Difference between rankine and coulomb earth pressure theory pdf

The coulomb theory is similar to rankine except that. The primary difference between rankine and coulomb earth pressure theories is that coulombs considers a frictional retaining wall. Although the rankine s theory also extended for the c phi soil. Coulombrankine earth pressure keystone retaining walls. Enumerate the assumptions made in rankine s theory. If we frame it in the other way, interface between the soil and retaining wall is not assumed to be friction less, as it is in rankine s theory. Earth pressures can be estimated by utilizing equations rankine or coulomb or by graphical means. One of the most basic and common step in design of an earthretaining wall is estimation of the earth pressure. Neither the coulomb nor rankine method explicitly incorporated cohesion as an equation parameter in lateral earth pressure computations.

Coulomb s or rankine active earth pressure coefficient, pressure, horizontal resultant and moment. So, these were the same assumptions for the rankine s theory, but this theory can also be applied for the c. The large difference between the minimum and the maximum lateral stress is characteristic for frictional materials such as soils. It assumes that the soil is cohesionless, the wall is frictionless, the soilwall interface is vertical, the failure surface on which the soil moves is planar, and the. Jun 28, 2016 in the case of driving forces, the later al pressure is reduced from vertical pressure by a coef ficient ko or ka, and increased in the case of resisting forces by a coefficient kp. Could anyone please explain what is the difference between active and passive earth pressure when we talk about weight retaining walls. Rankine s earth pressure coefficients for inclined ground reconsidered by slip line method volume 1 issue 1 2016. Difference between rankines theory and coulombs theory. The comparative results show that in terms of distribution and magnitude of active earth pressure, rankine s theory possesses the highest match to the plaxis analysis. The three methods of inputting active soil pressure are the equivalent fluid pressure efp method, rankine method and coulomb method.

Rankines earth pressure coefficients for inclined ground. Theory of earth pressure and bearing capacity lecture 7. Rankines active earth pressure with a sloping cohesionless backfill surface. Sep 04, 20 when calculating the active or passive earth pressure at retaining walls, if there is friction between wall and soil, and that friction angle is given, then we use coulomb formula that long one even if there is no incination of backfill or wall correct. Rankines theory of earth pressure civil engineering. Rankines theory specifies calculation of earth pressure based on mohrcoulomb. This relationship is compared with solutions from finite elements fe results.

The possible stresses in a soil are limited by the mohr coulomb failure criterion. Rankine earth pressure theory and coulomb s earth pressure theory. A gravity retaining wall, shown in the figure below, is used to support a granular backfill that has a unit weighty17. Caquot and kerisel 1948 developed tables of earth pressure coef. Mar 21, 2016 coulomb s earth pressure theory 46 47.

The coulomb theory was developed in the 1776 and the rankine. In this video i have discussed the coulomb s theory of earth pressure in brief. Coulombrankine earth pressure there are two commonly accepted methods for calculating simple earth pressure, coulomb and rankine theory. Lateral earth pressures slide 24of 26 rankine state of stress earth pressure theory.

The rankine method does not take the friction between wall and soil into account. Munesh sir this is a special video on the request of some students. Jan 04, 2019 the primary difference between rankine and coulomb earth pressure theories is that coulomb s considers a frictional retaining wall. So, these were the same assumptions for the rankines theory, but this theory can also be applied for the c. Bell 1915 appears to be the first published source of the equation in the above form. In the case of driving forces, the later al pressure is reduced from vertical pressure by a coef ficient ko or ka, and increased in the case of resisting forces by a coefficient kp. A generalized logspiralrankine limit equilibrium model. There are two commonly accepted methods for calculating simple earth pressure, coulomb and. In contrast, active earth pressure increases with increasing soil unit weight and height of wall.

In other words, the interface between the soil and the retaining wall is not assumed frictionless as it is in rank. When calculating the active or passive earth pressure at retaining walls, if there is friction between wall and soil, and that friction angle is given, then we use coulomb formula that long one even if there is no incination of backfill or wall correct. Rankine extended earth pressure theory by deriving a solution for a complete soil mass in a state of failure, as compared with coulomb s solution which had considered a soil mass bounded by a single failure surface. With the equivalent fluid pressure efp method, the soil active pressure is defined by an equivalent fluid pressure in psf per foot of depth e.

Mj 08 o semi infinite soil o cohesionless backfill o homogenous soil o the top surface is a plane which may be inclined or horizontal. In other words, the interface between the soil and the retaining wall is not assumed frictionless as it is in rankine theory. There are three type of lateral earth pressure as shown in figure 4. The solution is then compared with rankine s theory of active and passive earth pressures. Comparative study of different theories on active earth pressure. This equation was developed by coulomb about 1776 in a considerably different form. Definition of key terms active earth pressure coefficient ka. Passive earth pressure developed by increasing the lateral pressure from oe to od of fig. The rankine earth pressure theory is extended herein to an inclined c. Coulomb s active earth pressure theory can be extended to take into account the forces caused by an earthquake. I am a bridge designer and have always designed long heeled retaining walls with either atrest or rankine active lateral earth pressure theory. Coulomb s earth pressure theory for sand for active state coulomb made the following assumptions in the development of his theory. Loads and forces acting on retaining wall and their. The earth force acting on the back face of the retaining wall is determined by considering the limit equilibrium of the mobilized soil wedge, which is treated as a rigid body bounded by the face.

Rankine extended earth pressure theory by deriving a solution for a complete soil mass in a state of failure, as compared with coulombs solution which had considered a soil mass bounded by a single failure surface. Another popular method to estimate the earth pressure is the logarithmicspiral method proposed by terzaghi 1943. Both are lateral pressure exerted by the soil on a retaining wall, but why do we call one active and the other passive. Later it was extended to include cohesive soil by bell in 1915. The rankine s theory under predicts true orientation of failure surface while the other one that is coulomb s theory overpredicts that of failure surface. The rankine formula for earth pressure differs from coulomb s by ignoring the friction between the wall and the backfill, angf 0. Lateral earth pressure earth retention engineering eng. Although it seems presumptuous, it is likely that the new findings will cause most of the 28 million contributions on the subject of earth pressure to become meaningless. What is the difference betwen active pressure and passive.

Rankine s theory has the highest compatibility to finite element analysis among all theories. Pdf rankines earth pressure coefficients for inclined. These assumptions and approaches such as wedge analysis, stress analysis, logspiral and so on used in the development of earth pressures theories determine the accuracy with which a given earth pressure theory will estimate the earth pressure on a given restructure. Difference between rankine and coulomb earth pressure. Originally, the rankine s theory considered the case of only cohesionless soils. If wall friction angle between retained soil and the wall is equal. The rankine method of lateral earth pressure calculation this equation, which derived by william rankine, is the development of coulomb formula. When discussing active and passive lateral earth pressure, there are two relatively simple classical theories among others that are widely used. Favored by the transportation agencies aashto and fhwa. Ce 540 class presentation on rankine earth pressure theory, module 2. Rankines assumptions for earth pressure theory for active. Comparative study of different theories on active earth pressure article pdf available in journal of central south university of technology 1910. Applications for rankine, coulomb, and terzaghi horizontal earth.

There is friction between the wall and soil and takes this into account by using a soilwall friction angle of. The passive earth pressure occurs when the wall moves towards from the earth and increases pressure. The coulomb theory was developed in the 1776 and the rankine theory was developed in the 1857 and both remain the basis for present day earth pressure. In other words, the interface between the soil and the retaining wall is not assumed frictionless as it is in rankine theory 2. Earth pressure from strip footings on an anchored sheet. Rankine, coulomb, boussinesq, culmann, lateral earth pressure, earth pressure coefficient.

Rankine approached the lateral earth pressure problem with the following assumptions. It can be used to estimate forces on buried structures such as retaining walls, basement walls, and foundations. May 25, 2011 there are two commonly accepted methods for calculating simple earth pressure, coulomb and. May 28, 2017 in this video i have discussed the coulomb s theory of earth pressure in brief. The primary difference between rankine and coulomb earth pressure theories is that coulomb s considers a frictional retaining wall. Pdf rankines earth pressure theory for nonlinear failure. The additional pressure is found as the difference between the combined pressure from self weight of the soil and the strip footing and the pressure. The comparative results show that in terms of distribution and magnitude of active earth pressure, rankines theory possesses the highest match to the plaxis analysis. There is no adhesion or friction between the wall and soil. Rankine theory does not include wall friction, for sloping backfill, the resultant is parallel to the slope. Parametric studies were also done to study the responses of active earth pressure distribution to varying parameters. The lateral earth pressure is a function of vertical pressure. Difference between rankine and coulomb earth pressure theory.

Rankine s theory maximumnormal stress theory, developed in 1857 by william john macquorn rankine, is a stress field solution that predicts active and passive earth pressure. Basic difference between ncma and aashto ncma aashto lh ratio. The coulomb theory was developed in the 1776 and the rankine theory was developed in the 1857 and both remain the basis for present day earth pressure calculation. A generalized logspiralrankine limit equilibrium model for. In addition to coulomb and rankines earth pressure theory, other theoretical solutions have been developed to compute lateral earth pressure. In soil mechanics, what is the essential difference between rankine. Coulomb made the following assumptions in the development of his theory. The difference between hand calculation methods could be reduced by adding a new.

In soil mechanics, what is the essential difference between. Firstly we will learn rankine earth pressure theory the most important and then coulomb earth pressure theory. Rankine active lateral earth pressure this theory is based mainly on the assumption of neglecting friction between. It should be emphasized that, depending on the backfill sloping angle, the active and passive thrusts cal culated with these methods could be quite. There are two commonly uses lateral earth pressure theories. Comparison with active and passive earth pressures 1 introduction in this simple example, slopew is used to determine the theoretical active and passive earth pressures, and the position of the critical slip surfaces for a homogeneous vertical cut slope. Plaxis model for comparison between different theories on active earth. The backfill is a dry, cohesionless, homogeneous, isotropic soil. The soil is homogeneous and isotropic, which means c. What are the differences between rankine and coulomb analyses when calculating lateral forces.

Coulombs theory of earth pressure soil mechanics youtube. Like rankine s model, the coulomb theory addresses the static condition and presumes a planar sliding surface in the soil medium. Coulombs earth pressure theory for sand for active state coulomb made the following. For soils with cohesion, bell 1915 developed an analytical solution that uses the square root of the pressure coefficient to predict the cohesions contribution to the overall resulting pressure.

I have always learned that coulomb lateral earth pressure was for short heeled walls and that the vertical soil pressure could not be used in the overturning calcs when coulomb was used. The difference between oa and oc is the circle diameter and is also the. Most walls are designed for resisting active earth pressure since any rotation that tends to produce failure is usually large enough to allow the active or minimum pressure to develop. The primary differentiation between rankine s theory and coulomb s theory is that the coulomb s theory considers a frictional retaining wall. Mohr circle at rankine states in cohesive soils in the active state. Coulomb s theory will be the same with only difference mentioned above active force applied directly on the wall. Your question will get much more useful responses if you first read, e. Earth pressure and retaining wall basics for nongeotechnical. See aashto standard specifications for highway bridges. Whenever there is a need to bind soil between two different elevations in a terrain where the landscaping needs to be done for specific purposes like a tankbunds or roads in mountainous regions, or a garden, a retaining wall is constructed.

Rankine earth pressure theory and coulombs earth pressure theory. If the soil retained by the wall is c soil, because coulombs theory deal only with granular soil pure sand. Pdf comparative study of different theories on active earth pressure. Increasing soil friction angle and wall friction causes decrease in active earth pressure. The active earth pressure occurs when the wall moves away from the earth and reduces pressure. Rankine considered soil in a state of plastic equilibrium and used essentially the same assumptions as coulomb, except that he assumed no wall friction or soil cohesion. Rankine passive earth pressure the magnitude of the wall movements. The difference between the logspiral curved failure. Association ncma and described in their design manual for seg. Equilibrium which rankine s earth pressure theory is based on. Rankine earth pressure theory coulomb earth pressure theory the rankine theory assumes. Apr 24, 2016 1 coulombs1776 earth pressure theory 2 rankine 1857 earth pressure theory these two theories are still in use in their original form and in some modified forms to calculate the earth pressure.

So, these were the same assumptions for the rankine s theory, but this theory can also be applied for the c phi soil under the coulombs theory. Comparative study of different theories on active earth. As previously stated, if there is not sufficient lateral displacement, the wall pressure is indeterminate between k0 and ka. Coulombs theory cant be used in the following cases. The result of my studies is a modern earth pressure theory based on coulomb s classical earth pressure theory, pure basic physics, and natural soil characteristics.

Originally, the rankines theory considered the case of only cohesionless soils. Chapter 9 design of cantilevered and anchored walls using. This theory is based mainly on the assumption of neglecting friction between the soil and the wall, so no shear forces are developed on soil particles. We will use rankine theory to discusses the stability of these types of failures.

As originally proposed, rankines theory is applied to uniform cohesionless soil only. Active earth pressure coefficient ka is the ratio between the lateral and vertical. According to this engineer manual, an appropriate smf value allows. In soil mechanics, what is the essential difference.

An analytical approach is then proposed to compute the static passive and active lateral earth pressures for a. Yet, there are limited studies on comparison between the theories. Rankine versus coulomb earth pressures earth retention. Coulomb theory considers wall friction and angle of slope, both are included in the equations for earth pressure constant k, the resultant force is making an angle, equal to the friction of the wall, from the plane normal to wall.