Geotechnical Engineering
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Why is the degree of saturation of soil treated as constant throughout the consolidation process?
aviratdhodare
The degree of saturation is the ratio of the volume of water to the volume of voids. Consolidation happens when the soil is in a fully saturated condition. That is, after all, air from voids got expelled by compaction of soil it will be fully saturated and then the consolidation starts. Thus as theRead more
The degree of saturation is the ratio of the volume of water to the volume of voids. Consolidation happens when the soil is in a fully saturated condition. That is, after all, air from voids got expelled by compaction of soil it will be fully saturated and then the consolidation starts. Thus as the volume of water reduces by consolidation, the volume of voids also reduces at the same rate. So there will be a constant degree of saturation. Finally, almost all water gets expelled out and the volume of voids will become negligible and then the plastic rearrangement of soil particles (secondary consolidation) will take place.
See lessWhat is the equation of A-line in the plasticity chart?
aviratdhodare
Plasticity chart is a graph between plasticity index (IP) and liquid limit (WL) in percentage which is used for classification of fine-grained soils as per the Indian Standard Soil Classification System(ISSCS). If more than 50% percent of soil passes through 75micron sieve, then it is classified asRead more
Plasticity chart is a graph between plasticity index (IP) and liquid limit (WL) in percentage which is used for classification of fine-grained soils as per the Indian Standard Soil Classification System(ISSCS). If more than 50% percent of soil passes through 75micron sieve, then it is classified as fine-grained soil.
Equation of A-line as represented in the given chart relates plasticity index and liquid limit as
IP = 0.73 (WL – 20).
The equation of A-line gives value of plasticity index ranges from 0 to 58.4 corresponding to values of liquid limit from 0 to 100%.
The plasticity characteristic of fine grained soil based on different liquid limit range is shown below.
From the plasticity chart,
CL: Clay with low plasticity
ML: Silt with low plasticity
CH: Clay with high plasticity
MH: Silt with high plasticity
OH: organic soil with high plasticity
CI: Clay with intermediate plasticity
MI: Silt with intermediate plasticity
OI: organic soil with intermediate plasticity
The soil fall above A-line in plasticity chart are clayey soils and that fall below A-line are silt and organic soils. If plasiticity index ranges between 4–7%, soil is represented in dual symbol. That is CL-ML.
See lessWhat is adsorbed water, and how does it affect the permeability of soil?
aviratdhodare
For fine-grained soils there will be a microscopic water layer bound around the grains due to some electrochemical process. This water is called adsorbed water or hygroscopic water. Adsorbed water fills the voids of the soil. For clayey soil, the adsorbed water is in the diffused double-layer form.Read more
For fine-grained soils there will be a microscopic water layer bound around the grains due to some electrochemical process. This water is called adsorbed water or hygroscopic water. Adsorbed water fills the voids of the soil. For clayey soil, the adsorbed water is in the diffused double-layer form.
The presence of adsorbed water around soil grains consumes a considerable amount of void space. It will intact reduce the permeability of soil though already voids contain some amount of water. Due to the reduction in effective pore space, water is not free to move through soil and thus reduces the permeability.
See lessHow can we differentiate clay and silt apart from its sizes?
aviratdhodare
Silt is composed of fine-grained clay in usual parlance. However, note the Wiki comment: Though silt and clay are classified as fine soils, they have some differences between them. – Clay particles are very smaller in size compared to silt particles, even though all soils with particle size <0.07Read more
Silt is composed of fine-grained clay in usual parlance. However, note the Wiki comment:
Though silt and clay are classified as fine soils, they have some differences between them. – Clay particles are very smaller in size compared to silt particles, even though all soils with particle size <0.075mm are classified as either silt or clay. – Clay contains clay minerals, while silts do not contain clay minerals.
Ribbon test – clay will form a ribbon if a mixture of water and clay is rolled in hand – clay will join with other particles of clay to form a molecular string fused to each other. Silt will not work for this.
A non-technical test is to see whether the soil is a fertile plant-growth footing. True clay isn’t. Example: kudzu jungles here in Appalachian supposed “clay country.”
See lessWhat is the best method for ground improvement technique?
aviratdhodare
Mech stabilization Cement stabilization Lime stabilization Bituminous stabilization Chemical stabilization Thermal stabilization Electrical stabilization Stabilization by grouting Stabilization by geotextiles & fabrics By Vibration Vibro-compaction Vibro stone columns Dynamic compaction Rapid imRead more
By Vibration
Vibro-compaction
Vibro stone columns
Dynamic compaction
Rapid impact compaction
Vibratory probing
Compaction piles
Blasting
By Adding Load or Increasing Effective Stress
Pre-compression
Vertical drains
Inundation
Vacuum pre-loading
Dewatering fine-grained soils
Pressure berms
By Structural Reinforcement
Reinforced soil
Soil nailing
Root or micro-piles
Slope dowels
Embankment piles
By Structural Fill
Removal and replacement
Displacement
Reducing load
By Admixtures
Lime columns (Swedish method)
Lime and cement columns (Japanese method)
Mix-in-place by single auger or Deep Soil Mixing
Lime stabilization of slopes
Lime stabilization of pavements
Cement stabilization of pavement
By Grouting
Grouting processes
Permeation grouting
Hydrofracture grouting
Jet grouting
Compaction, squeeze and compensation grouting
Cavity filling
By Thermal Stabilization
Artificial ground freezing
Artificial ground heating
By Vegetation
See lessWhat is negative pore water pressure in soil?
Kuldeep Singh
Negative pore water pressure is a condition in soils when they are partially saturated. What happens is, surface tension is developed on the surfaces of water in the pores. There are surfaces since the pores are partially filled. This surface tension pushes and pulls other particles in the soil andRead more
Negative pore water pressure is a condition in soils when they are partially saturated.
What happens is, surface tension is developed on the surfaces of water in the pores. There are surfaces since the pores are partially filled. This surface tension pushes and pulls other particles in the soil and thus, effectively creates a pore water pressure in the downward direction.
This has an increasing effect on the effective stress.
σ’ = σ – (-μ)
So, the effective stress becomes even higher than the total stress. This means the soil will tend to provide even higher stress reactions than what it’ll do if completely dry.
See lessExplain the construction & use of New Mark’s influence chart?
Suyogmuralkar
Hi devilart, This method is used to compute the vertical and horizontal stresses of any shape ,irregular geometry below any point outside or inside The chart as shown in the above figure essentially consists of n no. of radial lines and m no. of concentric circles. To find out vertical stressRead more
Hi devilart, This method is used to compute the vertical and horizontal stresses of any shape ,irregular geometry below any point outside or inside
The chart as shown in the above figure essentially consists of n no. of radial lines and m no. of concentric circles.
To find out vertical stress at any point below or outside the loaded area, Plan of the loaded area is drawn such that depth Z at which stress is being computed equals the length AB as shown on
N = No. of blocks. Bina Nusantara.
Further, the plan is placed over influence chart such that the point below which stress is required coincides with the center of chart Then count the number of influence area (N) covered by the plan
See lessWhat is disturbed and undisturbed soil sample?
GK
Disturbed soil samples: The soil samples whose natural structural integrity gets changed, during the process of collection, to a considerable amount is called disturbed soil samples. These changes could be in the soil structure, in the stress condition, in its texture, in the water content and voidRead more
Disturbed soil samples:
The soil samples whose natural structural integrity gets changed, during the process of collection, to a considerable amount is called disturbed soil samples. These changes could be in the soil structure, in the stress condition, in its texture, in the water content and void ratio, in chemical properties, etc.
Undisturbed soil samples:
In undisturbed soil samples the natural soil structure, the stress condition, its texture, the water content, and the void ratio, the chemical properties do not get changed during sampling.
See less