Deformation Of Embankment Research Articles

Field test of geosynthetic-reinforced floating pile-supported embankments on soft soil

This study conducted field tests on geosynthetic-reinforced floating pile-supported embankments to evaluate the load transfer mechanism and embankment deformation during embankment construction. Vertical pressures on pile caps and subsoils between piles, geosynthetic strains, settlement of pile caps and subsoils between piles, and settlement of the embankment at different elevations were measured throughout the embankment construction. Test results showed that the maximum settlement of the pile cap was approximately 66% of subsoils between the piles. Due to the large settlement of the floating piles, the soil arching was not significantly mobilized. The geosynthetic reinforcement exhibited a maximum tensile strain of 0.2% at the end of embankment construction, indicating a mobilization of low tensioned membrane effect. The predicted equal settlement heights at adjacent piles center and the diagonal pile center were close with an average value of approximately 1.23 times the pile net spacing. The measured vertical pressures on subsoil between piles were compared with calculated results using available analytical models from the literature. The analytical models underestimated the vertical pressures on the subsoils between piles, while the modified Terzaghi's model showed better agreement with the measured results than other analytical models.

Prediction of huge earthquake-induced deformation of in-service embankments using crushed mudstone as a soil material with slaking and proposal of countermeasures

Evaluating the seismic resistance of embankments using crushed mudstone as a geomaterial is an urgent and crucial requirement. In this study, a ground investigation was conducted on the actual embankment. Based on the results, the seismic response of the embankment, simulating progressed slaking, was conducted by elastoplastic finite deformation analysis using two major types of earthquake motion: epicentral and subduction zone earthquakes. Based on the results of the geotechnical investigation, the embankment could be divided into three layers owing to differences in physical properties, and slaking progressed below the groundwater level in the embankment. The embankment did not exhibit large deformation during the epicentral earthquake owing to the short duration. For the subduction zone earthquake, the developed shear strain was from the two large acceleration groups and the subsequent smaller accelerations, resulting in large deformation. Seismic loading caused the gradual loss of the overconsolidation and decay of the structure which reduced the embankment strength. This analysis revealed that shear strain developed at the slope toe and the lower part of the embankment. Furthermore, the analysis after the earthquake was also conducted to examine whether or not countermeasure method is feasible for emergency restoration. The seismic resistance was greatly improved when a combination of ground improvement and replacement/counterweight fill methods were used to reinforce these areas, which is not only during but also after the earthquake. This study can contribute to the understanding of the seismic behavior of soil structures using materials undergoing internal deterioration and to the development of countermeasure methods for such structures.

Hydro-thermal processes and deformation of highway embankment in the active layer in a high-latitude permafrost region of Inner Mongolia in Northeast China

Construction of embankments in the permafrost region significantly changes the heat exchange conditions and hydrothermal transport processes between permafrost and the external environment, causing changes in the state of permafrost under the embankment, which in turn affects the long-term stability of embankment impacts. Considering more complex forest environment and higher technical standard for expressway than ordinary highway, the hydrothermal and deformation characteristics of the embankment are investigated through a full-scale field experimental embankment of the Genhe-Labdalin highway. Further, the study delves into the influence of changes in the active layer thickness, hydrothermal processes, and water above the frozen layer on embankment stability. The main conclusions are as follows: 1) The permafrost table, temperature, moisture and deformation of the embankment showed lateral heterogeneity, with the three-former showing a “concave shape” and the left side (sunny slope) being lower than the right side (shady slope). 2) The permafrost table appears to be unconnected (thawing interlayer), creating preferential flow, thaw zones and even through-thaw zones. 3) Accompanied by the freezing and thawing process of the embankment, the deformation of the pavement is less delayed. These findings will be helpful for better understanding the hydrothermal characteristics of embankments in different frozen ground regions, and for providing important technical guidance to ensure the safe operation of engineering projects.

Experimental and Numerical Study on Lightweight-Foamed-Concrete-Filled Widened Embankment of High-Speed Railway.

To study the performance of lightweight foamed concrete (LWFC) in widened embankments of high-speed railways, this study first conducted numerous strength, permeability, and water immersion tests to investigate the mechanical properties and water resistance of LWFC with designed dry densities of 550, 600, and 650 kg/m3. Secondly, a field test was performed to analyze the behavior of the deformation and the internal pressure within the LWFC-filled portions. Furthermore, a parametric study via numerical modeling was performed to investigate the effects of four key factors on the performance of the LWFC-filled, widened embankments. Results showed that LWFC possesses adequate bearing capacity and impermeability to meet high-speed railway embankment widening requirements. However, water seepage reduces LWFC strength. The additional pressure from LWFC filling increases initially but then decreases once dehydration occurs. The settlement induced by LWFC accounted for 71% of the total filling height, which is only 37.5% of the total settlement after construction. The parametric study results show that the maximum settlement of widened and existing portions induced by LWFC was 46.3-49.6% and 48.3-53.2% of those induced by traditional fillers due to the LWFC's lower density as well as their better self-supporting ability. Making an appropriate reduction in the thickness of the retain wall installed against the LWFC-filled widened embankment of the high-speed railway generates a few variations in the lateral deformation of the wall. Furthermore, the effects of the pile offset on the deformation of the LWFC-filled embankment were more sensitive compared to the diameter of the piles.

Numerical simulation of rainfall-induced deformations of embankments considering the coupled hydro-mechanical behavior of unsaturated soils

This paper presents numerical simulations of the deformation response of unsaturated embankments subjected to rainfall infiltration using a coupled hydro-mechanical constitutive model for unsaturated soils. The constitutive model accounts for the influence of degree of saturation on the stress–strain behavior and the influence of void ratio on the water retention behavior. The constitutive model was implemented in the finite difference program FLAC, calibrated using triaxial test data, and validated using measurements of wetting-induced deformations of embankment models from centrifuge tests. The validation demonstrates that the constitutive model can capture the coupled hydro-mechanical behavior of unsaturated soils under wetting conditions. Simulations of the hydro-mechanical response of unsaturated embankments subjected to rainfall infiltration indicate that the differential settlement across the top surface of the embankment between the centerline and shoulder increases significantly during rainfall infiltration, which could result in severe damage to overlying transportation infrastructure. As the rainfall infiltration increases, shear strains accumulate and form a potential failure surface at a shallow depth of approximately 2 m from the slope surface. Insights into the hydro-mechanical response of unsaturated embankments subjected to rainfall infiltration gained will be useful for considering climate change effects in design and construction of compacted embankments.

Assessing the Settlement and Deformation of Pile-Supported Embankments Undergoing Groundwater-Level Fluctuations: An Experimental and Simulation Study

The intensification of extreme weather phenomena, ranging from torrential downpours to protracted dry spells, which trigger fluctuations at the groundwater level, poses a grave threat to the stability of embankments, giving rise to an array of concerns including cracking and differential settlement. Consequently, it is crucial to embark on research targeted at uncovering the settlement and deformation behaviors of pile-supported embankments amidst changes in water levels. In tackling this dilemma, a series of direct shear tests were carried out across a range of wet–dry cyclic conditions. The results confirmed that the occurrence of wet–dry cycles significantly impacted the resilience of silty clay. Additionally, it was observed that the erosion of cohesion and the angle of internal friction initially diminished sharply, subsequently leveling off, with the first wet–dry cycle exerting the most substantial influence on soil strength. Employing a holistic pile-supported embankment model, simulations revealed that variations in the groundwater level, fluctuations therein, varying descent rates, and periodic shifts in the groundwater level could all prompt alterations in soil settlement between embankment piles and could augment the peak tensile stress applied to geogrids. In summary, the orthogonal experimental method was utilized, indicating that, in terms of impacting embankment settlement under periodic water-level changes, the factors ranked in descending order were the following: pile spacing, pile length, embankment height, and the height of the groundwater table.

Numerical investigation on the deformation of railway embankment under normal faulting

Active faults in the earthquake region are consistently regarded as a potential geological hazard to the construction and operation of railway engineering. However, the effects of normal faulting on railway embankments have not been investigated thoroughly. For bridging this knowledge gap, three-dimensional finite element analysis considering the influence of faulting offset, the soil layer’s thickness, the fault dip angle and the embankment cross-fault angle are conducted to clarify the normal faulting effects on the railway embankment. Emphasis is given to the stress and strain characteristic in the fault rupture outcropping regions on the embankment, the deformation of the embankment centerline for design purposes, and the determination of the affected zones for railway embankment preservation. The analysis shows that the normal fault rupture outcropping regions on railway embankment are tensile yield in most cases. The existence of the soil layer and its thickening would widen the affected zones and the regions where the fault ruptures outcrops. The fault dip angle and the cross-fault angle of the embankment have a complex effect on the behaviors of the crossing embankment. The depth of the subsidence zone of the embankment would increase with the decrease of the fault dip angle and the large fault dip angle would change the primary fault rupture to be a compressive one directly above the fault line. If the embankment crosses the fault line obliquely, the curvature radius of the centerline would hardly meet the design code.

Experimental Study on Erosion Process of Expressway Embankment Subjected to Tsunami After Earthquake

On March 11, 2011, the Great East Japan Earthquake triggered tsunamis that reached extensive areas along Japan’s Pacific coast. There have been instances where embankments built on plains for expressways mitigated the impact of tsunami damage. In the vicinity of the Sendai-tobu highway, the presence of an embankment approximately 10 m high altered the course of the advancing tsunami, thereby preventing flooding. Establishing a multiplied defense system using road embankments necessitates understanding the deformation and collapse mechanisms of road embankments impacted by tsunamis following seismic motion. In this study, overtopping experiments were conducted by first applying seismic motion to model embankments, followed by introducing the first wave of breaking bores, and then simulating prolonged overtopping by the tsunami. The experimental findings indicated that within the embankments impacted by the tsunami, there was an immediate increase in what is presumed to be pore air pressure following the arrival of the breaking bores, followed by a rise in pore water pressure during subsequent overtopping. Moreover, embankments subjected to seismic motion exhibited accelerated erosion following the overtopping. These results imply that when embankments settle due to an earthquake, leading to relatively higher anticipated inundation depths and the potential for overtopping, it is crucial to implement measures to prevent the settlement of the crest for embankments expected to serve as part of a multiplied defense system.

Deformation characteristics of red-mud embankment under monotonic and cyclic loads

The rapid growth in the production of the red mud has led to the shortage of land for stockpiling in recent years. Although red mud has been considered as the filling material for embankments, the deformation characteristics of a red-mud embankment under traffic loads has not yet been clarified. To promote its application in embankment construction, a series of centrifuge model tests of red-mud embankment under monotonic and cyclic loads were conducted. The deformation and failure processes of red-mud embankment under normal and overproof traffic loads were analyzed. The results show that the deformation characteristics of red-mud embankment varied significantly depending on the value of the external load. The deformation induced by monotonic load was greater than that induced by the cyclic load of the normal traffic load. The monotonic and cyclic loads of normal traffic load induced similar influential areas, and their deformation processes can be divided into rapid and slow growth parts. Shear failure occurred in the red-mud embankment under overproof traffic load. The same load increment induced more deformation of red-mud embankment after failure. Under reasonable dry density and water content, the deformation of red mud was acceptable, thus meeting the engineering requirements of embankment construction.

Field research on supersized rectangle pipe-jacked tunnels beneath a navigable river in the urban area

With technological progress in recent years, supersized rectangular jacked pipe tunnels have been increasingly used for developing urban road-crossing nodes, owing to their convenient construction and economic benefits. However, owing to the weak waterproofing performance of the joint, jacked supersized rectangular pipes have been employed beneath a navigable river. This study used on-site monitoring data of an underground expressway with supersized rectangular jacked pipe tunnels in Shanghai. Additionally, we analyzed the deformation of the ground surface and embankment and the mutual influence of jacked adjacent pipes. The results revealed the following. 1) the over-excavation of the jacked pipe causes partial surface subsidence. The jacking parameters were adjusted through feedback to control the surface deformation. 2) The spatial deformation of the old embankment were stabilized, suggesting the successful realization of micro-disturbance jacking construction. 3) The secondary disturbance of the soil due to post-construction causes a slight sinking and tilting trend of the former jacked tunnel.

Analysis of deformations of road embankments founded on displacement columns improving soft subsoil

Drilled displacement columns, constructed in the form of unreinforced or reinforced concrete elements, are currently a very commonly used method of improving soft subsoil, creating an alternative to more expensive pile foundations. A frequently used solution for improving soft soils of road or railway embankments is to design a regular pattern of columns of relatively small diameter. Columns along the perimeter of the improved area are reinforced with rigid steel profiles, while the internal ones are made as concrete elements. Column heads are usually covered with a load transfer platform (layer of compacted granular fill) which is additionally reinforced with geosynthetics. The application of soil improvement with displacement columns is not always successful. It is due to the errors and shortcomings occurring at the design stage, including simplifications in modelling, to construction faults, which may include insufficient experience of contractors and/or improper supervision. Referring to the real object that failed, the article provides the results of numerical parametric analyses taking into account the influence of the key design parameters such as: the stiffness of the load transfer layers, the amount and stiffness of the geosynthetic reinforcement as well as the column spacing. The article presents comparisons of numerical results obtained with the finite element analyses for various approaches to geometry modelling (axisymmetric, 2D and 3D). The simulations indicate that the use of the axisymmetric model of a single column in routine design may lead to the deformations exceeding the serviceability limit states.

Fragility assessment for the rainfall-induced embankments on silty soils

The fragility curve expresses the probability that an asset exceeds some serviceability state for a given level of environmental perturbation or other loadings. It is an important component in the quantitative risk analysis and resilience evaluation of infrastructure exposed to natural hazards. Incidences of over-settlement of embankments are increasingly reported due to more intense and longer-duration rainfall events. This paper develops fragility curves for the rainfall-induced embankment settlement. For this purpose, an embankment incorporating enhanced seepage and displacement analysis within unsaturated soil conditions is modelled based on a reported case history. A Monte Carlo simulation is used for rainfall infiltration and embankment deformation analysis under various rainfall scenarios. Probability values are obtained to achieve three levels of damage states in terms of road embankment settlement. The parametric analysis produces the exceedance probability curves for various rainfall intensities, saturated permeabilities and embankment slope angles. This work offers an efficient tool for assessing fragility to rainfall-induced excessive settlement of embankments.

Long-term freeze–thaw cycle behavior of high-speed railway embankment in frozen soil regions and its effects on train-track dynamic interaction system

The high-speed railway embankment built in cold regions has a long-term freeze–thaw cycle behavior, and the frost heave of soil will inevitably affect the smoothness of the track structure laid on the embankment, resulting in the deterioration of the train running performance and the dynamic behavior of the ballastless track system. This work is motivated by the research to investigate the long-term freeze–thaw behavior of the embankment in frozen soil regions and its effects on the train-track dynamic interaction system. Based on this motivation, the temperature-deformation field model of the embankment and the train-track dynamic interaction model (TTDIM) are established as an integrated model. The additional track irregularity triggered by the frost heave deformation of the embankment is regarded as the excitation source in the TTDIM to achieve the co-analysis of two sub-models. Through an illustrative example, the evolution characteristics of the freeze–thaw cycle behavior of embankment is fully revealed. Moreover, the effects of time-varying frost heave deformation of embankment on the performance of train-track interaction are quantified from the aspect of representative responses and safety evaluation indexes. This paper provides a valuable model and research thought reference for the analysis and assessment of the performance of train-track interaction under the long-term freeze–thaw cycles of the embankment in frozen soil regions.

Research on the deformation and damage process of crushed-rock highway embankment in permafrost areas

Research on the deformation and damage process of crushed-rock highway embankment in permafrost areas

Experimental study on a new type of FBG-3D printed geogrid in embankment reinforcement

Fiber Bragg Grating (FBG) has been widely used in many civil engineering applications to sense strains and deformations. Combining the advantages of geosynthetics and FBG, this paper creatively presents a new type of FBG-3D printed geogrid, which allows reinforcement and accurate deformation monitoring. Geogrid is directly used as the packaging structure of FBG sensor, and the complete coordinated deformation between the grating monitoring areas of FBG sensor and geogrid is obtained through calibration test. A series of model tests were carried out with FBG-3D printed geogrid to study the influence of reinforcement layers and reinforcement spacing on the bearing capacity and deformation of embankment under cyclic loading. The test results showed that geogrid effectively improved the footing settlement, slope displacement of reinforced embankment under cyclic load, and the effect was more obvious with the decrease of geogrid spacing. The strain data inside the embankment was accurately collected by FBG sensors. Relevant research provides valuable suggestions for the development and application of new geosynthetics.

Numerical analysis of a monitored piled-supported embankment of an airport runway

This paper presents a 3D finite element analysis of deep soil mixing column-supported embankments (CSEs) with a geosynthetic platform. The numerical model simulated the CSE for the expansion (≈1.0 km) of the existing runway at the Salgado Filho International Airport, in the city of Porto Alegre. The numerical model using Abaqus software was calibrated by comparing numerical calculations with good quality instrumentation data. Deep Soil Mixing (DSM) columns were used to improve the soil foundation. A novel approach to modeling the geosynthetic is also presented based on the mechanical properties of this material. The load transfer mechanisms and deformation of the column-supported embankments were analyzed by means of numerical and field results. Additional aspects such as the critical height and the pattern of vertical stress distribution in the columns and embankment as well as the stress distribution in the geosynthetic reinforcement were also investigated. The numerical model reproduces the vertical stress measured by the total stress cells installed above the columns and between the columns. The numerical model shows that the soil reaction of the thick compacted layer used as a work platform reduced the arching and membrane effect in the embankment.

Analytical method for evaluating the tensioned membrane effect in the geosynthetic-reinforced unsaturated embankment soil subjected to localized sinkholes

In karst regions, the occurrence of sinkholes is a common cause of roadway failures, leading to significant embankment deformation and instability. The advantages of geosynthetic reinforcement have been proven in practice in numerous countermeasures to lessen the impact of localized sinkholes, and associated design methodologies have been developed. However, some existing design methods assume there is no deformation in geosynthetics embedded in soils, and the effect of matric suction in soils is not considered either. This study suggested an analytical approach that took into account the strain in the geosynthetic reinforcements as well as the impact of matric suction. The developed design method was used to conduct parameter studies under various matric suction conditions. The method was validated against the experimental results, and the feasibility of the developed method was also compared with the existing design methods. The findings demonstrate that, in comparison to the method created here, existing design methodologies produce more conservative results. The strain and the deflection of the geosynthetic calculated using the suggested method are lower than those provided by the current design methodologies.

Lateral deformation of expressway embankment on the Qinghai–Tibet Plateau: field observation and theoretical model

ABSTRACT This study discusses a two-year-long field observation of the lateral deformation and ground temperature of an experimental expressway embankment on the Qinghai-Tibet Plateau. The distribution features and evolution process of lateral deformation were obtained and analysed. The results showed that the maximum lateral deformation over 2 years was higher than 14 mm and continues to increase. Large lateral deformations occur only at two depths and can be disregarded at other depths. In layers with large lateral deformation, the cumulative lateral deformation grows periodically during the thawing period and decreases during the freezing period. The distribution and evolution features of the monitored lateral deformation indicated that it was caused by thermal stress, and the lateral deformation may be identified as creep–springback deformation under variable thermal stress conditions. Finally, a creep model under a periodic thermal load was established to verify the effectiveness of the proposed lateral deformation mechanism in explaining the lateral deformation behaviour of embankments. The calculations showed that the proposed mechanism can explain the crucial features and accumulation of lateral deformation. The results and analyses reported in this study can provide new references for research on road deformation and disease development.

Effect of clay with high water adsorption capacity on process of secondary consolidation of peat

Introduction. Primary consolidation of peat, underlying an embankment, is completed 3 to 5 years after its filling. It is followed by secondary consolidation, caused by removal of bound moisture from micropores. At this stage, the settlement rate depends on the degree of peat decomposition, temperature, content of various chemicals in the pore water, vibration effects, and other factors. To reduce the embankment deformation, caused by the secondary consolidation, peat is either modified by binding compounds, having filling agents, or other actions are taken to accelerate the settlement process for a short term and to decelerate it thereafter using temporary surcharge, electroosmosis and other actions.
 
 Materials and methods. The authors studied the effect of peat dehydration using clayey materials with high water adsorption capacity, such as bentonite and saponite waste generated by the diamond mining industry. 100 days oedometer tests were carried out. In the course of testing, vertical cylindrical elements, made of the above materials, were installed in the specimens. These cylindrical elements occupied about 10 % of the specimen volume.
 
 Results. Bentonite inclusions, formed without any peat extraction, had a powerful effect on development of deformations. Intensive dehydration of peat led to a 2–4 times increase in the coefficient of secondary consolidation сαε. Following 25 to 30 days of intensive settlement, the value of the cαε coefficient went down by an average of 1.5 times relative to its initial value. The effect of elements, made of saponite-containing waste, turned out to be different. The value of the cαε coefficient increased by 11 to 15 %, but 20 to 30 days later it went down by an average of 2 times relative to the initial value. Higher resistance of elements to vertical loading served as the factor preventing the development of settlement.
 
 Conclusions. Clay has a high water adsorption capacity, and its intrusion into peat results in accelerated water migration from micropores and boosts the rate of secondary consolidation. In addition to peat dehydration, secondary consolidation was accelerated by mechanical compaction in the process of adding clay into specimens followed by clay swelling.

Performance of a Subgrade-Embankment-Seawall System Reinforced by Drainage PCC Piles and Ordinary Piles Subjected to Lateral Spreading

Coral sand is widely distributed in coastal areas and used as a soil foundation in an increasing number of projects. Historical records show that the liquefaction and lateral spreading of coral sand foundations occurred many times during earthquakes, resulting in serious geological and engineering disasters. Based on a rigid drainage pile, a PCC pile (Large Diameter Pipe Pile by using Cast-in-place Concrete) and drainage body are innovatively combined into a new drainage PCC pile, to reduce the harm caused by liquefaction and lateral spreading of the coral sand foundation. In this study, the seismic response of the subgrade-embankment-seawall system on the coral sand liquefaction site was simulated using a shaking table. The excess pore water pressure ratio, acceleration, average foundation settlement, seawall displacement, embankment deformation, and pile body bending moment of the ordinary pile foundation and new drainage PCC pile foundation under seismic loads of PGA peak ground acceleration = 0.05 g , PGA = 0.1 g , and PGA = 0.2 g on the coral sand site were analyzed and compared. Compared with ordinary pile foundations, the excess pore water pressure ratio, pile bending moment, seawall displacement, foundation settlement, and embankment deformation of the new drainage PCC pile foundation were markedly reduced, while acceleration increased, which showed that the new drainage PCC pile had a positive anti-liquefaction effect on the coral sand foundation.