Embankment Collapse Research Articles

ТЕОРЕТИЧЕСКОЕ ОБОСНОВАНИЕ ТРАНСПОРТЕРА ДЛЯ ВЫГРУЗКИ КОРНЕПЛОДОВ ОВОЩНЫХ КУЛЬТУР И КЛУБНЕЙ КАРТОФЕЛЯ ИЗ ХРАНИЛИЩА

The need to develop specialized machines and equipment for laboratory and field research on potato breeding is due to the fact that the methodology of breeding processes and the first stages of seed production involves comparing many plants of different origins and selecting the best for further work up to the creation of a new variety or transfer of seeds for propagation in production conditions. The large variability of machines for unloading vegetables and potatoes does not adequately prevent damage to vegetable and potato products, which is due to the imperfect design of such machines, including the imperfection or absence of patterns of automated control of the technological process of work and justification of the parameters of their working parts. The purpose of the study is to substantiate the parameters of the conveyor for unloading vegetable crops and potatoes into storage and to determine the patterns of formation of the control signal of the transfer function of automatic control of operation. The power required to move the pick-up depends on the maximum pressure force of introducing the intake element into the embankment, the mass of the pick-up and the rolling resistance coefficients of the running wheels of the pick-up and transport sections. The length of the unloading conveyor of the machine is determined by the reserve zone to prevent wheels from hitting the tubers, their maximum difference in the embankment, the height of the layer, as well as the angle of inclination of the unloading conveyor. The width of the conveyor belt for unloading products from storage is determined by the values of the coefficient of friction of root crops on the surface of the belt, the coefficient of working time utilization and the forward speed of the conveyor belt. After removing the collapsed mass of tubers, the line of crumbling slopes and the limiting equilibrium are a straight line, characterized by an empirical equation for determining the coordinates of the tuber collapse point, the height of the tuber layer and the embankment collapse coefficient. When the feeder tubers are introduced into the surface of the embankment, the formation of slopes occurs in four stages: the formation of a natural slope, a limiting equilibrium slope, a shedding slope and a product collapse slope.

Deformation Pattern and Failure Mechanism of Railway Embankment Caused by Lake Water Fluctuation Using Earth Observation and On-Site Monitoring Techniques

The prediction of railway embankment failure is still a global challenge for the railway industry due to the complexity of embankment failure mechanisms. In this work, the pre-failure deformation and the settlement from abnormal deformation to the final failure were investigated based on earth observation and on-site monitoring with a focus on the deformation stage and failure mechanism of railway embankments. Some new viewpoints are suggested: (1) the differential settlement of ~19 mm revealed via InSAR at the failure region of the embankment may have been caused by internal erosion after rapid drawdown. The cumulative settlement was found to increase with the decline of the lake water level. (2) The railway embankment experienced three phases of primary, secondary, and accelerated creep phases, similar to the evolution of most landslide or dam failures. However, the train loading and seepage force may have aggravated the secondary consolidation, promoting the embankment to enter the accelerated creep phase quickly. The deformation pattern was presented as an exponential curve trend. (3) The formation mechanism of embankment collapse can be summarized as “seepage failure-creep-shear slip-collapse” failure under repeated train loading and rapid drawdown. This work provides some clues for early warnings and for the development of maintenance plans.

The Stability of Sidoarjo Mud Volcano Embankment Induced By The Excess Pore Water And Mud Pressure Based On Numerical Simulation

Sidoarjo mud volcano is a geology phenomenon which is the worst in terms of disaster to the people and environment. This is partly due to the overpressure at depth and as well as the cracks and fracture existence. Furthermore, the overpressurization impacts the increasing of pore water pressure and causing the reduction of effective stress. The complexity of the subsurface’s physical condition causes the instability of the embankment. This paper presents the evaluation of the stability of the embankment under the ideal and the presence of subsurface pressure conditions. The numerical simulation using Plaxis 2D has been conducted to determine the change of pore water pressure due to subsurface pressure and the safety factor of an embankment. The results show the subsurface pressure impact the increasing of pore water pressure around 208 kPa consequently. It reduces the safety factor around 4-30% from the ideal condition. The safety factor of embankment in the existing condition is still less than the minimum requirement which is 1,5 in both modeling conditions. The embankment collapse was caused by the landslide that leads upstream of the embankment as the effect of the tendency of upstream side landslides that is greater than the downstream side.

Experimental and DEM-CFD Coupling Investigations on the Characteristics and Mechanism of Seepage Erosion for Cohesionless Soil

Seepage erosion is one of the main reasons for the local collapse or instability of embankments. To investigate the characteristics and mechanism of seepage erosion for cohesionless soils, model tests using an independently developed seepage erosion device and numerical simulations based on a discrete element method-computational fluid dynamics (DEM-CFD) coupling model were carried out. The results show that the seepage erosion process of cohesionless soil could be characterized by four stages: stable seepage, upward migration of fine particles, boiling of sand samples, and erosion damage. The skeleton structure of a soil sample under seepage flow was continually changed due to the loss of fine soil particles, which resulted in a significant decrease in the sample strength and could, ultimately, lead to the failure of the sample. The results of this study can provide references and bases for the design, construction, and long-term service of embankments or earth dams under complex seepage conditions, reducing the risk of seepage erosion.

Influence of deep-cement-mixing column rows on the performance of geosynthetics-reinforced column-supported railway embankment

Knowledge regarding the stability of geosynthetics-reinforced column-supported railway embankment (GRCSE) on soft foundation is of great significance for transportation infrastructure safety design, and deep-cement-mixing (DCM) columns constructed under the toe of an embankment is used to improve the performance of GRCSEs. This study conducted two centrifuge model tests to simulate the failure of a constructed embankment in a 40-g environment. The failure mechanism of each component in the GRCSE system and the effect of additional DCM column rows near the embankment toe on the GRCSE performance were analysed. The particle image velocimetry (PIV) technique was used to draw further insights from the results. The tests revealed that a failed column within the GRCSE system led to the progressive failure of adjacent columns, coupled with the progressive and retrogressive propagation of shear strains in the soft soil, which resulted in embankment collapse. The addition of DCM column rows near the embankment toe reduced the local shear strain accumulation in the soft foundation and thus improved the overall stability. The incremental tensile strain of the geosynthetic reinforcement in various phases was different in the cases with and without additional DCM column rows. Moreover, the effects of various factors of DCM rows, including row number and length, on the GRCSE stability were numerically analysed.

Laboratory Study on Entire Range Suction Measurement and Microstructure Change of Granite Residual Soil

The shear strength of unsaturated granite residual soil (GRS) will decline rapidly when moisture content increases, because of loss of matric suction in the soil. This can lead to slope instability and embankment collapse during rainfall. Determining the matric suction of GRS accurately at different conditions can improve the accuracy of stability analysis. Generally, matric suction can be characterized as the soil–water characteristic curve (SWCC), and it is closely related to soil microstructure. In this study, the entire range of matric suction was measured using a combination of pressure plate method, filter paper method, and vapor equilibrium method. Microstructure change was investigated based on mercury intrusion porosimeter tests, in which the pore size distribution (PSD) curves of GRS samples with different initial densities and moisture content were measured. The PSDs of samples before and after wetting were also measured and compared to investigate the influence of water intrusion. Test results indicate that the combination of measurement methods can cover the entire matric suction range. The microstructure of GRS with different initial conditions presents a clear bimodal PSD. At the same density, the increase in initial moisture content can increase intra-aggregate pores and decrease inter-aggregate pores. When initial density increases, only the volume of inter-aggregate pores decreases. Wetting can decrease inter-aggregate pores and increase intra-aggregate pores. Finally, the Li model is applied in SWCC fitting for tested samples, the result of which performs well with a high correlation coefficient (R2 > 0.95) and is recommended for GRS analysis.

Study on the Mechanical Properties of Flexible Prefabricated Highway Structural Systems considering the Effect of Two-Way Fluid-Structure Interaction

The rainfall often causes changes in the physical performance of the embankment, which leads to disasters such as embankment collapse and road surface settlement and cracking. Past research has tended to be limited to traditional embankment seepage models and is mostly based on the assumption that surface precipitation is uniform and rainfall intensity is constant. To adapt to the changes and development of the times, based on the water leakage mode of the flexibly assembled highway embankment, a new rainfall calculation model of the reinforced soil embankment is constructed and combined with the solid-fluid coupling physics theory, the sedimentation amount and slope stability of the embankment are analyzed at multiple levels, the mechanical properties of the new embankment under rainfall conditions are summarized, the factors affecting the settlement of the embankment and the stability of the slope are explored, and the reference model is provided for the construction of the new embankment, and the existing construction process is improved through multilevel cause analysis. We improve and develop the existing theoretical system to reduce the probability of road diseases, improve the efficiency of road construction, and reduce the cost of road maintenance.

Characterizing the river migration process based on migration events of individual bends: a case study of the lower Yellow River, China

Frequent channel shifts in the Lower Yellow River easily leads to embankment collapse causing geomorphological processes necessary to characterize. This paper segmented the river centreline from its component unit-bends and established a migration event model to characterize the migration process of rivers. The inflection points on the river centreline can be used to segment individual bends. Three types of migration events, disappearance, lateral migration and decomposition, are defined for the first time to categorize river migration. Furthermore, these migration events can be rapidly detected using the Meander Migration Index. The four-tuple BMModel (Bend Migration Model), including events, spatial positions, bend types and migration attributes, systematically quantifies the river migration process. In addition, these results can be implemented with an integrated PyBend (Python-Bend migarition) package, providing promising technical support for the studies of river migration and evolution over long time series.

Disturbance legacy of a 100-year flood event: large wood accelerates plant diversity resilience on gravel-bed rivers.

Understanding biodiversity resilience after a major disturbance is a key issue in basic and applied science. Plant diversity in gravel-bed rivers is affected by flood events, which are one of the most effective disturbance agents in the flow regime, affecting species distribution, and ecosystem dynamics. Although disturbance plays a critical role in community assembly mechanisms, how plant diversity recovers after a severe disturbance, such as a 100-year flood event remains unknown. The present study examined how the disturbance legacy of large wood in gravel-bed river ecosystems contributes to the resilience of plant diversity. The present study demonstrated that the resilience of plant species in disturbance legacy sites, namely deposited large wood sites, was higher than that in open habitat sites. Indicator species analysis revealed that perennial plants were the most important indicator species of disturbance legacy sites. These results suggest that perennial species richness contributes to the resilience of high plant diversity across the disturbance legacy sites in this region. After major flood events, land managers often remove large wood and debris jams to avoid secondary disasters, such as embankment collapse. However, we suggest that large wood should be retained on the gravel beds to aid the recovery of biodiversity and ecosystems. Furthermore, understanding the relationships between disturbance legacies and ecosystem resilience can contribute to the formulation of strategies for sustainable ecosystem management and biodiversity conservation in the future.

Collapse test studies on coarse grain sulfite saline soil as an embankment fill material

For the construction of roads in coarse-grained saline soil areas, coarse-grained sulfite saline soil is often used as an embankment fill material because of the limited choice of local embankment fillers. Because the NaCl in coarse-grained sulfite saline soil dissolves easily in water, when coarse-grained sulfite saline soils are used as embankment fillers, it can easily cause embankment collapse deformation when it meets water. The main objective of this study was to clarify the collapsibility properties of coarse-grained sulfite soils as embankment fillers; the relevant parameters concerning coarse-grained sulfite soils as embankment fillers were provided for embankment engineering. First, through the artificial preparation of typical coarse-grained sulfite saline soils, collapse tests under different salt contents, different initial moisture contents, different initial compaction degrees, and different particle gradations were carried out. Second, natural coarse-grained sulfite saline soils were selected to carry out the collapse tests, and the results were compared with the results of the above-mentioned collapse tests. The results showed that the higher the sulfite content in coarse-grained soil was, the greater the amount of collapse was. A larger embankment compaction degree had a good inhibitory effect on the collapse deformation. The collapsibility of coarse sulfite soils was less relatively when the soil water content was between 100% and 133% of the optimum water content, the compaction degree was 93%, and the soluble salt content was less than 2%. For coarse-grained sulfite saline soil, the larger the proportion of coarse particle was, the smaller the collapsibility ratio was.

Influence of geosynthetic reinforcement on the stability of an embankment with rigid columns embedded in an inclined underlying stratum

Incompressible dipping substrata are commonly encountered in engineering practice. Compared to horizontal underlying strata, the inclined underlying stratum increase the risk of collapse of embankments reinforced with columns because it weakens the restraint of the column base. The objective of this study is to investigate the effectiveness of geosynthetics on improving the embankment stability when the underlying stratum is inclined. The influence of geosynthetic tensile stiffness on the ultimate surcharge and failure mechanism is studied. A deep-seated failure with column tilting occurs when the geosynthetic tensile stiffness is low, whereas a lateral sliding occurs when the geosynthetic tensile stiffness is high. To illustrate the contribution of geosynthetics, the distribution of the lateral pressures acting on the columns is analyzed.

Internal Erosion Failure of Uniform Sands under Confinement and Constricted Seepage Exit

Seepage water may move soil particles and cause internal erosion of soils, leading to sinkholes and the collapse of embankments and slopes. To account for the effects of confinement and constricted seepage exit, a test apparatus was developed to study the internal erosion of granular soils under various confining pressures, particle sizes, and sizes of the seepage exit opening. As indicated in the literature, the behavior of internal erosion has been largely studied by laboratory experiments and field investigations, and mechanical models that help describe the failure mechanism of internal erosion are less prevalent. A hydro-mechanical model that incorporates the fluid drag force and the shear strength of soil was therefore developed for quantifying the internal erosion experiments conducted in this study. The experimental results showed that the greater the confining pressure or the particle size, the greater the critical velocity; the greater the seepage exit opening, the smaller the critical velocity. The critical velocity predicted by the proposed hydro-mechanic model compares reasonably well with the experimental data. In addition to the confining pressure, particle size, and size of the seepage exit opening, the proposed model also showed that the friction angle and porosity of the soil are factors influencing the critical velocity, which is consistent with the experimental findings of this study.

Base Soil Reinforcement with Vertical Crushed Stone Columns in Cryolithozone

Stabilization of permafrost soils of the roadbed base, constructed with assumption of thawing, thanks to improvement of their strength characteristics, requires development and selection of rational structural and technological solutions. The objective of the study was to analyze the effectiveness of use of vertical columns of crushed stone in the permafrost zone and their influence on strength characteristics of the soil base. The study has used general scientific methods, modeling, simulation and comparative analysis. This article proposes a method for improving strength properties of soil of the roadbed base within Obskaya–Salekhard section of the Northern Latitudinal Railway thanks to reinforcement of the roadbed base made with vertical columns of crushed stone, which increases stability of the structure. The proposed basic technological model of construction of the roadbed includes the following main stages: preparatory stage, 1 stage – arrangement of vertical columns of crushed stone and granular subbases, 2 stage – additional compaction with a vibratory roller in case of mismatch of stability of bearing capacity and precipitation of the base to operating standards. The studied object of the transport infrastructure was simulated both without the use of technology for reinforcing it with vertical columns of crushed stone and with its use. The stability coefficient was calculated, and the theoretical surface of embankment collapse was obtained using Midas GTS NX and Plaxis 2D software packages. The stability test of this structure was carried out both in a flat and in a threedimensional setting. The efficiency of using vertical columns of crushed stone to strengthen the embankments constructed on permafrost soils has been shown.

The strain energy development on subsoil-embankment because of seismic wave direction

The strain energy is associated with seismic embankment resistance and it needs more examine for understanding types of embankment collapse owing to the morphology of nonlinear deformation occurrence on the subsoil-embankment because of the applied seismic wave at different directions. In this study, a numerical simulation was performed to assess the strain energy function on subsoil-embankment because of the seismic wave in different directions. The seismic wave of three directions separately numerically was applied on the embankment-subsoil model and the strain energy development at each model was compared. This type of embankment seismic design has not been described in the literature by means of ABAQUS, for assessing the embankment seismic failure mechanism. The results reveal that the strain energy morphology associated with the direction of the seismic wave controls the failure mechanism of the subsoil-embankment. The direction seismic wave could be produced strain energy up to 10%, and this strain energy causes the morphology of nonlinear deformation of the model. The founding of this simulation is supportive in understanding a relationship between strain and seismic wave types of embankment collapse.

On the methods of risk evaluation for embankment collapse

On the methods of risk evaluation for embankment collapse

Coupled DEM-CFD Analysis of the Initiation of Internal Instability in a Gap-Graded Granular Embankment Filter

Internal instability is a form of internal erosion that can occur in embankment dams or flood embankments where the finer fraction of the material is washed out under the action of seepage flow; if undetected this process can progress to cause embankment collapse. Gap-graded materials are particularly susceptible. Skempton and Brogan [1] proposed that a key contributor to instability is the reduced stress transmitted by the finer fraction and that the magnitude of this reduced stress could be inferred from the hydraulic gradients observed at the initiation of particle migration in experiments. Here Skempton and Brogan’s hypothesis is assessed at the particle scale using a discrete element method (DEM) model coupled with computational fluid dynamics (CFD). This contribution discusses validation of the coupled DEM-CFD software prior to describing the simulation of a permeameter experiment. The simulation generated particlescale data at the initiation of instability by considering a gap-graded sample subject to at a hydraulic gradient of 1.0 (upward flow). The results provide insight into the instability mechanism, most notably showing that while the particles that move under seepage flow do indeed transmit relatively small effective stress, a finite proportion of the particles that move transfer relatively large stresses.

노후 코어형 필댐의 잠재 위해성 유형 분류

최근 국내 필댐 및 저수지의 노후화가 급속도로 진행되고 있으며, 이에 따른 제체의 손상이나 붕괴사고가 잇따르고 있다. 그러나 필댐의 핵심적인 차수기능을 담당하는 코어층에 대한 열화와 잠재 위해성 분류에 대한 연구는 거의 미진한 실정이다. 본 연구에서는 노후화가 진행 중인 13개 기존 코어형 필댐에 대해(준공 후 경과년수 9-52년, 댐 높이 22-67 m), 무수보링에 의한 코어층 시추 지반조사와 표준관입시험, 2D 및 3D 전기비저항탐사, 물성·역학시험을 수행하여 공학적 기반의 잠재적 위해성 유형을 국내 최초로 분류, 제시하였다. 중심코어층에 대한 무수보링 시추 지반조사 결과, 코어재 잠재 위해성 유형을 국부적 포화대, 신속한 공내수 유입, 조립질 혼재 코어재, 상대적 저 강성의 네 종류로 분류하였다. 코어형 필댐의 잠재 위해성 유형 중국부적 포화대 유형은 코어존 내 유로의 성장 및 발달에 의한 내적침식의 가능성이 존재하므로 가장 위험한 위해성으로 분류 되었으며, 코어재의 열화 등급에 따라 적절한 차수능 회복을 위한 보수보강이 필요한 것으로 판단되었다. 그 외 세 가지 위해성 유형은 즉각적인 조치보다는 지속적인 모니터링과 정기 검사의 강화가 필요할 것으로 검토되었다. 본 연구대상 댐의 분석 결과, 준공 후 경과년수와 댐 코어재의 열화 양상과는 상관성이 크게 없는 것으로 나타났다. 본 연구 결과는 코어형 필댐의 노후화에 따른 댐의 안전관리와 성능개선에 있어 유용한 자료로 활용 가능할 것으로 판단된다. As greater numbers of fill dams and reservoirs become old, the risks of damage or embankment collapse increases. However, few studies have considered the deterioration and hazard classification of the internal core layers of fill dams. This study reports the results of geotechnical investigations of 13 earth-cored fill dams in Korea, based on no-water borehole drilling, Standard Penetration Test, and 2D and 3D electrical resistivity surveys along with in situ and laboratory testing. High-capacity no-water boring minimized core layer disturbance while providing continuous core sample recovery. The results allow the classification of potential hazards related to the existing core layers based on both visual inspection of the recovered samples and the results of engineering surveys and tests. Four types of potential hazard are classified: locally fluidized core with a high water content, rapid water inflow to a borehole, cores with granular materials, and relatively low stiffness of core. Among these, the locally fluidized core is the most critical hazard that requires remedial action because it is related to the potential internal flow path and internal erosion. The other three hazard types are of medium importance and require careful monitoring and regular inspection. Of note, there was no correlation between age and core deterioration. The results are expected to aid the safe management and potential upgrading of aging cored fill dams.

東北地方太平洋沖地震における火山灰質盛土被害の分析

東北地方太平洋沖地震における火山灰質盛土被害の分析

Change in the hydromechanical characteristics of embankment material due to compaction state conditions

In recent years, earthquakes and heavy rains have frequently caused soil embankments to collapse. In order to prevent the collapse of embankments, it is well known that sufficient compaction and drainage control are necessary. Although numerous research findings have described compacted soils, compaction management has been essentially based on simple parameters such as dry density, degree of saturation or air content. It is important for the construction of a stiff embankment that the effect of compaction condition on the mechanical properties and inherent anisotropy of compacted soil should be recognized in detail. In the present study, the relationships between the compaction condition and the mechanical properties obtained from laboratory tests using saturated specimens are presented. Specifically, undrained monotonic and cyclic shear strength, shear modulus, and permeability are reported. The arrangements of soil particles were also observed with a microscope. From the observation of fabric characteristics of soil particles, an inherent anisotropy of compacted soil is discussed. Furthermore, a conceptualization of the relationship between the fabric of soil particles and the mechanical characteristics for each compaction condition is suggested.

実験的検討による地震後の降雨による盛土崩壊メカニズムについて

地震後における盛土の降雨耐力低減メカニズムを把握するため，振動台で加振した模型盛土を用いた散水実験および三軸試験装置を用いた単調載荷時の任意の軸ひずみの時点での変水位透水試験を実施した。本模型実験条件の範囲では，加振終了後ののり肩部の鉛直変位が大きい場合には，加振が無い場合の60%程度の累積降雨でのり面に変状が発生した。また，加振によってクラックが発生した実験ケースでは，間隙水圧増分が局所的に大きくなることを確認した。一方，変水位透水試験では，載荷履歴の有無や載荷時のひずみの大きさが透水係数に与える影響は小さいことがわかった。以上の模型盛土実験および変水位透水試験の結果から，加振による変状の程度によっては，加振履歴が無い場合と比較してクラックが主たる要因となって透水性が高くなり，散水中の水位上昇速度が速くなると考えられる。