Bridge Approach Embankment Research Articles

Replacement of Weathered Clay Shale Using Soil Cement for Bridge Approach Embankment in Purwakarta - Indonesia

Clay shale is a sensitive soil material that easily experiences weathering if exposed to open air, sunlight, water. Weathered clay shale is commonly located near the surface and has a soft consistency due to surface water infiltration. Referring to this condition, weathered clay shale is prone to experience soil movement if backfill work is conducted on the top side of weathered clay shale material. Therefore, to minimize the potential of soil movement during backfilling, soil replacement using soil cement is recommended to be conducted to gain higher soil shear strength and to prevent excessive water infiltration to the fresh clay shale. To gain further understanding, a comprehensive study about the replacement of weathered clay shale using soil cement for bridge approach embankment in Purwakarta was carried out. This study comprises site observation, field data collection, laboratory test, explanation about implementation and quality control. The stages in implementation of soil cement is carried out in several stages such as : evaluation of soil condition on the project site, checking the suitability of local soil for the soil cement stabilization, conducting field test trial mockup followed by quality control, conducting crumb test and mechanical properties test for soil cement mixture. Based on assessment results, the soil cement mixture shall be directly compacted after the soil cement mixture is homogeneous to prevent segregation and shall be given a curing time of at least 3-7 days without additional water to gain better soil shear strength. Furthermore, according to the crumb test result, soil cement material was identified as quite impermeable which is verified by evidence that there was no significant change in water content and the soil cement sample could still stand firm after soaked for 7 days.

Assessment of Soil Liquefaction to a Highway Bridge Approach Embankment

Assessment of Soil Liquefaction to a Highway Bridge Approach Embankment

Evaluation of passive pile analysis methods using three-dimensional finite element analysis

ABSTRACT Piles in soft soil supporting bridge abutments are often exposed to passive loading induced by adjacent bridge approach embankment. Several methods for analysis of passive piles have been developed, but the international design specifications do not recommend a specific method for the analysis of passive piles. Therefore, the applicability of existing empirical and analytical analysis (conventional) methods is examined by comparing their outputs with those of a validated finite element model (FEM) at various adjacent embankment stress levels, and construction times, soft clay thicknesses, and pile spacing to diameter ratios. Outputs of both conventional methods and FEM show that increasing the embankment stress, thickness of soft clay layer, and pile spacing to diameter ratio results in an increase in the lateral pile displacement, maximum bending moment, and lateral pressure, and vice-versa on increasing embankment construction time. The outputs of the conventional analysis methods are compared to the FEM outputs and are underestimated except for few cases. The conventional analysis methods may yield better predictions at pile diameter-to-spacing ratio equals 3–4 for a soil preloaded prior to pile construction to a degree of consolidation greater than 50%.

Study on Long‐Term Performance of Geogrid‐Reinforced and Pile‐Supported Embankment at Bridge Approach

Bridges have been widely used in highway and railway engineering, especially in mountain areas. The differential settlement between bridge abutment and approach embankment is one of the most challenging problems, and it will result in “bumps” to affect the driving safety and comfortableness at the end of a bridge. The geogrid‐reinforced and pile‐supported embankment (GRPS embankment) is proposed to mitigate the differential settlement at the bridge approach. In this paper, the model tests and numerical studies are carried out to study the long‐term performance of the GRPS embankment considering the consolidation of subsoil. Firstly, a series of model tests are conducted to evaluate the long‐term performance of the GRPS embankment using a specially designed model box. Then, the numerical model is constructed using the finite element software MIDAS, and the numerical model is verified from the model test results. Finally, a parametric study is conducted to investigate the influences of pile net spacing, pile modulus, and filling modulus.

Settlement characteristics of bridge approach embankment based on scale model test

In order to analyze the effects of backfill materials, geometries and slab setting on the settlement of bridge approach embankment, scale model was built based on the structural characteristics of bridge approach embankment, and scale model tests were carried out under different conditions. The results show that when graded gravels were selected as the backfill materials, the effect of setting approach slab to reduce the differential settlement is more prominent. When lime soils were selected as the backfill material, approach slab can moderate the longitudinal settlement slope. When using different backfill materials, the ultimate settlement of the positive trapezoidal backfill geometries is less than that of the inverted trapezoid, and the backfill geometries have little effect on the settlement slope.

Analytical and Numerical Analysis of Additional Stress in Foundation of Bridge Approach Embankment

A good estimation of additional stress of a bridge approach foundation overlying embankment is of great importance in order to accurately calculate the differential settlements of foundation due to the axisymmetric distribution of the additional stress. Current design method commonly adopted in road and railway engineering in China is derived from the classical elastic theory and simply considers the embankment load by its self-weight (γh) without taking into account the influence of the width-to-height ratio. This may lead to an overestimation of additional stress and consequently an uneconomical overdesign. This study attempts to mitigate the gap by developing a new analytical solution. Based on the Boussinesq’s elastic theory, the proposed solution considers a constrained boundary condition associated with bridge abutment and incorporates a new concept of ground reaction, which takes into account the embankment load including the influence of the embankment width-to-height ratio. The proposed solution was finally validated by numerical analysis and shows a better performance in terms of additional stress estimation over the traditional calculation method. Overall, the proposed method proved to be a better alternative tool for the design of bridge approach embankment.

Evaluation on the dynamic performance of bridge approach backfilled with fibre reinforced lightweight concrete under high-speed train loading

In China, high-speed rails are often constructed over bridges in the region of soft soils. Differential settlement could occur in the foundation soils between bridge abutment and approach embankment that causes “bumps” to affect the smoothness at the end of a bridge. A three-dimensional finite element model is developed to investigate the use of fibre reinforced lightweight concrete in the transition zone of bridge approach for high-speed railways. Time-frequency analysis is performed using the method of Fast Fourier transform. The sensitivity analysis of rail speed, density of backfills, and the structural type of the trapezoidal shaped transition zone is conducted.

Long-Term Performance of a Highway Embankment Built with Lightweight Aggregates

This paper presents the results from a field and numerical studies performed to understand the long-term performance of a bridge approach embankment designed with lightweight, expanded clay and shale (ECS) aggregates to mitigate the settlements on a soft soil foundation. The ECS aggregates and traditional select fill were used to build southern and northern approach embankments, respectively, for a bridge on State Highway 360 in Arlington, Texas. An extensive series of laboratory tests were conducted to obtain the engineering behavior of ECS and the select fill materials before the construction. These properties were then used in the finite element modeling to simulate the embankment sections to verify the long-term performance. The embankment sections were instrumented with vertical inclinometers to monitor the lateral movements for more than four years. This data was used to validate the numerical models with an acceptable amount of accuracy. Then a parametric study was conducted for varied heights of embankments, thicknesses of foundation soil and also compression/recompression indices of foundation soil to develop design charts. The numerical, as well as field data, indicate that there is a two-thirds reduction in settlement of the foundation soil with the use of the lightweight material. The pre-consolidation pressure and the overconsolidation ratios govern the settlement behavior of the foundation soil due to lightweight embankments. The design charts can be useful in either predicting the embankment settlements for a given ECS embankment configuration or determine the allowable height of the ECS embankment for a specified settlement value when constructing in similar foundation soil encountered in this study.

Comparison of Coupled Flow-deformation and Drained Analyses for Road Embankments on CMC Improved Ground

The use of controlled modulus columns (CMC) is gaining increased popularity in the support of rail and road bridge approach embankments on soft soils. The further columns are driven into the competent firm soils, the further the design will rely on the inclusions to take the bulk of the vertical loads, as they become rigid inclusions. The advantage of this design approach is that it produces increased control over the settlement, but as a result the columns will attract greater loads, including bending moment and shear force in situations where non-uniform loading or ground conditions exist. The load on the composite soil-CMC is uniformly distributed by the upper layer of granular load transfer platform (LTP), which also includes a layer of reinforcement. Finite difference program FLAC3D has been used to numerically simulate an embankment on the improved ground with end-bearing CMC. A geosynthetic reinforcement layer has been simulated using the inbuilt FLAC3D geogrid element. In this paper, a comparison has been made between the drained and coupled flow-deformation analyses. The force in the reinforcement layer, in particular, has been compared for the two analysis approaches. It was found that according to the numerical simulation, the drained analysis provides lower estimates of the settlement, lateral displacement; and therefore, predicts less tension in the geosynthetic layer.

Numerical modelling of prefabricated vertical drains and surcharge on reinforced floating column-supported embankment behaviour

The short-term and long-term performance of reinforced, deep mixing method (DMM) floating-column supported embankments with and without prefabricated vertical drains (PVDs) are investigated using a fully 3D coupled model. The concurrent use of PVDs with the other two forms of soft ground improvement significantly shortens time for subsoil consolidation and also substantially reduces post-consolidation lateral displacements and post-construction crest settlements. The combined use of PVDs and surcharge preloading to meet a requirement of 100 mm post-construction crest settlement for a bridge approach embankment is examined. Compared to a comparable case with surcharge preloading but without PVDs, the synergistic effects of PVDs and 0.5 m fill surcharge preloading diminish the calculated post-construction crest settlement from 0.228 m to 0.036 m and reduce the post-consolidation horizontal movement below the toe at the ground surface level from 0.115 m to 0.067 m even though embankment is constructed 5 times faster in the case with PVDs.

Research on the Stress-Strain Law of Abutment Approach Embankment Filled with Liquid Fly Ash

Because of the narrow condition of bridge approach embankment, the large compacting machines can not use in the embankment construction. The differential settlement between abutment and approach embankment was easy to produce. Coupled with the the structural differences of the abutment and embankment, how to ensure abutment stable and prevent bridge head bump has been an engineering roadblock in the abutment approach embankment filling engineering. The key factor to solve the problem of the roadblock is reducing the horizontal thrust of embankment on abutment and the difference in settlement between road and bridge. Test results showed that liquid fly ash is a new lightweight value material of self-compacting, which has higher strength, stiffness and smaller density. Using liquid fly ash as the bridge-approach embankment filling material can effectively reduce the horizontal thrust of embankment on abutment and decrease its own settlement deformation. ANSYS computational analysis showed that when we use liquid fly ash filling the bridge approach embankment, the horizontal thrust of the same position will increase with the increase of the filling height, and the value is lesser than the horizontal thrust of soil filling subgrade. Pavement settlement increases with the filling height increasing, but it is significantly less than the general soil filling subgrade.

Equivalent Static Analysis of Piled Bridge Abutments Affected by Earthquake-Induced Liquefaction

Deformation of bridge approach embankments caused by earthquake-induced liquefaction in the underlying soils can impose large force and displacement demands on the piled abutments. An equivalent static analysis (ESA) procedure that accounts for the beneficial coupling of the embankment displacements with the mobilized bridge/pile restraining forces is evaluated against the results of three centrifuge tests involving three nonpiled embankments and three piled embankments. The centrifuge tests, which showed that the restraining forces from the different pile configurations reduced the embankment displacements by 20–80%, relative to those of the nonpiled embankments, are briefly summarized. The ESA procedure is described and applied to the centrifuge tests using different sets of input parameters to isolate the questions of how well liquefaction-induced displacements are estimated for embankments without piles, and how well the relative pile pinning effects are estimated. The results of nonlinear deformation analyses (NDAs) of the same centrifuge tests are compared with those from the ESAs and are used to illustrate important differences in their capabilities. The relative merits of the ESAs and NDAs for evaluating the performance of pile abutments affected by liquefaction are discussed.

An Innovative Friction-Based Seismic Isolator Utilizing Bridge Approach Embankments

An unconventional fusing mechanism reducing the longitudinal response of earthquake resistant bridges is presented. The suggested mechanism is an economical alternative to seismic isolation practice consisting of a concrete slab, connected to the bottom flange of the deck, embedded in the approach fill. The system resists to the deck seismic movements through friction forces developed at both ends of the bridge between the surfaces of the slab and the adjacent crushed material of the embankment. The performance of the proposed mechanism is investigated and a methodology for use with a dynamic response spectrum analysis is suggested and implemented. Furthermore, an experimental investigation was conducted for two loading speeds of a test specimen at a simple but realistic setup. Results of this very promising low-cost “damper” are presented.

Evaluation of the New Technique of Geogrid-Reinforced and Pile-Supported Embankment at Bridge Approach

Differential settlement between the bridge approach embankment and bridge abutment is a major issue in bridge engineering. To mitigate the differential settlement, a new ground-improvement technique, a fixed-geogrid-reinforced and pile-supported embankment (referred to as a FGT embankment) was proposed. To investigate the performance of the FGT embankment, a numerical analysis was performed for a trial bridge approach embankment in Changzhi, China. The numerical model was carefully calibrated to ensure good representation of the realistic conditions. The comparison analyses and parametric study were conducted to evaluate the effects of the traffic load, long-term tensile stiffness of the geogrid, and long-term elastic modulus of the soil. The results show that the FGT embankment can reduce the settlement, enhance the stability, and offer a better performance measure for the construction of a high embankment at the bridge approach.

Dynamic responses of bridge-approach embankment transition section of high-speed rail

Based on the vehicle-track coupling dynamics theory, a new spatial dynamic numerical model of vehicle-track-subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0–5 m zone behind the abutment should be specially designed. The results of the study from vehicle-track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction (K 30) is greater than 190 MPa within the 0–5 m zone behind the abutment and greater than 150 MPa in other zones.

Dynamic Analysis of Bridge-Approach Embankment Transition Segment

Dynamic responses of coupled system were analyzed when the speed of train was 350km/h and the transition was filled with graded broken stones mixed 5% cement. Results indicate that setting form of bridge-approach embankment section has little effect on dynamic responses, thus designers can choose it on account of practical circumstances. Based on the study from vehicle-track dynamics, we suggest that the coefficient of subgrade reaction (K30) should be greater than 190MPa within 0-5m zone behind abutment and be greater than 150MPa in other zones.

Properties and Applications of Cement-Treated Sand-Expanded Polystyrene Bead Lightweight Fill

AbstractTo mitigate settlement problems associated with bridge approach embankments over soft soil, a newly-developed lightweight material was proposed in this study. This lightweight material consisted of expanded polystyrene beads, the hydraulic sand from the Yangtze River, and cement. The mechanical properties of the mixed lightweight material were determined through a series of laboratory tests, including standard Proctor tests, unconfined compression tests, California Bearing Ratio (CBR) tests, unconsolidated-undrained tests, and consolidated-undrained tests. The laboratory results showed the favorable properties of the lightweight material and that it can be used as a backfill material in highway embankment projects. A field study was also conducted to verify the performance of the embankment backfilled with this lightweight material, which resulted in a smaller settlement than the embankment backfilled with lime-stabilized soil (with and without any other ground improvement). Sand cone and CBR test...

Design of embankments supported on controlled modulus columns

<p>In recent years, the use of controlled modulus columns (CMC) to support road or rail embankments over soft ground at bridge approaches has gained popularity in Australia. Despite their higher cost per unit area of ground treatment compared to other methods, CMC are often the preferred method of treatment when time is of the essence. CMC enable accelerated construction of bridge abutments due to their speed of installation and ability to limit lateral soil and abutment pile movements during embankment construction. In Australia, most CMC supported embankments to date have been designed using similar principle as piled embankments, with the columns treated as structural elements to take all the applied loads. The authors believe that there is scope for CMC to be more cost-effective if they are designed to function as geotechnical elements.</p><p>This paper examines a number of CMC design issues, including the effect of columns stiffness and spacing on settlement reduction, the need for load transfer platform over the columns, and what if the columns crack when their bending moment capacity is exceeded, and do columns need to be reinforced. An economic design approach is recommended and two case studies are provided to illustrate the use of CMC to support bridge approach embankments.</p>

Performance of an embankment supported on soft soil reinforced by stone columns

This paper presents a case study of a bridge approach embankment constructed on a soft soil reinforced by stone columns. The soft soil consisted of highly plastic clay with an undrained shear strength as low as 4 kPa. The thickness of the soft soil ranged from 2·5 to 8·5 m. The stone columns were installed through the soft soil by vibro-replacement technique. The stone columns were extended about 0·5 m into the underlying dense to very dense sand, sandstone or mudstone. The overall performance of the treated soil under the embankment load was evaluated using settlement plates. The field measurements were compared to the predictions of the analytical and finite-element methods. Most of the methods predicted settlements that are comparable to the measured values. Furthermore, the finite-element analysis shows that for deep deposits of soft soil, floating stone columns with a length/depth ratio of 0·5 can be as effective as the end bearing stone columns. Furthermore, the settlement reduction factor decreases with the increase in the area replacement ratio. Beyond an area replacement ratio of 0·4, the decrease in the settlement reduction factor is insignificant.

Earthquake-Induced Deformation Analysis of a Bridge Approach Embankment in Missouri

Earthquake-induced deformations for a bridge approach earth embankment are predicted using a calibrated numerical model. The constitutive soil model is a modified hyperbolic model that uses Masing rules and incremental pore pressure relations. The model was calibrated using both laboratory and field data. A shaking table physical model was used to verify the numerical simulation. Additionally, the upper San Fernando dam was modeled to reproduce the deformations in the 1971 earthquake. The subsurface and embankment soil conditions were characterized using field and laboratory methods. The model developed was used to predict the earthquake-induced deformations of an approach embankment to Bridge A1466 in the NMSZ near Hayti, Missouri, where strong earthquakes M > 7.0 are anticipated in the next 50 years.