Consistency index
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The document discusses thixotropy, sensitivity, and activity in soils. Thixotropy refers to the regain of shear strength in soils over time after being remolded such as during pile driving. Sensitivity indicates the loss of strength from remolding and is measured as the ratio of undisturbed to remolded strength. Activity is measured as the ratio of plasticity index to clay fraction and indicates the water holding capacity of clayey soils.
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This document discusses the consolidation of soil. It defines important terms like compression, compressibility, and consolidation. It outlines the differences between compaction and consolidation. The importance of consolidation theory is that it provides information on total settlement, time for settlement, and types of settlement. Terzaghi's spring analogy is described to explain the consolidation process. A one-dimensional consolidation test procedure is outlined. Important definitions related to consolidation like compression index, swelling index, and coefficients are provided. The document also discusses normally, under, and over consolidated soils and how to determine preconsolidation pressure. Terzaghi's one-dimensional consolidation theory and solution are presented. Methods to determine degree of consolidation and coefficient of consolidation from laboratory test data are
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i have made all the slide according to poly diploma civil and also for civil engineering
my gmail account - laxmans227@gmail.com
these are 100% correct but in case of some error comment down or contact me
follow me for all updates
if u have any doubt fell free to ask on comment section
software - power point presentation 2015
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i have made all the slide according to poly diploma civil and also for civil engineering
my gmail account - laxmans227@gmail.com
these are 100% correct but in case of some error comment down or contact me
follow me for all updates
if u have any doubt fell free to ask on comment section
software - power point presentation 2015
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2. The SPT N-value provides an approximate measure of soil resistance and a disturbed soil sample. It can be used to estimate soil strength parameters and bearing capacity through empirical correlations.
3. However, the SPT is highly dependent on the equipment and operator used, as factors like hammer efficiency, drill rod length, and borehole diameter can affect the N-value. Corrections are required
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- Soils fail primarily in shear when the shear stress along a failure plane reaches the soil's shear strength.
- The shear strength of soils is governed by the Mohr-Coulomb failure criterion, which consists of cohesive and frictional components that depend on effective stresses.
- Laboratory tests like direct shear and triaxial tests are used to measure the shear strength parameters (c, φ) of soils by simulating the in-situ stress conditions.
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The Proctor compaction test is used to determine the optimal moisture content and maximum dry density of soils. It involves compacting soil samples in a mold using a standardized compactive effort at different moisture contents. The dry density is measured for each sample to create a compaction curve showing the relationship between dry density and moisture content. The peak of the curve indicates the optimum moisture content and maximum dry density, which represent the conditions when the soil is most dense and has the highest load-bearing capacity. The test is important for determining how to properly compact soils in the field.
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Consistency index
- 2. The word Thixotropy is derived from the two words:thixis meaning touch,and tropo,meaning to change.Therefore,thixotropy means any change that occurs by touch. The loss of strength of a soil due to remoulding is partly due to change in the soil structure and partly due to disturbance caused to water molecules in the absorb layer.Some are reversible.If a remoulded soil is allowed to stand,without loss of water,it may regin some of its lost strength.In soil engineering,this gain in strength of the soil with passage of time after it has been remolded is called thixotropy.
- 3. Thixotropy of soils is of great practical importance in soil engineering.For example,when a pile is driven in to ground,the loss of strength occurs due to disturbance caused.Thixotropy indicates how much shear strength will be regained after the pile has been driven and left in place for some time.
- 5. A cohesive soil in its natural state of occurance has a certain structure.When the structure is disturbed,the soil becomes remoulded,and its engineering properties change considerly.Sensitivityof a soil indicates its weakening due to remoulding. It is defined as the ratio of undisturbed strength to the remoulded strength at the water content
- 6. S.no. Sensitvity Soil Type 1. <1.00 Insentive 2. 1.0-2.0 Sensitive 3. 2.0-4.00 Little sensitive 4. 4.0-8.00 Moderately sensitive 5. 8.0-16.0 Extra sensitive 6. >16.0 Quick
- 7. For most clays,sensitivity lies between 2and 4.Clays considred sensitive have values between 4 and 8. In case of sensitive clays,remoulding causes a large reduction in strength.Quick clays are unsutible. These turn into slurry when remoulded. High sensitivity in clays is due to a well-devloped flocculent srtucture which is disturbed when the soil is remoulded.
- 9. Activity of soil is the ratio of plasticity index and the percentage of clay fraction(minus 2µ size).Thus A=Ip/F Where Ip=plasticity index,F=clay fraction. The clay fraction F is percentage finer than 2µ size
- 10. The amount of water in a soil mass depandes upon the type of clay mineral present. Activity is a measure of the water holding capacity of clayey soils.The changes in the volume of a clayey soil during swelling or shrinkage depend upon the acyivity.
- 11. A number of samples of a particular soil are taken and their plasticity index and clay fraction determineded. If a plot is obtained between the clay fraction and plasticity index,it is observed that all the points for a particular soil lie on a straight line The slope of the line gives the activity of soil. The steeper the slop,the greater the activity. The lines with different slopes are obtained for different soils.
- 12. 140 120 100 80 kaolinite 60 Illite Montomorillonite 40 20 0 0 10 20 30 40
- 13. Sr.no Activity Soil type 1. A<0.75 Inactive 2. A=0.75 to 1.25 Normal 3. A>1.25 Active