Showing papers on "Lateral earth pressure published in 1986"

Static earth pressures with various wall movements

Abstract: In this paper the writers first present experimental results obtained for the distribution of the active stresses due to a sand backfill behind a rigid wall rotating about the top. The experimental evidence shows that the stress distribution is nonlinear and that, due to arching, the stress near the top of the wall increases beyond the level of the at‐rest stress. Consequently, the point of application of the lateral thrust is much higher than one‐third from the wall base. Arching effects increase with increasing soil density. Secondly, comparisons of the active earth pressure distributions are made for three different wall movement modes: (1) Rotation about top; (2) rotation about heel; and (3) translation. Total active resultant forces and the points of application of these forces are summarized.

Compaction‐Induced Earth Pressures Under K0‐Conditions

Abstract: Analytical models and procedures are presented for the evaluation of peak and residual compactioninduced lateral earth pressures either in the free field or adjacent to vertical, nondeflecting soil...

A numerical study of the effects of wall deformation on earth pressures

Abstract: When designing any earth retaining structure it is necessary to estimate the limiting earth pressures. This is usually achieved by assuming a linear pressure distrigution and by using active and passive pressure coefficients obtained by either limit equilibrium, stress field solutions of limit analysis. These coefficients are approximate in a theoretical sense, do not distinguish between modes of wall movement, and provide no pre-failure information. In practice, wall movements are dependent on the construction method and support conditions provided. Any effect of such movements on earth pressures is therefore of practical interest. In this paper the finite element method is used to investigate the effect of the mode of wall movement on the generation of earth pressure. Both smooth and rough walls are considered. It is shown that the distribution of earth pressure is highly dependent on the assumed mode of deformation. The resultant forces on the wall are also affected, but to a lesser degree. The, effect of soil dilatation, the initial horizontal stress and the distribution of soil stiffness with depth are also examined.

Mechanical stresses on an expanding cylindrical root analogue in granular media.

Abstract: Previously published studies of the mechanical impedance of granular media to root growth have shown that the rate of elongation of barley roots was halved by a lateral cell pressure of 0.02 MPa, applied externally to the growing media. It was incorrectly assumed that this lateral pressure was always the pressure on the growing root. In this paper, the stress distribution around a growing root was modelled both theoretically and experimentally by a thin cylindrical rubber tube, which was expanded radially in two granular materials in a modified triaxial cell. The theoretical model which simulated the deformation of the granular material around the expanding rubber root analogue was controlled by the elastic stiffness parameters, bulk and shear modulus in the early stages and later, at larger diameters, by the plastic yield parameters, cohesion and friction angle. This theoretical stress-strain model was validated experimentally by the good agreement with the results obtained using the thin rubber tube in the two granular materials. Using the theoretical model with root diameters similar to those for barley roots, it predicted soil pressures on the 'root' surface of 0.2-0.3 MPa for lateral triaxial pressures of the order of 0.02 MPa. This result was similar to the predictions made using earlier analytical models. The model also predicts lower mechanical impedance for finer roots, and strongly suggests that cylindrical expansion of the root behind the tip is effective in relieving soil pressure ahead of the elongating root.

FE Analyses: Compaction-Induced Stresses and Deformations

Abstract: Analytical models and a finite element analysis methodology are presented for evaluation of compactioninduced soil stresses and resulting soilstructure interaction effects. These analytical methods...

Pull-out capacity of single batter piles in sand

Abstract: The pull-out capacity of single rigid vertical and batter piles in sand and subjected to axial loading has been investigated. Good agreement was found when test results on instrumented model piles ...

Passive Pressure During Seismic Loading

Abstract: The results of a parametric study (based on a Mononobe-Okabe analysis) of passive earth pressure resistance of cohesionless soils under dynamic loading are presented. Since passive resistance decreases with increasing ground acceleration while the failure zone increases in size, retaining structures designed for static loading conditions may prove to be inadequate under seismic loading. The mathematical equivalence of the active and passive earth pressure problems is demonstrated and a number of ambiguities (surrounding the passive earth pressure problem) in the literature are resolved.

Stresses from loads over rectangular areas

Abstract: In this note, correct solutions based on Gray's (previous investigator who has studied the distribution of stresses below rectangular shaped footings subjected to various contact pressures) work are presented and extended to the case of optimally designed rectangular footings subjected to biaxial bending with one corner having zero contact pressure. Formulas are provided to determine the vertical stress beneath the zero loaded corner and the diagonally opposite corner having the maximum soil pressure. A design example illustrating the use of the equations is given. Design formulas based on the Boussinesq equation have been developed for vertical stress determination when a footing is subjected to biaxial bending and one corner is allowed to have zero contact pressure.

Lateral soil pressures and displacements of rigid piles in homogeneous soils under eccentric and inclined loads

Abstract: The lateral soil pressures, tip load, and displacements of instrumented single rigid model piles in homogeneous loose sand and soft clay under vertical eccentric and central inclined loads have been investigated. A comparison of the test results with theoretical pressure distributions and displacements of the pile for the working load range has been made. Reasonable agreement has been found between the observed and predicted displacements and suggested nondimensional p-y curves. The analyses are also compared with the results of some field case records.

Back pressured pneumatic pressure cell

Abstract: An improved back-pressured pneumatic pressure cell is provided along with a method of using the same. The device includes at least one sensing cell mounted on a blade for insertion into the soil. The cell includes a perforated outer ring and a perforated central disk separated by a threshold. A resilient membrane covers the outer ring and central disk. A first back-pressure is applied through the perforations of the outer ring to the membrane, while a second back-pressure is applied through the perforations of the central disk to the membrane. The second pressure is slightly less than the first pressure. When the first pressure reaches the soil pressure, the seal between the membrane and the threshold is broken, thereby permitting a momentary reverse flow of pressure through the perforations of the central disk until the first and second pressures equalize, as monitored by a differential pressure gauge. A valve regulates the pressure differential between the first and second pressures. The first pressure, and accordingly the soil pressure, is indicated on a main pressure gauge.

Excavation in Hard Clays of the Keuper Formation

Abstract: For the construction of a lock on the Main-Danube-Canal in South Germany a 30 m deep cut had to be excavated in the overconsolidated clays and claystones of the Keuper formation. The strength of this material depends on the degree of weathering, on the stress level and on the duration of loading. For the design of a tied back pile wall, soil strength parameters were selected on the basis of laboratory tests and engineering judgement. Measurements of anchor-forces and wall movements showed the time dependent increase of earth pressure on the wall. The measured performance of the tied back wall supplements the conventional stability analyses in the assessment of the degree of safety.

Numerical analysis of flexible retaining walls ---computer applications in geotechnical engineering. proceedings of a symposium, university of birmingham, england, april 1986

Abstract: A numerical method for analysing the behaviour of flexible retaining walls which allows soil-structure interaction to be modelled is presented. The method differs significantly from the traditional subgrade reaction approach in the ways that the soil stiffness and earth pressure limits are modelled. Three stiffness matrices are used in the analysis. One matrix represents the wall in bending while the other two represent the soil on each side of the wall. Each soil stiffness matrix is assembled using pre-calculated flexibility matrices obtained from finite element computations for elastic soil blocks. Earth pressure limits are determined from consideration of forces applied to the soil which allows the known effect of soil arching to be modelled. This occasionally permits pressures to locally exceed active and passive limits. The analysis has been incorporated into a computer program which is sufficiently economic and simple to be used as part of the general design process. Examples of its use are given.(a) for the covering abstract of the symposium see IRRD 815626.

Reinforcing work of deep ground layer by mixing and solidification

Abstract: PURPOSE: To obtain sufficient strength to horizontal forces by a method in which a solidifying agent, e.g., cement, etc., is injected into a soft ground and mixed with stirring to form solidified soil columns, and before the soil columns harden, a material having high tensile strength, e.g., steel bars, etc., is inserted in an arranging manner into the soil columns for reinforcement. CONSTITUTION: Plural soil cement column rows 10 are concurrently formed by using many stirring mixers set in rows, and three (for example) reinforcing bars 12 are linearly inserted biasedly to one side into each of the column rows 10 before they harden. After the column rows 10 are completely hardened, one side (the opposite of the side where the reinforcing bars 12 are biasedly set) of the column row 10 is excavated, whereupon soil pressure is acted in the direction of arrow A from the opposite side of the excavated side, and a tensile force acts on the side where the soil pressure acts and a compressive force acts on the opposite side. Since the bars 12 are set biasedly to the soil pressure-acting side for reinforcement, great reinforcing effects can be obtained by a minimum number of the reinforcing bars 12. COPYRIGHT: (C)1987,JPO&Japio

Factors Affecting the Performance of a Pneumatic Earth Pressure Cell

Abstract: Twenty pneumatic total earth pressure transducers of type SOLINST were installed on a bridge abutment. It was found that their performance was affected considerably by temperature, and to a lesser extent, by the installation procedure and the type of soil in contact with the pressure cells. In order to quantify these influences, an extensive laboratory investigation was undertaken. From this experimental study, correction factors were obtained and applied to the field data. It is suspected that other pneumatic pressure cells will be affected similarly and field measurements need to be corrected.

Shear Mobilization on Laterally Loaded Shafts

Abstract: From the results of a pressure cell instrumented rigid shaft embedded in stiff clay and subjected to horizontal static loading the side shear mobilization rate, and its contribution to equilibrium, is found. These measurements show that under working load side shear 'drag' on the side of the shaft contributes the majority of mobilized soil resistance. At ultimate load the soil pressures mobilized in front of the shaft contribute most to equilibrium. Measured undrained shear strengths from the unconfined compression test are shown to provide only 70% of the field mobilized side shear required for equilibrium. Measurement of the soil to pile wall adhesion, mobilized down the cast in situ concrete pile wall, is well represented by the vertical soil to soil failure planes initiated in the pressuremeter test.

A New Boundary Stress Transducer for Small Soil Models in the Centrifuge

Abstract: The need to obtain reliable boundary stress measurements in centrifugal models of reinforced earth retaining walls has led to the development of a new form of boundary stress transducer. A rectangular sensitive face 100 mm long by 10 mm wide has been chosen to capture sufficient soil grains to give a representative soil pressure. Calibrations of the transducers under a layer of sand in the centrifuge were in good agreement with the deadweight calibrations. When used in a series of centrifuge model tests, the new transducers performed reliably in an environment that was anticipated to have a relatively large stress gradient.

Soft ground improvement work

Abstract: PURPOSE:To perform improving operations with good efficiency by a method in which a powdery soil stabilizer and compressed air are jetted in a stirring blade and then separated from each other, and the flow rate of recovery air is controlled in such a way as to balance earth pressure with the pressure of air. CONSTITUTION:A mixture of a soil stabilizer with compressed air is jetted from a nozzle 5 through a stabilizer supply tube 4 in a hollow rotary shaft 1 and then separated from each other. The soil stabilizer is adhered to soil in the open bottom 6 and mixed with soil by a stirring blade 3. The pressure of soil in the blade 3 is measured by a measure 10, and the pressure of air in the blade 3 is also measured by an air pressure guage 13. Both the measured values are compared in a controller 10 and the opening degree of the valve 16 of a recovery hose 9 is adjusted by sending signals to a flow regulator 15 in such a way as to balance the soil pressure with the air pressure.

Pressure feeder of soil and sand

Abstract: PURPOSE:To raise the pressure feeding efficiency of soil by a method in which a soil pressure detector is provided with a fixed distance in the neighborhood to the tank of a pressure feeding pipe connected to the tank pressure losses during the soil pressure-feeding period are calculated, and on the basis of the calculation results, the amount of a tackifier to be charged is determined. CONSTITUTION:A soil trap tank 2 has a pressure-feeding pump 1 on its one side, a soil pressure-feeding pipe 3 on the other side, and a soil inlet and a tackifier supply port 5 in its upper part. In the neighborhood of the soil trap tank 2 side of the pipe 3, the first and second soil pressure detectors 8 and 20 are provided to the pipe 3 with a fixed axial distance L. Pressure losses due to the pressure difference of both the detectors are detected by an arithmetic unit 21, and on the basis of the pressure losses, the amount of a tackifier to be charged is adjusted by using a charger 11. The exactness of the charging amount of the tackifier can thus be enhanced.

Device for measuring home position of earth pressure and hydraulic pressure

Abstract: PURPOSE:To reduce the time for measurement by providing a total pressure detecting part of a total pressure gage and a hydraulic pressure detecting part of a hydraulic pressure gage in proximity to a flat plate-shaped detecting body. CONSTITUTION:A tapered part 4 is formed to the top end of the flat plate-shaped detecting body having the total pressure detecting part 2 of the total pressure gage and the hydraulic pressure detecting part 3 of the hydraulic pressure gage. A converter housing part 7 for housing a hydraulic pressure converter 5 and a total pressure converter 6 is formed to the rear part thereof and further an inserting rod attaching part 7a is formed to the rear part thereof. The earth pressure and hydraulic pressure act to the total pressure receiving plate 8 of the part 2 and the hydraulic pressure from which the earth pressure component is removed acts to the hydraulic pressure receiving chamber 10 in the rear part of a filter 9 in the part 3 when the body 1 is pushed into the earth. Liquid such as kerosene is filled in the chamber 10 of the hydraulic pressure gate 11 and the total pressure receiving chamber 13 of the total pressure gage 12. Said chambers are connected to the total pressure converter 6 and the hydraulic pressure converter 5 by a tube 14 for the hydraulic pressure gage and a tube 15 for the total pressure gage and the pressures are converted to the electric signals proportional to the pressures.

Apparatus for detecting hardness of soil for rice field working machine

Abstract: PURPOSE:To make it possible not only to suppress the hooking of impurities such as straw present in mud but also to reduce the extrusion amount of mud, by providing a pressure receiving film like body and a pressure sensor to an earth body. CONSTITUTION:A cylindrical case 13 having an opening part formed to the front part thereof in an advance direction is provided to an earth body 12 in a state thrusted in soil and a flexible pressure receiving film body 14 closing said opening part is attached to the front lower end part of the case 13 while the case 13 and a hose 15 are hermetically sealed with a non-compressive fluid such as water. Further, a pressure sensor 16, which converts the change in the pressure acted on the film like body 14 and propagated through the sealed fluid to an electric signal to continuously detect the same as the specific hardness of soil, is provided to the end part of the hose 15 extended in the vicinity of the operation part of a main machine. A pressure sensing chamber 17 opened to the lower part of the earth body 12 is formed to an earth pressure detector S3(S4) and a pressure receiving film like body 18 closing said opening part is attached while the sensing chamber 17 and a hose 19 are sealed with a fluid and, further, a pressure sensor 20 for continuously detecting the change in pressure is provided.

At-rest to active earth pressure transition

Abstract: An approximate analytical procedure is described to estimate the developed lateral earth pressures behind a rigid retaining wall experiencing outward tilt about the base with horizontal cohesionless backfill soil Included are various stages of wall tilt, starting from an at-rest condition to a full-active condition The at-rest condition is defined as a stage of no-wall tilt, whereas the full-active condition occurs when the soil elements along the entire depth of the wall are in an active state The predictions from the developed method of analysis are compared with model test measurements The comparisons show very good agreement at various stages of retaining wall tilt Finally, examples are provided to illustrate the transition of the lateral earth pressures behind a smooth and a rough retaining wall

Sliding preventing device for retaining wall

Abstract: PURPOSE:To increase the sliding resistance force of a whole retaining wall, where necessary, by a method wherein an auxiliary plate is horizontally positioned to the end surface of the bottom plate of the retaining wall, and the bottom plate and an auxiliary plate are intercoupled by means of a wire. CONSTITUTION:After a retaining wall A is built on a foundation concrete 7, an auxiliary plate 1 is installed in the direction of an earth pressure and horizontally to an end surface 2a of a bottom plate 2 of a retaining wall A. After the bottom plate 2 and an auxiliary plate 1 are intercoupled by means of a pin 3 and a wire 4, filling with soil D is effected. This enables increase of a sliding resistance force only at a necessary place, and permits building of the retaining wall which has increased efficiency.

Method of building simple retaining wall

Abstract: PURPOSE:To simplify construction and to build a retaining wall being excellent indraining ability, by a method wherein a retaining wall is formed,a nd afer a water permeable sheet is horizontally laid on the back of the retaining wall, soil is rolling-compacted on the sheet to orderly build banking layers between which the water permeable sheet is located. CONSTITUTION:Strut 2 are pressed in a ground, and a retaining wall panel 3 is engaged between the struts 2 to build a retaining wall A. The one end of the water permeable sheet 1 is folded back arond a locking rod 4 to secure the one end by heat fusion and bolt locking, and the one end of the sheet 1 is secured to the retaining wall A. Soil is conveyed to the back of the retaining wall A and is spread on the water permeably sheet 1 for rolling compaction to build a banking layer G1, and following banking layers are built in a similar manner as described above. This reduces an earth pressure exerted on the retaining wall, markedly improves safety of the retaining wall through prevention of fall-down of the same, enables rapid drainage of water, and enables prevention of production of an exessive gap water pressure in a banking.