Showing papers on "Lateral earth pressure published in 2000"

Foundation Design: Principles and Practices

Abstract: (NOTE: Most chapters include Questions and Practice Problems, Summary, and Comprehensive Questions and Practice Problems.) I. GENERAL PRINCIPLES. 1. Foundations in Civil Engineering. The Emergence of Modern Foundation Engineering. The Foundation Engineer. Uncertainties. Building Codes. Classification of Foundations. 2. Performance Requirements. Design Loads. Strength Requirements. Serviceability Requirements. Constructibility Requirements. Economic Requirements. 3. Soil Mechanics. Soil Composition. Soil Classification. Groundwater. Stress. Compressibility and Settlement. Strength. 4. Site Exploration and Characterization. Site Exploration. Laboratory Testing. In-Situ Testing. Synthesis of Field and Laboratory Data. Economics. II. SHALLOW FOUNDATION ANALYSIS AND DESIGN. 5. Shallow Foundations. Spread Footings. Mats. Bearing Pressure. 6. Shallow Foundations-Bearing Capacity. Bearing Capacity Failures. Bearing Capacity Analyses in Soil-General Shear Case. Groundwater Effects. Allowable Bearing Capacity. Selection of Soil Strength Parameters. Bearing Capacity Analyses-Local and Punching Shear Cases. Bearing Capacity on Layered Soils. Accuracy of Bearing Capacity Analyses. Bearing Spreadsheet. 7. Shallow Foundations-Settlement. Design Requirements. Overview of Settlement Analysis Methods. Induced Stresses beneath Shallow Foundations. Settlement Analyses Based on Laboratory Tests. Settlement Spreadsheet. Settlement Analyses Based on In-Situ Tests. Schmertmann Spreadsheet. Settlement of Foundations of Stratified Soils. Differential Settlement. Rate of Settlement. Accuracy of Settlement Predictions. 8. Spread Footings-Geotechnical Design. Design for Concentric Downward Loads. Design for Eccentric or Moment Loads. Design for Shear Loads. Design for Wind or Seismic Loads. Lightly-Loaded Footings. Footings on or near Slopes. Footings on Frozen Soils. Footings on Soils Prone to Scour. Footings on Rock. 9. Spread Footings-Structural Design. Selection of Materials. Basis for Design Methods. Design Loads. Minimum Cover Requirements and Standard Dimensions. Square Footings. Continuous Footings. Rectangular Footings. Combined Footings. Lightly-Loaded Footings. Connections with the Superstructure. 10. Mats. Rigid Methods. Nonrigid Methods. Determining the Coefficient of Subgrade Reaction. Structural Design. Settlement. Bearing Capacity. III. DEEP FOUNDATION ANALYSIS AND DESIGN. 11. Deep Foundations. Types of Deep Foundations and Definitions. Load Transfer. Piles. Drilled Shafts. Caissons. Mandrel-Driven Thin-Shells Filled with Concrete. Auger-Cast Piles. Pressure-Injected Footings. Pile-Supported and Pile-Enhanced Mats. Anchors. 12. Deep Foundations-Structural Integrity. Design Philosophy. Loads and Stresses. Piles. Drilled Shafts. Caps. Grade Beams. 13. Deep Foundations-Axial Load Capacity Based on Static Load Tests. Load Transfer. Conventional Load Tests. Interpretation of Test Results. Mobilization of Soil Resistance. Instrumented Load Tests. Osterberg Load Tests. When and Where to Use Full-Scale Load Tests. 14. Deep Foundations-Axial Load Capacity Based on Analytical Methods. Changes in Soil during Construction. Toe Bearing. Side Friction. Upward Load Capacity. Analyses Based on CPT Results. Group Effects. Settlement. 15. Deep Foundations-Axial Load Capacity Based on Dynamic Methods. Pile-Driving Formulas. Wave Equation Analyses. High-Strain Dynamic Testing. Low-Strain Dynamic Testing. Conclusions. 16. Deep Foundations-Lateral Load Capacity. Batter Piles. Response to Lateral Loads. Methods of Evaluating Lateral Load Capacity. p-y Method. Evans and Duncan's Method. Group Effects. Improving Lateral Capacity. 17. Deep Foundations-Design. Design Service Loads and Allowable Definitions. Subsurface Characterization. Foundation Type. Lateral Load Capacity. Axial Load Capacity. Driveability. Structural Design. Special Design Considerations. Verification and Redesign during Construction. Integrity Testing. IV. SPECIAL TOPICS. 18. Foundations on Weak and Compressible Soils. Deep Foundations. Shallow Foundations. Floating Foundations. Soil Improvement. 19. Foundations on Expansive Soils. The Nature, Origin, and Occurrence of Expansive Soils. Identifying, Testing, and Evaluating Expansive Soils. Estimating Potential Heave. Typical Structural Distress Patterns. Preventive Design and Construction Measures. Other Sources of Heave. 20. Foundations on Collapsible Soils. Origin and Occurrence of Collapsible Soils. Identification, Sampling, and Testing. Wetting Processes. Settlement Computations. Collapse in Deep Compacted Fills. Preventive and Remedial Measures. 21. Reliability-Based Design. Methods. LRFD for Structural Strength Requirements. LRFD for Geotechnical Strength Requirements. Serviceability Requirements. The Role of Engineering Judgement. Transition of LRFD. V. EARTH RETAINING STRUCTURE ANALYSIS AND DESIGN. 22. Earth-Retaining Structures. Externally Stabilized Systems. Internally Stabilized Systems. 23. Lateral Earth Pressures. Horizontal Stresses in Soil. Classical Lateral Earth Pressure Theories. Lateral Earth Pressures in Soils with c ...o and ... ...o 0. Equivalent Fluid Method. Presumptive Lateral Earth Pressures. Lateral Earth Pressures from Surcharge Loads. Groundwater Effects. Practical Application. 24. Cantilever Retaining Walls. External Stability. Retwall Spreadsheet. Internal Stability (Structural Design). Drainage and Waterproofing. Avoidance of Frost Heave Problems. 25. Sheet Pile Walls. Materials. Construction Methods and Equipment. Cantilever Sheet Pile Walls. Braced or Anchored Sheet Pile Walls. Appendix A: Unit Conversion Factors. Appendix B: Computer Software. References. Index.

Static and seismic passive earth pressure coefficients on rigid retaining structures

Abstract: The passive earth pressure problem is investigated by means of the kinematical method of the limit analysis theory. A translational kinematically admissible failure mechanism composed of a sequence...

Distribution of earth pressure on a retaining wall

Abstract: On the basis of Coulomb's concept that the earth pressure against the back of a retaining wall is due to the thrust exerted by a sliding wedge of soil between the back of the wall and a plane which passes through the bottom edge of the wall and has an inclination of θ, a differential equation of first order is set up by considering the equilibrium of the forces on an element of the wedge. A theoretical result for the unit earth pressure on a retaining wall is obtained. A comparison is made between Coulomb's formula and the formula presented here, and the earth pressure calculated by the formula presented here is also compared with experimental observations.

Lateral earth pressure at rest and compressibility of municipal solid waste

Abstract: The paper presents the results of laboratory testing of municipal solid waste samples subjected to one-dimensional compression with measurement of lateral stresses. The details of a large-size split-ring apparatus specially developed for this research are presented along with the data on earth pressure at rest and compressibility characteristics. The results show the influence of fibre content on the coefficient of earth pressure at rest in waste materials. The "delayed compression" behaviour observed in the laboratory is shown to be similar to the concepts developed by Bjerrum for normally consolidated sensitive marine clays. Issues such as validity of laboratory testing and sample-size effects are also discussed.Key words: earth pressure at rest, municipal solid waste, compressibility.

Calculation Models For Dam Foundations With Geotextile Coated Sand Columns

Abstract: As against conventional column foundations, coated columns can be used as ground improvement in very soft soils. The radial support is guaranteed through the composite between the geotextile coating and the surrounding soil, while the geotextile is under ring tension forces. Therefore this foundation system will be employed widely to found buildings, especially embankments on very soft or organic soils like peat. Numerical and analytical models for calculation and design of the new foundation system will be reflectet. INTRODUCTION By the foundation of buildings on soft soils often an improvement of the soft soil with the already known column foundations was carried out for example compacted sand columns or vibro displacement granular piles. In very soft soils like peat this columns normally can not be used, because the horizontal support in this soils is not sufficient. By the new foundation method ‘geotextile coated sand columns’, sand columns are inserted down to the bearing layer. These columns are coated with a geotextile of polyester threads, which guarantees the filter effect and the horizontal support. By using this new developed system a safe and flexible foundation on very soft soils with low settlements, especially for dams or traffic roads embankments, can be achieved. CONSTRUCTION PROCEDURE Two construction methods are developed by the Josef Mobius Baugesellschaft GmbH, Hamburg, Germany, which are called the excavation method and the displacement method. By the excavation method a casing with a diameter between 0,8 m and 1,5 m is vibrated into the ground and after that the soil in the casing is excavated. Opposite to that by the displacement method a steel tube with a much smaller diameter of about 0,6 m to 0,8 m is placed into the subsoil. According to the displacement principle, the two base flaps of the casing are closed and displaces the soft soil to the sides of the casing. Then the geotextile with a somewhat larger diameter as the column is inserted into the casing. This is delivered from the factory and cut in length on the construction site. On the one hand this is due to the construction, on the other hand it ensures the partial mobilisation of the passive earth pressure, which increases the horizontal support. After inserting the geotextile and the filling of the column the casings are pulled using vibration, which causes compaction of the sand-gravel mixture in the column. BEARING BEHAVIOUR The geotextile coated sand columns are a bearing component, although the column must be horizontally supported. In contradiction to a conventional not coated column, where the horizontal support of the soft soil σh,s,tot must be equal to the horizontal pressure σh,c in the column, geotextile coated columns can be used as soil improvement in very soft soils, due to the radial supporting effect of the coating σh,geo = f(Fr) combined with the surrounding soft soil σh,s,tot. At the same time the coating is demanded to ring tension forces Fr. So the horizontal support of the soft soil σh,s,tot, which depends on the vertical pressure on the soft soil σv,s, can be much smaller, and a large settlement reduction is given due to the load concentration over the sand columns. Finally a load-dependent equilibrium state, with a flexible and self-regulating bearing behaviour is reached. At the same time a settlement acceleration is observed, since the columns behave as large vertical drains. After construction time, only small settlements will occur. 1 Dr. Marc Raithel, Geotechnique Consultants Kempfert +Partner, Mannheim, Germany 2 Prof. Hans-Georg Kempfert, Institute of Geotechnique, University of Kassel, Germany CALCULATION METHODS Numerical calculation using FEM For the numerical calculation the program PLAXIS (Finite Element Code for Soil and Rock Analyses) was used. An advantage of this program is the possibility to use several soil models. For the soft soil the Soft Soil Model (SSM), a model of the Cam-Clay type was used. For the sand and gravel of the column material the Hard Soil Model (HSM), a modified model on the basis of the Duncan/Chang model, was used. The calculation of the bearing and deformation behaviour leads to a three-dimensional problem. The program PLAXIS allows only calculations with an axial symmetric model or a cross model. In practice a threedimensional calculation model is hardly used. Therefore in the numerical analysis the problem is simplified and the calculation is split up into two separate models. By the examination of a single column (according to the ‘unit cell concept’) and the use of an axial symmetric calculation model the ring tension forces for the design are determined. To investigate the deformation behaviour of the whole system, for example a dam foundation, a cross model is used. The coating can not be simulated directly, because the columns must be substituted by walls of equal area ratio. Therefore a substitute shear parameter is defined, which is used for the column material after activation of ring tension forces. The definition and derivation of the substitute shear parameter as well as comparative calculations are shown in Raithel (1999) and Raithel and Henne (2000). Analytical Calculation model Assumptions and boundary conditions The analytical, axial symmetric calculation model (according to the ‘unit cell concept’) with the essential boundary conditions is shown in figure 1.

Performance of geosynthetic-reinforced walls supporting bridge and approaching roadway structures

Abstract: This paper describes a unique field application in which a geosynthetic-reinforced soil system was designed and constructed to support both the foundation of a two-span bridge and the approaching roadway structure. The reinforced soil system not only provides bridge support, but it was also designed to alleviate the common bridge bump problem. This structure was considered experimental and comprehensive material testing and instrumentation programs were conducted. These programs would allow assessment of the overall structure performance and evaluation of Colorado Department of Transportation and AASHTO design assumptions and procedures for reinforced soil structures supporting both bridge foundations and approaching roadway structures. Large-size direct shear and triaxial tests were conducted to determine representative shear strength properties and constitutive relations of the gravelly backfill used for construction. Three sections were instrumented to provide information on external movements, internal soil stresses, geogrid strains, and moisture content during various construction stages and after the structure opening to traffic. Results from a pilot (Phase I) instrumentation program and some preliminary results from a more comprehensive (Phase II) instrumentation program are presented in the paper. The results suggest that current design procedures lead to a conservative estimation of both the backfill material strength and horizontal earth pressures, and that the overall performance of this structure, before its opening to traffic, has been satisfactory.

Practical Foundation Engineering Handbook

Abstract: Part 1 Soil problems in civil engineering: the nature of soils water behaviour in soils site preparation and land planning. Part 2 Soil mechanics and foundation design parameters: soil mechanics - evaluation of soil properties, clay mineralogy, soil classification, soil and water relations, capillary and pore pressure, kinetic water, strength concepts foundations - bearing capacity of shallow foundations, stress distribution and settlement, bearing capacity of piers and piles. Part 3 Foundation construction and engineering: concrete - constituent materials, computation of average compression strength and mix proportioning, quality assurance, mechanical properties, cold and hot weather concreting, pumping of concrete fundamentals of reinforced concrete foundation design procedures in concrete construction - piers and pile foundations earth pressure and retaining systems.

Dynamic response of flexible retaining walls

Abstract: Making use of an extension of a recently proposed, relatively simple, approximate method of analysis, a critical evaluation is made of the response to horizontal ground shaking of flexible walls retaining a uniform, linear, viscoelastic stratum of constant thickness and semi-infinite extent in the horizontal direction. Both cantilever and top-supported walls are examined. Following a detailed description of the method and of its rate of convergence, comprehensive numerical solutions are presented that elucidate the action of the system and the effects of the various parameters involved. The parameters varied include the flexibility of the wall, the condition of top support, and the characteristics of the ground motion. The effects of both harmonic base motions and an actual earthquake record are examined. Special attention is paid to the effects of long-period, effectively static excitations. A maximum dynamic response is then expressed as the product of the corresponding static response and an appropriate amplification or deamplification factor. The response quantities examined include the displacements of the wall relative to its moving base, the dynamic wall pressures, and the total wall force, base shear and base moment. Copyright © 2000 John Wiley & Sons, Ltd.

Determination of passive earth pressure coefficients by the method of triangular slices

Abstract: A new procedure is proposed for determination of passive earth pressure coefficients using triangular slices within the framework of the limit equilibrium method. The potential sliding mass is subd...

Numerical modelling of full-scale tests on drystone masonry retaining walls

Abstract: The behaviour of four drystone masonry retaining walls of different geometry has been modelled numerically using the discrete element code UDEC, and the results have been compared with the field trials carried out by Burgoyne in Ireland in 1834. By using appropriate soil and wall mass densities, strengths and stiffnesses, it was possible to reproduce in the numerical analyses the field behaviour observed by Burgoyne. Reasonably close agreement was obtained between the horizontal components of earth pressures calculated in the numerical analyses and using the earth pressure coefficients given by Caquot and Kerisel. Basal stress distributions calculated using the condition of equilibrium of the wall were also broadly consistent with those resulting from the numerical analyses. The results also confirm both the influence of the geometry of a drystone masonry retaining wall on its performance and ultimate stability, and the soundness of Burgoyne's engineering judgement in specifying his programme of field tests.

Model tests on single piles in soft clay

Abstract: Laboratory model tests in soft clay were conducted to investigate the behaviour of single piles subjected to lateral soil movements ('passive' pile), and to determine the ultimate soil pressure act...

Investigations of soil retaining structures damaged during the Chi-Chi (Taiwan) earthquake

Abstract: Three soil retaining structures which failed during the Chi‐Chi (Taiwan) Earthquake are investigated through surveying, boring, soil testing and slope stability analyses. Overturning and translational sliding of leaning‐type concrete retaining walls used to stabilize highway embankments on colluvial deposits on hillsides are observed. Investigation into a geosynthetic reinforced wall with modular block facing indicates that the earth pressure resisting function of the facing elements and the vertical spacing of the reinforcement played important roles in the seismic stability of the wall. Furthermore, additional studies on the deformation of block walls and related testing methods for evaluating reinforcement‐block connecting force are required. An investigation into a slumped 40m‐high wrap‐around reinforced slope shows that an unorthodox design tended to ‘stabilize’ a possible unstable slope by using a marginally stable reinforced wall.

Active earth pressure in cohesive soils with an inclined ground surface

Abstract: An analytical solution is developed to determine the active lateral earth pressure distribution on a retaining structure when it consists of a cohesive backfill (internal friction angle ϕ > 0, cohe...

Braced excavations: temperature, elastic modulus, and strut loads

Abstract: Relationships between strut loads, earth pressures, temperatures, and the measurements provided by strain gauges are presented in this paper. A braced excavation up to 20-m deep, 9–20 m wide, and > 650-m long constructed in competent glacially derived sand, silt, and clay soils (including glacial till) provided a significant amount of data for analysis. The excavation was supported by soldier piles and lagging with pipe struts and was covered with decking during construction. A direct correlation between incremental changes in strut load and temperature was observed during the course of the project. The few existing relationships between strut load and temperature were reexamined and were found to produce back-calculated elastic modulus values that were either without comparison or inconsistent with data from field tests and published sources. The relationships derived as a result of this work are supported by limited case-history data from other published sources and are consistent with practical application of elastic deformation concepts and published soil modulus values.

Ground Improvement for Liquefaction Mitigation at Existing Highway Bridges

Abstract: The feasibility of using ground improvement at existing highway bridges to mitigate the risk of earthquake-induced liquefaction damage has been studied. The factors and phenomena governing the performance of the improved ground were identified and clarified. Potential analytical methods for predicting the treated ground performance were investigated and tested. Key factors affecting improved ground performance are the type, size, and location of the treated ground. The improved ground behavior is influenced by excess pore water pressure migration, ground motion amplification, inertial force phasing, dynamic component of liquefied soil pressure, presence of a supported structure, and lateral spreading forces. Simplified, uncoupled analytical methods were unable to predict the final performance of an improved ground zone and supported structure, but provided useful insights. Pseudostatic stability and deformation analyses can not successfully predict the final performance because of their inability to adequately account for the transient response. Equivalent-linear dynamic response analyses indicate that significant shear strains, pore water pressures and accelerations will develop in the improved ground when the treated-untreated soil system approaches resonance during shaking. Transient seepage analyses indicate that evaluating pore pressure migration into a three-dimensional improved zone using two-dimensional analyses can underestimate the pore pressures in the zone. More comprehensive, partially-coupled analyses performed using the finite difference computer program FLAC provided better predictions of treated ground performance. These twodimensional, dynamic analyses based on effective stresses incorporated pore pressure generation, non-linear stress-strain behavior, strength reduction, and groundwater flow. Permanent

Lateral Load Behavior of Jetted Piles

Abstract: Water jetting can be utilized as an effective aid to impact pile driving when hard strata are encountered above the designated tip elevation. When jetting, the immediate neighborhood of the pile is first liquefied due to high pore pressure induced by the water jet and subsequently densified with its dissipation. In addition, the percolating water also creates a filtration zone further away from the pile. Hence, jetting invariably causes substantial disturbance to the surrounding soil that results in a noticeable change in the lateral deformation behavior. Currently, no definitive criteria are available to quantify the possible reduction in the lateral strength of driven piles when jetting is employed. This paper presents the results of an experimental study performed with model piles installed using (1) impact driving and (2) jetting in a sandy soil (with 10% clay) compacted to different unit weights under unsaturated as well as saturated conditions. The beam theory and polynomial approximations are used to convert measured load-strain data to conventional lateral pressure-deformation characteristics (p-y curves). Then, the effect of jetting on the lateral load behavior of piles is presented in terms of non-dimensional empirical curves. An example is also provided to illustrate how the results can be utilized to synthesize p-y curves for jetted piles based on available p-y curves for impact-driven piles in the same soil.

Methods of earth pressure calculation for excavation

Abstract: The earth pressure calculation formula considering effects of both displacement and time was put forward according to characteristics of excavation A formula of soil resistance reflecting the effect of excavation was also proposed, Next, based on LBACK FEM program of elastic foundation beam, the earth pressure calculation program and parameter back-analysis program was modified Some good calculation results are achieved Finally, one historic cases are studied with the new method of earth pressure calculation

Development and field testing of multiple deployment model pile (mdmp)

Abstract: A model pile is a calibrated tool equipped with instrumentation capable of monitoring the pile/soil interaction over the pile history. Monitoring includes the installation, pore pressure dissipation combined with consolidation and soil pressure equalization, and ultimately the pile behavior under loading and failure. The model pile installation and soil structure interaction simulate the actual field conditions of full-scale piles. As such, the obtained information can be utilized directly (e.g., skin friction) or extrapolated (e.g., pore pressure dissipation time) to predict the soil's response during full-scale installation. The Multiple Deployment Model Pile (MDMP) was developed as an in situ tool for site investigations. The MDMP instrumentation is capable of monitoring the pile/soil interaction throughout the life cycle of a driven pile: (1) dynamic force and acceleration readings at the pile top and along the pile during driving; (2) pore water pressure and radial stresses during equalization; and (3) skin friction, end-bearing resistance, and local (subsurface) displacement during static loading. These measurements allow the observation of pile capacity gain (a.k.a. "set-up" or "freeze") and accurately monitor the load-transfer relations. The MDMP was successfully deployed twice in Newbury, MA during March 1996. The obtained dynamic measurements allowed the evaluation of the pile's static capacity and clarified the difficulties associated with dynamic analysis of small-scale penetration. Pile capacity gain with time was examined based on normalization procedures developed by Paikowsky et al. (1995). The excess pore water pressure dissipation, variation of radial effective stresses, and pile capacity gain with time were determined for the two tests. The obtained results show that the MDMP is capable of providing accurate soil-structure interaction relations during static load testing. The measurements indicate a complex mechanism governing capacity gain that combines pore pressure dissipation and radial stress redistribution over time. These findings are used to predict the time-dependent behavior of full-scale instrumented piles and to re-evaluate the capacity gain phenomenon. The obtained results explain some unanswered questions and allow the development of procedures incorporating pile capacity gain in design and construction.

Model Shaking Tests of Soil Retaining Walls Situated on Sand Slope

Abstract: Model shaking tests using an irregular base acceleration record during the 1995 Kobe earthquake was performed to investigate the failure mechanism and seismic stability of three types of soil retaining walls (RWs) situated on slope. A conventional leaning-type RW exhibited brittle failure when subjected to a relatively low base acceleration. A reinforced soil RW with a full-height rigid facing showed a coherent seismic-resistant behavior. A leaning-type RW reinforced with large-diameter soil nails at the top and bottom of RW exhibited the highest seismic-stability among the three types of RWs. The wall showed small displacements even when subjected to a base acceleration higher than 1g. This type of RW is considered as effective in improving the seismic performance of existing leaning type RWs. It was also found that the distribution of dynamic earth pressure increment could be approximated basically by a trapezoid or triangle distribution, but also depending on the input base acceleration and the pattern of shear bands developed in the foundation and the backfill.

Elastic earth pressures on rigid walls under earthquake loading

Abstract: Elastic dynamic earth pressures induced by earthquakes are computed by analyzing a wall-foundation-backfill system. Both foundation and backfill are considered viscoelastic; the foundation is a semi-infinite space and the backfill, a uniform layer of constant thickness. A simple analytical solution is developed by assuming an approximate backfill-foundation interface condition and adopting the least squares method. The response functions computed indicate the large influence of the various system parameters on earth pressure, including the foundation characteristics as well as wall geometry and mass. The transient response of the system is also studied by obtaining spectra for base shear. A large number of seismic records are analyzed to obtain average spectra and a total of three correction functions are used to take into account the foundation stiffness and density as well as wall inertia. A simple design method is proposed to estimate the maximum base shear.

Effect of Clamping Mechanism on Pullout and Confined Extension Tests

Abstract: Two different clamping mechanisms are commonly used in pullout and confined extension tests of geosynthetics The first method of extending the clamps inside the soil to a sufficient length that ensures the confinement of the whole specimen length during testing The frictional resistance of the part of clamping plates inside the soil is subtracted from the results to obtain the resistance of the geosynthetic specimen The second method consists of clamping the geosynthetic specimen outside the soil In this method, displacement measurements are taken in the confined part of the specimen in the soil and, hence, the readings are not influenced by the possible slippage of the specimen between the clamps A comparison of test results using both installation techniques is presented and the boundary effects associated with both installation techniques is presented and the boundary effects associated with both mechanisms are evaluated In the tests where the clamps were extended inside the soil, earth pressure near the front facing was measured in order to evaluate the frictional resistance of the clamping plates Soil pressure measurements were taken after applying the confining pressure and during the test to monitor the development of vertical stresses at the vicinity of the clamping plates The measurements showed an apparent increase of vertical pressure above the clamps The results were corrected for the increase of the vertical pressure die to frictional resistance of the clamping plates When the clamping plates were connected to the specimens outside the box, displacements were measured along the specimen length These measurements were extrapolated to determine the front displacement of the specimen at the pullout load application point The use of the extrapolated front displacement resulted in a more reasonable load-displacement relationship for the geosynthetic specimen

Finite Element Analysis of Concrete Box Culverts

Abstract: This paper presents the finite element results of a parametric investigation of three precast concrete box culverts subject to various soil covers and loading conditions. The three culvert sizes had a constant rise of 8 ft (2.4m) and different span length of 12 ft, 18 ft, and 24 ft (3.6m, 5.4m, and 7.2m). Six possible soil covers were also considered (0, 2, 4, 6, 8, and 10 ft). As the soil depth increases, the wheel loads were projected on the top slab using ASTM C890 formula. Lateral earth pressure was applied on the vertical walls which depends on the depth of the box culvert. The finite element method was used to analyze the structural behavior of the three-dimensional box culvert under different loading conditions using SAP 2000. The culverts were modeled using SHELL elements with six degrees of freedom at each node. The FEA results were compared with AASHTO plane frame analysis. In addition to live loads, all structures were subjected to three independent load cases: (a) overburden pressure alone, (b) overburden plus lateral earth pressure, and (c) overburden plus lateral plus bearing pressure.

Effects of foam soil conditioning on epbm performance

Abstract: The paper discusses effects of the use and performance of an earth pressure balance machine (EPBM) in various ground types. Some of the benefits anticipated include: improved soil consistency; reduced balling and sticking of clays; improved cohesion of granular materials; and, greater control of earth pressures in the tunnel chamber. The paper also presents some preliminary results of the experimental laboratory work.

Method for constituting earth pressure wall and earth pressure wall constituting pipe

Abstract: PROBLEM TO BE SOLVED: To construct a strong earth pressure wall with little deformation even if a large external force is received by using a hard material-made deformed pipe formed of a circular pipe having a dent formed by partially denting the circular arc and extending in the pipe axial direction as an earth pressure wall constituting pipe. SOLUTION: The locking part 57 of a deformed pipe 5 is provided in the direction making contact with a deformed pipe of the same kind already pushed into the ground. The deformed pipe 5 to be pushed next is set in the ground so that its dent 54 is turned in the direction of a deformed pipe to be pushed in later with its locking part 57 being fitted to the clearance and meshed with the locking part 57 of the first buried pipe. Thereafter, the deformed pipe is propelled in the same manner as the pushing of the first pipe to push the second pipe into the ground while circularly excavating the ground or discharging the excavated earth and sand. At this time, the second pipe can be progressed in the state perfectly closely fitted to the first buried pipe since the locking part 57 is meshed with the locking part 57 of the first pipe.

Calibration of an earth pressure cell

Abstract: In this study, researchers devised a scheme for calibration of earth pressure cells to observe their response to various loading configurations and to recommend a procedure for field installation. Transducers designed to provide an estimate of normal stress within a soil, earth pressure cells have provided readings that conflict with known loading conditions. Initial calibration tests used hydraulic oil as the pressurizing medium in both hydrostatic and uniaxial pressure conditions, which mimic the manufacturers' procedure for pressure cell calibration. Researchers designed a new testing device to permit the application of uniaxial soil pressure to the earth pressure cells using various types of soil and load configurations. As a result of calibration tests, a field installation procedure was developed and recommended. In the laboratory, a thin-walled steel cylinder with a geotextile bottom was filled with uniform silica sand of a known density, and the earth pressure cell was placed within the sand. The entire apparatus was carried into the field and installed in the desired locations. Once in place, the steel cylinder was pulled up out of the ground, leaving the cell and geotextile behind. Preliminary field data indicate that soil calibration and placement procedure provide reasonably accurate measurements.