Showing papers on "Lateral earth pressure published in 1976"

Bearing capacity and settlement of pile foundations

Abstract: Conventional bearing capacity of driven and bored piles in sand and nonplastic silt is limited to short piles above the critical depth of penetration. The bearing capacity of longer piles can be estimated from the limiting values of the point resistance and skin friction using either the friction angle of the soil or preferably the results of static and standard penetration tests directly. For driven and bored piles in clay and plastic silt, conventional bearing capacity theory using the undrained shear strength of the soil represents mainly the failure condition at the pile points. The positive and negative shaft resistance some months after pile installation is governed by the drained shear strength of remolded soil and can be estimated from skin friction factors, provided the earth pressure coefficient at rest of the deposit is known. The ultimate load of pile groups and the settlement of pile foundations are examined.

Stress-Path Independent Behavior of Cohesionless Soil

Abstract: The strains induced in cohesionless soil by changes in stress vary considerably depending on stress level (defined as a stress ratio), confining pressure, and on whether the changes in stress involve primary loading, unloading, or reloading. The nature of stress-path dependency, the principles that govern deformations in cohesionless soil, and prediction of soil response for a variety of stress-paths have been investigated. Based on the results of triaxial tests it was found that except for the maximum previous stress level experienced, the stress history has little influence on the behavior of cohesionless soil. However, for stress-paths involving unloading or reloading, stress-path does have an influence on the strains, and the stress-path with the higher average stress level produces the larger strains. An elastoplastic stress-strain theory was used to calculate the strains for the stress-paths investigated and generally good agreement between calculated and measured strains was obtained. It is shown that the plastic deformations in cohesionless soil can be determined from the state of stress, the increment in stress level, and the increment in total work.

Strength of reinforced soil

Abstract: Two theoretical models for the behaviour of reinforced soil at failure are proposed. Both refer to a horizontally reinforced soil mass which fails by expanding in the direction of the reinforcement. In the first model reinforcement is seen as producing an intrinsic prestress, or lateral restraint, when failure conditions are approached. Second model reinforcement is assumed to induce horizontal and vertical shear stresses into the originally geostatic conditions. If the lateral prestress or induced shear stress has a constant value related to the strength of the reinforcement, a cohesion intercept results. If they are proportional to the initial vertical stress, an increase in the angle of friction results. These conditions correspond to failure by rupture of the reinforcement and failure by slippage between the reinforcement and the soil. Triaxial test results presented support the concept of friction angle increase while the cohesion-effect has been recognised for some time. The concept of reinforcing efficiency is introduced for interpreting the test results. Reference is made to the Reinforced Earth Technique which takes advantage of the reinforcing effect although standard design procedures usually assume anchored wall elements subjected to active earth pressure.

At-Rest Lateral Earth Pressure of Consolidating Clay

Abstract: Two clay slurries with different controlled chemistries (flocculated and dispersed) were consolidated in large-diameter rigid cylindrical slurry consolidometers. During two cycles of consolidation and rebound, the axial deformations, pore pressure, and both axial and radial stresses were measured directly, thereby providing a continuous record of the stress and strain history of each sample. The coefficient of lateral earth pressure at-rest, K\do, was found to remain essentially constant during the loading phase of a loading-unloading cycle, but its value increased gradually during unloading until it exceeded unity when the overconsolidation ratio was about 2. Several indirect approaches were used to compute K\do from shear strength parameters determined from triaxial compression tests on specimens trimmed from block samples of the same two clays for which direct measurements were obtained, and the results were found to be in good agreement. Within the scope of the test data, neither pore fluid chemistry nor the associated clay fabric exerted much influence of the measured (during loading) values of K\do, which were in the range of 0.70 ±\N0.05.

Lateral Earth Pressure at Rest in Soft Clay

Abstract: The lateral earth pressure at rest in a soft cohesive soil as determined by five different methods at Backebol, Sweden is compared and analyzed. The agreement between the results using a thin earth pressure cell and a self-boring pressuremeter was satisfactory. It was found that the results from conventional pressuremeter tests were difficult to interpret. This method as well as the hydraulic fracturing method seems to overestimate the lateral earth pressure at rest for very soft clays. The lateral earth pressure as determined by a total stress cell (Camkometer) installed in an excavated borehole was low and erratic.

Lateral support systems and underpinning. volume ii. design fundamentals

Abstract: This report provides current information and design guidelines on cut-and-cover tunneling for practicing engineers. The main emphasis is on the geotechnical aspects of engineering. Included in this volume is a state-of-the-art summary of displacements and lateral pressure. Other topics are basic concepts of soil mechanics, ground water in open cut, passive resistance, design aspects of lateral earth pressure, stability analysis of sheeted excavations, bearing capacity of deep foundations, and construction monitoring. Detailed explanations of design methods and literature citations are included. Other reports prepared as part of the study are FHWA-RD-75-128, Volume I, Design and Construction; FHWA-RD-75-130, Volume 3, Construction Methods; and FHWA-RD-75-131, Concepts for Improved Lateral Support Systems.

Lateral Support Systems And Underpinning. Volume I: Design And Construction

Abstract: This volume is a convenient reference on the design and construction of lateral support systems and underpining which are often required in conjunction with cut-and-cover or soft ground tunneling. The design recommendations and construction methods described herein are a summary of the more detailed information presented in the companion volumes of this study. Included in this volume are discussions of displacements, lateral earth pressure, ground water, passive resistance, stability analysis, bearing capacity, soldier piles, steel sheeting, diaphragm walls, bracing, tiebacks, underpinning, grouting, and freezing. An overview compares the relative costs of the construction methods used in lateral support systems and underpinning. Other reports developed from the study are FHWA-RD-75-129, Volume II, Design Fundamentals: FHWA-RD-75-130, Volume III, Construction Methods; and FHWA-RD-75-131, Concepts for Improved Lateral Support Systems.

Performance of a strutted excavation in quick-clay

Abstract: THIS ARTICLE DESCRIBES THE ERECTION AND BEHAVIOUR OF A TIMBERED EXCAVATION MEASURING 11 M DEEP AND 11.5 M WIDE, FOR USE IN THE CONSTRUCTION OF A RAILWAY TUNNEL IN OSLO. THE SOIL CONDITIONS CONSIST OF A 3 M COVERING LAID OVER SENSITIVE TO MEDIUM SENSITIVE CLAY WHICH BECOMES QUICK AT A DEPTH OF 9 M. THE STEEL SHEET PILE WALL WAS SUNK TO A MAXIMUM DEPTH OF 17 M BELOW SURFACE LEVEL I.E. AS FAR AS THE ROCK FOUNDATION. IT WAS THEN STIFFENED AT 3 M HORIZONTAL INTERVALS WITH 7 DIFFERENT POSITIONINGS OF INCLINED STEEL BRACING. DURING ERECTION EXTENSIVE MEASUREMENTS WERE TAKEN OF THE FOLLOWING: (1) VERTICAL AND HORIZONTAL MOVEMENTS; (2) PORE WATER PRESSURE IN THE CLAY; (3) EARTH PRESSURE ON THE SHEET PILE WALL; (4) STRESS ON THE BRACING. MEASUREMENTS QUOTED COMPARE FAVOURABLY WITH PREVIOUS RESULTS YIELDED BY NON-STRUCTURE SENSITIVE CLAYS. THE COVERING ABSTRACT FOR THE CONFERENCE IS IRRD NO 306088.

Earth pressure on precast panel retaining wall

Abstract: Earth pressure cells are used to measure lateral earth pressures acting on a precast panel retaining wall. Force transducers are used between the panel and the supporting structural members to measure the total force exerted on the panel by the backfill material. Measurements of panel movements are made during and after backfilling. Data are presented for measured pressures, forces, and movements covering a period of 443 days. Physical and engineering properties of the backfill material are determined. Reasonably good correlation between the forces calculated from the pressure cell measurements and those measured by the force transducers tend to verify the accuracy of the measured earth pressures. Measured pressures in the upper elevations of the wall correlate fairly well with theoretical active pressures computed according to Coulomb and Rankine. However, measured pressures in the lower elevations are considerably higher than the theoretical active pressures.

Displacements around tunnels in soils

Abstract: This report summarizes one year of research on ground movements around tunnels in soil. Data from available case histories of tunnels constructed in sands and gravels, stiff clays, and soft clays is combined with the results of field observations and a model study to describe sources and volumes of ground lost around tunnels, the relationship between volume of ground lost and volume of surface settlement, and the shape of the surface settlement trough. Horizontal strains occurring with the surface settlement trough are described, and their implications for building damage are discussed. The volume of surface settlement is affected not only by the volume of lost ground, but also by the volume of expansion or compression in the soil around a tunnel. The surface settlement trough can be approximated by relationships presented by Peck (1969), except in cases where the settlements are very small (elastic) or very large (greater than 0.5 percent of the tunnel depth). In these cases, the settlement trough may be wider or narrower, respectively, than estimated. The results of field and analytical studies of interference effects between settlement troughs for multiple tunnels are presented. The results of a field observation program of settlement measurements on the Washington, D.C. Metro Section F2a tunnels are presented. A third section of the report is a progress report on a model study in which ground movements around a model tunnel in sand were measured using photogrammetric procedures and displacement gages.

Effect of horizontal reinforcement on stability of earth masses

Abstract: Reinforced earth consists primarily of soil whose engineering properties and performance have been improved by the introduction of small quantities of frictional material that possesses a relatively high tensile strength and modulus of elasticity. This practical concept has been applied to the problem of stabilizing slopes, retaining walls, pavements, and other applications as described in the literature review. The objectives of this study were: (a) to investigate the uncertainties concerning the stress-strain distribution and the interrelation between the reinforcement and the surrounding soil, and (b) to evaluate the performance of neoprene-coated hylon fabric (membrane) versus galvanized steel as reinforcing material within a cohensionless soil mass. These two pbjectives were directed toward the feasibility of using the concept of reinforced earth in Corps of Engineers projects. Based on the instrumentation measurements collected during construction and during loading of the structure to failure, it appears that the Rankine earth pressure theory provides a good approximation for the measured lateral pressure when the wall is carrying little or not surcharge load. The curve connecting the points where maximum tensile stress occurred in the reinforcing ties did not coincide with the theoretical Rankine failure surface. An improved method of defining the effective length of reinforcing tie, compatible with full-scale field test results, to be used in computing tie pullout should be developed. The field test conducted at the U.S. Army Engineer Waterways Experiment Station indicated that the reinforced earth concept provides another alternative for constructing earth structures which may prove to be more economical when compared with conventional methods under certain conditions.

Pile foundations - single piles

Abstract: INITIALLY THE BEHAVIOUR OF PILES IN COMPRESSIBLE AND INCOMPRESSIBLE SOIL AND THE TWO MODES OF FAILURE ARE DEALT WITH. THE PAPERS REVIEWED IN THIS GENERAL REPORT DEAL WITH THE CALCULATION OF POINT RESISTANCE BASED ON THE THEORY OF ELASTICITY, MODEL TESTS AND THEIR THEORETICAL EVALUATION WITH THE AID OF THE FINITE ELEMENT METHOD, AND WITH PROBLEMS OF MODELLING SIMILARITY. THE SECOND PART CONTAINS DETAILS OF LOADING TESTS AND THEIR RESULTS AS WELL AS THEIR RELATIONSHIP TO SOUNDING METHODS AND THEIR EVALUATION. THE PAPERS DEAL WITH SUCH TOPICS AS LOADING TESTS ON VARIOUS TYPES OF PILES IN DIFFERENT SOIL STRATA, THE RELATIONSHIP BETWEEN BEARING CAPACITY AND STANDARD PENETRATION TESTS, THE DETERMINATION OF EARTH PRESSURE FACTORS AND POINT RESISTANCE, VERIFICATION OF SOIL PARAMETERS OBTAINED USING PRESSIOMETERS BY MEANS OF TEST PILES, THE INFLUENCE OF POREWATER PRESSURES AND TIME DEPENDENT SETTLEMENT BEHAVIOUR, THE RELEVANCE OF SOIL PARAMETERS FOR CALCULATIONS, MEASUREMENTS AND INSTRUMENTATION ON A LARGE DIAMETER BORED PILE, AND AN EXTRAPOLATION METHOD FOR DETERMINING THE BEARING CAPACITY FROM A DIMENSIONLESS LOAD-SETTLEMENT GRAPH. THE THIRD PART DEALS WITH ASPECTS OF THE RELATIONSHIPS BETWEEN SOUNDING METHODS AND PILE BEHAVIOUR AND THEIR USE FOR PREDICTING SOIL BEARING CAPACITY AND PILE LOADS. THERE ARE REPORTS ON A SELF-DRILLING FRICTION PROBE, AN INSTRUMENT FOR MEASURING POREWATER PRESSURE DURING DRIVING, THE RELATIONSHIP BETWEEN CONE PENETROMETER AND STANDARD PENETRATION TESTS, AND TWO NEW TYPES OF PILE - A GROUTED STEEL PILE AND A VIBRATED IN-SITU CONCRETE PILE. THE COVERING ABSTRACT FOR THE CONFERENCE IS IRRD NO 306088.

Performance of a thin metal retaining wall with multiple anchorage

Abstract: The construction and performance of a new type of retaining structure is described. The wall, at the head of a steep canyon, was built by anchoring a thin metal face to the backfill area with multiple metal tiestraps anchored to a continuous deadman. The forces in the tiestraps, the distribution of these forces, the distribution of stresses in the soil and backfill, and the deformation of the wall and within the backfill were measured with appropriate strain and fluid settlement gauges and pressure cells. Subject to the limitations imposed by the facts that the instrumentation and the results produced from the pressure cell observations showed considerable variability, the following conclusions are drawn: (a) conventional earth-pressure analysis gives reasonable forces for tiestrap wall design, but consideration in future designs should be given to the effects of sloping surcharges; (b) stresses in the backfill near the wall face are less than those indicated by conventional earth-pressure analysis; (c) a tieback wall deforms in the active sense in spite of the presence of the tiestraps. The potential failure surface within the backfill can be predicted with reasonable accuracy using Coulomb earth-pressure analysis, but the actual surface may define a smaller active zone; (d) the outward wall movements were not unreasonably large, but were of sufficient magnitude to reduce the total force necessary to stabilize the backfill at the active value; (e) the vertical movements in the backfill exceed those accounted for by lateral wall movement and were weather-related; and (f) the wall was still moving at the end of the rainy season, but at a rate significantly smaller than before. Further movements appear to be likely, but tolerable. /Author/

Finite element analysis of the performance of rigid plate soil pressure cells

Abstract: The author gives an account of a study of the performance of rigid plate soil pressure cells intended for measuring the pressure at the interface between a retaining wall and the soil backfill, with particular reference to finite element analysis. The program used was that developed at TRRL by Fellows and Castledine, which is based on constant strain triangular elements and involves the calculation of external vertical nodal applied loads by waterhouse's method, and included a facility for allowing the application of radial external loads. Figures include a typical distribution of vertical stress over the face of the pressure cell, a calibration chart for cells of different stiffness used in a range of soil types and the change in cell factor with radius. It was found that a 10 per cent change in nodal stress at the edge of a plate produced a change of less than 3 per cent in the cell factor and that the cell factor was linearly dependent on the displacement of the cell plate. Comparisons were made between experimental and calculated relations between applied and 'measured' cell pressures for a washed sand and a sandy clay. Similar results were obtained and although the finite element anaysis predicts a smaller cell error than was actually obtained, it was concluded that the finite element analysis method provides a reasonable guide to the probable performance of a cell mounted flush with a rigid surface.

Lateral earth pressures exerted by compacted granular materials

Abstract: The paper describes refined techniques for measuring lateral earth pressures, with particular attention being given to those pressures exerted by compacted granular materials. Experiments were carried out under laboratory conditions on a small (300 mm high) retaining wall, and the results are compared with those obtained behind a large (14 M high) retaining wall, which formed part of a motorway construction. Particular mention is made concerning the calibration of the measuring devices. Earth pressure coefficients for the at-rest, active and passive conditions are tabulated for three granular materials and for different states of compaction. Pressure distributions across and down the walls are investigated for varying wall movements, and under differing amounts of compaction. The laboratory and full-scale results give very reasonable agreement, and it is suggested that the more usual methods of earth pressure calculation for the structural design of bridge abutments, wing walls and retaining walls, be revised. To this end, a design method is presented which could be readily used by practising engineers. /Author/TRRL/

Earth filling type pool

Abstract: PURPOSE:To provide an earth filling type pool in which thermal stress is balanced with earth pressure and no excess load is exerted to the bottom fixture by contraction resulting from temperature difference

Active earth pressure on retaining walls of finite length

Abstract: 1. The active earth pressure on retaining walls of finite length is considerably less than that determined by the Coulomb theory. 2. The coefficient of pressure decrease depends on the soil parameters and ratio K=B/H. When K>5 the solution approximates the Coulomb solution. 3. The slope angle of the slip plane of the soil for walls of finite lengthis greater than the angle determined by the Coulomb theory. 4. The curves of intensity of the earth pressure have a curvilinear outline. The center of the pressure is located higher than under conditions of the two-dimensional problem.

Measurement of ground-lining pressure distribution around two tunnels in stiff stony clay

Abstract: This thesis describes the design, construction and calibration of a hybrid hydraulic/electrical type of earth pressure cell and the subsequent use of these cells for the measurement of radial ground pressures bearing 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 and a preliminary discussion is directed towards theoretical aspects of ground/lining interaction mechanics The tunnels studied were 320 m diameter and at depths of 1177 m and 1239 m to the crown Lining/soil radial interaction pressures were found to be almost uniformly distributed about the tunnel, these recorded pressures being almost one-half the maximum possible overburden pressure calculated on a ɤ z basis Furthermore, these ultimate pressures were achieved after a period of only 7 to 8 days following lining erection and grouting Ultimate measured lining ring distortions were also realized after this 7 day period This relatively rapid stabilisation of ground pressure contrasts with a much more protracted, on-going distortion reported by other workers in other materials, but is 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 than has hitherto been considered prudent