In the next sections, we will deal with two active and passive earth pressure theories. The component of pressure in a horizontal direction which a mass of earth exerts on a wall explanation of active earth pressure. When a soil mass pushes against a retaining structure, the pressure is known as active pressure. Both are lateral pressure exerted by the soil on a retaining wall, but why do we call one active and the other passive. Active pressure is less than resting pressure, while passive pressure always exceeds resting pressure. A large force is required to move the wall to a greater distance until shear failure is reached where a sliding wedge is formed. The main purpose of retaining wall construction is to retain soil.
The coefficient kh is defined as the ratio of the horizontal component of. For the active and passive rankine cases, a sufficient yielding of the wall is necessary for a state of. Mar 21, 2016 definition of key terms active earth pressure coefficient ka. Active and passive earth pressure coefficients computation of a general active case horizontal pressure from surface loads effect of ground water and filter on wall pressures earth pressure due to compaction earth pressure on rigid retaining walls near rock faces. Active passive earth pressure3 free download as powerpoint presentation. This video focuses on rankines lateral active and passive earth pressure.
We focus on explaining what it is, where it comes from, and spend a bit of time explaining the formula. Active vs passive earth pressure engineering stack exchange. Two theories are used to calculate lateral earth pressure active and passive. Active earth pressure generated in each individual cell is resisted by an equivalent passive earth pressure generated by the adjoining cells. The magnitude of the passive earth pressure that resists the movement of a structure is controlled by the amount the structure moves and the direction in which it moves, strength and stiffness of. Earth pressure active earth pressure passive earth pressure. Failure here is defined to be the state of stress which satisfies the. Studies for rankines active earth pressure equation assumed11 that the direction of active earth pressure is parallel to the backfill ground ag but has not clearly specified the wall friction angle this is based on the assumption that the ground pine ag. The increase in the lateral earth pressure causes decrease in the diameter of mohrs circle as shown by mohrs circles ii and iii, and mohrs circle reduces to a point, as represented by points a 4 and b, which become concurrent. Lateral earth pressure can be defined as the pressure exerted by the soil against a retaining structure on a surface of a surrounding soil mass.
Definition of passive earth pressure the maximum value of lateral earth pressure exerted by soil on a structure, occurring when the soil is compressed laterally, causing its internal shearing resistance along a potential failure surface to be completely mobilized. Q is the moment of the passive earth pressure and p. This typically occurs when the wall is restrained from movement such as along a basement wall that is restrained at the bottom by a slab and at the top by a floor framing system. Lateral earth pressure is the pressure that soil exerts in the horizontal direction. Coulombs failure mechanism is considered in the analysis. Firstly we will learn rankine earth pressure theory the most important and then coulomb earth. What is the difference betwen active pressure and passive. Macuh a simple method is proposed for calculating the active and passive earth pressure coef. Earth pressure and retaining wall basics for nongeotechnical. The solution is then compared with rankines theory of active and passive earth pressures. Mod4 lec24 active and passive earth pressure and differential water pressure. Experiments were performed at the university of california, san diego to record the passive earth pressure forcedisplacement relationship behind a 1. In the active earth pressure case, the failure is due to the. Active earth pressure, inclined cohesive backfill, intermediate principal stress.
Earth pressure at rest at rest earth pressure occur when there is no wall rotation such as in a braced wall. Rankines theory maximumnormal stress theory, developed in 1857 by william john macquorn rankine, is a stress field solution that predicts active and passive earth pressure. Definition of active earth pressure the minimum value of lateral earth pressure exerted by soil on a structure, occurring when the soil is allowed to yield sufficiently to cause its internal shearing resistance along a potential failure surface to be completely mobilized. A if the wall is pushed into the unit weight of soil soil mass, the principal f c tan stress h will increase. The magnitude of the passive earth pressure that resists the movement of a structure is controlled by the amount the structure moves and the direction in. Active and passive earth pressure coefficients by a. Active and passive earth pressure tables crc press book the problem of earth pressure on retaining structures is one of the oldest in soil mechanics. Active and passive earth pressure tables crc press book. When a sentence is written in the active voice, the subject performs the action. These assumptions lead to hydrostatic or triangular pressure distributions when calculating.
The influences of the cohesive force, adhesive force, and the fill surface form were considered in this method. Passive earth pressures with various wall movements by yungshow fang, l associate member, asce, tangjiang chen, 2 and binferng wu 3 abstract. The lateral earth pressure is a function of vertical pressure. This kind of pressure is known as active earth pressure. Passive earth pressures with various wall movements. The maximum stable value of k is called the passive earth pressure coefficient, k p.
The lateral earth pressure is important because it affects the consolidation behavior and strength of the soil and because it is considered in the design of geotechnical engineering structures such as retaining walls, basements, tunnels, deep foundations and braced excavations. Active earth pressure coefficient for vertical wall rankine. It is the ratio of horizontal and vertical principal effective stresses when a retaining wall moves away by a small amount from the retained soil. 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. Active earth pressure if a retaining structure is permitted to move away from the soil allowing its lateral expansion, the earth pressure decreases with the increasing expansion. The term effective means that the submerged unit weight of soil. Lateral earth pressure there are 3 states of lateral earth pressure 1. Passive earth pressure, retaining wall, surface of rupture, log spiral 1. Passive earth pressure follows from the following formula.
Active and passive earth pressure coefficients by a kinematical approach article pdf available in geotechnical engineering 1552. Passive earth pressure article about passive earth pressure. Calculation of passive earth pressure of cohesive soil. This paper presents experimental data of earth pressure acting against a vertical rigid wall, which moved into a mass of dry sand with a stressfree horizontal.
Kp passive earth pressure passive is more like a resistance 10. Passive earth pressure the coulomb theory passive earth. Estimation of the active earth pressure with inclined cohesive. Passive lateral earth pressure, bearing capacity, and. Pdf active and passive earth pressure coefficients by a. Passive earth pressure forcedisplacement relationships. The amount of outward displacement of the wall necessary is about 0.
It is the ratio of horizontal and vertical principal effective stresses when a retaining. Passive lateral earth pressure, bearing capacity, and shear. Apr 01, 2014 mod4 lec24 active and passive earth pressure and differential water pressure. The point of application of active thrust is determined from the condition of moment equilibrium. There are three type of lateral earth pressure as shown in figure 4. At rest earth pressure active earth pressure passive earth pressure the at rest pressure develops when the wall experiences no lateral movement. Active thrust on an inclined retaining wall with inclined. Active and passive voice voice refers to the form of a verb that indicates when a grammatical subject performs the action or is the receiver of the action. Figure 112 idealization of active and passive earth pressure from a k0 developed by inserting a wall of zero thickness and volume into a soil mass as in a. Explore vip membership cantilever walls when designing sheet retaining walls it is normal to assume that the effective lateral stresses acting on the wall are given by simple rankine active and passive zones. Earth pressure is the lateral force exerted by the soil on any structure retaining the soil.
This volume comprises tables which facilitate calculations in problems of limit equilibrium. Could anyone please explain what is the difference between active and passive earth pressure when we talk about weight retaining walls. The total passive earth pressure is determined through coulombs theory by considering the equilibrium of the wedge of soil abc. Practically, some centimeters movement is sufficient to completely realize passive pressure. In order to facilitate the calculation of coefficient of passive earth pressure, using the proposed equations, a modified coefficient of passive earth pressure is provided. The wall may be restrained from moving, for example. The soil inducing the active pressure is breaking away from another body of soil eg the soil behind a retaining wall would usually break away and crumble and is in tension. 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. Further increase of the lateral earth pressure from the front soil makes it higher than the vertical stress. How movement affects development of the active and passive earth pressure is illustrated. Active earth pressure the mazindrani theory rankine active earth pressure the coulomb theory. When the wall moves away from the backfill, there is a decrease in the pressure on the wall and this decrease continues until a minimum value has reached after which their is no reduction in the pressure and the value will become constant. Jan 18, 2018 this video focuses on rankines lateral active and passive earth pressure.
Active earth pressure article about active earth pressure. Passive earth pressure provides a mechanism to resist lateral foundation movement, resulting in either an increase or a decrease in the demand placed on the other structural. It is also usual to use ka for the tan2 term as shown previously in fig. The horizontal pressure that an earth mass exerts on a wall. Active and passive earth pressure coefficients by a kinematical. Rankine earth pressure theory and coulombs earth pressure theory. Earth pressure coefficients active earth pressure, passive. A pressure is exerted on the wall, which is the passive earth pressure p p, inclined at an angle.
Further expansion will cause a shear failure of the soil in which a sliding wedge tends to move downward and outward. Apr 24, 2016 lateral earth pressure there are 3 states of lateral earth pressure 1. The active earth coefficient is smaller than the passive one, values are typically 0. Rankines lateral earth pressure active and passive. The active and passive definitions are derived from the role the back fill material plays in the two cases. Retaining and sheetpile walls, both braced and unbraced excavations, grain in silo walls and bins, and earth or rock contacting tunnel walls and other underground structures require a quantitative estimate of the lateral pressure on a structural member for either a design or stability analysis. The problem of active and passive earth pressures acting against rigid retaining. Rankine active pressure coefficient however the active earth pressure condition will be reached only if the wall is allowed to yield sufficiently. Based on the sliding plane hypothesis of coulumb earth pressure theory, a new method for calculation of the passive earth pressure of cohesive soil was constructed with culmanns graphical construction. Earth pressure active earth pressure passive earth.
Passive earth pressure article about passive earth. Sliding soil wedge theory is the basis for most of the theories by which lateral earth pressure is computed. 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. Definition of key terms active earth pressure coefficient ka.
Jan 02, 2019 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. Active passive earth pressure3 physical quantities. Rankine and coulumbs theory on active and passive pressure against earth structures. The approach used is based on rotational logspiral failure. It can be classified as earth pressure at rest, active earth pressure, and passive earth pressure. Rankines earth pressure coefficients for inclined ground. This is rankines active earth pressure formula for a vertical structure. 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 resultant force is angled parallel to the backfill. Your question will get much more useful responses if you first read, e. Loads and forces acting on retaining wall and their. A state of passive pressure exists when the movement of the wall is such that the soil is compressed horizontally. Figure 2 rankine active or passive pressure with inclined backfill. Field measurements on deep retained excavations have shown that the average earth pressure load is approximately uniform with depth with small r eductions at the top and bottom of the excavation.
1242 1294 1367 1553 886 1070 553 1163 177 835 121 284 549 999 552 862 684 233 519 1657 947 1598 1633 366 1481 505 816 1399 436 666 372 402 1189 378 1006 773