Solution
- Write down the consolidation settlement equation; Δ H = H C c ( 1 + e 0) log ( p 0 ' + Δ p) p 0 ' ...
- Find the initial effective stress at the mid layer of the clay stratum ( p0’ ); p 0 ' = γ sand × 1.5 + ( γ sand ...
- Find Δ p Δ p = Increase of stress at the mid point of the clay layer due to the footing. ...
- Apply values in the consolidation equation.
What is the U in consolidation settlement?
Obtaining a reliable stress profile from the applied load. 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 equal to 1 (i.e. 100% consolidation) 1. Immediate Settlement
How to calculate 1-D consolidation settlement?
Calculation of 1-D Consolidation Settlement The consolidation settlement can be determined knowing: - Initial void ratio e 0 - Thickness of layer H - Change of void ratio e It only requires the evaluation of e Calculation of 1-D Consolidation Settlement It only requires the evaluation of e Calculation of 1-D Consolidation Settlement
How much primary consolidation is required for a settlement fill?
Typically estimate as 10-20% of primary consolidation Add this number to fill thickness for fill quantity estimates Settlement Fill Subgrade Hydraulic Mechanical Immediate/Construction
How to calculate settlement in construction?
•For settlement calculation, the pressure increase s z can be approximated as : q z where s m represent the increase in the effective pressure in the middle of the layer. Compressible Layer s z under the center of foundation Approach 1: Middle of layer (midpoint rule) s z = s
What is consolidation settlement?
Some time is required for excess pore water pressed to dissipate and increase the stress to be transferred to the soil skeleton. This gradual increase in the effective stress in the clay layer will cause settlement over a period of time and is referred to as consolidation settlement.
How do you calculate soil settlement?
Total settlement for cohesive soils are generally estimated by the sum of immediate settlement, primary consolidation and secondary compression, where immediate settlement usually constitutes a significant portion of the total settlement.
How do you calculate settlement time?
7:5111:50Settlement and Time Calculations for Double Drainage ConsolidationYouTubeStart of suggested clipEnd of suggested clipI'm going to put that in as a decimal zero. Point four three times my two inches. And that's goingMoreI'm going to put that in as a decimal zero. Point four three times my two inches. And that's going to be my settlement over time which in this case is one year.
Is consolidation same as settlement?
Debt consolidation and debt settlement are strategies for making debt manageable, but they are different methods and bring different results. Debt consolidation reduces the number of creditors you'll owe. Debt settlement tries to reduce the amount of debt you owe.
How do you calculate settlement?
Settlement amounts are typically calculated by considering various economic damages such as medical expenses, lost wages, and out of pocket expenses from the injury. However non-economic factors should also play a significant role. Non-economic factors might include pain and suffering and loss of quality of life.
What is consolidation settlement of soil?
When soil is loaded undrained, the pore pressures increase. Then, under site conditions, the excess pore pressures dissipate and water leaves the soil, resulting in consolidation settlement. This process takes time, and the rate of settlement decreases over time.
What will be the time required for 90% consolidation?
The time for a clay layer to achieve 90% consolidation is 15 years.
What is the rate of consolidation?
The primary settlement of a cohesive soil s(t) results from the volume of water squeezed out. It tends towards a limit value s(t = ∞) which represents the maximum value or the final settlement. Their ratio is called the degree of consolidation uk.
What is CV in consolidation?
cv is the coefficient of consolidation and is a measure of the rate at which the consolidation process proceeds. In many consolidation problems in which the total stress σ remains constant throughout.
What is primary consolidation settlement?
Primary consolidation: Soil settlement during which the excess pore water pressure is transferred to the soil's skeleton.
What is the total settlement?
Total settlement refers to the overall change in vertical distance. Differential settlement involves an expected amount that the total settlement will vary between points over a horizontal distance, which can be caused by variations in the foundation soil profile and wall height over a certain distance.
What is settlement of soil?
What is Settlement? Settlement is the downward movement of the ground (soil) when a load is applied to it. The load increases the vertical effective stress exerted onto the soil. This stress, in turn, increases the vertical strain in the soil. This increase in vertical strain causes the ground to move downward.
What is the total settlement?
Total settlement refers to the overall change in vertical distance. Differential settlement involves an expected amount that the total settlement will vary between points over a horizontal distance, which can be caused by variations in the foundation soil profile and wall height over a certain distance.
How do you calculate soil removal?
Simply multiply the length by the width by the depth or use our simple volume calculator. Circular areas are also easy to calculate. Simply multiply 3.1415 (π) by the radius, by the radius again, by the depth or use our simple volume calculator.
What is allowable settlement?
The allowable settlement is defined as the acceptable amount of settlement of the structure and it usually includes a factor of safety.
What is the pore water pressure of a piezometer?
For the piezometer at GL − 17, the pore water pressure was reduced to − 60 kPa before subjected to embankment load, and became about − 48 kPa at the termination of the vacuum operation. After that, the pore water pressure returned to its hydrostatic condition.
What was the pressure of the airtight sheet during the consolidation settlement?
Vacuum pressure measured under the airtight sheet was maintained constantly at about 80 kPa along to the consolidation settlement between October 2008 and December 2009. The water discharge at the beginning of vacuum pumping was about 400 m 3 /day and gradually decreased during consolidation settlement to about 200 m 3 /day.
What is the consolidation settlement?
For fine-grained soils, the consolidation settlement often is the major component of the total settlement. As noted previously, consolidation settlement is the time-dependent volume change that occurs as the excess pore water pressure, developed during load application, gradually dissipates and is transferred to the soil skeleton. The consolidation settlement is given by
What is secondary settlement?
Secondary settlement continues after consolidation settlement is complete, as the soil structure gradually readjusts to the new level of effective stress. This process continues indefinitely. The prediction of secondary settlement is of considerable importance with clays of high plasticity and with micaceous and organic soils, but it typically is of minor concern with coarse-grained soils and overconsolidated, low plasticity, inorganic clays. Secondary settlement often is computed from the relation
What are the phases of settlement?
As stated above, when a load is applied to the foundation, three distinct phases of settlement occur: immediate or elastic (ρ e ), consolidation (ρ c ), and secondary settlement (ρ s ):
What is the estimated average degree of consolidation in 2024?
The estimated average degree of consolidation in 2024, according to non-Darcian flow, becomes 84%, corresponding to a settlement of 2.1 m.
What is wick drain?
A wick drain is a prefabricated drainage strip that consists of a plastic core surrounded by a nonwoven polypropylene geotextile jacket. The geotextile (a filter fabric) allows passage of water into the core that is then pumped out.
Who suggested a simple graphic construction to determine the preconsolidation pressure s’?
Casagrande (1936) suggested a simple graphic construction to determine the preconsolidation pressure s’
What is the OCR of NC soils?
oFrom the definition of NC soils, they always have OCR=1.
Is a surcharge reasonable simplification?
reasonable simplification if the surcharge is of large lateral extent water squeezed out
What is t100 in a lab?
Where t100 (lab) and t100 (f) = time taken for primary consolidation to complete in the laboratory df, dlab = are respectively maximum drainage paths in the field and laboratory. For one-way drainage d= thickness of the layer of interest or sample thickness in the laboratory, for two-way drainage d = half of the thickness of the layer of interest/sample.
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.
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.
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 happens after primary consolidation?
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 K o -state (at-rest state).
What is the total settlement of a foundation?
The total settlement of a foundation is the sum of the elastic settlement and the consolidation settlement. Consolidation settlement comprises two phases: primaryand secondary. The fundamentals of primary consolidation settlement were explained in detail in Chapter 2.
What is secondary consolidation settlement?
Secondaryconsolidation settlement occurs after the completion of primary consolidation caused by slippageand reorientationof soil particles under a sustained load. Primary consolidation settlement is more significant than secondary settlement in inorganic clays and silty soils. However, in organic soils, secondary consolidation settlement is more significant.
Why do we substitute in the equation of Se?
Substitute in the equation of Se in order to get the elastic settlement of sandy soil.
What are the two major categories of settlement?
The settlement of a shallow foundation can be divided into two major categories: (a) elastic, or immediate settlement and (b) consolidation settlement.
What is the plate load test?
The ultimate load-bearing capacity of a foundation, as well as the allowable bearing capacity based on tolerable settlement considerations, can be effectively determined from the field load test, generally referred to as the plate load test. The plates that are used for tests in the field are usually made of steel and are 25 mm (1 in.) thick and occasionally, square plates that are 305 mm X 305 mm (12 in. X 12 in.) are used.
How to calculate settlement of a foundation?
First of all, you have to determine the average stress in the clay layer below the centre of the foundation, and then you can calculate the settlement using the appropriate equation: ∆𝜎�𝑣=4��[ �2��(𝐻
How to test a plate?
To conduct a plate load test, a hole is excavated with a minimum diameter of 4B(B is the diameter of the test plate) to a depth of Df, the depth of the proposed foundation. The plate is placed at the centre of the hole, and a load that is about 1/4 to 1 /5 of the estimated ultima te load is applied to the plate in steps by means of a jack. During each step of the application of the load, the settlement of the plate is observed on dial gauges. At least one hour is allowed to elapse between each application. The test should be conducted until failure, or at least until the plate has gone through 25 mm (1 in.) of settlement.
How to study consolidation load data?
THEORETICAL INTERPRETATION FOR THE APPLICATION OF TEST DA’TA The consolidation-load and consolidation- time data may be studied in greater detail by further analysis of the test curves. A con- venient way to study consolidation-load data is to plot void ratio against pressure. This curve may be plotted by arithmetic scales or with the pressure values to a logarithmic scale, depending on the type of material. The usual method is to use a semilogarith- mic plot sheet, as in Figures 4 and 5. When using such a plot for clayey soils the rec- ognized theories 6y7 related to this plotting method are very often helpful. Load Consolidation The shape of the consolidation curve for 6 Terzaghi, K:, and Peck, R. B., U Mechanic in ngineerine: Prac i e Wiley &‘S%s,%ew York, 1948, ki &I%? 7 Taylor, op. cit., pp. 217-219. a natural clay soil, initially deposited in very loose condition and gradually loaded with increasing overburden and structural pressures (referred to as normally-loaded soil), has been found to be an approximately straight line on a semilogarithmic plot. It may be represented by the empirical equation, e = e, - c, Loglo- P, +AP . (1) PO where C, = compression index
What is the one dimensional consolidation test?
LIMITATIONS OF THE ONE -DIMENSIONAL CONSOLIDATION TEST As seen in the descriptions of the appa- ratus and the testing procedure, the one- dimensional consolidation test represents the settlement of a soil structure that has total lateral restraint, and in which there is drainage only in the vertical direction. It is quite apparent that these conditions are not truly comparable to the conditions found in most foundations. The degree of reliance to be placed on settlement studies based on this type of test depends on how nearly the foundation conditions will approach those of the test specimen In any event, sound rea- soning is necessary to make the best appli- cation of the data. In general, it is felt that the actual structural loading most compa- rable to the laboratory test loading is that exerted on a compressible stratum at rel- atively great depth and of fine material of finite thickness, and which is bounded above and below by dense free-draining materials. In order for the consolidating load to be uni- form over a reasonably large portion of the stratum, the structural loading would have to cover a rather large surface area. The laboratory testing equipment, pri- marily intended for use in the study of the consolidation of clays, limits the grain size to minus No. 4 (4.76 mm diameter). Actu- ally, the maximum grain size should be considerably smaller than No. 4 for best results in estimating settlement. It has been found by experiment that gravelly material reduces consolidation. I4 l4 Gibbs, Harold J., “The Effect of Rock Content and Placement Density on Not only do the gravel particles replace compressible soil, but there is a definite indication that particle interference of the gravel reduces the consolidation of the fine material. This reduction in consolidation becomes more pronounced as the rock con- tent becomes greater. Although this effect does occur with small rock contents, in general it is believed that the effect is only slight for rock contents less than 25 percent. In the case of a settlement study for a stratum near the surface and for a small loaded area, lateral bulging may be of con- siderable importance. Under these condi- tions the soil would not have complete lateral confinement and much settlement may be attributed to the shifting of material and not to consolidation Figure 10 is a diagram- matic sketch that illustrates the action of the settlement of a loaded area. I5 The solid lines below footing represent an idealized pressure bulb or zone within which appre- ciable stresses are caused by the loading on the footing. The displaced posi- tions of these lines are shown by the dashed lines with the magnitude of change consid- erably exaggerated. If the settlement is caused principally by the squeezing out of the soil from under the loaded area, the zone and the element shown in the center of the zone are distorted with little change in Consolidation and Related Pore Pressure in Embankment Construction,” Proceedings ASTM, Volume 50, 1950, pp. 1343-1360. I5 Taylor, op. cit., p. 570. Loading Intensity, q
What does a sudden downward bend in soil mean?
A sudden downward bend may indicate a break- down of soil structure at a particular load- ing, whereas normally the shape of the con- solidation curve is concave upward. Figure 2 (load-consolidation curve for a moist clay) shows that the addition of water after appli- cation of the final load does not affect con- solidation. Yet some soils, such as those tested when they are initially quite dry, may show effects due to saturation that will be indicated by a change in settlement at the time water is added. This feature is fre- quently important in arid regions where ordinarily dry soils will eventually become wetted through the operation of hydraulic structures. Another characteristic may be obtained from the load release data. The position of the load release point indicates the amount of the elastic rebound. For an ordinary soil, it will, in general, be only a portion of the total settlement. On other hand an expansive characteristic is seen in a specimen which rebounds almost its initial volume or beyond it. Many more
What is the primary consolidation, secondary compression and decation of dredged fill?
Primary Consolidation, Secondary Compression and Desiccation of Dredged Fill (PSDDF) commonly used to estimate settlement
Can PSDDF be used for subgrade settlement?
Do not use PSDDF for subgrade settlement
Consolidation
- When the construction of the foundation is done(application of additional load), pore water pressure in the saturated clay increases as the hydraulic conductivity of the clay is very small. Some time is required for excess pore water pressed to dissipate and increase the stress to be t…
Primary Consolidation
- The definition of primary consolidation is discussed above under the terminology. Let’s the method of primary Consolidation settlement calculation There are two different stages of soil. 1. Normally Consolidated Soil 2. Over Consolidated Soil It is required to assess the consolidation of soil is done based on the above states. In simple terms, the normally consolidated soil is experie…
Secondary Consolidation
- Secondary consolidation settlement occurs after the completion of dissipation of the excess pore water pressure developed immediately after the application of load. The settlement caused due to the plastic adjustment of the soil fabrics at the end of the primary consolidation is called secondary consolidation. Secondary Consolidation also can be explained as slippage and reorie…
Types of Tests to Find Consolidation Settlement
- One dimensional consolidation test
- Oedometer Test
- Incremental Loading Oedometer