Fill Slopes Research Articles

Flowslide on a fill slope triggered by a burst water pipe: a case history

This paper presents a case study in Hong Kong of a flowslide occurred on a fill slope triggered by a burst water pipe buried near the slope crest. The onset of failure was recorded by nearby pedestrians and the video was immediately posted in social media which had caught noticeable public attention. The flowslide resulted in a temporary closure of an undermined road section at the slope crest. The debris travelled over 500 m down the natural hillside within a country park. No casualties were reported. History of the site was studied. Information was collected to establish the chronological order of events happened before the flowslide. Post-landslide investigations including field mapping in the source area and along the debris trail, ground investigations, and a fluid-coupled numerical study were undertaken to examine the probable cause and mechanism of the failure. It is diagnosed that the high mobility of this landslide would be caused by the saturation of a loose fill layer in the slope due to water egress from the burst pipe which in turn might have triggered a static liquefaction of the loose fill. Lessons learnt from this case history and measures to minimize similar landslide hazard on other fill slopes with similar settings are discussed.

Three-dimensional stability of a fill slope reinforced by a frame beam anchor plate

The frame beam anchor plate is a new supporting structure reinforcing fill slopes. At present, only a few studies have evaluated its static stability based on the two-dimensional plane assumption. In this paper, the limit analysis method is combined with the three-dimensional spiral failure mechanism to evaluate the factor of safety (Fs) of a slope supported by a frame beam anchor plate. The pseudo-static approach is used to express the seismic effects. When calculating the internal energy dissipations, both the pull-out failure of anchor plates and tensile failure of tie rods are considered. The accuracy of the approach is verified by comparison with calculation results from the finite element method. Parameter analysis summarizes the influence law of each supporting structure design parameter on the Fs. Therefore, this study develops a theoretical basis for evaluating slope stability reinforced by frame beam anchor plates, which can better guide the design of slopes reinforced by this supporting structure.

Experimental Study on the Protective Effect of High Alcoholysis Polyvinyl Alcohol (PVA) Solution Spraying on Loess Fill Slopes

Loess has high water sensitivity and exhibits poor characteristics such as weak cementation and high porosity. Under heavy rainfall, loess fill slopes are prone to erosion and landslides, posing serious threats to public safety and property. In light of these serious threats, this study employed the method of spraying polyvinyl alcohol (PVA) solution to improve loess fill slopes and systematically examine its protective effects. Through field investigations and combined laboratory and outdoor tests, this study comprehensively evaluated the mechanical properties, anti-aging and anti-erosion performance of loess after PVA solution spraying. Scanning electron microscopy was used to reveal the mechanism of PVA action at the microscopic level. The results showed that after treatment with PVA solutions of varying concentrations, the mechanical properties of loess samples were significantly enhanced, while also exhibiting excellent anti-aging and water resistance performance. Additionally, PVA-treated loess fill slopes exhibited excellent rain erosion resistance. A microscopic structural analysis showed that PVA fills the internal pores of loess, strengthens inter-particle bonding, and uses its hydrophobic groups’ water-repellent action to effectively enhance slope stability and erosion resistance. In conclusion, PVA treatment not only significantly enhances the protective effects of loess fill slopes but also holds important value in improving soil sustainability and environmental protection.

Evaluation of the Efficiency of WARSEM Model and the Effect of Fill Slope Information on Changing the Model Results

Evaluation of the Efficiency of WARSEM Model and the Effect of Fill Slope Information on Changing the Model Results

Analysis of the Stability of a High Fill Slope under Different Gradients and Precipitation Conditions

The stability problem of high fill slopes has always been a research hotspot. Its failure mechanism is complex and prominent, featuring strong concealment, a short occurrence time and great harmfulness. In this paper, the stability of a high fill slope under rainfall conditions will be studied by using indoor tests, numerical simulations, etc. The study is based on a high fill slope in Yichang City. The evolution law of high fill slope stability under the maximum rainfall condition is revealed. The results show the following: The influence of moisture content on stress–strain curves is reflected in both the curve’s shape and the peak value of deviatoric stress. Under the constraint of confining pressure, the curve decreases and the peak value of deviatoric stress decreases with the increase of moisture content at the same confining pressure. The safety factor obtained by a rigid body limit equilibrium analysis and numerical calculation indicates that the safety factor for a 30° slope meets the requirements for slope stability evaluation and remains in a fundamentally stable state. An on-site investigation suggests that surface failure and shallow failure may be primary failure modes for this slope; therefore, it is recommended to implement slope protection measures. This study provides valuable references for similar high fill slopes.

Efficient optimization parameter calibration method-based DEM simulation for compacted loess slope under dry–wet cycling

Dry–wet cycles can cause significant deterioration of compacted loess and thus affect the safety of fill slopes. The discrete element method (DEM) can take into account the non-homogeneous, discontinuous, and anisotropic nature of the geotechnical medium, which is more capable of reflecting the mechanism and process of instability in slope stability analysis. Therefore, this paper proposes to use the DEM to analyze the stability of compacted loess slopes under dry–wet cycles. Firstly, to solve the complex calibration problem between macro and mesoscopic parameters in DEM models, an efficient parameter optimization method was proposed by introducing the chaotic particle swarm optimization with sigmoid-based acceleration coefficients algorithm (CPSOS). Secondly, during the parameter calibration, a new indicator, the bonding ratio (BR), was proposed to characterize the development of pores and cracks in compacted loess during dry–wet cycles, to reflect the impact of dry–wet action on the degradation of bonding between loess aggregates. Finally, according to the results of parameter calibration, the stability analysis model of compacted loess slope under dry–wet cycling was established. The results show that the proposed optimization calibration method can accurately reflect the trend of the stress–strain curve and strength of the actual test results under dry–wet cycles, and the BR also reflects the degradation effect of dry–wet cycles on compacted loess. The slope stability analysis shows that the DEM reflects the negative effect of dry–wet cycles on the safety factor of compacted loess slopes, as well as the trend of gradual stabilization with dry–wet cycles. The comparison with the finite element analysis results verified the accuracy of the discrete element slope stability analysis.

Effects of temporary erosion control blanket and grass cover on the rates of runoff and sediment in the cut and fill slopes of forest roads using a rainfall simulation test

Effects of temporary erosion control blanket and grass cover on the rates of runoff and sediment in the cut and fill slopes of forest roads using a rainfall simulation test

Time-dependent change of natural vegetation on forest road fill slopes and its effects on erosion decrease

Time-dependent change of natural vegetation on forest road fill slopes and its effects on erosion decrease

Stability Evaluation Method of High Fill Loess Foundation Based on Numerical Simulation

In order to understand the stability evaluation method of high fill loess foundation, the author proposes a study on the stability evaluation method of high fill loess foundation based on numerical simulation. The author first established a three-dimensional finite element model of a multi-level high fill slope using PLAXIS 3D software based on a loess high fill slope engineering project in a certain section of northwest China. The study investigated the effects of changes in fill materials, fill boundaries, slopes, and unloading platforms on slope stability. Secondly, based on the vertical and horizontal displacement of the top and foot of each level of slope under step-by-step filling, the distribution pattern of the most dangerous points of each level of slope and the overall deformation trend of the slope were analyzed. The results indicate that the cohesion and internal friction angle of the filling material are key factors affecting the stability of high fill slopes. Reducing the height of the steps at the boundary between the filling and the undisturbed soil, deepening the width of the steps, reducing the slope, and widening the unloading platform can all improve the stability of the slope. During the construction of lower slopes, there is a significant vertical displacement mutation, while the horizontal displacement mutation is relatively slow; After the construction is completed, the deformation situation is good, and the vertical and horizontal displacement of the higher slope during construction changes greatly, with uneven distribution; After the completion of construction, the consolidation settlement period is long and the deformation is large; Emphasis should be placed on strengthening deformation monitoring at high altitudes after construction is completed. Finally, the platform width can be selected within this range based on the actual engineering situation. After the platform width is greater than 3.6m, as sufficient platform width has been reached at this point, further increasing the platform width has little impact on the safety factor, and the curve gradually flattens out. The research results have determined the stability influencing factors, deformation trends, and development laws of loess high fill slopes in the northwest region, providing a scientific basis for further research on deformation control of loess high fill slopes.

Field study on vegetation eco-protection technology for red sandstone fill slope against water damage

The construction of fill slopes becomes a critical aspect when there is a need to change the terrain or create new terrain. However, due to the poor engineering properties of the fill material, especially when red sandstone with notable disintegration properties is used, the risk of slippage or collapse may occur. This material is prone to erosion and disintegration under the action of natural factors such as heavy rainfall, leading to severe soil erosion and slope instability. In addition, the construction of fill slopes inevitably causes the destruction of native vegetation, exacerbating environmental problems. To address these problems, an novel ecological approach for preventing water damage to red sandstone fill slopes was developed using the vegetation–high-performance turf reinforcement mat –anchor–drainage pipe–synergistic slope protection system. Three test red sandstone slopes with different protection methods (unprotected, three-dimensional (3D) protection mesh, and vegetation ecological protection system slopes) were constructed, and the feasibility and reliability of ecological protection against water damage to red sandstone fill slopes were analysed via the field test method. The results showed that the vegetation ecological protection system can effectively inhibit soil erosion and increase the survival rate of vegetation roots. Moreover, the the high-performance turf reinforcement mat provides a strong protective complex through interactions with vegetation roots, anchors, and drains, which significantly enhances slope stability. Under heavy rainfall conditions, the vegetation ecological protection system can effectively limit slope erosion due to water scour, thus maintaining the structural integrity of the slope.

Optimizing stability design of support system for the parallel tunnels excavation crossing a fill slope

Optimizing stability design of support system for the parallel tunnels excavation crossing a fill slope

Study on large scale direct shear test on soil-rock mixture with multiple grain grades in high fill slope engineering

Soil-rock mixtures are multiphase natural geological materials composed of mineral particles of multiple grain sizes, and have significant natural characteristics of multiscale material groups. In order to investigate the shear strength characteristics and deformation failure characteristics of soil-rock mixtures with multiple grain sizes under in-situ conditions in fill engineering, samples of soil-rock mixtures with multiple grain sizes under in-situ conditions were prepared, and large-scale in-situ direct shear tests were conducted under natural and water-soaked conditions. The test results showed that the shear strength of soil-rock mixtures is relatively high, and after saturated by water immersion, its shear strength decreases significantly, mainly manifested in the decrease of internal friction angle while the cohesion remains basically unchanged. The cohesion of soil-rock mixtures with multiple grain sizes is mainly provided by the shear-breaking cohesion of coarse particles such as gravel in the soil-rock mixture, and its degree of exertion is controlled by the grading characteristics and particle morphology of the soil-rock mixture and affected by constraints. The reason for the significant decrease in shear strength of soil-rock mixtures with multiple grain sizes after water-soaked saturation can be explained as follows: the clay film covering the surface of coarse particles becomes soft after water immersion, resulting in a significant decrease in the sliding friction resistance between coarse particles and the clay film, as well as the occlusion friction resistance generated by the rotation transfer between coarse particles through the clay film interface.

Most suitable plant communities for the slope reclamation of the Zhengzhou-Xinxiang section of the Beijing-Hong Kong-Macao expressway.

The construction of expressways in China has produced diverse habitats along slopes characterized by steep gradients, uneven water distribution, poor soil conditions, and no routine maintenance. Manually planting beneficial species is an essential method of effectively improving slope soils to prevent soil erosion. However, few studies have evaluated the reclamation effects and plant community composition and structure used to restore slopes along expressways. This study focused on the Zhengzhou-Xinxiang section of the Beijing-Hong Kong-Macao Expressway. A total of 10 representative plant communities were evaluated using the analytic hierarchy process (AHP)-fuzzy integrated evaluation method. The sites were divided into four layers, namely, plant communities, soil nutrients, soil physical properties, and other ecological factors, and 14 indicators were assessed. The evaluation results showed that four of these plant communities (PCs) were excellent, three PCs were good, one PC was normal, two PCs were poor. The four excellent PCs had high Shannon-Wiener index, pielou index, richness index or community productivity. It is worth noting that most excellent plant community structures were tree + shrub + herb. Based on these results, we recommend that fill slopes should be restored using a combination of trees, herbs, and shrubs; also, the vegetation should include native plants, such as B. papyrifera, U. pumila, A. fruticosa, and Cynodon dactylon (L.). This study could provide ideas for plant community composition and structure of new highway slopes in similar climate environment, and provide theoretical support for plant community composition and structure and soil improvement for the existing slope.

Stability analysis of loess fill slope supported by frame prestressed anchors considering tensile strength cut-off

In the stability analysis of loess fill slope, the fissure nature of loess is often ignored, which makes the stability calculation of fill slope too conservative. Based on the upper limit theory of plastic limit analysis, the stability analysis model of loess-filled fissured slope supported by frame prestressed anchors was established. Considering the tensile strength cut-off yield property of soil, the stability coefficient of slope was calculated, and the influence of different factors on slope stability was analyzed. The results show that ignoring the fissures in loess will overestimate the stability of the fill slope, and the support structure can significantly improve the stability of the loess-filled fissure slope. The research results of this paper can further enrich the stability analysis theory of loess-filled fissured slope supported by frame prestressed anchors, which is of great significance to guide engineering practice.

Lessons from the 2016 Kaikōura earthquake for design of cut and fill slopes in New Zealand

Lessons from the 2016 Kaikōura earthquake for design of cut and fill slopes in New Zealand

High fill slope collapse: Stability evaluation based on finite element limit analyses

The stability of high fill slopes, which are typically encountered when building airports in mountainous areas, is influenced by complex geotechnical profiles, the fill strength, reinforcement, and rainfall conditions. On 3 October 2009, a catastrophic landslide occurred at Panzhihua Airport in Sichuan Province, China. Investigations indicated that this event was attributable to the presence of carbonaceous mudstone. However, the overall stability of the high fill slope in different construction phases has not been explored. In this study, finite element limit analyses were performed to examine the overall stability of a critical section of the high fill slope in 11 cases that differed in terms of their strength parameters, reinforcement, and rainfall conditions. The results indicate that the original slope stability determined using parameters based on the laboratory shear tests of fill materials was overestimated. Furthermore, the original slope reinforcement with three rows of stabilising piles was ineffective. The safety factor of the pile-reinforced slope was computed to be 0.95 when rainfall infiltration was considered, and the predicted slip surface coincided with the actual failure surface. Random field limit analyses of this slope indicated that the failure probability increased under the assumed rainfall infiltration conditions. Remediation plans could ensure stability against landslides. Overall, reliable parameters and methods must be used to calculate the stability of high fill slopes.

Case study: 3D mobilized strength of compacted fill

Water infiltration can cause softening of compacted structural fill and a reduction of the shear strength from the peak compacted strength to the fully softened strength (FSS) with an accompanying reduction in drained factor of safety (FoS). This study presents two-dimensional (2D) and 3D stability analyses of a compacted fill slope failure that occurred 6 years after construction due to water leaking from a connection between the main and lateral water pipes in the water supply system. The compacted fill material primarily consists of high plasticity fine-grained soil. The 3D FoS at the end of construction is 2.44 using the peak compacted strength envelope. However, the 3D FoS is close to unity (1.0) when the FSS is assigned to the compacted fill material with the appropriate piezometric surface, which means the 2 H:1 V compacted fill slope softened to the FSS within 6 years. This is an interesting FSS case because the failure surface is 4 m deep and semi-circular, which differs from infiltration cases that exhibit a shallower and more planar surface.

Progressive deformation and failure mechanism of loess fill slopes induce by rainfall: insights from flume model tests

Progressive deformation and failure mechanism of loess fill slopes induce by rainfall: insights from flume model tests

Effect of bioengineering treatments on reduction of soil erosion from road cut slope and fill slope

Effect of bioengineering treatments on reduction of soil erosion from road cut slope and fill slope

Seismic Stability Limit Analysis of Unsaturated Soil Slopes Reinforced by Frame Beam Anchor Plates

The frame beam anchor plate (FBAP) reinforced slope has been popularized and applied in some fill slope projects. Nevertheless, the existing design method ignores the influence of earthquake action and the suction effect of unsaturated soils. The stability of unsaturated soil slopes reinforced with FBAPs under an earthquake is analyzed based on the upper bound theorem of limit analysis and pseudo-dynamic method to solve the above problems. The influence of the suction effect on the effective weight and strength of unsaturated soils under one-dimensional steady seepage conditions was considered in the derivation of the energy balance equation. A simplified method based on the volume integral of the rotating body is used to calculate the external work rate. Two possible failure modes of anchorage structures are considered when solving internal energy dissipation. Results show that the influence of suction and seepage conditions on slope stability decreases with the increasing soil pore size distribution parameter n and saturated hydraulic conductivity ks. Also, the stability of the slopes is significantly improved with the increase of total rows of anchor plates. Likewise, the stability of slopes decreases with the increase in the horizontal seismic coefficient kh and amplification coefficient fa.