Coastal Soils and thier properties

1. Term Paper presentation National Institute of Technology, Calicut Dept. Of Civil Engineering(Environmental Geo-technology) Topic: Coastal Soils Presented By : Shashidhara K G (M200222CE) Topic Guide: Sankar Sir

2. Contents • Introduction • Costal line of India • Type of Coastal Soils • Engineering And Geotechnical Properties Of Soil • Grain Size Distribution • Specific Gravity • Atterberg Limits • Shear Strength • Problems associated with Coastal Soils • Engineering solutions for Such problems • Ground Improvement techniques for coastal soils • References Dept. of Civil Engineering

3. Coastal soils • What is soil? General Definition: Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Engineering definition: soil deposit may be defined as all naturally occurring, loose/uncemented/weakly cemented/relatively unconsolidated mineral particles, organic or inorganic in character, lying over the bed rock which is formed by weathering (disintegration) of rocks. What are coastal soils? The Soil that are transported by different medium and deposited near coastal Lines or those are formed and resides in the same place of coastal area are called as coastal soils Dept. of Civil Engineering

4. Why Study of Coastal Soils is Important in India ? Indian Coastal region lies between Arabian sea and western Ghats in west and in east it lies between eastern Ghats and bay of Bengal. India has total 7516.6 km mainland coastal line. The coastal area includes states such as Gujarat Maharatsra Karnataka Kerala Goa Tamilnadu Andrapradesh Orissa And eastern states. Dept. of Civil Engineering

5. Coastal soils Type of coastal soils in India Indian coastal regions have accumulated different types of soil as shown in geographical representation of soil In the map. Majorly it contains • Alluvial soil(43%) • Red and yellow soil(18.5%) • Laterite soil • Acid saline soils Dept. of Civil Engineering

6. Coastal Alluvial Soils: coastal alluvial soil is formed by deposition of materials or sediments (alluvium) brought in down by rivers that consist of silt, sand, clay, etc.. • The soils of the coastal plains are very deep with sandy texture. The texture generally ranges from sand to loamy sand with greyish brown to reddish brown and yellowish red color. • Sand content ranges from 80% and clay up to 15%. Even though these soils have high water table, the water holding capacity is poor due to the predominance of sand. • Alluvial soil can be mixed with other type of soil called as mixed alluvial. These soils are developed from fluvial sediments of marine, lacustrine and riverine sediments or its combinations. They occur below 20m MSL in the lowland plains, basins, valleys and along the banks of major rivers. • Wheat, rice, maize, sugarcane, pulses, oil seed etc. are cultivated mainly Dept. of Civil Engineering

7. Red and yellow soils • These are found mostly in the southern parts of Indian coastline district. • These are mostly very deep and homogeneous in nature. The texture of the soil generally ranges from sandy clay loam to clay loam with red to dark red color. Gravels are rarely noticed in these soils • It can be Seen mainly in low rainfall area. It has Porous, friable structure. • It appears Red because of Ferric oxide. The lower layer is reddish yellow or yellow. • Wheat, cotton, pulses, tobacco, oilseeds, potato etc. are cultivated. Dept. of Civil Engineering

8. Laterite soil • Laterite and laterite soil are the weathering products of rock in which several course of weathering and mineral transformations take place • Become so soft when wet and so hard when dried. • Can be seen In the areas of high temperature and high rainfall. • Formed as a result of high leaching. • Lime and silica will be leached away from the soil. • We can see presence of gravel in laterite soils. • Laterite soils are generally suitable for most of the dry land crops. It is mainly cultivated with coconut, arecanut, banana, tapioca, vegetables, yams, pepper, pineapple, fruit trees etc.. Dept. of Civil Engineering

9. Acid saline soils • Acid saline soils are present throughout the coastal area in patches with very little extent •  The area under these soils comprise of low-lying marshes, waterlogged and ill drained areas near the rivers and streams, which are subject to tidal waves. Sea and backwater tides make these soils saline. • During monsoon season, when rainwater and fresh water from rivers enter the fields, salinity is partially washed off. • The area under these soils occur mostly on plains at or below sea level. A wide variation in texture from sandy loam to clay is noticed with dark grey to black color. • Paddy is the only crop that can be cultivated. Dept. of Civil Engineering

10. Engineering and geological properties of soil (Based on case study) • Engineering properties of soils play a significant role in stability of civil engineering construction works particularly in road construction, foundation, embankments, bridges and dams to mention a few. This made imperative, the testing of soils on which foundation or superstructure would be laid • The testing would determine their geotechnical suitability as a construction material • The increasing rate of building collapse, tilting and development of huge cracks in structures requires a thoughtful solution. This could be provided by detailed study of the geotechnical properties of the subsoil layers, calculation of the bearing capacity of soil, and careful examination and recommendation of foundation parameters • Geotechnical properties studied includes: • grain size • moisture content • specific gravity • undrained cohesion • angle of internal friction • Atterberg Limits • SPT N-value and • CPT Qc values. Dept. of Civil Engineering

11. Grain Size Distribution • The test is performed to know the percentage of different grain sizes contained within the soil. The distribution of different grain sizes affect the engineering properties of soil which in turn their usability as construction material. • The grain size distribution shows that samples from Site A is clayey-siltySand having 78% sand, 14% silt, and 8% clay composition. • Samples from Site B could be described as gravelly silty-clayey Sand having 71% sand, 12% cay, 11% silt, and 6% gravel compositions. • C Site could be described as gravelly silty-clayey Sand having 75% sand, 12% silt, 8% clay, and 5% gravel compositions SPECIFIC GRAVITY The result of specific gravity of the three soil samples, A site, B site and C site are 2.69, 2.67, and 2.65. Comparing this results with some standard results or values, the three samples could be referred to as SAND. Dept. of Civil Engineering

12. NATURAL MOISTURE CONTENT • Natural moisture content of 40 to 59% was obtained for A site, 39 to 48% for Bsite and 55 to 78% for C site. • ATTERBERG LIMITS Dept. of Civil Engineering

13. Undrained Triaxial Compression Test • These values show that the soils have low bearing capacity due to low undrained cohesion and angle of internal frictionvalues. Dept. of Civil Engineering

14. STANDARD PENETRATION TEST Standard penetration test is an in-situ field test done to measure of the relative density of sand and consistency of clays. Dept. of Civil Engineering

15. Cone penetrometer test • This test was carried out using a 2.5 ton Dutch cone penetrometer equipment. It is an in- situ test done on the study area to depths of 9.0 m, 9.5 m, and 9.5 m respectively. • The resistance to the penetration of the cone (QC) was recorded at intervals of 0.25 m and plotted against depth to form a resistance profile. The profile was correlated with borehole data to provide information on variation of strata with depth and material strength across each site Based on the two field test (CPT and SPT) carried out on the three sites and several laboratory experiment done, the allowable bearing capacity was calculated and found low. Shallow foundations are not recommended without Ground improvement Dept. of Civil Engineering

16. Problems associated with Coastal Soils • 1 LIQUIFACTION : Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking. Liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes. • The coastal setting (in particular, young coastal areas, <300 years old) is especially prone to liquefaction because near surface soils are dominated by well-sorted sandy Aeolian deposits and a shallow water table exists. Dept. of Civil Engineering

17. Coastal Erosion • Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of waves, currents, tides, wind-driven water, waterborne ice, or other impacts of storms. Dept. of Civil Engineering

18. Critical Foundation Problems • Foundations used for inland construction are generally not suitable for coastal construction. Some examples of foundation systems that have a history of poor performance in erosion prone areas are slab-on ground, spread footings, and mat (or raft) foundations. • Foundation in coastal areas may fail because of low bearing capacity, liquefaction, Differential settlement and Erosion of coastal soils Dept. of Civil Engineering

19. Salinity of Coastal Soils • Soil salinity is the salt content in the soil; the process of increasing the salt content is known as salinization • A salt is simply an inorganic mineral that can dissolve in water. Many people associate salt with sodium chloride common table salt. In reality, the salts that affect both surface water and groundwater often are a combination of sodium, calcium, potassium, magnesium, chlorides, nitrates, sulfates, bicarbonates and carbonate. • In general, salts decrease the plasticity index, soil compressibility, swelling characteristics, and optimum moisture content while increasing the permeability, maximum dry density, shear strength, and bearing capacity of soil. Dept. of Civil Engineering

20. Prevention of Coastal erosion • Hard structural/engineering options use structures constructed on the beach (seawalls, groynes, breakwaters/artificial headlands) or further offshore (offshore breakwaters). These options influence coastal processes to stop or reduce the rate of coastal erosion.. Dept. of Civil Engineering

21. Coastal erosion prevention by geotextile tubes • Geotextile tube is one of the geosynthetics structures that are increasingly used in coastal protection. Geotextile tubes are made from high-strength geosynthetic fabrics that allow the water to flow through pores while retaining the filling materials. • Based on the results of stability analysis and hydraulic model tests, a double-lined geotextile tube installed with zero-water depth above crest was found to be the most stable and effective for wave absorption than other design plans Dept. of Civil Engineering

22. Engineering Solution for Foundation problems • Deeply embedded pile or column foundations are required for construction in Coastal area • In addition to meeting the requirements for conventional construction, these foundations must: (1) elevate the building above the Base Flood Elevation (BFE), and (2) prevent flotation, collapse, and lateral movement of the building, resulting from loads and conditions during the design flood event (in coastal areas, these loads and conditions include inundation by fast-moving water, breaking waves, floating debris, erosion, and high winds). Dept. of Civil Engineering

23. Pile foundations may be designed with grade beams (typically from wood or concrete). Grade beams provide many benefits: • When incorporated with reinforced concrete or masonry column foundation systems (or with wood piles), grade beams provide lateral stiffness to prevent the need for diagonal cross-bracing or knee-bracing. • Properly designed and constructed, grade beams facilitate load redistribution and can reduce the potential for collapse during extreme events. • Grade beams can allow builders to accommodate the inevitable variations that always seem to affect pile placement. Dept. of Civil Engineering

24. Other Ground Improvement Techniques • Dynamic compaction: Dynamic compaction is a method that is used to increase the density of the soil when certain subsurface constraints make other methods inappropriate. It is a method that is used to increase the density of soil deposits. The process involves dropping a heavy weight repeatedly on the ground at regularly spaced intervals. • Rapid Dynamic Compaction:This technique is a recently developed soil improvmenttecnique, use for compaction of granular soils up to 5 m deep, as alternative to Dynamic Compaction method. Dept. of Civil Engineering

25. Stone Column Stabilization: Stone column are universally used to increase the bearing capacity of the soil and reduce the liquefaction potential of soil. The soil have low plasticity like silt and clay are vulnerable to liquefaction, the reinforced stone column can increase the strength and tension of soils. The pore water dissipation in stone column accelerated by volume reduction process called consolidation with the help of aggregates. In order to enhance the consolidation rate by different admixtures and materials in the stone column like quarry dust and geosynthetics etc. Dept. of Civil Engineering

26. Chemical Stabilization: Loose soils can be stabilized using chemicals like • Lime • Cement • Bitumen • Other Chemicals like Sodium Chloride, Sodium Silicate • Geo textiles. • Lime column Stabilization :This deep stabilization method, the lime column method, can be used to stabilize road embankments, different types of fills and natural slopes as well as excavations. Lime columns can also be used to reduce settlements and increase the rate of settlements for embankments, pipes and light constructions. Dept. of Civil Engineering

27. Case study of Coastal soil Stabilisation using sodium silicate • For this study, a series of laboratory tests were conducted to determine the potential of Sodium Silicate (TX-85), a liquid-type chemical soil stabilizer, to improve the properties of coastal soil. • The soil samples were subjected to a series of laboratory tests, which includes the pH and Unconfined Compression Strength (UCS). The dosages of Sodium Silicate mixed with the soil were 4, 5, and 7% by soil sample weight, with curing intervals of 3 hours, 24 hours and 48 hours, respectively. • The optimal dosage of Sodium Silicate observed in this study is 4%, at 48 hours curing period. This combination of stabilizer dosage and curing period produced the highest strength increment, where the UCS value increased by 90.3%, from 262.1 kPa to 498.8 kPa. Dept. of Civil Engineering

28. Table : Summary of UCS test results for silt soil treated with Sodium Silicate (SS) Dept. of Civil Engineering

29. The optimal dosage of Sodium Silicate observed in this study is 4%, at 48 hours curing period. This combination of stabilizer dosage and curing period produced the highest strength increment, where the UCS value increased by 90.3%, from 262.1 kPa to 498.8 kPa. Dept. of Civil Engineering

30. REFFERENCES • 1. Abdulquadri.O, Alaberea and Olaoluwa E. Emmanuelb.,(2018) ‘Engineering Geological Properties of Coastal Plain Sands in Selected Areas in Ikoyi Area, a typical Coastal Sedimentary Terrain’, World Scientific News. • 2. R.Srinivasan, D.C.Nayak, K.Singhand S.K Reza.,(2016) ‘Landforms soils relationship in coastal Odisha-Major Problems and management’, Popular Khethi. • 3. Adiana Erica Amalaudin.,(2019) ‘Shear strength of Coastal soil treated with Sodium Silicate’, IOP Conference series: Material science and Design. • 4. A Madhan Kumar .,(2016) ‘Comparision of properties of Cohesive soils Along East Coast of India’, IGC • 5. ‘Problems of salination land in coastal areaofindia and suitable protection measures’.,(2017) Ministry of water resource, India. • 6. ‘Home builders guide in coastal area’., US Dept. of Homeland security. Dept. of Civil Engineering

31. Dept. of Civil Engineering