Bridge Approach Settlement Research Articles

Bridge Approach Settlement and its Mitigation Schemes: A Review

The primary function of the bridge approach is to provide a seamless transition from the highway or railway embankment to the bridge structure. However, a sudden change in elevation (drop/bump) at the transit of these two has often been observed. This sudden drop/bump acts as a potential cause for motorist discomfort, impact on the bridge deck, and cracks on the pavement surface. This phenomenon of ground settlement or deformation that can occur near the approach or abutment of a bridge for various reasons is often referred to as bridge approach settlement (BAS). Several researchers have contributed to formulating the reasons behind BAS and have proposed several mitigation techniques. This manuscript provides a comprehensive literature review on the causes of BAS, the contribution of various research works on mitigation techniques, and experimental, numerical, and field studies of various BAS mitigation schemes. The causes and mitigation techniques are categorized based on major components of the bridge structure, that is, the foundation, abutment, backfill soil, bridge approach, and bridge deck interface. Each of these mitigation schemes has advantages and disadvantages, and the best approach will depend on several factors, such as the type of soil, the loading conditions, and the design of the bridge and its approaches. The feasibility of various mitigation schemes is also reviewed with respect to their efficacy and ease of use.

A Response-Type Road Anomaly Detection and Evaluation Method for Steady Driving of Automated Vehicles

Serious Road anomalies caused by bridge approach settlement, pavement rutting, etc., not only seriously affect traffic safety and user experience but also aggravate the damage of road structure. It is more relevant to automated vehicles (AVs) as they are currently not designed to measure the pavement roughness directly. Without prior-collected road anomalies information, AVs’ active suspension control system can only passively reduce the negative impact of road anomalies to a certain extent. This paper proposed a response-type road anomaly detection and evaluation method by collecting the vibration data from AVs. A mechanical estimation model for the height of anomaly (HoA) is constructed to evaluate the degree of road anomaly. Passenger’s comfort is evaluated by three featured indicators: maximal acceleration, weighted root-mean-square acceleration, and jerk. A full-car simulation model is programmed based on the Simulink platform to reveal the relationship among road anomalies, comfort, and speed, which helps design a steady driving velocity profile for AVs. The results show that the root-mean-square error of road anomalies estimation is about 0.63cm. AVs’ comfort can be improved significantly by employing the proposed steady driving strategies.

Bridge approach settlement mitigation using expanded polystyrene foam as light backfill: Case study and 3D simulation

This paper presents the behavior of the bridge approach structure, which was repaired by using expended polystyrene foam as a replacement fill on Soft Bangkok Clay. The bridge approach began construction 20 years before a project. The settlement from consolidation and ground subsidence was high at 1.35 m at the end of the bearing unit before remedial measures. The settlement of the bridge approach structure before the project began and after completion was presented. After remedial measures, settlement rates tend to decrease after 100 days. The behavior of the bridge approach structure was modeled by using finite elements. The time-dependent strain of EPS geofoam can be predicted by an empirical equation by optimizing method. 3-dimensional finite element analysis can predict the overall behavior of bridge approach structure using EPS as fill material with time-dependent stiffness. The prediction before and after remedial measurement of the embankment was using similar model parameters. Important considerations to simulate EPS embankment behavior were long-term stiffness degradation of EPS block and ground subsidence.

Iterative Method for Predicting Uneven Bridge Approach Settlement (BAS) Caused by Vehicle Loads

With the development of the transportation, the bridge approach settlement (BAS) received great attention which can result in structure deterioration of the bridge and road, costly maintenance, and hazardous driving conditions. Therefore, accurate prediction of BAS is important. In this paper, a methodology using the iterative procedure is presented to predict the long-term BAS. In this method, the dynamic deviator stress is obtained by a 3D finite element road model and the settlement is calculated by an empirical model with the dynamic deviator stress. Then, the settlement is used as the excitation of the vehicle model for updating the load in the 3D road model. After several iterative calculations, the long-term BAS can be obtained. The comparison between the iterative method and the empirical method is presented. Also the parametric study of the empirical equation is performed. A simplified equation considering the iterative procedure is proposed for engineering practice. Computed results showed that the permanent settlement predicted by the iterative method is larger than that calculated by the empirical method. Also, the parameters of the empirical equation have great effects on the settlement prediction. The applicability of the new empirical equation is also proved.

Performance of Settled Bridge-Approach Slabs with Polyurethane-Foam Injection

Abstract Bridge-approach settlement costs hundreds of millions of dollars in repairs annually. Polyurethane-foam injection by two different processes: (1) a patented deep-injection process, and (2) a non-patented process (directly under the slab) were investigated to study the effectiveness of the slab lifting and leveling. A method of evaluating localized roughness by using areas bound by deviation curves was developed. Three field projects were investigated, one of which was repaired over 6 years ago. The deviation curves from these sites are very repeatable, as the plots often overlap. Evaluating the localized roughness, such as the bridge-approach settlement, using the areas bound by deviation curves seems to be a reasonable approach. The slab lifting with polyurethane foam, using either process, was successful at all three sites. The slabs were all raised to the desired elevation, improving safety and ride quality. The roughness was reduced by as much as 70 %. The falling weight deflectometer (FWD) deflections were reduced by as much as 60 % at many monitored locations. It is believed that when there are no other factors to cause the embankment to lose soil, the polyurethane-foam injection can be used to lift the settled approach slabs. Flowable fill should be used to fill any visible voids prior to the polyurethane-foam injection. The advantage of the patented deep injection process over the non-patented process is inconclusive.

Rapid Accelerometer Measurements of Vehicle Bumps at Bridge Approaches

Bridge approach settlement (BAS) is one of the most common problems in highway and bridge construction. The settlement can result in unsafe driving conditions, rider discomfort, structural deterioration of bridges, and long-term maintenance costs. BAS research has focused mainly on causes, hazards, and countermeasures, with little emphasis on BAS measurement. This paper presents a rapid vehicle-mounted accelerometer method for BAS measurement and proposes a comprehensive BAS measure consisting of three indexes that measure user physical and psychological comfort as well as the impact on bridge structures. A wavelet transform is used to identify the reaction position. Power spectral density analysis and one-third octave band filtering are applied to calculate the weighted root mean square acceleration as an index of comfort. Adopting the annoyance rate concept from experimental psychology, an annoyance rate model was developed that includes a membership function and the distribution of user comfort levels. A quarter-car model and a linear time invariant (LTI) system were used to estimate the equivalent impact coefficient as an index of durability. Furthermore, a collective system equipped with z-axis accelerometers and a GPS device was created, and small-scale field tests were conducted in Shanghai, China. A velocity correction equation was generated to correct the evaluation model. The test results demonstrate the stability and efficiency of the rapid measurement system.

Ballast Settlement Ramp to Mitigate Differential Settlement in a Bridge Transition Zone

Differential settlement in railroad track transitions, often associated with differences in track stiffness, may apply considerable impact load and may cause rapid deterioration of track geometry. Such differential settlement commonly seen in bridge approaches may lead to problems in ride comfort, track safety, and reliability. Ballast and subballast layers have been identified as a major cause of differential settlement related to the particulate nature of the aggregate deformation behavior causing degradation and breakdown associated with increased track usage. This paper describes an innovative field approach that successfully demonstrated the use of engineered ballast materials for reducing or mitigating the differential settlement problem in a bridge transition zone. Discrete element method (DEM) simulations were used to predict full-scale track deformations of four ballast materials having different gradations and aggregate shape properties. An imaging device was used to create accurate particle size distributions and shapes for measuring and quantifying by indexes the ballast aggregate shape properties, that is, particle flatness and elongation and angularity. On the basis of the results of the DEM modeling study, a bridge approach settlement ramp was constructed and tested at the Transportation Technology Center's Facility for Accelerated Service Testing. The results showed that the settlement ramp approach could be achieved by constructing ballasted track with proper selection of materials in each section of track transition zone. This study also demonstrated that the DEM simulation approach combined with image analysis could be used as a quantitative tool for predicting the ballast performance and providing help in design of track transitions.

Forensic Investigation of Mechanically Stabilized Earth (MSE) Approaches

Abstract A forensic study was performed to determine: (1) the extent of voids in the retaining wall backfill in the first 1 m behind the wall panels; (2) the extent of moisture in the suspected wet areas where the District is planning to add turnarounds under the bridges; (3) severity of bridge approach settlement and its ride quality; and (4) whether or not there is global stability concern for FM (Farm to Market) 310, FM 1304, and Chatt Rd. mechanically stabilized earth (MSE) walls. Ground penetration radar (GPR), dynamic cone penetration (DCP), drilling, elevation surveys, and instrumentation was performed in this study. Although voids and soft layers were found under the concrete slab, they are all near the MSE wall. Periodic survey results from April 2006 to March 2007 indicate that there is no significant settlement (<10 mm). The piezometer measurements in the MSE walls indicate that the water table was low. The safety factor was found to be 1.4, which is above the minimum requirement of 1.3. Therefore, it was concluded that there is no global stability issue. Longitudinal profiles collected in June 2006 and July 2007 indicated that the maximum settlement in one year was found to be 6 mm for the Chatt Rd. overpass. Although there are some settlements on other overpasses, they are all less than 5 mm. There are no criteria on annual allowable settlement for bridge approaches. Thus, it was decided to continue to monitor the approach slabs without any immediate rehabilitation.

Evaluation and Recommendations for Flowfill and Mechanically Stabilized Earth Bridge Approaches

To alleviate the common bridge bump problem, the Colorado Department of Transportation (CDOT) has employed three new alternatives for bridge abutment backfill since 1992: flowfill, mechanically stabilized earth (MSE) using well-graded granular Class 1 backfill (reinforced soil mass as in MSE walls), and MSE using free-draining Class B filter material. However, the occurrence of bridge bump problems is still reported. A study evaluated CDOT current practice for design and construction of bridge approaches and then developed recommendations to improve this practice (improve performance and reduce costs) on the basis of the results of the following: (a) best practices for bridge approaches collected from CDOT staff and reported in the literature, (b) evaluation of the performance and cost-effectiveness of Colorado's MSE and flowfill bridge approaches, and (c) identification of the causes of significant bridge approach settlement problems observed in some of Colorado's MSE and flowfill bridge approaches. Evaluation procedures and forensic investigations were developed and applied to obtain the information needed for the first two items. Flowfill should remain a viable alternative for certain field and construction scenarios that justify its higher costs. MSE approaches with both Class B and Class 1 backfill materials should be routinely used in future CDOT projects with documentation of their performance and cost (construction and repair costs) for a future evaluation. Comprehensive recommendations are presented to mitigate the observed bridge approach settlement problem; the most important recommendations are for improved support and drainage systems for the sleeper slab where the settlement problem occurs.

Remedial treatment of soil structures using geosynthetic-reinforcing technology

The advantages of geosynthetic-reinforcing technology to construct new soil structures including; (a) a relatively short construction period; (b) small construction machines necessary; and (c) a higher stability of completed structures, all contributing to a higher cost-effectiveness, are addressed. A number of case successful histories of geosynthetic-reinforced soil retaining walls have been reported in the literature (e.g., [Tatsuoka, F., Koseki, J., Tateyama, M., 1997a. Performance of Earth Reinforcement Structures during the Great Hanshin Earthquake, Special Lecture. In: Proceedings of the International Symposium on Earth Reinforcement, IS Kyushu ‘96, Balkema, vol. 2, pp. 973–1008; Tatsuoka, F., Tateyama, M, Uchimura, T., Koseki, J., 1997b. Geosynthetic-reinforced soil retaining walls as important permanent structures, 1996–1997 Mercer Lecture. Geosynthetics International 4(2), 81–136; Tatsuoka, F., Koseki, J., Tateyama, M., Munaf, Y., Horii, N., 1998. Seismic stability against high seismic loads of geosynthetic-reinforced soil retaining structures, Keynote Lecture. In: Proceedings of the 6th International Conference on Geosynthetics, Atlanta, vol. 1, pp.103–142; Helwany, S.M.B., Wu, J.T.H., Froessl, B., 2003. GRS bridge abutments—an effective means to alleviate bridge approach settlement. Geotextiles and Geomembranes 21(3), 177–196; Lee, K.Z.Z., Wu, J.T.H., 2004. A synthesis of case histories on GRS bridge-supporting structures with flexible facing. Geotextiles and Geomembranes 22(4), 181–204; Yoo, C., Jung, H.-S., 2004. Measured behavior of a geosynthetic-reinforced segmental retaining wall in a tiered configuration. Geotextiles and Geomembranes 22(5), 359–376; Kazimierowicz-Frankowska, K., 2005. A case study of a geosynthetic reinforced wall with wrap-around facing. Geotextiles and Geomembranes 23(1), 107–115; Skinner, G.D., Rowe, R.K., 2005. Design and behaviour of a geosynthetic reinforced retaining wall and bridge abutment on a yielding foundation. Geotextiles and Geomembranes 23(3), 234–260]). Techniques for analyzing the seismic response of reinforced walls and slopes have also been developed (e.g. Nouri, H. Fakher, A., Jones, C.J.F.P., 2006. Development of horizontal slice method for seismic stability analysis of reinforced slopes and walls. Geotextiles and Geomembranes 24(2),175–187). Several typical cases in which embankments having a gentle slope and conventional-type soil retaining walls that were seriously damaged or failed were reconstructed to geosynthetic-reinforced steepened slopes or geosynthetic-reinforced soil retaining walls are also reported in this paper. It has been reported that the reconstruction of damaged or failed conventional soil structures to geosynthetic-reinforced soil structures was highly cost-effective in these cases. Rehabilitation of an old earth-fill dam in Tokyo to increase its seismic stability by constructing a counter-balance fill reinforced with geosynthetic reinforcement is described. Finally, a new technology proposed to stabilize the downstream slope of earth-fill dams against overflowing flood water while ensuring a high seismic stability by protecting the slope with soil bags anchored with geosynthetic reinforcement layers arranged in the slope is described.

GRS bridge abutments—an effective means to alleviate bridge approach settlement

Field tests of segmental block-faced geosynthetic-reinforced soil (GRS) bridge abutments and piers have demonstrated excellent performance characteristics and very high load carrying capacity. One important feature of GRS abutment is that it can potentially eliminate the use of piling when situated over a weak foundation. This will not only reduce the costs but also reduce “bridge bumps” often experienced at the ends of a bridge resting on a pile-supported abutment. This study was undertaken to investigate the potential of GRS bridge abutments to alleviate bridge approach settlements. The study was conducted by the finite element method of analysis using the computer program DACSAR. The program was first calibrated by comparing its results with the measured data of the Founders/Meadows bridge abutment recently constructed by the Colorado Department of Transportation. A parametric study was then conducted to examine the effects of different foundation soils, ranging from loose sand to stiff clay, on the performance of a GRS abutment. Special attention was placed on the maximum vertical and horizontal movements of the abutment as well as the approach settlement characteristics. The study indicated that the finite element computer code DACSAR is a reliable analytical tool for analyzing the performance of GRS bridge abutments and that the GRS abutment is an effective means to reduce differential settlements between the abutment and the approach embankment.

GRS bridge abutments—an effective means to alleviate bridge approach settlement

GRS bridge abutments—an effective means to alleviate bridge approach settlement

Discussion of “Tensile Reinforcement Effects on Bridge-Approach Settlement” by Gregory J. Monley and Jonathan T. H. Wu

Discussion of “Tensile Reinforcement Effects on Bridge-Approach Settlement” by Gregory J. Monley and Jonathan T. H. Wu

Discussion of “Tensile Reinforcement Effects on Bridge-Approach Settlement” by Gregory J. Monley and Jonathan T. H. Wu

Discussion of “Tensile Reinforcement Effects on Bridge-Approach Settlement” by Gregory J. Monley and Jonathan T. H. Wu

Tensile reinforcement on bridge-approach settlement : Monley, G J; Wu, J T H J Geotech Engng Div ASCE V119, N4, April 1993, P749–762

Tensile reinforcement on bridge-approach settlement : Monley, G J; Wu, J T H J Geotech Engng Div ASCE V119, N4, April 1993, P749–762

Alleviating bridge approach settlement with geosynthetic reinforcement : Proc 4th International Conference on Geotextiles, Geomembranes and Related Products, The Hague, 28 May–1 June 1990 V1, P107–111. Publ Rotterdam: A A Balkema, 1990

Alleviating bridge approach settlement with geosynthetic reinforcement : Proc 4th International Conference on Geotextiles, Geomembranes and Related Products, The Hague, 28 May–1 June 1990 V1, P107–111. Publ Rotterdam: A A Balkema, 1990