Faculty of Engineering – Cairo UniversityThird Year CivilSoil MechanicsSpring 2015 Soil Settlement Settlements are vertical deformations of a soil mass under the effect of an applied stress causing vertical movement of the supported structure
What is settlement in civil engineering?
This downward movement of the ground is called settlement. Many civil engineering projects include placing of loads on the ground, which produces increase in vertical effective stress. This increase in vertical stress is important because it produces vertical strain in the soil.
What is the settlement of the ground?
Settlement: When a load is applied on the ground, it increases the vertical effective stress. This stress increases the vertical strain in the soil. This increase in vertical strain causes the ground to move downward. This downward movement of the ground is called settlement.
What are the two major problems with soil settlement analysis?
Two Major Problems with soil settlement analysis are: Obtaining a reliable stress profile from the applied load. ΔH = total settlement, ΔHc = consolidation settlement, ΔH = secondary compression, U = average degree of consolidation.
What is sub-surface settlement?
Sub-surface settling, settlement in landscaping, soil settling – those are just different ways to say the same thing: the soil under your home and surrounding area is becoming more compact over time. This natural process includes three types of settlement: immediate, consolidation (i.e. ‘primary’), and creep settlement (i.e. ‘secondary’).
What is the difference between total settlement and differential settlement?
Total settlement is the magnitude of downward movement. Differential settlement is non-uniform settlement. It is "the difference of settlement between various locations of the structure. Angular distortion between two points under a structure is equal, to the differential settlement between the points divided by the distance between them.
What is the final settlement of a foundation?
Generally, the final settlement of a foundation is of interest and U is considered equal to 1 (i.e. 100% consolidation) 1. Immediate Settlement. Immediate settlement takes place as the load is applied or within a time period of about 7 days. Predominates in cohesion less soils and unsaturated clay.
Why is the leaning tower of Pisa undergoing consolidation settlement?
The lean is caused by consolidation settlement being greater on one side. This, however, is an extreme case. The principal settlements for most projects occur in 3 to 10 years.
How much settlement is acceptable for a road embankment?
A fixed-end arch would suffer greatly if the abutments settle or rotate. For road embankments, storage silos and tanks a settlement of 300mm - 600mm may be acceptable, but for machine foundations the settlement may be limited to 5mm 30mm. Different types of construction materials can withstand different degrees of distortion. For example, sheet metal wall panels do not show distress as readily as brick masonry.
What happens if soil shears fail?
A soil shear failure can result in excessive building distortion and even collapse. Excessive settlements can result in structural damage to a building frame nuisances such as sticking doors and windows, cracks in tile and plaster, and excessive wear or equipment failure from misalignment resulting from foundation settlements.
What is secondary consolidation?
Secondary consolidation may be the larger component if settlement in some soils, particularly in soils with a large organic component. Secondary consolidation is associated with both immediate & consolidation type settlements, although it is usually not of much significance with immediate settlements.
What is the value of m in a settlement?
m = number of corners contributing to settlement ΔHi. At the footing center m= 4; and at a corner m = 1, at a side m = 2.
What is soil mechanics?
Soil mechanics is a scientific field of the civil engineering discipline that studies the mechanical behavior of soil. Soil mechanics is critical in civil engineering as it describes the principles that govern the way civil infrastructure projects such as buildings, bridges, tanks, embankments, dams, and tunnels, are supported by the soil.
How to derive soil mechanical properties?
To derive soil’s mechanical properties, in-situ and laboratory testing are performed and analytical solutions or constitutive models are used to simulate its behavior.
Who prepared the permeability and seepage PowerPoint?
Permeability and Seepage Powerpoint Presentation. Prepared and donated by Professor Sivakugan, James Cook University , Australia.
Who is Professor John Burland?
World-leading geotechnical engineer Professor John Burland introduces viewers to the world of soil mechanics. If playback doesn't begin shortly, try restarting your device. Videos you watch may be added to the TV's watch history and influence TV recommendations.
Who prepared the Consolidation of Clays PowerPoint?
Consolidation of Clays Powerpoint Presentation. Prepared and donated by Professor Sivakugan, James Cook University, Australia.
Is soil a fluid or solid?
Soil mechanics differs from classical fluid mechanics or solid mechanics as the soil is (a) a heterogeneous mixture of solid particles (gravel, rock, sand, silt, and clay), liquid, and gas (three-phase system), and (b) is a particulate material. Understanding and predicting soil’s behavior is complex as it is stress-dependent and nonlinear.
What is soil settling?
Soil settling is a natural process that occurs during and after construction. Before any building is constructed, contractors need to do below grade work to safeguard the integrity of a structure above ground. With any new home comes a foundation, which requires digging up earth with excavators, levelling the ground, and pouring concrete. In that process the soil around the foundation becomes loose until it settles again through immediate, consolidation or creep settlement.
How does soil settle?
Immediate settlement occurs when a load – for example a piece of heavy machinery – rests on the soil and rearranges the particles to become more compact almost instantly. Consolidation settlement happens with the gradual squeezing out of water, and creep settlement occurs when the soil is under a constant load over time. [i] Due to the variation, soil settlement can transpire 3-5 years following construction, and in some cases even decades.
What happens when soil settles?
In the least damaging cases, soil settling can lead to depressions or divots in the land. In the worst cases – like the Leaning Tower of Pisa – soil settling can lead to titled buildings.
What does it mean to move into a new subdivision?
Moving into a brand-new subdivision is an exciting prospect – a never-lived-in home typically means everything is in good working order. However, outside the house, new homeowners also inherit the soil which can sometimes be in less-than-peak condition.
What are the three types of settlement?
This natural process includes three types of settlement: immediate, consolidation (i.e. ‘primary’), and creep settlement (i.e. ‘secondary’).
How can settlement be managed?
In most cases, settlement can be managed through accurate assessments of what’s under the surface and good compacting practices. Yet as Mother Nature would have it, not everything is in our control. Excessive settlement can happen when there is highly expansive soil, frost, drought, flooding, poor drainage, vibration, or the alternate wetting and drying of soil. [ii]
Is creep settlement a responsibility of the new homeowner?
Despite what you may think, those voids caused by soil settlement are the responsibility of the new homeowner. Builders and engineers can do everything possible to make sure the soil is consolidated before finishing a home, but creep settlement is beyond their control. Plus, builder liability for soil settlement years after construction would be prohibitively costly, and would guarantee that no business could keep their doors open for long.
What is downward movement of the ground called?
When downward movement of the ground occurs over a large area due to increase in vertical strain in the soil. Then this movement is sometimes called Subsidence.
What is the term for the movement of the ground downward?
This increase in vertical strain causes the ground to move downward. This downward movement of the ground is called settlement .
Fig. 9.7 Void ratio to effective pressure curves
curve, primary compression being made up of (i) a reversible part and (ii) an irreversible part. Once the consolidation pressure is extended beyond the original consolidation pressure value (the preconsolidation pressure ), the e p curve follows the trend of the original compression curve.
Typical values of mv are given in Table 9.3
In the laboratory consolidation test the compression of the sample is one-dimensional as there is lateral confinement, the initial excess pore water pressure induced in a saturated clay on loading being equal to the magnitude
Why does soil settle?
Soil Settlement generally due to stress and environmental changes causing the volumetric change in soil mass
When is the top layer of soil considered over consolidated soil?
Third stage, If the top layer of soil is eroded by river current or dry out by dissication, then soil at point x is considered at over consolidated soil (O.C.) When σvm >σvo →OCR>1.0
Where are the recent clays in Southeast Asia?
Distribution of recent clays in Southeast Asia System of aquifers under the Chao Phraya plain
What are the results of confined compression test plotted as?
Results of confined compression test plotted as void ratio versus stress on natural scale.
Soil Settlement and Soil Shear
- A soil shear failure can result in excessive building distortion and even collapse. Excessive settlements can result in structural damage to a building frame nuisances such as sticking doors and windows, cracks in tile and plaster, and excessive wear or equipment failure from misalignment resulting from foundation settlements. It is necessary to in...
Components of Settlement
- The components of settlement of a foundation are: 1. Immediate settlement 2. Consolidation Settlement, and 3. Secondary compression (creep) ΔH = ΔHi + U ΔHc + ΔHs ΔH = total settlement, ΔHc = consolidation settlement, ΔH = secondary compression, U = average degree of consolidation. Generally, the final settlement of a foundation is of interest and U is considered e…
Immediate Settlement Calculations
- Where q0 = intensity of contact pressure in units of Es (Undrained Modulus of Elasticity) B’ = least lateral dimension of contributing base area in units of ΔHi Es, μ = Elastic Soil Parameters. A major problem is of course to obtain correct stress-strain modulus Es. Es can be found from laboratory tests like unconfined compression tests, Triaxial compression tests, and in-situ tests like SPT, C…
Consolidation Settlement Calculations
- After primary consolidation the soil structure continues to adjust to the load for some additional time. This settlement is termed secondary consolidation/secondary compression. At the end of secondary consolidation the soil has reached a new Ko-state (at-rest state). Secondary consolidation may be the larger component if settlement in some soils, particularly in soils with …
Settlement Limits
- Total settlement is the magnitude of downward movement. Differential settlement is non-uniform settlement. It is "the difference of settlement between various locations of the structure. Angular distortion between two points under a structure is equal, to the differential settlement between the points divided by the distance between them. Theoretically, no damage will be done to a structur…