Showing papers on "Lateral earth pressure published in 1974"

Craig's Soil Mechanics

Abstract: 1. Basic Characteristics of Soils 2. Seepage 3. Effective Stress 4. Shear Strength 5. Stresses and Displacements 6. Lateral Earth Pressure 7. Consolidation Theory 8. Bearing Capacity 9. Stability of Slopes

Soil arching in slopes

Abstract: A METHOD OF ANALYSIS IS PRESENTED FOR EVALUATING THE ARCHING PHENOMENON IN SOIL CREATED BY RIGID PILES PLACED IN POTENTIAL SLIDES. IT IS BASED ON THE STRENGTH OF SOILS ALONG FAILURE PLANES. THE EARTH PRESSURE IS TRANSFERRED TO THE PILES BY THE SHEAR STRENGTH SIMILAR TO TERZAGHI'S HORIZONTAL TRAP DOOR. IT ILLUSTRATES THAT EXPERIMENTS CONDUCTED SUPPORT THE PREDICTED ARCHING PHENOMENON. THIS METHOD CAN BE USED AS A FIRST APPROXIMATION TO EVALUATE LOAD ACTING ON PILES PLACED FOR THE PURPOSE OF STABILIZATION OF SLIDING SLOPES. /AUTHOR/

Soil Arching in slopes

Abstract: A method of analysis is presented for evaluating the arching phenomenon in soil created by rigid piles placed in potential slides. It is based on the strength of soils along failure planes. The earth pressure is transferred to the piles by the shear strength similar to Terzaghi's horizontal trap door. It illustrates that experiments conducted support the predicted arching phenomenon. This method can be used as a first approximation to evaluate load acting on piles placed for the purpose of stabilization of sliding slopes.

Soil Liquefaction by Torsional Simple Shear Device

Abstract: In this paper the writers explain the unique features of the new torsional simple shear device for soil liquefaction study. This device enables the investigator to subject the soil to uniform shear strains with well-known stress components and boundary conditions. From the experimental results obtained, the writers propose a unique relationship between the stress ratio and the number of cycles to liquefaction. This relationship is independent of the initial values of the ratios between the horizontal and the vertical stress components. Also, the writers propose a rational and analytical procedure for accurately identifying the beginning of initial liquefaction during the experiments.

Performance of Tied-Back Walls in Clay

Abstract: Parametric finite element studies are described that illustrate the relative performances of braced and tied-back wall systems. Key factors in the different performances of the two systems are isolated and the degree of their influence demonstrated. Circumstances are shown where tied-back wall systems perform better than braced wall systems and vice versa. Additionally, the influence of prestress load, wall stiffness, tie-back stiffness, excavation depth, and tie-back spacing on tied-back wall performance are investigated. By judicious choice of these parameters it is shown that the designer can significantly reduce wall movements and soil settlements.

Soil probes for measuring various soil parameters

Abstract: A soil probe comprises a tube which carries at its lower end a soil probe tip portion. An annular exterior wall of the tip portion is elastically deformable and has on its inner surface strain gauges arranged to measure the surrounding soil pressure acting on this wall transversely to the axis of the probe. The probe tip portion also contains a water pressure gauge in communication with the exterior of the probe for measurement of the soil water pressure. The two measurements provided by the probe allow the intergranular soil pressure to be derived.

New Concepts in Consolidation and Settlement Analysis

Abstract: The paper describes modifications which have to be made to the Terzaghi Consolidation Theory in order that the theory properly represents actual consolidation conditions in the laboratory and in the field The resulting theory is called the Modified Terzaghi Consolidation Theory The relationship between void ratio or strain and intergranular pressure is required for a silt or clay soil During consolidation, a silt or clay soil follows a strain-intergranular pressure path different from the path assumed in the Terzaghi Consolidation Theory The Terzaghi Theory is modified for dissipation of hydrostatic excess pressure For primary compression the Terzaghi Consolidation Theory is valid However, the virtual initial hydrostatic excess pressure is in error Definitions are given for the various types of preconsolidation loads

Reinforced earth retaining walls

Abstract: In a discussion of this paper, participants observe that model tests carried out by the authors appeared to partially substantiate the lateral earth pressure the theory used to postulate failure modes and develop analysis and design equations. This theory for computing lateral pressures is based on the existence of a "plastic wedge" which is assumed to develop behind retaining structures and, as such, the concept is essentially an ultimate strength concept. The discussants express reservations with respect to the applicability of this theory and the applicability of the model tests for the prediction of the behavior of full-scale reinforced earth walls. Alternative failure mode, an alternate conceptual approach for describing the behavior of reinforced earth by representing it by an equivalent "composite material" with associated orthotropic "composite properties", and the composite continuim concept are discussed. The Rankine method for computing tension in the strip is also discussed. In a second discussion, the need is expressed for additional information on the influence of the length of ties on the breaking failure height. The mechanical behavior of reinforced earth walls is reviewed and the discussant observes that reinforced earth walls provide a good example of the difference between the potential failure line defined by the equations of statics and the actual failure line, obeying equations of kinematics. A third discussion covers the aspect of tension in the ties and questions the theory underlying the authors methods.

Studies on Anchored Flexible Retaining Walls in Sand

Abstract: This paper describes an experimental investigation of the behavior of laboratory scale (0.6-m) flexible retaining walls in sand supported by up to three levels of anchors. It is concluded that the behavior of a tied-back wall is influenced to a large extent by the flexibility of the wall as well as the anchor inclinations and initial design assumption. With wall flexibility increase, the bending moments in the wall decreased, the decreases for single-anchored walls being in agreement with the moment reduction curves of Rowe. For all walls there was an initial loss in anchor load value on prestressing. Further load changes occurred with construction, the greatest changes occurring with the most flexible walls.

Field measurements of lateral earth pressures on a cantilever retaining wall

Abstract: This paper presents results from a research study on determination of lateral earth pressure for use in retaining wall design. The broad objective of the study is to develop improved design procedures for retaining walls. The limited objective of the phase of the study covered in this paper is to measure the pressure acting on a typical cantilever retaining wall and to compare the measured pressures with theoretical pressures determined by Rankine and Coulomb theories. Tarra Tec pneumatic and Geonor vibrating wire pressure cells were used to measure lateral earth pressures. Procedures used to calibrate the pressure cells are presented. Measurements of the lateral movement of the wall were made during and after backfilling. Data covering a period of 14 months are presented. These data include graphs of earth pressure and wall movement versus time and graphs of pressure distribution versus depth. Engineering properties of the backfill materials are presented. Computed earth pressures based on the Rankine and Coulomb active case are compared with measured pressures. A significant finding is that the measured pressures near the base of the wall are higher than the active pressures. They are nearly equal to the at-rest pressures that are possible as a result of the small movements that occurred at the base of the wall.

Dynamic Passive Earth-Pressure Problem

Abstract: An incremental method is proposed for the study of stress and strain fields in a dynamic passive earth-pressure problem, where an initially vertical retaining wall is considered to translate or rotate with specified acceleration into a dry loose sand medium. The proposed incremental approach of this work enabled us to treat the problem of dynamic passive earth pressure as a mixed boundary value problem. At the beginning of the wall displacement, the dynamic normal earth pressure distribution is generally larger than the static pressure distribution. The dynamic mass ratio at the beginning of the wall displacement is shown not to depend on the amount of wall movement nor on the wall acceleration.

Design of Biaxially Loaded Rectangular Footings

Abstract: A biaxially loaded rectangular footing, loaded such that a portion of its area is not exerting pressure on the soil, does not lend itself to a direct or closed-form solution. Numerical methods are available for analysis of such footings. Charts to aid in the design of the footings are presented. These charts are based on equations of equilibrium. Linear and parabolic stress-strain distributions of soil are considered. The use of charts is illustrated by two examples.

Novel method for constructing subjacent foundation

Abstract: Trenches are formed around the periphery of the area intended to be reinforced. Openings are then drilled from the surface, such openings being in rows, and selected rows being of different depths. By using freezer points the soil is then frozen solid. There is next formed a series of spaced channels extending through unfrozen soil from one trench to the opposite trench and after being excavated the channels are filled with hardenable material such as concrete. The sections which are adjacent to these hardenable sections may be then thawed and excavated and thereafter filled with hardenable material to form a complete mat the surface of which is adapted for sustaining soil loads and the weight of any structure thereon. The trenches are then filled with soil or hardenable material. BACKGROUND OF THE INVENTION Because of the overstressing of soil by a foundation (frequently accompanied by non-uniform distribution of soil pressures), or because soils are inadequate to sustain surface loading, objectionable settling can occur for buildings and the like. It is a common remedial practice to employ corrective action by the construction of grillages, needles, piers, caissons, piledriving, etc. Unfortunately these conventional shoring techniques are complicated, are frequently uneconomical, and for that reason are unsatisfactory solutions for settlement problems of existing structures. For even further reasons, it becomes extremely critical to avoid pile driving where there is a shortage of working space and where disturbances are intolerable because of the possibility of cracking existing structure and endangering neighboring foundations. For these reasons, conventional underpinning methods are frequently contraindicated. A classic example is the leaning Tower in Pisa which will not readily admit of any of these foregoing techniques and which is unfortunately now settling at a dangerous rate from which can be projected the ruination of the building before too long a period. Because the conventionally used systems for underpinning are unacceptable there must be developed new and different systems for providing a subjacent foundation which will obviate the difficulties of the prior art techniques including shoring, etc. Where used in the specification, the terms "subjacent foundation" is meant to include a foundation which is disposed at a level below an existing foundation level but not necessarily directly below or in contiguous relation with the existing foundation. OBJECTS OF THE INVENTION It is an object of the present invention to develop a new and improved technique adapted for subjacent support of existing structures and which will preclude settlement or at least retard it to an acceptable rate. In a further object of the invention, to use subjacent foundations to eliminate or reduce excessive and unequal settlement of existing or future structures, and also for the construction of a future structure on soil with an underlying strata of low bearing capacity such as quicksand, and undesirable clay formation. By constructing first a subjacent foundation below the undesirable soil formation and using a method to be described, the undesirable soil formation above the subjacent foundation can be consolidated by grouting methods or by lime, etc. in order to increase its bearing capacity. Therefore the subjacent foundation serves four objects; 1. It is used to transmit the structure load to soil strata which have high bearing capacity. 2. It is used to distribute the structure load over an extensive subjacent foundation area, resulting in low soil pressure. 3. It is used as a base for soil consolidation. 4. It is used to intercept the downward flow of grouting (cement, chemical, or clay). After the weak soil formation is thus consolidated, the foundation which receives directly the structure load is constructed on the consolidated soil. A further object of the present invention is to provide a method for providing subjacent support of existing buildings wherein the subjacent support can be installed with minimal disturbance to the existing adjacent structures or so as to avoid damage to such structures. A still further object of the present invention is to provide remedial underpinning or remedial subjacent support by providing interlocking sections of a hardenable material such as concrete to distribute the supported load through a larger area of such soil stratum and thereby reduce the soil pressure on the underlying stratum. The result is to eliminate or reduce further settlement of the surface structure. An overall object of the present invention is to provide a new method for providing subjacent support by a system of partial excavations wherein such excavations occur in stages, with the soil being successively substituted by a hardenable material and in which the finished substitute consists of a mat of hard durable concrete which extends as a supportive subjacent foundation. Other objects and feature of the present invention will become apparent from a consideration of the following description which proceeds with reference to the accompanying drawings wherein an example of the invention is illustrated by way of illustration and not by way of limitation.

Some design and performance considerations of diaphragm type pressure cells using strain gauges

Abstract: The two basic types of earth pressure cells that are commonly used are the piston type, which has a very rigid active face (where a change in pressure is reflected by the movement of the whole of this face), and the diaphragm type, which consists of a fairly flexible diaphragm clamped to a rigid edge. One of the intrinsic disadvantages of the diaphragm type of earth pressure cell is that it is most vulnerable to non-uniform stress distribution across its diaphragm. To overcome this problem special attention is paid to providing a uniform stress distribution during calibration and also trying to attain a fairly uniform distribution in the field by placing the cells with extreme care. However, it must be realized that a non-uniform distribution of earth pressure is the norm rather than the exception in nature. Even the most carefully placed earth pressure cell cannot avoid some degree of minor non-uniformity in pressure distribution. It is the purpose of this note to investigate this effect of non-uniform stress distribution on a diaphragm type earth pressure cell which uses strain gauges on the active diaphragm. From these studies, it is intended to find some means of minimizing the effect of this non-uniform pressure distribution in the initial design stage and of detecting the degree of this non-uniformity in pressure distribution so as to be able to assess the acceptability of the earth pressure cell readings during the final operation stage. /TRRL/

Response of model reinforced earth walls to seismic loading conditions

Abstract: This report presents the results of ongoing studies aimed at developing a rational design method for reinforced earth retaining walls. The described method is based on results obtained from small laboratory scale walls subjected to horizontal sinusoidal loading with a shaking table. Tests show that the walls respond like a non-linear damped elastic system to the input vibrations. From measurements of the peak tie forces, an empirical design force envelope was developed which is a function only on input acceleration. It is suggested that the design earth pressures for an actual wall subjected to earthquake loading be based on this design force envelope using a base acceleration determined by response spectra modal participation factor techniques. Data are also presented of soil-tie friction under static and vibratory loading. Recommendations are given for calculating the size and spacing of ties including appropriate safety factors. The report is divided into pseudo static studies, vibration studies, and a summary paper.

Passive pressure in sands with uniform surcharge on backfill

Abstract: An extensive retaining wall model testing program is described which includes a study of the shape of rupture surface and pressure distribution, and the validity of existing theories. The experimental apparatus was designed to allow three types of wall movement, translation, and rotation about the top and bottom of a rigid steel wall 45.0 cm high. Dry sand was used for backfill. The results are reported of tests which include a condition when a uniform surcharge was applied on the backfill. Figures are presented which show the observed rupture surfaces for different types of wall movement and surcharge intensity for the dense and loose sands respectively. The data indicate that the shape of failure depends on the nature of wall movement and that it is curved in all cases. The size of the passive wedge increases with sand density as predicted by theory. The rupture surface observed in the case of rotation about the top is closer to Coulomb's wedge. The stress distribution obtained for wall rotation about the bottom is shown. The values of the coefficient of passive earth pressures, Kp, obtained in all the tests where a uniform surcharge was applied are slightly less than those where no surcharge was applied. The value of Kp for dense sand is found to be greater than for loose sand, Kp is a maximum for the case of wall rotation about the bottom, and minimum for wall rotation about the top. These data reflect that the typed wall movement has an effect on the stress distribution on the wall.

Earth pressure observations on a retaining wall in expansive clay, gouger street mail exchange, adelaide

Abstract: A section of a basement retaining wall in Adelaide, 25m long and 7.5m high, has been extensively instrumented. The basement is located in a moisture-sensitive expansive clay subjected to changes in the moisture environment. The instrumentation comprises twenty-four earth pressure cells at the wall/clay interface and thrity-one psychrometers in the clay mass behind the wall. Earth pressures are being measured, together with changes in the moisture environment, for comparison with current design assumptions, and with predictions from more advanced method of modelling the interacting retaining wall.clay system. The instrument installation was accompanied by a comprehensive sampling and laboratory testing program, designed to measure material properties relevant to available models of material behaviour. The results of the laboratory testing and the field observations for the first two years are presented and discussed. /Author/

Discussion of construction norms: Earth pressure on lock chamber walls

Abstract: 1. Upward deflections of lock chambers in winter (observed everywhere) are the principal cause of additional earth pressure, which considerably increases the active earth pressure according to Kulon. 2. An analysis of lock operations under wintertime conditions shows that standard requirements [11] should be revised to account for chambers undergoing repair, since the calculated load on the wall has increased to passive pressure as determined by Eq. (1) with respect to wall friction. The angle of friction should be considered in accordance with the observed data at 2–5° less than the angle of internal earth friction. 3. The direction of overall resultant earth pressure on the wall as the chamber tends to rise coincides with the direction of the active earth pressure, exceeding it by 2–3 times. 4. The increase in earth pressure on the chamber walls as noted from soil dynamometer readings is, to a considerable extent, compensated for by friction along their rear faces. This causes stresses in calculated cross sections of the walls to increase slightly, but the load on the bottom increases correspondingly, which conforms to the observed data. 5. For unloaded lock chambers (and for wide chambers, dry docks, for example) it is difficult to ensure a standard safety factor against floating. A calculation of passive pressure by Eq. (1) solves this problem and permits one to obtain additional savings from a decrease in the amount of concrete in the chambers and from a more simplified drainage system. 6. Calculation methods for lock chambers constructed as docks, allowing for deformations in the wall and bottom, and earth friction resistance along the rear faces of the walls, gave earth pressure values close to the actual.

Comparison between theoretical and measured earth pressures acting on a large motorway retaining wall

Abstract: The opportunity was taken during the construction of the M1 motorway to instrument and observe a large motorway retaining wall in yorkshire. The initial results of the investigation were reported in an article published in the june, 1970, journal by messrs sims, forrester and jones and entitled "lateral pressures on retaining walls". These results indicated that the earth pressures on the wall were increasing with time and also that the accepted design theory for retaining walls was based upon concepts of earth pressure incompatible with those found by measurement. Now, after five years, an equilibrium condition appears to have been reached. It has been found that finite element analysis, based upon elastic concepts compare favourably with the initial recorded earth pressures, and, in addition, it appears that the increase in earth pressure that has been recorded since the motorway was opened in 1968 may be caused by the traffic using the motorway retained by the wall. (A) ;TRRL;

An investigation of diaphragm earth pressure cells

Abstract: Experience with earth pressure cells has shown that their calibration performance is dependent on several factors, the most important being temperature, cell geometry, soil deformation characteristics and stress state. With previous published design criteria, cells can be designed specifically for given pressure ranges and material types. Cells were constructed for use in a red clay from griffith, NSW and subjected to a detailed theoretical and experimental investigation, whereby their behaviour could be adequately quantified for this specific application. As a result, many apparent anomalies in earth pressure cell performance can now be explained. Several new design criteria emerged permitting earth pressure cells to be used in given applications with even greater confidence. For example, sensitivity to temperature, soil type and stress state can be reduced to known acceptable levels (a).

Apparatus and instruments for the laboratory study of multi–anchored flexible retaining walls

Abstract: A laboratory setup is developed to study the earth pressure distribution on a multi-anchored flexible retaining wall, the bending moments in the wall, the forces in the anchoring wires, and the movements of the wall and retained soil during excavation of the front side of the wall. The wall was constructed from narrow aluminum panels, five such panels being clamped together at the top and bottom to form the central test area. Three such sections were used to make up a total width of 1,008 m. Electrical resistance strain gages were fixed to the wall (a) to record the bending stress and (b) to determine earth pressures, using small cantilevers cut in a panel. Other transducers were made and inserted to measure the normal and shear reactions at the base. Lateral displacements of the wall were transferred by 1-mm-dia rods through the soil to dial gages outside the test flume. During excavation, counterbalanced horizontal wale beams were used on the front side of the wall to distribute the forces of the anchor wires over the width of the wall. These beams were used at three levels corresponding to the locations of the anchor wires. The wires, which provide support to the wall, passed through the retained soil to a fixture on the frame where the loading was measured by miniature proving rings instrumented with small strain gages. The paper is deficient in that no mention is made of the order of the forces or stresses to be measured or of the sensitivity of the various transducers constructed. Further, although the paper shows the use of electrical resistance strain gages in various novel situations, it is restricted to readers who are involved in laboratory modeling of this and similar problems. We must wait for promised later papers to discuss the results and a design procedure for flexible tied walls.