Showing papers on "Lateral earth pressure published in 1999"

Determination of pile base resistance in sands

Abstract: Advances in the design of axially loaded piles are desirable because significant cost savings may result. Well-designed piles settle by amounts that are well tolerated by the superstructure and induce strains around the pile base that are far removed from failure. To investigate the development of base resistance for a given soil condition and increasing settlements, piles embedded in sand are modeled using the finite-element method with a nonlinear elastic-plastic model. Based on the load-settlement response obtained from the finite-element analysis and cone penetration resistance obtained from cavity expansion and stress rotation analyses, values of normalized base resistance, defined as base resistance divided by cone penetration resistance, are obtained. The relationship between base resistance and cone resistance is useful in the design of deep foundation using cone penetration test results. The effect of the initial coefficient of earth pressure at rest K0 on normalized base resistance values is als...

Seismic Earth Pressure on Retaining Structures

Abstract: A simple kinematic method to predict the seismic earth pressure against retaining structures is developed. The fundamental solution to the free-field seismic response considering nonlinear, plastic behavior of soil is included in the retaining wall analysis for the first time. Perturbation to the free-field response caused by soil-structure interaction effects for different types of wall movement is considered. Results from this kinematic method are compared with those obtained from finite-element analysis and observed from laboratory shaking table tests performed on model retaining walls.

Tieback walls in sand : Numerical simulation and design implications

Abstract: A three-dimensional nonlinear finite-element analysis is used to study the influence of various design decisions for tieback walls. The numerical model simulates the soldier piles and the tendon bonded length of the anchors with beam elements, the unbonded tendon with a spring element, the wood lagging with shell elements, and the soil with solid three-dimensional (3D) nonlinear elements. The soil model used is a modified hyperbolic model with unloading hysteresis. The complete sequence of construction is simulated including the excavation and the placement and stressing of the anchors. The numerical model is calibrated against an instrumented case history. Then a parametric study is conducted. The results give information on the influence of the following factors on the wall behavior: Location of the tendon unbonded zone, magnitude of the anchor forces, embedment of the soldier piles, and stiffnesses of the wood lagging and the piles. The implications in design are discussed.

Metal culvert response to earth loading: performance of two-dimensional analysis

Abstract: The results of finite-element analyses conducted before and after testing of a 9.5-m span low-profile metal arch culvert are presented here. A two-dimensional procedure that models the elastic-plastic response of both structure and soil during backfilling has been used. A plasticity-based procedure to provide an upper bound for the effect of soil compaction on metal culvert response during side filling is introduced and used in the analysis of field response. The procedure involves application of passive earth pressures after layer placement to simulate the highest values of residual horizontal earth pressure. The pretest and posttest analyses are compared with measurements of field response previously published by Webb et al. Predictions for culvert deformation and bending moments generated during backfilling were excellent. The new procedure to include the effects of compaction during construction was effective in capturing culvert peaking during placement of the side fill and increases in bending moment. Both pre- and posttest predictions for deformation and moment successfully captured the culvert response during burial and the effect of backfill soil density. The posttest predictions include consideration of the top-loading applied during placement of the side fill. The predictions of deflection follow measured values during application and subsequent removal of those temporary surcharge loads. Estimates of soil stresses acting normal to the external surface of the culvert were shown to be close to those measured in the field. The analysis indicates that shear strength is fully mobilized in wedge-shaped zones of the backfill adjacent to the culvert. Those zones diminish in size once backfill is placed over the crown. The residual horizontal earth pressures that are modeled during compaction act to reduce the size of the plastic zones.

Passive earth pressures in the presence of hydraulic gradients

Abstract: The paper describes a variational approach applied to the limit equilibrium method for calculating the effective passive pressures of a cohesionless soil, taking into consideration the seepage flow. It is shown that in the general case of non-homogeneous and non-isotropic hydraulic properties of the soil medium, the shape of the slip surface which verifies the three limiting equilibrium equations of the soil mass at failure is a log-spiral. It is also shown that the passive earth pressure calculation is independent of the normal stress distribution along this surface. The variational limit equilibrium method is equivalent to the upper bound method in limit analysis for a rotational log-spiral mechanism. Numerical results of the coefficients of passive earth pressures in the presence of seepage flow are presented and discussed. Cet article presente une approche variationnelle appliquee a la methode du prisme de rupture permettant le calcul de la pression passive effective des terres en presence d'ecoulemen...

Stress Paths in Relation to Deep Excavations

Abstract: The mechanical behavior of many soils such as stiff clays depends on their current effective-stress states and stress history. For improving design and analysis of soil-structure interaction associated with deep excavations in these soils, it is important to understand effective-stress changes around excavations caused by both horizontal and vertical stress relief. In this paper, total and effective-stress variations adjacent to a diaphragm wall during construction of a 10–m-deep excavation in stiff fissured clay are reported and discussed. Interpreted field stress paths are compared with some relevant laboratory triaxial stress path tests, which simulate the horizontal and vertical stress relief in the field at an appropriate stress level. The interpreted field effective-stress paths in front of the wall are found to be similar to laboratory stress paths determined in undrained extension tests. Field stress paths behind the wall do not correspond particularly well with those from laboratory undrained compression tests, except when the stress state approaches active failure. The conventional undrained assumption does not seem to hold for the soil located immediately behind the wall during a relatively rapid excavation in the stiff clay.

Computational model for the simulation of the shield tunneling process in cohesive soils

Abstract: A two-dimensional computational model is developed here in order to simulate the continuous advance of the Earth Pressure Balance (EPB) Shield during the tunneling process in cohesive soils. The model is based on the combination of the plane strain “transverse–longitudinal” sections that can incorporate the three-dimensional deformation of the soil around and ahead of the shield face. This model is capable of prediciting the soil response due to the shield tunneling before the event, especially in soft ground conditions. An elasto-plastic finite element analysis that is based on the coupled theory of mixtures for inelastic porous media for finite deformation is used in this work to describe the time-dependent deformation of the saturated cohesive soils. The results of this model are compared with the in situ field measurements of the N-2 tunnel project excavated in 1981 in San Francisco using the EPB shield tunneling machine. Reasonable agreement is found between the observed field measurements and the predicted deformations of the soil using the proposed numerical simulation. Copyright © 1999 John Wiley & Sons, Ltd.

Applied Analyses in Geotechnics

Abstract: Formation and physical properties of soil. Stress distribution within a soil mass. Seepage flow. Transient flow: elastic and consolidation settlements. Shear strength of soils. Modelling of soil behaviour: limit and critical states. The stability of slopes. Limit analysis applied to the bearing capacity of shallow foundations. Loading capacity of pile foundations. Lateral earth pressure exerted on retaining structures. Design of sheet-pile and diaphragm walls. Analysis of the expansion of cylindrical cavities in an infinite soil mass. Centrifuge modelling of soil behaviour. Finite element modelling in geotechnics. References. Index.

Determination of spatial earth pressure on circular shaft constructions

Abstract: Based on the Distinct Element Method, three dimensional calculations were carried out to determine the spatial earth pressure of sand on circular shaft constructions with respect to their deformation. For this purpose the commercial program PFC3D has been applied using a linear sliding contact model. The program confines itself to homogenous rigid balls. To define the required parameters (normal stiffness kn, shear stiffness ks and contact friction μ), the well known plane earth pressure according to Coulomb is calculated as calibration. Due to the rotational symmetry, the spatial earth pressure calculation is limited to only one sector. Simultaneous model tests were executed to check the results. Although a simple DEM with only a few parameters is applied, the calculation results fit very well to those of the tests and classic theories.

Net pressure analysis of cantilever sheet pile walls

Abstract: There are many methods for the analysis and design of embedded cantilever retaining walls. They involve various different simplifications of the net pressure distribution to allow calculation of the critical retained height. In the UK, it is commonly assumed that net pressure consists of the sum of the active and passive limiting pressure values. In the USA, the net pressure is commonly simplified by a three-line rectilinear pressure distribution. Recently, centrifuge tests have led to a proposed semi-empirical rectilinear method in which an empirical constant defines the point of zero net pressure. Finite element analyses presented in this paper examine the net pressure distribution at limiting equilibrium. The study shows that the point of zero net pressure for a best-fit rectilinear approximation is dependent on the ratio between the passive and active earth pressure distributions at limiting conditions. A simple empirical equation is proposed which defines the point of zero pressure. The predictions f...

The effect of the bending rigidity of a wall on lateral pressure distribution

Abstract: A two-dimensional model retaining wall system was developed to investigate the effect of the bending rigidity of a wall, supported at the top and bottom, on the lateral pressure distribution at com...

Undrained shear strength of a glacial clay overconsolidated by desiccation

Abstract: Block samples of a Boston Blue clay crust were used in a detailed study of the relationship between undrained shear strength and consolidation pressure in the compression and extension shear modes. The glacial silty clay sample that was mainly composed of quartz, feldspar, illite and chlorite has developed an overconsolidation ratio near to 3·0 by desiccation. The in situ coefficient of earth pressure at rest was near to 0·9 as compared to K0p = 0·56 of the normally consolidated young clay in the compression range beyond the preconsolidation pressure. In the compression range, for each consolidation-shear mode, undrained shear strength to vertical consolidation pressure ratio as well as shearing-induced pore water pressure to vertical consolidation pressure ratio, friction angle mobilized at yield, and the coefficient of earth pressure at rest, were constant and independent of consolidation pressure. The mobilized undrained shear strength of the normally consolidated young clay obtained by consolidating s...

Instrumented soil reinforced retaining wall: analysis of measurements

Abstract: A vertical retaining wall, 4m high and 10m long, was constructed by reinforcing the backfill with geogrids. The reinforcing layers were instrumented with strain gauges, tensile geogrid load transducers and horizontal displacement sensors. In addition, total soil pressure transducers were installed inside the structure to monitor the internal state of stress of the reinforced wall. The aim of this research is to better understand the behavior of reinforced structures. In particular, the development of slip surfaces and the tensile forces acting in the reinforcements were investigated. By this analysis it was possible to assess current design approaches and related safety factors in terms of either long term tensile failure, pullout, direct sliding or compound failures. Data related to reinforcement tensile strains and loads, applied vertical pressures, rainfall and construction sequences were collected for two different geogrids over a period exceeding 10,000 hours.

Filling structure of underground water tank

Abstract: (57) [Abstract] [Problem] The pressure resistance against the earth pressure from the surroundings is large, Provided is a groundwater tank filling structure that does not cause side plates to be destroyed by earth pressure or to fall off due to an earthquake. SOLUTION: In a filling structure in which a packing body 4 provided with pillars 42 is arranged vertically and horizontally in a groundwater tank 1 and filled up and down, and a side plate 5 is provided on the outer periphery thereof, the pillars 42 of the packing body 4 are provided. Between the side plates 5, The structure spans five spaces. With such a structure, even if earth pressure acts on the side plate 5 from the surroundings, the side plate 5 is supported from the inside by the projecting rod 9, so that it can sufficiently withstand the earth pressure and the side plate 5 is not broken. And the strut 9 Is fixed to the side plate 5, there is no fear that the side plate 5 will fall off when an earthquake occurs. Further, an intermediate plate may be provided between the vertically and horizontally adjacent fillers, and the strut may be bridged between the intermediate plate and a side plate or an intermediate plate facing the intermediate plate.

Cut-beam type earth retaining timbering and pit excavation method

Abstract: PROBLEM TO BE SOLVED: To enable support of even a relatively large span earth retaining wall by providing an assembled beam composed of beam members and a slant member connecting them to each other and an assembled support pile composed of pile members erected on both side of the assembled beam and a reinforcing member containing the slant member. SOLUTION: Beam members for assembly 12a, 12b are formed of H steel, while a slant member 12d is fixed to a lower side of a lower flange and a slant member 12c is fixed to an upper side of an upper flange. In this case, an assembled support pile is constituted of pile members 16a, 16b abutting on the beam members 12a, 12b and being held from both sides, slant members fixed to the pile members 16a, 16b at its opposed ends, and horizontal members 17. The members 17 are arranged to abut on the beam 12 and to hold same from both upper and lower sides. The support pile is prevented from being deformed bendwise even if a horizontal force is applied from the beam 12 by means of the horizontal member 17 and the slant member extending in the direction to cross at right angles with the beam 12. Accordingly, even if the beam 12 is subjected to a large soil pressure between relatively large span earth retaining walls 11a, 11b, generation of bucking is prevented and the retaining wall can be supported.

Self-sustaining earth retaining wall and self-sustaining earth retaining wall construction method

Abstract: PROBLEM TO BE SOLVED: To provide a self-sustaining earth retaining wall and a self-sustaining earth retaining wall construction method having a comparatively shallow excavation depth, a large plane scale, and good construction efficiency without requiring any support on the side of excavation. SOLUTION: An earth-retaining wall is constructed in a part or the whole perimeter of the ground part constructing a footing or the like, and in an independent earth-retaining wall excavating the ground part inside of the earth-retaining wall up to a specific depth, a part or whole of the earth-retaining wall 10 is constituted of a sloped earth-retaining wall 11, the sloped earth-retaining wall 11 is inclied to the outside relative to the vertical line, and anchor body 12 is provided in the ground near to the ground surface on the outside of an active sliding Aea1 of the outside ground G on the upper surface of the sloped earth- retaining wall 11, and the upper surface of a core 11Ba is connected to the anchor body 12 through a tension member 13. Earth pressure acting on the earth-retaining wall is reduced by making the earth-retaining wall as the sloped earth-retaining wall, and since earth pressure acting on the sloped earth-retaining wall transferred to the anchor body 12 through the tension member 13 is received by passive earth pressure acting on an anchor part of the anchor body 12, and a material cost or the like of the earth-retainign wall can be reduced.

Mechanical Behavior of Interconnected Concrete-Block Retaining Wall

Abstract: A new type of retaining wall constructed with interconnected H-type concrete blocks is proposed. Advantages of such a wall include stability, proper drainage, allowance of large displacements or differential settlements, ease of constructability, and cost-effectiveness. Because of the individual action of the H-type concrete blocks, a discrete element method is used to perform the numerical analysis for the proposed retaining wall and retained soil. Some typical models of H-block retaining walls were presented to calculate the mechanical behavior of the block wall and retained soil. Calculations show that this type of retaining wall behaves well and is stable. To verify the adequacy of discrete element method (DEM) on the analysis of H-block walls, a field test was conducted, and comparisons were also made between the numerical and monitoring results.

Influence of Geogrid Reinforcement on Lateral Earth Pressures Against Model Retaining Walls

Abstract: Large-scale model retaining wall tests were carried out using reinforced and unreinforced granular backfill and geogrid layers that were not attached to the wall facing. The objective of this study was to observe the lateral earth pressures on the model retaining walls under a range of surcharge pressures, which ranged from an at-rest to active-state condition. In so doing, the effectiveness of unattached geogrid reinforcement layers in reducing the lateral earth pressures was demonstrated. It was shown that unattached geogrid layers effectively reduce the coefficient of active earth pressure. The coefficients of earth pressure at rest, Ko, and at an active state, Ka, were examined, and the formulation of the coefficient of earth pressure-displacement curve was proposed. Interface shear stresses induced along the geogrid layers were also examined under different surcharge pressures. An apparent coefficient of lateral stress for the geogrid reinforcement was defined and compared with the corresponding coef...

Measurement of earth pressures on concrete box culverts under highway embankments

Abstract: To obtain a better understanding of the stresses acting on cast-in-place concrete box culverts, and to investigate the conditions which resulted in a culvert failure under about 12 meters of backfill, two sections of a new culvert were instrumented. The measured earth pressure distribution was found to depend upon the height of the embankment over the culvert. For low embankment heights (less than one-half the culvert width), the average measured vertical earth pressures, weighted by tributary length, were about 30% greater than the recommended AASHTO pressures. The measured lateral pressures were slightly greater than the AASHTO pressures. As the embankment height increased, the measured weighted average vertical stress exceeded the AASHTO pressures by about 20%. Lateral pressures which exceeded the vertical pressures were recorded at the bottom of the culvert walls, and small lateral pressures were recorded on the upper locations of the wall. The high lateral pressures at the base of the wall are consistent with the results from finite element analyses with high density (modulus) backfill material placed around the culvert.