ● Habitat disturbance ● Air quality and dust control ● Noise pollution ● Waste management ● Environmental monitoring 56
- 57. FUTURE TRENDS AND INNOVATIONS ● Advanced geotechnical hazards ● Improved materials and anchors ● Biotechnical solution ● Smart monitoring and sensors ● Automation and robotics ● Self drilling soil nails ● Green and sustainable practices ● Remote and unmanned systems 57
- 58. ● Prefabricated and modular systems ● Climate adaptation and resilience ● Integration with other technologies 58
- 59. ONGOING RESEARCH AND POTENTIAL ADVANCEMENT ● Advanced material development ● Optimization of nail design ● Sustainability and environmental impact ● Climate resilience ● Automated installation technologies ● Real time monitoring and sensor integration ● Performance based design guidelines ● Smart construction practice ● Education and training 59
- 60. CONCLUSION ● Mitigation efforts focused on landslides are of paramount importance due to the severe consequences these natural disasters can have on both human lives and the environment. ● Landslides can result in loss of life, property damage, and disruption of infrastructure, making them a significant hazard in many regions around the world. ● Mitigation strategies encompass various preventive measures such as slope stabilization, early warning systems, and land use planning. 60
- 61. ● Soil nailing has proven to be a valuable tool in safeguarding infrastructure, protecting the environment, and enhancing public safety. ● This geotechnical technique has proven its worth in addressing the pressing challenges posed by unstable slopes and landslide-prone areas. ● By proactively addressing landslide hazards through mitigation, we can safeguard communities, protect ecosystems, and minimize the economic and social impacts of these destructive events, ultimately fostering a safer and more sustainable future. ● Its proven track record, cost-effectiveness, and adaptability make it a cornerstone in the effort to protect lives, infrastructure, and the environment from the devastating consequences of landslides. 61
- 62. ● As in advance in our understanding of geotechnical engineering and environmental challenges, soil nailing will continue to play a pivotal role in creating safer and more resilient landscapes worldwide. 62
- 63. THANK YOU 63