Embankment Structure Research Articles

Влияние демпфирования по Рэлею на устойчивость земляного полотна железной дороги в условиях сейсмического воздействия

Purpose: to consider the problem of railway subgrade stability under seismic conditions. Show the need to increase stability during an earthquake. Determine the possibility of increasing seismic resistance by introducing a damping layer into the structure. Determine the optimal damping parameters, taking into account the rational use of subgrade materials. Methods: calculations of embankment stability are carried out using the method of G. M. Shakhunyants. An earthquake is taken into account through an increase in shear forces acting on the cells of the sliding massif. The maximum accelerations of the compartments are determined based on the results of finite element method dynamic calculation of a stress-strain state of the embankment during an earthquake, which is specified through an accelerogram. Results: the effectiveness of using a damping layer in the embankment structure, introduced to increase seismic resistance, has been shown. The dependence of the stability coefficient of the embankment on the Rayleigh parameters of the material composing the body of the entire embankment has been determined. For the best material parameters, the optimal thickness and position of the damping layer in the structure are determined, at which the stability coefficient takes on a standard value and the volume of the damping layer is minimal. Practical importance: as an alternative to the normative approach, the possibility of increasing the stability of a railway embankment under earthquake conditions by introducing a damping layer into the structure is presented. An algorithm for selecting optimal damping parameters has been determined in order to increase seismic resistance.

RESEARCH SOLUTIONS FOR PRECAST CONCRETE REVETMENTS USING ALB-REBAR TO RETAIN CORAL SAND FOR OFFSHORE ISLANDS IN VIETNAM

Gravity revetment solutions are a popular choice for shore protection at atolls under the harsh conditions of ocean waves. The precast revetment option is preferred to reduce shipping costs for materials and ensure quick construction. This article studied precast concrete revetments with ALB composite material reinforcement and conducted experimental research to determine the shear resistance characteristics of coral sand and the friction characteristics of concrete materials with coral sand. Based on the experimental parameters, the authors calculated the stability of the ALB embankment structure against the effects of wave loads during storms. With experimental data obtained from coral sand samples prepared with equivalent density in the field, the results showed that the stability coefficient of the revetment is significantly higher than the one obtained from the traditional calculation concept.

Dominant conservation parameters to control environmental destruction of oxbow lake in Kapuas River Basin, Indonesia

Global climate change has significantly impacted the ecosystem of a specific aquatic region, including its lake area. Lakes provide immense benefits in efforts to meet various needs and enhance community well-being. These include the provision of raw water for clean drinking, household and urban water supply, industry, supplemental irrigation for agriculture, hydroelectric power generation, and various other purposes. However, fluctuations in river water availability trigger adjustments in both the river flow patterns and their inherent characteristics. These modifications in land features and ecosystems have consequently brought the morphological transformations in rivers throughout the adjacent region. The characteristics and functions of oxbow lakes must be preserved, and conservation efforts must be undertaken. To maintain their functionality, it is essential to conduct a study to determine the dominant parameters that influence the characteristics of oxbow lakes. This study aims to identify the primary parameters for conservation efforts in oxbow lakes. Based on a field survey of physical conditions, most oxbow lakes exhibit suboptimal conditions, as nearly all water storage areas are already overgrown with wild vegetation and possess high sediment levels. It is essential to continuously monitor several parameters to maintain the performance of oxbow lakes. The results of this research show that the dominant parameters for the oxbow lake in west Kalimantan are divided into 3 (three) aspects: reservoir, oxbow lake embankment structure, and oxbow lake embankment crest.

Tsunami hazard evaluation of river embankment structures incorporating their vulnerability to seismic strong motion

Development of coastal areas in Japan for various land uses since the 1960s has contributed to industrial upgrades and improved the efficiency of transportation networks. However, there are concerns about the vulnerability of developments on alluvial plains and reclaimed lands to geological events, like ground subsidence due to liquefaction during large earthquakes. Realistic assessment of earthquake and tsunami hazards and evaluation of possible countermeasures require accurate estimation of the amount of subsidence that can be expected from liquefaction at coastal and riverside sites supporting various structures. In this study, to evaluate the amount a river embankment structure might be expected to settle as a result of strong motion from an assumed Nankai Trough great earthquake, we conducted a numerical simulation using the soil–water coupled finite deformation analysis code GEOASIA. We then investigated the effect of the estimated embankment subsidence on tsunami inundation, which was simulated by using nonlinear shallow-water equations and a grid spacing as fine as 3.3 m. The influence of urban structures on the inundated area was taken into account by using a structure-embedded elevation model (SEM). The results showed that subsidence of river embankments and the collapse of parapet walls on top of them would increase both the depth and area of inundation caused by a tsunami triggered by a Nankai Trough scenario earthquake. Our findings underscore the importance of evaluating not only earthquake resistance but also vulnerability of coastal and riverside structures to strong motion in tsunami hazard analyses. Furthermore, the importance of tsunami inundation analysis using a SEM for predicting the behavior of tsunami flotsam in urban areas was demonstrated.

Thaw bulb formation surrounding warm-oil pipelines and evaluation of the cooling performance of a new air convection pipeline embankment structure

The first China-Russia crude oil pipeline (CRCOP-I) and the second China-Russia crude oil pipeline (CRCOP-II) went into operation in January 2011 and January 2018, respectively. On-site monitoring data have indicated that the seasonal thawing depth (STD) of a borehole 2 m away from CRCOP-I reached 10.8 m by the end of 2021. To improve mitigation measures of thaw settlement, an inverted T-shaped crushed-rock pipeline embankment (ITCPE) is proposed in this study. The long-term thermal activity of three types of pipeline embankments is predicted and compared with the underground structure. This study finds that none of the current pipeline structures has solved the thaw settlement issue for the CRCOP, whether with insulation layers, in an unprotected pipeline embankment (UPE), or in a traditional horizontal crushed-rock pipeline embankment (THCPE). However, the cross-ventilation attained in the proposed approach did mitigate thawing. It is estimated that after 50 years of operation, the natural permafrost table will be 2.9 m deep, whereas the proposed ITCPE central pipeline embankment could maintain the artificial permafrost table at a depth of 0.7 m. This study provides technical support for the CRCOP and provides a reference for the design and maintenance of other pipeline projects in permafrost areas worldwide.

Analisa Penilaian Kondisi Jembatan Sarolangun Batang Tembesi Dengan Metode Bridge Manajemen System (BMS)

Bridges are an important part of a road network system because they have a significant impact if the bridge collapses or if it does not function properly. A bridge is a structure that crosses a river or other traffic barrier, so the collapse of the bridge will reduce or hold back traffic, which as a result will disrupt the comfort of the public in traffic and disrupt economic relations. A bridge is a structure that crosses a river or other traffic barrier, which as a result disrupts people's comfort in traffic and disrupts economic relations (Bridge Inspection Guidelines 2012). Bridges are built so that pedestrians, vehicle or train drivers can cross these obstacles. However, it turns out that there are many types of bridges which of course vary both in terms of structure, strength and even construction costs. The main components of a bridge are the unity of the road embankment structure approaching the bridge, the sub-bridge structure and the bridge super-structure (BMS, 1993). The main objective of this research is to analyze the condition of the Sarolangun Batang Tembesi Bridge by observing it visually, assessing the technical condition of the bridge, and determining the priority order for bridge maintenance based on its condition value. However, the database results produced in this bridge management system are only limited to screening and ranking results in preparing bridge management programs (Directorate General of Highways, Bridge Management Systems, (1993), "IBMS General Procedure Guide", BMS, Department of Public Works of the Republic of Indonesia.

Field forensic and numerical investigation of thermal stability of a permafrost-protecting granular embankment structure of asphalt-pavement expressways in cold regions

The traditional crushed-rock embankment (CRE) has proven to be one of the most successful cooling embankment structures during the operation of Qinghai-Tibet Railway. However, it remains untested whether or not traditional CRE can maintain stability of permafrost foundation under expressways under strong heat absorption of asphalt-pavement and climate warming. For the study, field tests were performed to evaluate cooling performance of traditional CRE in wider-width expressways. Then, A heat transfer model of the CRE was established, and a novel inverted “M”-shaped crushed-rock embankment (MCRE) was proposed. Finally, large numbers of numerical simulations were further performed to comparatively evaluate thermal behavior and cooling performances for both traditional CRE and novel MCRE in wider-width expressway construction. The study shows that (1) the expressway accelerates degradation rate of permafrost foundation under traditional CRE; (2) traditional CRE shows obvious sunny-shady slope effect, which cannot guarantee thermal stability of expressway; (3) the novel MCRE for the expressway increases the entry of cooling energy and therefore accelerates heat dissipation from the permafrost foundation; and (4) the novel MCRE improves long-term thermal stability of the expressway. The research could provide important technical reference for the construction of wider-width expressways in permafrost areas in the future.

Settlement Calculation Method for Peat Soil Foundations

The calculation of the settlement of a peat soil foundation is based mainly on the formula obtained by data fitting or simply modifying the universal calculation formula. The deformation mechanism reflected by these calculation methods is indistinct. Therefore, several model tests were carried out using the embankment structure of the Dali–Lijiang expressway as a prototype, and the settlement was analyzed with the one-way consolidation deformation and in situ settlement of other researchers. First, the S − logt (S is the deformation) curve of peat soil showed no obvious inverse “S” change, which is different from that of soft soil or mucky soil. According to the S − t curve, the deformation process of peat soil can be divided into three stages. Second, the relationship between the compression modulus and load was analyzed and combined with the settlement calculation results. The compressive modulus between 12.5 and 25 kPa [En(0.125–0.25)] was proposed to be used when calculating the settlement of peat soil foundations by the layerwise summation method. Moreover, the compression modulus of the three consolidation stages was proposed to be used to calculate the settlement of peat soil foundations by the layered sum method. At the same time, the influence of confinement on the compression modulus of the third consolidation stage should be considered and corrected. The accuracy of the settlement calculation method proposed in this paper was higher than the accuracy of the standard layerwise summation method, regardless of whether the horizontal limiting conditions of the standard method are modified.

Fragility assessment of highway embankment resting on liquefaction-susceptible soil

Fragility curve defines the probability of a structure exceeding a damage level for various levels of loading intensity. The present study presents a vulnerability analysis of a road embankment structure exposed to liquefaction-induced deformation due to earthquake loading. The numerical simulations are based on 2D finite element analysis considering liquefaction-susceptible soil as an elasto-plastic effective stress-based UBC3D-PLM model. The model parameters are developed through a calibration procedure with respect to the laboratory test results from past literature. The level of damage is described in terms of peak embankment settlement (PES) with increasing ground motion intensity (PGA). The fragility analyses have been carried out using an incremental dynamic analysis (IDA) considering a set of 9 different ground motions, which have been scaled to 16 different intensity levels. A wide range of parameters, including the relative density of liquefiable foundation soil, the geometry of the embankment, the thickness of the liquefiable layer, and the effect of densification on embankment response, have been considered in order to evaluate the vulnerability response of embankment subjected to liquefiable foundation soil. Study envisaged the relative density and thickness of liquefiable layer as primary and embankment geometry as secondary parameters having significant effect.

A Study on Methods to Enhance the Stability of Riverbanks in Seaport Areas

In the construction of irrigation structures, especially the wharf structures, it is important to learn about the deformation and damage of river banks in the wharf area. From assessing the stability of the river banks, a solution can be proposed to enhance the stability of the seaports, ensuring their safety during operation. Currently, the number of seaports located in soft soil accounts up to half the total number of seaports in Vietnam. The process of planning, designing, and constructing the foundation of the seaports is not optimized in Vietnam. Some seaports have uncounted problems when they are constructed on the soft soil. This paper aims to develop a method to reinforce the foundation of the riverbank so that the stability of the seaports can be maintained and any undesired deformation, or landslide, can be avoided. This method can help stabilize the structure that protects the seaports. The results obtained for the embankment structure with a stable wharf and a deep sliding with K=2.014 is larger than the allowable coefficient [K] = 1.25 in 22TCN 207-1992.

Simulating the thermal regime of a railway embankment structure on the Tibetan Plateau under climate change

With global warming and its amplified effect on the Tibetan Plateau, the permafrost on the Tibetan Plateau has been significantly degraded, manifested by decreased permafrost thickness, increased active layer thickness, thermokarst, and surface subsidence, causing severe damage to infrastructure. To better understand and assess the future stability of the Qinghai-Tibet Railway, we used a laterally coupled version of the one-dimensional CryoGrid3 land surface model to simulate the thermal regimes of the railway subgrade under current climate conditions. By modeling ground subsidence (i.e., by simulating the melting of excess ice) we provide estimates of future subgrade stability under low (Representative Concentration Pathway 2.6 [RCP2.6]) and high (RCP8.5) climate warming scenarios. Our modeled results reveal satisfactory performance with respect to the comparison of measured and modeled ground thermal regimes. Under current climate conditions, we infer that mostly thaw-stable conditions as maximum thaw depths do not reach the embankment base. The sunny side of the embankment (southeast-facing) reveals being more vulnerable to suffering from thaw settlement or thermal erosion than the shady side (northwest-facing). The extent of future railway failure due to thawing permafrost will depend on the magnitude of the warming. For conditions typical of Beiluhe (situated on continuous permafrost in the central Tibetan Plateau), the railway embankment might largely maintain safe operation until the end of the century under a scenario of climate stabilization. In contrast, under strong warming the railway subgrade is likely to destabilize from the 2030s onwards and embankment subsidence is initiated at mid-century through the melting of excess ice.

Thermal control mechanism of ventilated–closed block layer composite embankment of expressway in warm permafrost regions

This study reveals the thermal control mechanism of a ventilated–closed block layer composite embankment structure by analyzing the heat transfer and temperature change based on the measured data of the high-grade highway experimental engineering in the Beiluhe area of the Qinghai–Tibet Plateau. During the cold season, natural convection occurred in the block layer when the upper boundary temperature was approximately 2 °C lower than that of the bottom boundary. In addition, heat from the foundation was transferred upwards through the block layer via heat convection. During the warm season, air inside the block layer was almost static, and external heat was transferred downwards through the block layer via heat conduction. The equivalent thermal conductivity of the block layer in the cold season was approximately 17.4 times that of the warm season, and heat release through the block layer was 9.65 times that of heat absorption, exhibiting a thermal semiconductor effect. The results show that the frozen soil foundation was in net exothermic state, the permafrost table continuously rose, and the mean annual soil temperature continuously decreased above 14 m depth. This research can contribute to thermal control technology development and construction scheme selection of expressway in permafrost regions.

Evaluating the performance of a novel ventilated embankment structure in warm permafrost regions by numerical simulation

Conventional ventilated embankments are commonly used on the Qinghai-Tibet Railway to reduce embankment settlement. However, the shortcoming of these systems may make them unsuitable for the Qinghai-Tibet Expressway (QTE). The heat absorption area of expressways in cold regions is significantly larger than that of railways, which results in a rapid temperature rise of the embankment above the permafrost, which significantly reduces the stability of the embankments. To facilitate the cooling of the expressway, the authors designed a novel ventilated embankment (NVE) structure and studied its cooling capacity. The results indicate that the NVE has a remarkable cooling effect. At the same location, the ground temperature under the NVE is clearly lower than that under the normal embankment. Moreover, the intelligent control ventilation mode of the NVE, which compares the soil and air temperatures to determine when to open and close ventilation pipes, provides better cooling performance than conventional ventilated embankments. To optimize the cooling effect of the ventilated pipe and construction of the subgrade, the following ideal pipe layout method is proposed: the pipe diameter is 0.4 m, the pipe spacing is 2.4 m, and the burial depth of the pipe is 0.0 m. With a decrease in site temperature and an increase in embankment height, the maximum pumping distance of the NVE increases. These results establish a theoretical basis for the future application of NVEs in engineering.

Evaluation of the long-term thermal stability of a crushed-rock revetment embankment in pan-Arctic permafrost regions under the effect of snow drift

In the pan-Arctic region, snow drift events usually result in heavy snow accumulations on both sides of road embankment which severely affects the energy exchange process at the embankment slopes and further changes the temperature distribution in the embankment and its subsoil. However, there is a lack of research on the prediction of snow distribution patterns around the embankment, which makes it difficult to accurately assess the impact of snowdrift on the thermal stability of the embankment in permafrost regions, and the embankment structure cannot be reasonably optimized accordingly. Herein, using the theories of two-phase flow and heat transfer, a numerical model is developed to evaluate the long-term thermal stability of embankments with different structures under the effect of snow drift. The results show that snow deposition occurs at the toe of the windward side slope and the whole leeward side of the embankment under the effect of snow drift. If the side slope of the embankment is reduced from 1:2 to 1:5 (vertical:horizontal), the snow accumulations on both sides of the embankment are significantly reduced, and the subsoil refreezes more effectively in cold season. When a crushed-rock revetment embankment (CRRE) with 1:5 side slopes is used, the soil beneath the embankment is sufficiently cooled, the warming of permafrost beneath both sides of the embankment caused by snow accumulation is eliminated, and the temperature distribution in the embankment and subsoil has a good symmetry in warm season. The crushed-rock revetment is thus proved to be an applicable and effective structure to ensure the long-term stability of the embankment in pan-Arctic permafrost regions.

Regulating the albedo and radiation absorption of engineering surfaces for cooling the embankments in high-altitude permafrost regions

Under the influences of global warming and strong solar radiation, the construction of the wide high-grade roads in high-altitude permafrost regions becomes more challenging. To reach the challenges and further improve the thermal-mechanical stabilities of the permafrost embankment, this study proposes a novel cooling embankment structure based on the heat-reflective coatings. The principle is to reduce and regulate the solar radiation absorption by the permafrost embankment surface, thus improving the temperature field of the embankment and preventing uneven settlement and other freeze-thaw damages of the embankment. First, a theoretical-empirical model is proposed to describe the transfer processes of incident radiations on the pavement and slope surfaces. Based on the model, we carry out a systematic study of the main factors influencing the solar radiation absorption of the embankment surfaces and their variation patterns. By analyzing the calculation results, we propose the regulating schemes of the heat-reflective coatings for the radiation absorption balance of the embankment surfaces. Meanwhile, the solar albedo properties of the heat-reflective coatings under different solar spectral are also studied. The results indicate that the heat-reflective coatings can significantly reduce the solar radiation absorbed by the embankment surfaces. It proves that the cooling embankment structure and albedo regulation schemes proposed in this paper are expected to be applied in practical engineering. Finally, we discuss the shortcomings of the current research and the next research plans.

Impact Assessment of Asphalt Concrete in Geogrid-Reinforced-Pile-Supported Embankment During High-Speed Train Traffic

Railroad structural behaviour is a significant factor for safety and comfort during high-speed train operation. Intending to improve railway performance, increase its bearing capacity, and reduce vibrations induced by train passage, asphalt concrete has become a material to be integrated into railway construction. Despite several studies evaluating asphalt concrete effect on the railway mechanical behaviour, its impact assessment remains poorly understood. This study investigates the impact of asphalt concrete material in the geogrid-reinforced-pile-supported embankment structure subjected to high-speed train moving. A 3D nonlinear finite element model was developed to simulate Harbin (Dalian (China) instrumented railroad test section accurately. The high-speed train moving load was modelled as a transitory dynamic load via a user-defined subroutine 3D load in which the track irregularity is incorporated. The established model was effectively validated by the vibration acceleration and stress measured in the field test section. The asphalt concrete viscoelasticity behaviour was incorporated into the 3D geogrid-reinforced-pile-supported embankment finite element model through the Prony series to characterise its mechanical response better. The impact of asphalt concrete material in maintaining a low and constant structural vibration, regardless of train weight level, moving speed variations, and weather conditions were investigated, analysed and discussed.

Shaking table test research on shear behavior of cross-fault geosynthetics reinforced and pile-supported embankment

Severe damages are likely to occur to the cross-fault embankment under seismicity due to shear behavior caused by the fault relative displacement, which will inevitably affect the operation of the railway lines. Previous researches on seismic shear behavior of the cross-fault embankment are mainly based on numerical simulations. To study the seismic shear behavior of the cross-fault embankment experimentally, shaking table tests were performed on two types of scaled-embankment models: the first one is the through-facing-geosynthetics reinforced and pile-supported embankment (TRPE), the second one is the wrapping-facing-geosynthetics reinforced and pile-supported embankment (WRPE). In the tests, reverse seismic excitations were inputted to two adjacent shaking tables simultaneously to simulate fault movements. The test results show that the impact of strike-slip movement is greater than thrust movement, and their coupling effect aggravates the acceleration and deformation responses of embankment structure. Under seismic excitation and filing-step effect, pore water pressure increases especially in WRPE which aggravates the deformation of piles. The comparison of seismic responses of TRPE and WRPE show that the TRPE presents better seismic performance than WRPE in cross-fault zone. The WPRE is more cost-effective. To guarantee the safety of the WRPE in cross-fault zone, the length of geogrid in WRPE should be long enough.

Theoretical approaches for modeling and calculating the consolidation of a composite weak bottom

The paper considers analytical relationships for determining the effective operation of a unidirectional fibrous composite material. A simplified version of the effective operation of a composite material when a load is applied is presented. The data of theoretical calculations, confirmed by the experience of designing and building embankments on composite pile foundations, are given. A proposal has been made for the high efficiency of the use of pile technologies for the subgrade of fast and high-speed highways. The paper defines the prerequisites and prepares the initial data for modeling and calculating the main condition for the safety of the subgrade of high-speed highways – the fulfillment of the specified deadlines and the degree of consolidation of the weak foundation. The necessity is shown, and the area of ​​effective application of options for strengthening weak soils with pile structures is determined. An analysis of international approaches to the assessment of the stress-strain state of the subgrade base reinforced with composite pile structures has been carried out. It is shown that the applied analytical ratios for determining the deformation and settlement of the soil mass between piles do not take into account the dynamics of changes in the properties of the weak foundation of the subgrade of high-speed highways, are based mainly on empirical data and need to be corrected. For a detailed study of the processes of consolidation, five stages of the formation of the embankment structure of the expressway are distinguished, differing in the duration of execution and loads on the weak foundation.

Risk assessment of engineering diseases of embankment–bridge transition section for railway in permafrost regions

AbstractThe embankment–bridge transition section (EBTS) is one of the zones where railway diseases occur frequently in permafrost regions. Disease risk assessment of EBTSs can provide guidance for maintenance. In this study, considering the engineering geological conditions, climate characteristics, and embankment structure types along the Qinghai–Tibet Railway (QTR) as well as based on the disease inventory of the QTR from 2010 to 2019, the logistic regression (LR), support vector machine (SVM), and combination‐weight‐based gay relation analysis (GRA) were used for disease risk assessment of the EBTSs along the QTR in permafrost regions. The results indicate that the LR and SVM models have a better capability for EBTS disease prediction than the GRA model, and the SVM model can select more disease samples in relatively larger regions than the LR model. Based on the SVM and LR models, the risk level of EBTSs is divided into four classes: low‐ (29.9%), moderate‐ (39.6%), high‐ (22.1%), and very high (8.4%) risk. Finally, we selected 272 EBTSs in high‐ and very‐high‐risk classes for key observation during the maintenance of the QTR in permafrost regions. This study provides a reference for the risk assessment of railways built in permafrost regions using data‐driven methods.

EVALUATION OF BUND STABILITY USING GEOSTUDIO SOFTWARE WITH GROUND IMPROVEMENT METHOD USING SAND-KEY AT RECLAMATION WORK ON SOFT SOIL

The use of sand-key reclamation works in soft and very soft soils to increase the stability of the bund construction. Reclamation using the hydraulic fill method requires a stable embankment structure to withstand the potential for landslides from landfills, and in sea areas with very soft subgrade soils, with small undrained cohesion values causes the bund to be unstable and do not exceed the critical limit. The purpose of this study is to evaluate the improvement of soft soil in bund construction so that it is stable using GeoStudio. The Bund stability analysis results show that the value of the sand-key depth depends on the variation in the depth of the seabed. At a seabed depth of -6 m, there is a sand-key depth of 7 m, -5 m the sand-key depth of 10 m, -4 m thesand-key depth of 10 m, -3 m the sand-key depth is 5 m. The final safety number of 1.404,1.438,1,675, and 1.354 respectively.