Fill Slopes Research Articles

Analysis on Instability of a High Fill and Deep Excavation Loess Slope

High filling and excavation of loess landslide happens more frequently, which serious impact on security of the project, but formation mechanism of the landslide is still not perfect, therefore this paper analyze from damage characteristics and influence factors of slope stability to evaluate its stability and summary such failure mode. Conclusion: ① The root cause of the formation of class landslide: the lithology of compacted layer is different from upper loose soil, and the clay is unevenly distributed, which lead to local shear strength lower ② Rainfall is the main predisposing factors of slope instability, which infiltrates slope, the weak surface throughout the entire slope.③ Failure mode is similar to the general loess landslide, but the position of slipping surface is more regular

Dynamic tensile cracking in slopes possibly induced by Rayleigh surface waves

The 1978 Miyagi-ken-oki earthquake generated crack openings in fill slopes in Sendai, Japan. Although the slopes were reinforced with steel pipe piles after this event, tensile cracking was induced again in the same slopes by the 2011 off the Pacific coast of Tohoku earthquake. This clearly indicates conventional countermeasures against dynamic slope failures, usually based on body wave interaction with slopes, are not always effective. Considering that similar open cracks in the top surfaces of slopes were also found in New Zealand and California, we may need to clarify the generation mechanism of such cracks with some new insights. Recently, it has been indicated that the effect of Rayleigh surface wave propagation on dynamic slope stability may become significant. In this contribution, therefore, by performing two-dimensional elastodynamic analyses of Rayleigh/body wave interaction with a geometrically simple model slope, we show Rayleigh waves may play a more dominant role than body waves in generating the open cracks, and emphasise the importance of taking into account the dynamic slope failures induced by Rayleigh waves. Surface waves may be produced also by nearby blasting, etc., and therefore, the results obtained here may be of crucial importance in comprehending the dynamic stability of slopes in general.

Energy approach to seismically induced slope failure and its application to case histories — Supplement

In the previous paper, an energy approach was applied to actual cases of seismically induced slope failures to back-calculated mobilized friction coefficients using gross earthquake energies at individual slopes. In this supplement, based on an observation in a simple shaking table test, the earthquake energy, not the gross energy but a part of it driving soil mass in downslope direction has been identified, and employed to reevaluate individual slopes using nearby acceleration records. It has been found that the reevaluation decreased the earthquake energy to a quarter of the gross value on average. Accordingly, it has significantly reduced the back-calculated friction coefficients for natural slopes and manmade fill slopes for small volume failures in particular, though correlations of the friction coefficient with pertinent parameters for slope failures are qualitatively unaltered.

A novel computational approach for large deformation and post‐failure analyses of segmental retaining wall systems

SUMMARYSegmental retaining wall (SRW) systems are commonly used in geotechnical practice to stabilize cut and fill slopes. Because of their flexibility, these systems can tolerate minor movements and settlements without incurring damage or crack. Despite these advantages, very few numerical studies of large deformations and post‐failure behavior of SRW systems are found in the current literature. Traditional numerical methods, such as the finite element method, suffer from mesh entanglement, thus are unable to simulate large deformations and flexible behavior of retaining wall blocks in SRW systems. To overcome the above limitations, a novel computational framework based on the smoothed particle hydrodynamics (SPH) method was developed to simulate large deformations and post‐failure behavior of soils and retaining wall blocks in SRW systems. The proposed numerical framework is a hybrid continuum/discontinuum approach that can model soil as an elasto‐plastic material and retaining wall blocks as independent rigid bodies associated with both translational and rotational degrees of freedom. A new contact model is proposed within the SPH framework to simulate the interaction between the soil and the blocks and between the blocks. As an application of the proposed numerical method, a two‐dimensional simulation of an SRW collapse was simulated and compared to experimental results conducted under the same conditions. The results showed that the proposed computational approach provided satisfactory agreement with the experiment. This suggests that the new framework is a promising numerical approach to model SRW systems. Copyright © 2014 John Wiley & Sons, Ltd.

가드레일에 차량 충돌 시 성토사면의 거동분석

가드레일에 차량 충돌 시 성토사면의 거동분석

The state-of-the-art centrifuge modelling of geotechnical problems at HKUST

Geotechnical centrifuge modelling is an advanced physical modelling technique for simulating and studying geotechnical problems. It provides physical data for investigating mechanisms of deformation and failure and for validating analytical and numerical methods. Due to its reliability, time and cost effectiveness, centrifuge modelling has often been the preferred experimental method for addressing complex geotechnical problems. In this ZENG Guo-xi Lecture, the kinematics, fundamental principles and principal applications of geotechnical centrifuge modelling are introduced. The use of the state-of-the-art geotechnical centrifuge at the Hong Kong University of Science and Technology (HKUST), China to investigate four types of complex geotechnical problems is reported. The four geotechnical problems include correction of building tilt, effect of tunnel collapse on an existing tunnel, excavation effect on pile capacity and liquefied flow and non-liquefied slide of loose fill slopes. By reporting major findings and new insights from these four types of centrifuge tests, it is hoped to illustrate the role of state-of-the-art geotechnical centrifuge modelling in advancing the scientific knowledge of geotechnical problems.

経験的サイト増幅・位相特性を考慮した強震動評価手法に基づく既往の大規模地震における宮城県白石市緑が丘団地での強震波形の推定

経験的サイト増幅・位相特性を考慮した強震動評価手法に基づく既往の大規模地震における宮城県白石市緑が丘団地での強震波形の推定

Influence of soil nail orientations on stabilizing mechanisms of loose fill slopes

Soil nailing has been used to upgrade substandard loose fill slopes in Hong Kong. Due to the possibility of static liquefaction failure, a typical design arrangement comprises a structural slope facing anchored by a grid of soil nails bonded into the in situ ground. Numerical analyses have been conducted to examine the influence of soil nail orientations on the behaviour of the ground nail–facing system. The results suggest that the use of steeply inclined nails throughout the entire slope could avoid global instability, but could lead to significant slope movement especially when sliding failure prevails, for instance, due to interface liquefaction. The numerical analyses also demonstrate that if only subhorizontal nails are used, the earth pressure exerted on the slope facing may cause uplift failure of the slope cover. To overcome the shortcomings of using soil nails at a single orientation, a hybrid nail arrangement comprising nails at two different orientations is proposed. The numerical analyses illustrate that the hybrid nail arrangement would limit slope movement and enhance the robustness of the system.

The Fitting Analysis of the Miscellaneous Filled Slope Deformation Monitoring

In this paper, through the analysis of miscellaneous fill slope horizontal displacement of supporting structure and the vertical displacement monitoring results, the simulation results are compared and analyzed with FLAC3Dsoftware, verify the support form the deformation in the controllable range, the actual monitoring data and simulation results in the difference between the standard allows range, fitting deformation curve can be used as a conventional deformation monitoring based on integral deformation analysis, advanced demonstration of engineering construction scheme optimization.

Analysis of Protection Engineering for High Slope in Western Henan Province

Multistage discharge gentle slope combined with wide platform was adopted in the protection for high slope of highway in loess area, but vertical slope was often adopted at construction engineering of high slope as there was no enough site space for step-slope under the construction of urbanization in the western loess region of Henan province. A typical loess high slope in Lingbao city was taken to discuss the prevention measures for upright loess high slope. Design parameters for slope protection was given in detail, approach on the control plan for deformation has both excavation slope of 35m high and fill slope of 30m high. While reinforcement scheme of anchor cable plus stiffened-cylindrical was used in slope protection, the reinforced retaining wall was used to support the filling slope, in addition, loess slope management must be prepared to slope drainage design and construction.

Seismic Performance Analysis of Fill Slope with Pre-Stressed Anchors

Pre-stressed anchors were widely used to strengthen slopes, in this passage the dynamic responses of fill slope with pre-stressed anchors under the effect of seismic load were simulated by ANSYS program. And it was mainly analyzed the effect of pre-stress anchors on seismic performances of slope under general earthquake. The results indicate that changing the value of pre-stress has little effect on slope deformation, but has larger effect on stress distribution in slope. And with the increases of pre-stress value, stress response on the top of slope is small, the stress concentration in slope is alleviated, while the stress on slope toe increases a little, the seismic stability of slope is improved to some extent. And these conclusions may provide some theory basis for slope seismic design and study.

Large model footing load test on reinforced coal ash slope

The use of coal ash in structural fills to support footings and pavements in low lying areas can be one of the cost effective and environmentally friendly solutions to disposal problems related to coal ash, because wastes can be consumed in large quantities in such applications. The difficulty with this ash disposal solution is that the structural fills may not meet the foundation requirements for bearing capacity and settlement, especially when footings and pavements are constructed near the crest of the ash fill slope. Inclusion of geosynthetic reinforcements as horizontal sheets within the fill may be one of the most viable techniques for improving the load bearing capacity of the coal ash slope. Most technical information available in the literature on the load bearing capacity of footings resting on the slopes is based on small scale laboratory model tests; hence practicing engineers cannot generally adopt the information realistically. Therefore, in the present study as described in this paper, large scale model footing tests were conducted in the laboratory to find out the effectiveness of use of single and multilayer geosynthetic reinforcements in improving the load bearing capacity of coal ash slope. The results were found to be encouraging and they may have practical applications.

Influence of Bentonite Content on the Static Liquefaction Behavior of Sand

The landslide with static liquefaction often occurs in loose fill slopes with silty sand for the rainfall, causing lots of casualties and property loss. This study performed a series of static CU triaxial tests to investigate the influence of Bentonite content on the static liquefaction behavior of sand. The results indicate that there exists a critical value, below what increasing the Bentonite content reduces the resistance to static liquefaction. However, above the value the resistance to static liquefaction is increased with the rise of Bentonite content. This conclusion can be applied to manage the disaster triggered by the landslide with static liquefaction.

Turbidity and suspended-sediment changes from stream-crossing construction on a forest haul road in West Virginia, USA

A forested headwater watershed in West Virginia was monitored to examine changes to in-stream turbidity following the construction of a 0.92 km (0.57 mi) haul road. Due to the design of the study, most of the sediment that entered the stream following road construction was known to result from the stream crossings and approaches to the crossings. Stream-water samples collected daily and sequentially during stormflow from 1999 through 2005 were used to interpret the effects of stream-crossing construction on turbidity and suspended-sediment concentrations (SSC). Daily and stormflow turbidity and SSC values increased as a result of the construction. Average sediment loads (kg per storm) and total annualized sediment loads (kg per year) also increased significantly, both by a factor of about 1.8. Sediment delivery to the stream was caused by mechanical introduction of soil during stream-crossing culvert installation and fill-slope construction in the crossing approaches, and by erosion of those areas due to delays in vegetation re-establishment. Inputs from stream-crossing construction affected the overall sediment regime of the stream; the turbidity-discharge hysteresis changed from the normal clockwise pattern to a counter-clockwise pattern for about seven months. As the crossing fills and approach fill slopes became re-vegetated, they stabilized, and annualized sediment loads declined. However, at the end of the study, sediment exports remained above pre-disturbance levels.

A suitable methodology for assessing impacts of successive rainfalls infiltration on road slope stability

Abstract Water precipitation in road slopes, pavements, and shoulders may cause disturbances such as erosion, increase of the water table level, decrease of the carriageway bearing capacity, and so on. Roads are normally equiped with drainage systems that are sized and implemented in accordance with the rules of art. These equipments are used for the collection and quick evacuation of water precipitation estimated on the basis of the return period that is taken into account. Despite that, rainwater can still infiltrate unprotected cut or fill slopes, and pavements for repeated and intense rainfalls, which may cause a raise in pore-water pressure and a decrease of the factor of safety of road slopes. Using laboratory rainfall simulation techniques, infiltration measurements were made on intact samples to determine with respect to soil properties, how cumulative rainfalls cause decrease in apparent cohesion and lead to slope failure. This paper focuses on describing the relationship between the rainfall characteristics, the changes in soil water profile, and the changes in apparent cohesion for sandy clay samples collected on the national road RN3 located in Haiti. For a set of consecutive rainfall events at around an interval of 24 hours, the results prove that when wetting front depth approaches 2 meters or more, the risk of landslide is proportionally high in a soil with apparent cohesion (Ca) initially high and an effective cohesion (c′) relatively low.

Three-Dimensional Modeling of Spatial Reinforcement of Soil Nails in a Field Slope under Surcharge Loads

Soil nailing has been one of the most popular techniques for improving the stability of slopes, in which rows of nails and a structural grillage system connecting nail heads are commonly applied. In order to examine the spatial-reinforcement effect of soil nails in slopes, a three-dimensional (3D) numerical model has been developed and used to back-analyze a field test slope under surcharge loading. Incremental elastoplastic analyses have been performed to study the internal deformation within the slope and the development of nail forces during the application of top surcharge loads. Different treatments of the grillage constraints at nail heads have been studied. It is shown that the numerical predictions compare favorably with the field test measurements. Both the numerical and the field test results suggest that soil nails are capable of increasing the overall stability of a loose fill slope for the loading conditions considered in this study. The axial force mobilization in the two rows of soil nails presents a strong dependence on the relative distance with the central section. With the surcharge loads increased near the bearing capacity of the slope, a grillage system connecting all the nail heads can affect the stabilizing mechanism to a notable extent.

An environmental assessment of forest stands damages caused by excavators during road construction in Beech forests

Construction of forest roads can cause short-term and long-term negative effects on forest ecosystems in different ways if they are not well planned and appropriately maintained. In this research, environmental damages caused by an excavator during road construction were examined in steep terrain covered by beech (Fagus orientalis L.) stands. The study was conducted along a 1.5 km road in western Blacksea Region of Turkey. All of the road construction operations were monitored during a construction period, and measurements of cross sections sizes and stand damages were measured during and after the construction activities. The road construction was evaluated according to the appropriate method and standards. The average widths of roadway, fill slope and construction zone were 4.82, 6.91, and 16.61 m, respectively. Along the 1,500 m road, forested area impacted was 24,915 m2 while the number of trees cut was 1,495 and rate of the damaged trees below the fill slope was found to be 24.7 %. In the study, based on the appropriate method and standards, less forested area might have been impacted (23 %). As a result of regression analysis, it was found that the rate of damaged trees increased as the values of the proportion of rocks, the width of the road surface and the width of the cut-slope increased. To reduce the negative effects of forest road construction on the environment, new forest road construction by excavators should be performed using appropriate methods within mountainous terrains.

Accelerating Anthropogenic Land Surface Change and the Status of Pleistocene Drumlins in New England

Drumlins are glacially derived landforms that are prominent in the landscape over much of southern New England. We carried out a comprehensive ground-based survey in a three-town study area in eastern Massachusetts with the goals of establishing the extent to drumlins have been altered and assessing the associated environmental consequences and probable driving factors. Results show that many drumlins have been significantly altered through levelling and truncation (creation of steep cut and fill slopes), with projects involving movement of 1−1.5×106 m3 of earth materials not now uncommon. Stormwater and wetlands infractions were documented at all the larger excavation sites and resulted in enforcement actions and fines in many cases; the broader environmental consequences of the loss/alteration of these forested uplands are harder to establish. The excavations are significant in terms of materials cycling: the movement of earth materials, when considered regionally, greatly exceeds natural denudation processes and is also greater than during other periods of high anthropogenic denudation. Our findings suggest that the region’s glacial landscapes are at risk given current development patterns. The accelerating rate of land-surface change is undoubtedly also generalizable to other fast-developing regions of the United States. The landform alterations documented are part of a changing pattern of land use and vegetation cover since the Colonial era and are linked to shortages of land for development, current development and building practices, and lack of explicit rationales for preservation of the region’s geoheritage.

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실물 재하시험을 통한 성토사면에 근접한 철도 전철주기초의 저항모멘트 평가

철도선로에 설치되는 전철주기초의 모멘트에 대한 거동을 파악하기 위한 실물 재하시험을 수행하였다. 현행 시공방법에 따라 현장타설방식으로 설치된 직경 75cm, 깊이 2.5m의 원형 전철주기초 2본에 대하여 실제 조건과 동일한 모멘트 위주의 하중을 가하여 기초의 파괴모멘트를 확인하였다. 성토사면이 기초의 저항모멘트에 미치는 영향을 평가하기 위하여 사면방향과 사면반대방향으로 각각 모멘트를 가하였다. 국내 설계기준에 따라 성토지형에 설치된 전철주 기초는 파괴 이전까지는 변위가 거의 발생하지 않다가 급격한 전도로 파괴되는 취성거동을 보이는 것을 규명하였다. 성토사면의 영향으로 기초의 파괴모멘트가 30% 정도 감소하는 것으로 평가되었으며, 이를 토대로 전철주기초 설계에서 사면의 영향을 고려하기 위한 지형계수(K)로 0.7을 제안하였다. 또한 실물 재하시험 결과로 나타난 파괴모멘트를 국내외 설계방법의 저항모멘트 산정 결과와 비교함으로써 그 적합성을 평가하였다. The moment responses of electric pole foundations for a railway were investigated using real-scale load tests. Large overturning moments were applied to two circular rigid piles with a 0.75 m diameter and a 2.5 m embedded depth; the circular rigid piles were installed in an actual railway embankment fill. Two different loading directions-toward the fill slope and toward the track -were applied to evaluate the influence of the fill slope on the moment capacities of the foundations. It was found that the failure of the foundations that were constructed according to Korean railway practices exhibited a sudden overturning pattern without any significant pre-failure displacement. The moment capacity toward the fill slope was less than the moment capacity toward the track by 30%. From the test results, the geometry factor (K), which accounted for the reduction of the moment capacity, due to the fill slope, was 0.7. Moment capacities determined from the load tests were compared with those predicted from three existing design methods, and their applicability was discussed.