how to find depth of influence in pile settlement

When computing settlement it is possible to account for the influence of the foundation depth by introducing the reduction coefficient κ1: for strip footing: for spread footing:

Full Answer

How to calculate the settlement of pile group by a single pile?

The key for calculating the settlement of pile group by a single pile is the analysis of the interactions among piles. Moreover, the consideration of the mutual reinforcing effects plays a very important role in analyzing the interactions between piles.

How do you find the interaction level of pile deformation?

The pile deformation can be determined relative to the greenfield settlement of the soil by finding the depth z at which the pile deformation equals the soil settlement. This depth z, relative to the length of the pile L ( z / L ), is in this paper called the interaction level.

How do you calculate pile foundations?

The following calculations were first derived by Vesic, and can be found in the USACE manual. See USACE EM 1110-2-2906- Design of Pile Foundations. w = ws+ wf+ wp where, w= vertical settlement of a single pile at the top of pile, m (ft)

How does bending stiffness affect the settlement of pile groups?

For pile groups, the settlement of the piles can be reduced if the horizontal soil deformation is reduced by the bending stiffness of the piles. This effect can be simulated for example in FEM calculations but is not taken into account in this paper as is the case for the uncoupled approaches commonly used.

How is pile depth calculated?

General factors to be considered for determining depth of foundation are:Load applied from structure to the foundation.Bearing capacity of soil.Depth of water level below the ground surface.Types of soil and depth of layers in case of layered soil.Depth of adjacent foundation.

How is influence factor calculated?

The influence factor is calculated in three points of reference: at the embedment depth of the foundation, at B/2 from the basement level ( I zp, max ) and at 2B from the basement of the foundation.

What is influence depth?

The influence zone depth is defined like region where the geostatical pressure reduced by excavation together with upper structure loading exceed the original geostatical pressure.

How do you find the zone of influence?

The depth of influence zone is calculated from the condition, that the original geostatic stress is equal to the new geostatic stress due to excavation plus the vertical stress influenced by the loads of upper structure.

How are settlements calculated?

13:2451:58Mod-01 Lec-11 Shallow Foundation - Settlement Calculation - I - YouTubeYouTubeStart of suggested clipEnd of suggested clipSoil layer NCC is equal to compression. Index. So either we can use this expression to calculate theMoreSoil layer NCC is equal to compression. Index. So either we can use this expression to calculate the consolidation settlement.

How do I calculate my soil settlement?

H = Thickness of the field consolidating stratum at the end of primary consolidation. Commonly initial thickness is used unless the primary consolidation is very large. Say more than 10% of initial thickness. t2 = t100 (f) + Δt = time for which secondary settlement is to be calculated.

What is the zone of influence pile?

For piles in clean sand, the influence zone above the pile tip is between 1.5 and 2.5D and the zone below the tip ranges from 3.5 to 5.5D, where D is pile diameter. For piles in more compressible silty sand, the influence zone extends between 0.5 and 1.5D above the pile tip and between 1.5 and 3D below the tip.

What is zone of influence?

Zone of Influence means the area of a receiving environment with the potential to be altered or changed as a result of an emission or discharge.

What is zone of influence in foundation?

The zone of influence is an area of engineering soils likely to be affected by loading due to engineering or building development. It always depends on the composition of the soil, but as a general rule, do not excavate anything steeper than a 45-degree angle from the bottom of the existing footings.

What is the angle of repose and zone of influence?

zone of influence, of a building or structure, the subject of a building development application, means the area determined by the assessment manager to be loaded by the footings or other load bearing elements of the building or structure taking into account the angle of repose.

What is Angle of Repose in footing?

The angle of repose, or critical angle of repose, of a granular material is the steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping. At this angle, the material on the slope face is on the verge of sliding. The angle of repose can range from 0° to 90°.

How much weight can soil support?

Soil capacity is measured in pounds per square foot (psf). The load-bearing capacity of soils range from 4,000 psf for sedimentary rock to as little as 1,500 psf for clay and silt. Soils that are a predominantly sand or gravel typically fall in the middle, from 2,000-3,000 psf.

What is influence factor?

The influence factor serves to distinguish the key role of cited authors in time and according to the duration of the influence (the average age for cited papers of dominant authors in different periods is between eight and ten years).

What is meant by factor influence studies?

1. The influencing factors are those factors that can affect some features of target object. Influencing factors can be used as control variables to determine the key influencing factors of an object.

What are the various factors of influence?

There are several important factors that influence decision making. Significant factors include past experiences, a variety of cognitive biases, an escalation of commitment and sunk outcomes, individual differences, including age and socioeconomic status, and a belief in personal relevance.

What is the shape of stress distribution below the ground surface?

3.3 Vertical stress distribution along a vertical line at radial distance „r‟ Page 17 *Under revision Stress isobar or pressure Bulb concept An isobar is a stress contour or a line which connects all points below the ground surface at which the vertical pressure is the same in fact an isobar is a spatial curved, ...

What causes the reinforcing effect in a pile group?

The reinforcing effect in pile group is mainly caused by the shear stress of the pile side. In this paper, the shear stress on the side of a single pile is connected to that on the side of a foundation pile in a pile group. The specific analysis is as follows:

How is pile side friction related to depth?

Under the different axial load of pile top, although the magnitude of pile side friction along depth is different, its curves are close to each other along the tangent direction of the corresponding side friction when the depth changes. In other words, the development of pile side friction along the depth under different load levels has a certain proportion relationship. They are similar in one-dimensional direction. One-dimensional similarity was introduced to describe this phenomenon. In this work, based on an example, the functional expressions between the skin friction and the depth of a single pile are obtained by fitting. According to the one-dimensional similarity of τ -z curves, the disparate functional expressions under different loads are derived.

How does pile J affect reaction force?

The reaction force will transmit along the radial direction and be applied on the pile i, which will make pile i produce the upward reduction. Substituting into ( 14 ), so, the reduction of the skin friction on pile i, can be computed by the following equation:

How much is the error between the measured value and calculated value of the foundation piles?

The error between the measured value and calculated value is only 6%. It is not hard to find that the method in this paper has a good consistency by comparing the calculated results of this paper with those measured by Mao and Jiang. Also, it can better predict the deformation behavior of pile group under similar conditions.

How much vertical load is a pile foundation?

The vertical load of the pile foundation is 15,984 kN in total. The effect of the bottom soil of the cap is neglected in the calculation. The elastic modulus of the pile is adopted as 30 GPa. Substituting the relevant parameters into the formula mentioned above, the calculated results are shown in Table 5.

What is the correlation coefficient of 9600 kN?

The correlation coefficient is 0.9725 when is taken as 9600 kN. And the value of equals 0.9568 when is 8400 kN. Comparing the measured value with fitting curve and derived curve, the results are shown in Figure 4. As can be seen from Figure 4, the fitting curve and the derived curve in this paper can well reflect the variation rule of pile skin friction along the depth. In addition, they are in good agreement with the experimental value.

When was shear displacement proposed?

The shear displacement method was proposed by Cooke in 1974. The soil displacement caused by the shaft shear stress is regarded as the logarithmic relation of radial distance away from pile. The interaction among piles can be considered by the superposition principle.

What are the components of immediate pile settlement?

In general there will be two components to immediate pile settlement: elastic compression of the pile and elastic compression of the soil/rock the pile is bearing in/on. If we ignore the case of a pile bearing on rock, the real question is how the load is transferred from the pile to the soil since that determines the amount of load in the different materials. Frankly that question is hard to answer with a high degree of confidence in most cases. To further complicate the situation, as any long term settlement or consolidation of the soils take place the amount of load transferred along the pile also changes causing additional elastic settlement.

Will Eng tips check this out?

The Eng-Tips staff will check this out and take appropriate action.

Is the elastic settlement of helical anchors small?

Given the relatively low capacity of most helical anchors, I would expect the elastic settlement to be small.

What is the key parameter for estimating pile settlement?

For estimations of pile settlement, the key geotechnical parameter is the stiffness of the soil. If the analysis is based on elastic continuum theory, the soil stiffness can be expressed by a Young’s modulus Es or shear modulus Gs. Both the magnitude and distribution of these moduli are important. It is clear that Es (or Gs) are not constants, but depend on many factors, including soil type, initial stress state, stress history, the method of installation of the pile, the stress system and stress level imposed by the pile and the pile group, and whether short-term or long-term conditions are being considered.

What is the original interaction factor?

The original interaction factors published by Poulos (1968) were based on the assumption that the soil was a homogeneous elastic medium, having a constant modulus with depth. This was clearly a great simplification of reality, and in subsequent years, some significant improvements and extensions have been made to the original interaction factor method, among the most important being:

Why is the analysis of piles subjected to lateral and moment loading more complex?

The analysis of piles subjected to lateral and moment loading is more complex because of the nature of the soil-structure interaction. Apart from their ability to transmit foundation loads to underlying strata piles are also widely used as a means of controlling settlement and differential settlement.

What happens if a pile does not extend above the soil surface?

If the pile does not extend above the soil surface it is found that the pile weight is usually similar to the force due to the overburden pressure. Thus

What are piles used for?

Piles are relatively long and slender members used to transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock having a higher bearing capacity. The method by which this occurs is the basis of the simplest pile type classification. We have two main Pile Types ( Types of Piles ): 1. End-Bearing piles.

What is a drive pile?

Driven (or displacement) piles: These piles are generally pre-formed before being driven, jacked, screwed or hammeredinto the ground.

What is the method used to determine the side resistance of a clay?

Both total stress and effective stress methods of analysis are used to estimate the side resistance for saturated clays. Here we consider only the total stress or α method.