Showing papers on "Lateral earth pressure published in 2008"

Analysis of the shaft resistance of non-displacement piles in sand

Abstract: The paper examines, using numerical modelling, the problem of the limit shaft resistance of non-displacement piles installed in sands. The modelling makes use of an advanced, two-surface-plasticity constitutive model. The constitutive model predicts the soil response in both the small- and the large-strain range, while taking into account the effects of the intermediate principal effective stress and of the inherent anisotropy of the sand. Finite element analyses of shearing along the pile shaft are performed in order to examine the development of limit unit shaft resistance and the changes in stress state around the shaft upon axial loading of the pile. Special focus is placed on the operative value of the lateral earth pressure coefficient when limit shaft resistance is reached. The analyses offer useful insights regarding the factors controlling the value of unit shaft resistance in sands. The simulations predict a significant build-up of horizontal effective stress for dense sands. Based on these simu...

Effect of Arching on Active Earth Pressure for Rigid Retaining Walls Considering Translation Mode

Abstract: It has been established by the researchers that owing to the arching effect, the active earth pressure distribution on a horizontally translating rigid wall is not triangular but nonlinear. This is attributed to the arching behavior exhibited by soil. Also, the shape of the failure surface plays a critical role in determining the magnitude of lateral stresses and the height at which the resultant active earth force is centered from the base of the wall. In the present study, various combinations of shapes of critical failure surface and arch shapes were studied to estimate the coefficient of active earth pressure on the rigid retaining wall in cohesionless soil. The results were compared with field results and those predicted by other theories. A critical review has been made based on the comparison of results obtained from the present analyses with experimental observations. Design charts for modified active earth pressure coefficient and height of application of lateral force have also been suggested.

Seismic active earth pressure behind a nonvertical retaining wall using pseudo-dynamic analysis

Abstract: This note describes a study on the seismic active earth pressure behind a nonvertical cantilever retaining wall using pseudo-dynamic analysis. A planar failure surface has been considered behind th...

Influence of Overburden Pressure on Soil — Nail Pullout Resistance in a Compacted Fill

Abstract: Soil nailing has been widely used in many places in the world in the last two decades because of its technical and economical advantages. The nail–soil interface shear strength is an important parameter in soil nail design. This parameter is governed by a number of factors, among which the influence of the overburden pressure (or soil depth) is the most controversial. There are differing views concerning the effect of overburden on the nail–soil interface shear strength. In order to examine the influence of the overburden pressure, a series of laboratory pullout tests on soil nails installed in compacted completely decomposed granite fill have been conducted using two pullout boxes. Numerical simulations have also been carried out and the results are compared with the pullout test data. The procedures of the pullout tests and new features of the pullout boxes used are briefly described. Changes of the vertical stress in soil close to the nail throughout the course of soil nail installation and pullout are...

Insight into seismic earth and water pressures against caisson quay walls

Abstract: Motivated by the need to explain the large displacement and rotation that numerous caisson-type quay walls suffered in the port of Kobe during the devastating 1995 earthquake, a detailed numerical analysis is presented for the response of such a wall from Rokko Island. Utilising the Pastor–Zienkiewicz elastoplastic constitutive model, an effective stress dynamic analysis is performed using as input the accelerogram recorded 32 m below the ground surface in the nearby Port Island. The evolution during shaking of lateral displacements, plastic strains and pore water pressures sheds some light on the complex interplay of several simultaneously occurring phenomena: the development of oscillatory inertia forces on the wall, in phase or out of phase with the backfill soil and water pressures; the simple-shear seismic deformation of the soil and the ensuing initial development of positive excess pore water pressures in the backfill and the foundation soil; the extensional deformation developing in the ‘active we...

Seismic Rotational Displacement of Gravity Walls by Pseudodynamic Method

Abstract: Prediction of the rotational displacements, induced by earthquake is a key aspect of the seismic design of retaining walls. In this paper, the pseudodynamic method is used to compute rotational displacements of the retaining wall supporting cohesionless backfill under seismic loading. The proposed method considers time, phase difference, and effect of amplification in shear and primary waves propagating through the backfill and the retaining wall. The influence of ground motion characteristics on rotational displacement of the wall is evaluated. Also the effects of variation of parameters like wall friction angle, soil friction angle, amplification factor, shear wave velocity, primary wave velocity, period of lateral shaking, horizontal, and vertical seismic accelerations on the rotational displacements are studied. Results are provided in graphical form with a comparison to the available pseudostatic result to validate the proposed theory. Present results give higher values of rotational displacements of...

Response and Modeling of Cantilever Retaining Walls Subjected to Seismic Motions

Abstract: @A series of nonlinear, explicit finite differ- ence analyses were performed to determine the dynamic response of a cantilever retaining wall subjected to earth- quake motions. This article outlines the calibration and validation of the numerical model used in the analyses and comparisons are presented between the results from the finite difference analyses and results from simplified techniques for computing dynamic earth pressures and permanent wall displacement (i.e., Mononobe-Okabe and Newmark sliding block methods). It was found that at very low levels of acceleration, the induced pressures were in general agreement with those predicted by the Mononobe- Okabe method. However, as the accelerations increased to those expected in regions of moderate seismicity, the induced pressures are larger than those predicted by the Mononobe-Okabe method. This deviation is attributed to the flexibility of the retaining wall system and to the observation that the driving soil wedge does not respond monolithically, but rather responds as several wedges. Ad- ∗ To whom correspondence should be addressed. E-mail: rugreen

Effects of frictional forces acting on sidewalls of buried box culverts

Abstract: The effects of frictional forces acting on the sidewalls of buried box culverts are presented as determined with finite element method (FEM) and detailed soil modelling. The possibility of reducing earth pressure on deeply buried concrete box culverts by the imperfect trench installation (ITI) method has been contemplated during the last several decades. There have been limited research results published primarily regarding the qualitative aspect of load reduction in ITIs. It was found during the course of this study that significant frictional forces develop along the sidewalls of box culverts and adjacent sidefills in ITIs. Current American Association of State Highway and Transportation Officials provisions do not consider these frictional forces, but they cannot be neglected in ITIs, as their effect is dominant. An optimum geometry for the soft zone in ITIs is presented to maximize earth load reductions. The soil–structure interaction at the box culvert–soil interface was found to have a significant effect on total earth pressure acting on the bottom slab. Predictor equations for earth load reduction rates were formulated for ITIs incorporating the optimum soft zone geometry based on the FEM. Copyright © 2007 John Wiley & Sons, Ltd.

Stability of waterfront retaining wall subjected to pseudodynamic earthquake forces

Abstract: This technical note pertains to the study of a waterfront retaining wall, retaining a partially submerged backfill, subjected to seismic forces. The pseudodynamic approach, which considers the effect of primary and shear wave propagation in the backfill soil and wall, is adopted for calculation of the seismic earth pressure considering wall inertia. The point of application of the seismic active earth pressure is also affected by seismicity. Hydrodynamic forces are considered in the analysis. It is observed that when the horizontal seismic acceleration coefficient is increased from 0 to 0.3, there is a 65% decrease in the factor of safety of the retaining wall in sliding mode. To investigate the effects of different parameters on design, a parametric study is done. It is observed that with increase in the value of ϕ from 25 to 35° , there is an increase in the factor of safety in the sliding mode by 50%. Comparison with a previous study suggests that the present pseudodynamic approach gives less conservat...

Performance of Sheet Pile Wall in Peat

Abstract: To study the performance of sheet pile wall in peat during roadway construction, a long-term instrumentation program was conducted over a period of two years, measuring total lateral earth pressures, sheet pile deflections, soil movements, and water table level variances during construction. The analysis of field data indicated: 1 The earth pressure distribution in peat matched well with the classic Rankine earth pressure; 2 the expected long-term postconstruction sheet pile movement due to the creep behavior of peat was not observed; 3 fully passive earth pressure in peat was mobilized once the maximum measured sheet pile deflection exceeded 0.8% of sheet pile length; and 4 arching effect due to the protruding cross section of sheet pile caused pressure differences of 3-10 kPa between the inside web and outside web of the sheeting. Then, all the construction stages were continuously modeled by finite-element method and the calculated results were compared with the field measurements. The comparisons showed that the calculated results were consistent with the field data and provided reasonable explanations and helpful insights to understand soil-structure interaction mechanism. Finally, some conclusions and suggestions for sheet pile design and construction in peat were reached.

At-Rest Earth Pressure of Overconsolidated Cohesionless Soil

Abstract: Earth pressure theories occupy a paramount position in the field of geotechnical engineering. An experimental investigation of the at-rest earth pressure of overconsolidated cohesionless soil acting on retaining walls was conducted. A prototype model of a vertical rough wall, retaining horizontal backfill, was developed in the laboratory. The model was instrumented to measure the earth pressure at selected points on the wall, the total earth force acting on the wall, and the overconsolidation ratio (OCR) in the sand mass. Tests were conducted on walls retaining homogeneous overconsolidated dense, medium, or loose sands. Test results showed that the coefficient of at-rest earth pressure increases with the increase of the OCR. The present experimental results were used to examine the empirical formulas available in the literature. It can be reported that these formulas compared well with the experimental results for OCR values up to 3. An empirical formula is proposed to predict the coefficient of at-rest earth pressure for overconsolidated cohesionless soils. The results obtained by this formula agreed well with the present experimental results for all values of overconsolidation ratios.

Effects of body waves and soil amplification on seismic earth pressures

Abstract: To design a retaining wall, conventional Mononobe–Okabe method, which is based on the pseudo-static approach and gives the linear distribution of seismic earth pressures in an approximate way, is used to compute the seismic earth pressures. In this paper, pseudo-dynamic approach is used to compute the seismic earth pressures on a rigid retaining wall by considering the effects of time, phase difference in shear and primary waves and soil amplification along with the horizontal and vertical seismic accelerations and other soil properties. Design value of the seismic active earth pressure coefficient is found to increase with increase in the seismic accelerations, phase difference in body waves and soil amplification, whereas the reverse trend is observed for the passive case. Influence of various soil parameters on seismic passive earth pressure is more significant than that for the active case under harmonic seismic loading. Results are provided in the combined tabular and graphical non-dimensional form for both the seismic active and passive earth pressures. Present results are compared with the available results in literature to validate the proposed non-linearity of seismic earth pressure distribution.

Earth pressure due to vibratory compaction

Abstract: This paper presents experimental data on the variation of lateral earth pressure against a nonyielding retaining wall due to soil filling and vibratory compaction. Air-dry Ottawa sand was placed in five lifts and each lift was compacted to achieve a relative density of 75%. Each compacted lift was 0.3 m thick. The instrumented nonyielding wall facility at National Chiao Tung University in Taiwan was used to investigate the effects of vibratory compaction on the change of stresses at the soil-wall interface. Based on the experimental data it has been found that, for a compacted backfill, the vertical overburden pressure can also be properly estimated with the traditional equation v=z. The effects of vibratory compaction on the vertical pressure in the backfill were insignificant. On the vertical nonyielding wall, extra horizontal earth pressure was induced by vibratory compaction. After compaction, the lateral earth pressure measured near the top of the wall was almost identical to the passive Rankine pressure. It is concluded that as the cyclic compacting stress applied on the surface of the backfill exceeded the ultimate bearing capacity of the foundation soil, a shear failure zone would develop in the uppermost layer of the backfill. For a soil element under lateral compression, the vertical overburden pressure remained unchanged, and the horizontal stress increased to the Rankine passive pressure. It was also found that the compaction-influenced zone rose with the rising compaction surface. The horizontal earth pressure measured below the compaction-influenced zone converged to the Jaky state of stress.

A numerical study on the use of geofoam to increase the external stability of reinforced soil walls

Abstract: The potential benefit of placing a panel of compressible (i.e. expanded polystyrene) geofoam behind the reinforced zone of mechanically stabilized earth (MSE) walls is investigated using a numerical modeling approach. A panel of geofoam is placed immediately behind the reinforced zone during the construction phase of an idealized plane-strain reinforced soil segmental wall model. The analysis procedure includes the modeling of soil compaction. The magnitudes and distributions of earth pressure behind the reinforced zone in the wall models with and without the geofoam panel are compared to quantify the reductions in lateral earth pressure, resultant lateral force and overturning moment expected due to the placement of the geofoam material. Predicted magnitudes of facing lateral deformation and reinforcement strains are also compared among cases studied in order to evaluate the effect of geofoam on wall serviceability. It is shown that placing geofoam behind the reinforced zone can reduce the maximum latera...

Finite element analysis of pipe buried in saturated soil deposit subject to earthquake loading

Abstract: A coupled stress-flow finite element procedure, based on dynamic Biot equations, was used to analyze the behavior of pipe buried in liquefiable soil. The governing equations, soil constitutive model, finite element discretization and solutions were described. The results of analysis were compared with two cases of dynamic centrifuge test of soil deposit and pipe conducted at 30 g acceleration field. The horizontal soil deposit was analyzed followed by the deposit having a buried pipe of diameter 10 cm (3 m in prototype). The deposit was composed of loose Nevada sand that was saturated with a viscous solution in satisfying the similitude rules of time for the dynamic event and diffusion phenomena. The response of the ground, such as acceleration and excess pore water pressure, and the earth pressure and uplifting of the pipe, were presented and compared. The results of analysis indicated that a coupled stress-flow finite element procedure where the soil was expressed by Pastor–Zienkiewicz Mark-III model was able to simulate the dynamic response of the soil and pipe up to the stage of liquefaction. Several other issues related to the analysis were discussed.

Large diameter tunneling close range down-traversing small diameter subway tunnel distortion control method

Abstract: The invention discloses a method for controlling distortion for deep large diameter shield tunnels to under-pass small diameter tunnels, which pertains to the technical field of tunnel engineering According to the method, the control range of the stratum loss ratio of newly established tunnels and the optimum value of the support pressure of the shield cut surface are acquired by using the finite-element method; soil pressure in front of the shield cut surface is kept relatively balanced by setting the optimal value of the support pressure, and the support pressure fluctuation range of the cut surface is controlled to range from minus 10kPa to plus 10kPa; the stratum loss ratio of the newly established tunnels is controlled within the allowed range According to the construction technique measures, a test propelling area is arranged before the shield reaches a cross position In the area, construction is carried out according to the situation of the existing underground tunnels above; and construction parameters are controlled and regulated to adjust the support pressure, the propulsive velocity and the amount of the grout to be injected in time; the shield passes through the cross position in combination with the optimal values of the construction parameters of the test propelling area The invention can not only ensure the construction of tunnels to be carried out safely and smoothly, but also minimize the influence of construction on ambient environment

Measuring Soil Pressure on a Buried Model Structure for the Validation of Quantitative Frameworks

Abstract: The paper presents the methodologies and results of an experimental study aimed at measuring the soil contact pressures which develop on a buried structure as it interacts with the surrounding soil under load. The study has been based on measurements made on model structures tested in a pressure chamber filled with a fine uniform sand. The buried model structure was a very rigid right cylinder designed such that it could be fitted with roofs of different thicknesses. The structure bottom and roof were instrumented with newly designed and constructed soil pressure cells based on the null response concept. The device is unaffected by the issues that affect the use of traditional soil pressure cells. The development of pressure on the structure was measured as uniform pressure was applied to the soil surface. The results illustrate the effect of roof stiffness on the development of pressure at the roof center. The midroof pressure was seen to increase with roof stiffness, however the development of pressure was also seen to be dependent upon the actual deflection. In the case of a flexible roof it was seen that the development of contact pressure is a nonlinear function of the pressure applied at the soil surface and is highly dependent upon stress history. In contrast, it was seen that pressure on a stiff roof develops as a linear function of pressure applied at the soil surface and is less dependent of stress history. The results of the model tests together with soil stiffness data supplied in the paper will be useful in the calibration and validation of numerical and analytical frameworks.

Construction method for shallow soil-covered river bed under shield tunnel

Abstract: The construction process for shielded tunnel to penetrate through river bed with shallow covered soil layer includes the following steps: engineering investigation, river bed analogy, calculation and analysis, research and determination of technological scheme, determining auxiliary measures and setting the initial shielding parameters, river bed penetrating construction, etc. The auxiliary measures include foundation consolidation, setting anti-floating plate, surface blasting weight, etc. The initial shielding parameters include earth pressure, earth output amount, propulsion speed, grouting amount, etc. During the construction, one computerized real-time monitoring system is adopted for comprehensive monitoring on tunnel sedimentation, displacement and other conditions. The construction process can ensure safety and avoid water inrush, collapse and other accidents.

Field Performance and Analysis of 3-m-Diameter Induced Trench Culvert Under a 19.4-m Soil Cover

Abstract: An induced trench installation was instrumented to monitor earth pressures and settlements during construction. Some of the unique features of this case study are as follows: (a) both contact and earth pressure cells were used; (b) part of the culvert is under a new embankment and part was installed in a wide trench within an existing embankment; (c) a large stockpile was temporarily placed over the induced trench; and (d) the compressible material was placed in two stages. The maximum vertical pressure measured in the field at the crown of the culvert was 0.24 times the overburden pressure. The maximum horizontal pressure measured on the side of the culvert at the springline was 0.45 times the overburden pressure. The column of soil directly above the compressible zone settled approximately 40% more than did the adjacent fill. The field results at the crown and springline compared reasonably with those observed with numerical modeling. However, the overall pressure distribution on the pipe was expected t...