Stress distribution in soil pdf

Explore Documents. Chapter 1 - Stress Distribution in Soil. Uploaded by JommarVocalTagalog. Document Information click to expand document information Description: Stress Distribution in soil. Did you find this document useful? Is this content inappropriate?

Report this Document. Description: Stress Distribution in soil. Flag for inappropriate content. Download now. Related titles. Carousel Previous Carousel Next. Jump to Page. Search inside document. Edwin Leon. Worked Examples Example 3 50Dr. Vertical Stress in Soil Vertical Stress caused by a strip load The fundamental equation for the vertical stress increase at a point in a soil mass as the result of a line load can be used to determine the vertical stress at a point caused by a flexible strip load of width B.

The term strip loading will be used to indicate a loading that has a finite width along the x axis but an infinite length along the y axis. Calculate the vertical stress at points, a , b, and c. The magnitude of the load is kPa. Calculate the vertical stress at points, A , B, and C. Worked Examples Example 4 59Dr. Vertical Stress in Soil Vertical Stress due to a uniformly loaded circular area 7 7'.

The increase in the stress at any point below a rectangular loaded area can be found by dividing the area into four rectangles. Variation of with m and nc n m 0. Abdulmannan Orabi IUST 2V:1H method A simple but approximate method is sometimes used for calculating the stress change at various depths as a result of the application of a pressure at the ground surface.

The transmission of stress is assumed to follow outward fanning lines at a slope of 1 horizontal to 2 vertical. Approximate Method For uniform footing B x L we can estimate the change in vertical stress with depth using the Boston Rule. Newmark Method 79Dr. Newmark Method 81Dr.

Abdulmannan Orabi IUST The use of the chart is based on a factor termed the influence value, determined from the number of units into which the chart is subdivided. Influence value 0. The influence chart may be used to compute the pressure on an element of soil beneath a footing, or from pattern of footings, and for any depth z below the footing. Newmark Method 83Dr. The footing plan will be placed on the influence chart with the point for which the stress is desired at the center of the circles.

Newmark Method The units segments or partial segments enclosed by the footing are counted, and the increase in stress at the depth z is computed as " c j Where I is the influence factor of the chart. Newmark Method 85Dr.

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Therefore, other charts and Tables are prepared to estimate of the stress increased due to a loaded area. Considering a circular loaded area with radius r is loaded with a surface stress of qo, the stress variation along the vertical axis through the centre may be estimated using the Equation proposed by Boussinesq for the vertical stress due to a concentrated surface load, as shown in the following Figure.

Z Y X y x z Q The loaded area is considered with small areas dA and the vertical stress at point D due to the concentrated force qodA acting over the small area. Integrating the stress due to force acting over small areas, the vertical stress increment is estimated, as given below as Equation [5].

The Equation [5] is rearranged to give Equation [6]. As the stress increment between any two adjacent circles is 0. Example Estimate the stress at a depth of 5m below the center of the rectangular loaded area shown below.

The rectangular area is loaded with a distributed load of kPa. Prepare the plan of the building so that the length AB given on the Newmarks chart is equal to the depth 5m. The plan of the building to the estimated scale is drawn on a tracing paper. Then the plan view of the building drawn on the tracing paper is placed on the Newmarks chart so that the centre of the rectangle coincides with the centre of the Newmarks chart.

Count the number of units M covered by the plan view of the foundation, the stress increment at 5m below the ground surface may be estimated by: MIqq o. Where, q - Increased intensity of soil pressure due to foundation loading at depth 5m, M Number of units covered by the plan view of the rectangle drawn to the scale mentioned above.

Pressure isobars, developed to estimate the vertical stress under a square and a strip footing, is given below. Figure Pressure Isobars based on the Boussinesq equation for square and strip footings. Newmark developed the Equation [7] to estimate the pressure under a corner of a square footing loaded with a pressure of qo. Example A 12mx 16m rectangular raft foundation, shown below, is used to support a square water tower.

Estimate the soil pressure at 5m below the foundation level at points A, B, and C using the Newmarks charts. Stress distribution through layered mediums Most natural soil deposits consist of layers of different properties.

If the difference in the stiffness is not very high, the methods described above may be used to estimate the stress distribution through such mediums.

However, if the stiffness between layers differ significantly, the above distribution methods developed for homogeneous mediums are not applicable. Therefore, different researchers have developed methods to estimate the stress distribution through layered soil mediums. Distribution of vertical stress through a two layer system Burmister developed the chart given below to estimate the vertical stress distribution through a two layer medium.

The chart is developed to estimate the vertical stress below the centre line of a circular loaded area and the thickness of the Layer I is assumed to be equal to the radius of the circular loaded area, as shown in the following Figure.

The stiffness ratio between the two layers is the governing factor in determining the stress distribution among layers. A B C A 16 m 12 m 4 m 2m The stress distribution given by the chart for the two layer system is of particular importance in foundation engineering, where shallow foundations are constructed in hard stiff filled layers, which overlies soft compressible layers.

In such situations, it is seen from the chart below that the stress applied on the bottom layer significantly reduced if the stiffness ratio is high. Another branch of civil engineering, where frequently layered mediums are encountered, is highway engineering.

The road subgrade and the pav. Lecture 7 stress distribution in soil. Mean Velocity and Shear Stress Distribution.