Showing papers on "Lateral earth pressure published in 1977"

Soil Restraint Against Horizontal Motion of Pipes

Abstract: The safe and economical design of buried pipes subjected to lateral motion requires an accurate knowledge of the subgrade reaction. Too often values of the coefficient of horizontal subgrade reaction, k\dh, reported in the literature are used without understanding the author’s intentions and without thought as to whether or not the conditions in the particular application are compatible to those in the literature. A survey of the available literature discloses that the numerical values and formulations proposed were such as to underestimate the soil restraint against flexible culverts and laterally loaded piles. These values are inadequate for the safe design of buried pipes laterally displaced by settlement, thermal expansion, earthquake shaking or wave action. The results of a laboratory testing program show the complex soil-conduit interaction and the associated failure mechanisms. An analytical method is presented to determine the load-displacement curve for any size pipe embedded at any given depth. A moderate size in-situ test was performed, which confirmed that the results of the laboratory model tests could be successfully applied to in-situ conditions.

An examination of some theories of earth pressure on shaft linings

Abstract: Various theories for determining the earth pressure on shaft linings in cohesionless soils are discussed, and results are presented for a Coulomb-type analysis with a conical sliding surface. The a...

Pore Pressure Development under Offshore Gravity Structures

Abstract: One of the important geotechnical considerations related to the stability of offshore gravity structures founded on sand deposits is that of potential loss of supporting capacity of the sand due to the pore pressures induced in it by severe storm loadings. In this paper a procedure is presented for evaluating wave induced pore pressures. The method takes into account the distribution of cyclic shear stresses in the profile, and the important factor of pore pressure dissipation. The analysis provides the complete time history of pore pressure response of the soil underlying the tank during the storm, and shows clearly that failure to include pore pressure dissipation effects would lead to radically conservative design. The results also provide a basis for evaluating the stability of the tank foundation on an effective stress basis and suggest that critical support conditions are most likely to develop around the outer edges of the structure.

Energy Method for Soil Stability Analyses

Abstract: A method for soil stability analyses applying principles of soil mechanics to the theory of plasticity (limit analysis approach) is presented. The rigorous theoretical background and the simplicity of both the method and the calculation procedure are encouraging application of the method in engineering practice. Attention is drawn to the implication of the boundary conditions of deformations (degrees-of-freedom of the investigated structure or support) for the analysis. Different numbers of degrees-of-freedom of a system generally yield different results for safety factor, bearing capacity, etc. The method can be used for bearing capacity, earth pressure, and slope stability analyses. It is applicable for: (1)Design and failure conditions; (2)short and long-term analyses; (3)soil with pore water that is either stagnant or in seepage motion; (4)layered medium; and (5)arbitrary number of degrees-of-freedom of structure or support.

Experimental retaining wall facility--lateral stress measurements with sand backfill

Abstract: As part of the TRRL research programme to investigate soil-structure interaction, a pilot scale earth retaining wall has been built at the Laboratory sufficiently large to avoid any scale effects influencing the results and to enable normal construction methods to be used. This report describes the experimental retaining wall and its facilities and gives details of the initial experiments to measure the lateral soil pressure by compaction of a washed sand, and the active and passive pressures produced when the wall was moved away from and into the soil respectively. The experimental evidence shows that the residual earth pressures produced by the compaction of sand behind a rigid retaining wall are significantly higher than would be expected from the self-weight of the soil alone. However, only very small movements (less than 4 mm) of the test wall away from the soil were sufficient to reduce the earth pressures to the active condition for a fill height equivalent to 3.4 metres. A study of the passive case showed that a peak lateral thrust occurred on a metre high test wall after a movement of about 25 mm of the wall into the soil. /Author/

At-rest lateral earth pressure of a consolidating clay

Abstract: It is pointed out that while the above paper reports a thorough study of the fundamental mechanism, the study also has the basic data to consider K sub 0 (t) during the process of consolidation under a particular loading increment. Supplementing selective data on the time-dependent behavior of K sub 0 (coefficient of earth pressure at rest) will provide invaluable information in establishing the appropriate rheological behavior of the particular clay sample-formation under study. A viscoelastic model has been considered as a first approximation to establish the time-dependent nature of K sub 0 clay formation during the geological time span. K sub o (t) is about unity at the initial stage of slurry depesition. Afterwards, K sub 0 (t) exhibits a low minimum value with the formation of soil skeleton during the initial stage of primary consolidation, and then reincreases and approaches equilibrium value in line with the stage of secondary consolidation.

Incremental plasticity analysis of frictional soils

Abstract: Three constitutive models of soil are used in finite element analyses of lateral earth pressure and bearing capacity. The three models are an elasto-plastic formulation derived from the Mohr-Coulomb law, a similar model with the plastic dilatancy removed, and a strain hardening model with a capped yield criterion. Stiffness formulations are described; the non-dilatant model has a non-symmetric stiffness. The results for the retaining walls are in close agreement with classical soil mechanics, but the bearing capacity analyses greatly overestimate the bearing capacity. The patterns of motion are, however, reasonable. Reasons for the discrepancies in the bearing capacity case include: (a) the elements are too stiff and do not permit sliding on discrete failure planes; (b) the bearing capacity problem is itself not well settled theoretically; (c) very fine element divisions are necessary in areas of strong stress gradients; and (d) rotation of principal stresses is significant. /Author/

Method and system for controlling earth pressure in tunnel boring or shield machine

Abstract: In a tunnel boring or shield machine, a method and system for controlling the earth pressure, in which the earth pressure in the chamber of the shield machine body is detected and the detected earth pressure is compared with a reference value to thereby produce a chamber earth pressure deviation signal. In response to the chamber earth pressure deviation signal, means for controlling the amount of conveying earth accumulated in the chamber to the exterior of the machine body and/or means for advancing the shield machine body into the working face are controlled so as to maintain the earth pressure in the chamber within a predetermined range so that the breakdown of the exposed face or earth stratum as well as the rising of the ground are prevented from occurring. In another method and system, the earth pressure at the working face is detected and the detected value is compared with a reference value to produce a signal representing the earth pressure deviation at the working face.

Pressures on Retaining Wall with Repeated Loading

Abstract: The pressures on earth retaining structures that support backfills carrying moving loads have always been estimated by using methods that assume these loads to be applied in a static condition: the effect of these loads being repeated is not considered. The failure of some structures like bride abutments and basement walls, which support loads from moving vehicles, made it necessary to carry out these investigations.

Earth pressure on precast panel retaining wall

Abstract: The discussers of the above paper point out that in estimating the total thrust on a panel in the wall, since the seasonal fluctuation in load indicated by the force transducers is low, it is probable that the pressure fluctuations suggested by the pressure cell observations are not entirely real but more a function of the cells response to temperature. The Terra Tec cell is discussed and the discussers' experience with similar cells is discussed. Pnenmatic earth pressure cells were used in the instrumentation of the piled-raft foundation of a building. The cells were embedded with their outer faces flush with the underside of the raft and in contact with sandy gravel. The influence of temperature on pressure cell readings under conditions of more-or-less constantly applied pressure was correction required for temperature was found to be much that heat of hydration of the raft concrete. The conrrection required for temperature was found to be much higher than the suggested by an earlier investigation. For a given change in temperature, the correction to be applied to the observations varied from cell to cell, reflecting in-situ variations in restraint.

Pressure on a retaining wall by an expansive clay

Abstract: A reinforced concrete retaining wall, 7.5 M deep, in the basement of the gouger street mail exchange, Adelaide, South Australia, supports stiff hindmarsh clay over most of its depth. Earth pressures on the wall and soil suctions in the clay have been monitored for several years. The initial earth pressures were zero. Subsequently a pressure increase occurred at the base of the wall and moved progressively up the wall with time reading a maximum value of five times the overburden pressure. A theoretical model using the finite element method of solution with non linear (hyperbolic) material parameters (previously developed to analyse the load moisture displacement response of expansive clays) was used to check the proposed mechanism of behaviour of the wall. The model gave earth pressures on the wall comparable in both magnitude and distribution to those observed. While the interaction problem was more complex than the model used, the results suggested that the interfacial conditions between the wall and clay, the movement of the wall and the magnitude and extent of the swelling of the clay may be significant factors. (A)

Design and Field Behavior of Reinforced Earth Wall

Abstract: The design and field behavior of the first reinforced earth wall in the United States are presented. Equations for designing the reinforcement and the skin plate were developed. It was concluded that the use of active earth pressure for calculating the stresses in the reinforcement is applicable to the front end portion of the reinforcement and its connection. For the middle portion of the reinforcement, the at rest earth pressure should be used in the design. The stresses in the skin plate can be analyzed by assuming a hinged-end condition and based on vertical deformation. The vertical deformation of the skin plate is proportional to the overburden pressure.

Field measurements of lateral earth pressures and movements on retaining walls

Abstract: Field data were obtained and analyzed from two instrumented full-scale retaining walls. The data presented in this paper cover a period of 1156 d for a cantilever wall founded on H-piles and a period of 769 d for a precast panel wall founded on drilling piers. The data consist of pressure cell and movement measurements from both walls. For the precast panel wall, the force trainsmitted from the panel to the supporting pilasters was measured with force transducers. Analysis of the data indicates that movements near the bases of both walls were not large enough to develop active pressures. Earth pressure measurements near the bases of both walls were close to at-rest pressure. Earth pressures changed with seasonal variations in temperature. Pressure changes occurred as a result of construction equipment activity both during and after backfilling. Vehicular traffic after completion of construction did not produce measureable pressure changes during the time periods covered by this study.

Ground-lining pressure distribution and lining distortion in two tunnels driven through stiff, stony/laminated clay

Abstract: This article describes the design, construction, and calibration of a hybrid electro-hydraulic type of earth pressure cell and the subsequent use of these cells for the measurement of radial ground pressures acting on concrete segmental tunnel linings at two locations in mixed clayey ground in north-east England. Also described is an accompanying programme of lining distortion measurement. The tunnels studied were 3.20 m dia. at depths of 11.77 m and 12.39 m to the crown. Terminal ground-lining interaction pressures were found to be almost uniformly distributed about the tunnel cross-section, these recorded pressures being one-half the theoretical maximum over-burden pressure calculated on a gamma z basis. Furthermore, these ultimate pressures were achieved after a period of only 7-8 days following lining erection and grouting-up. Lining distortion measurements support these observations. This rapid stabilisation of ground pressure at the lining contact contrasts with a much more protracted on-going pressure build-up and lining distortion reported by some other workers for different ground conditions, but is is certainly consistent with contractual experience which suggests that tunnel secondary linings could be safely erected, with little risk of brittle fracture, much earlier following primary lining construction that has hitherto been considered prudent. /Author/

Design aids for cantilever retaining walls

Abstract: Design aids are given for the complete design of reinforced concrete contilever retaining walls. A total of seven charts are prepared to design the retaining wall stem, footing length, heel and toe thickness, and to find the toe soil bearing pressure. A summary of equations used to develop the charts is included. The charts are drawn using the Strength Design Design Method of “Building Code Requirements for Reinforced Concrete (ACI 318-71).” Rankine earth pressure theory is used for a horizontal backfill, and the concrete ultimate strength is 3,000 psi with the steel yield strength of 60,000 psi. An example is included which shows the procedure of using the charts. These charts simplify the problem of designing a cantilever retaining wall by hand, and the charts are both accurate and efficient.

A method of determination of k - the lateral earth pressure coefficient for shaft friction

Abstract: The author discusses the limitations of the "static formula" and derives a theoretical expression for k taking into account the stress distribution around piles requiring detailed stress measurements and sophisticated studies. He assumes that the vertical effective stress adjacent to the pile shaft remains constant up to failure. Two equations for the shaft resistance are derived assuming failure takes place at the interface between the soil and the shaft. There is good agreement between predicted and values of K measured by J B Burland although the predictions assume that the failure takes place on a horizontal plane. No reason is given for the adoption of the horizontal plane as a failure plane as opposed to any other. /TRRL/

Consolidation with Triangular Pressure Generation

Abstract: In a previous technical note the writer has presented the analytical solution for the distribution of pore pressure in time and space for the case of an infinite, uniform, horizontal layer of soil with constant modulus and permeability in which excess pore pressures are generated linearly with time and dissipated by consolidation. Drainage can occur either at both faces or at one face. All the usual assumptions of classical consolidation theory apply. It turns out that the solution is a relatively simple extension of the Terzaghi consolidation theory.

Spreading of submarine slopes caused by trenching

Abstract: Submarine trenching for pipeline installation in potentially unstable sediments has recently been of increasing concern Although typical pipeline depths are less than 3 or 4 m, trenching operations generally cause local stress concentrations within the sediments and induce excess pore pressures The result of these stress concentrations and pore pressure increases may be spreading of submarine slumps that can endanger pipelines or other nearby installations A simplified analytical approach is described to estimate the extent of slump spreading caused by trenching It is shown that the spreading potential is affected by many geotechnical characteristics of the sediments in addition to geomorphic processes and the oceanographic regimes governing the area The primary geotechnical factors that influence spreading include the porepressure parameter Af , the degree of consolidation, the coefficient of earth pressure at rest, and the strength characteristics of the soil Dimensionless parameters are

Active pressure observations on a model retaining wall

Abstract: A series of tests on a small instrumented wall retaining a clay backfill were carried out by moving the wall away from the backfill and then preventing further movement of the wall. The short term earth pressures immediately following rapid wall movement were reasonably predicted by earth pressure theory. However, after cessation of this wall movement the earth pressures gradually rose to a value less than the at rest pressure. Attempts to predict the long term earth pressure were not particularly successful. (A)

Strata Pressures and Support Loads

Abstract: This chapter discusses the strata pressures and support loads. The determination of strata pressure is of interest in geotechnology, not only in relation to the absolute or relative state of stress in earth and rock masses but also in relation to the loads imposed by the soil or rock on structures erected within, against, or upon the earth material. In soil mechanics and foundation engineering, the correlation between calculated earth pressure and soil-structure interaction is a perennial problem. In rock mechanics, while considerable advances are being made, in theory and in practice, to solve the problem of determining in situ field or regional stress, and while the observation of direct loads imposed upon simple struts in tension or compression is commonplace, very little is known of the nature of the contact loads between rock masses and excavation support structures involving more complex and unknown stress distributions.