Cut Slopes Research Articles

Effect of Geographical Conditions on Moss–Soil Crust Restoration on Cut Rock Slopes in a Mountainous Area in Western Sichuan, China

Ecological restoration has great significance on cut rock slopes, which are considered extremely degraded habitats. The development of moss–soil crusts on cut rock slopes as a critical pathway to ecological restoration in mountain areas has been poorly reported. A total of 335 quadrats were selected on cut rock slopes with formation ages between 0 and 60 years to evaluate the evolution characteristics of moss–soil crusts under various geographical conditions (e.g., aspect, lithology, and altitude) in the mountainous area of western Sichuan, Southwest China. The results suggested that moss growth decoupled from soil accumulation within the crusts and was controlled by multiple factors. Moss growth depended on lithology, altitude, and age, while soil weight was mainly influenced by slope aspect. The development of mosses on limestone was better than on sandstone. Moss biomass varied with altitude, consistent with that of rainfall with respect to moss development dependent on moisture. Furthermore, moss development under a semiarid climate was more distinctly impacted by moisture with altitude relative to a humid region, likely owing to the higher sensitivity of the mosses to moisture in the former than in the latter. Moss biomass increased with recovery time, while the rate of moss biomass development was diverse in different geographical areas. The vegetation developed rapidly in low-altitude areas (~1000 m above sea level), resulting in moss biomass increasing from 0 to 24.08 g·m−2 with formation time increasing from 0.5 to 1.5 years and subsequently being restricted by the evolution of higher plants on cut rock slopes, leading to an insignificant difference in moss biomass between 1.5 and 60 years. In high-altitude areas, when the altitude changed slightly (from 2024 to 2430 m above sea level), the moss biomass on cut rock slopes increased linearly with increasing age from 5 to 27 years. Influenced by the surrounding fertile soils and moss bioaccumulation, there were high levels of soil major nutrient content, especially the organic matter content, which reached 377.42 g·kg−1. More soils accumulated on south-facing slopes than on north-facing slopes. This study provided field data to clearly reveal the influence of geographic factors on moss–soil crust development in natural restoration processes in high-altitude mountainous areas.

The Application of Porous Material in the Capillary Barrier System for Residual Soil Slope Stabilization

A drainage system that is used to flow excess rainfall infiltration is an excellent alternative to enhance lateral diversion capacity at the interface of Grade VI and Grade V soil slope layers thus delaying breakthrough occurrences. This study aims to explore the performance of porous transport layer on slope behavior via numerical simulation by GeoStudio SEEP/W. In this study, a 2-dimensional non-homogenous residual soil configuration model, which is composed of Grade VI and Grade V residual soil was constructed. Laboratory tests were conducted on the soil samples collected from the Faculty of Engineering, UTM JB to determine the soil properties as input parameters in numerical modeling. The soil slope model is designed as an infinite residual soil slope according to Jabatan Kerja Raya (JKR) design specification on the cut slope and fill slope with 27 ° inclination respectively. High rainfall intensities were chosen to represent rainfall infiltration in Johor. The slope model was modeled with a porous transport layer at the Grade VI and Grade V layer interfaces. The porous transport layer is introduced as the transport layer and its effectiveness is expected to be similar to the optimum compacted soil mix in the previous study. In addition, porous concrete as a transport layer is introduced and it must meet the adequate porosity and hydraulic conductivity requirements. The suction distribution pattern with depth and time was subsequently observed to identify the volume of infiltrated water and retention time in the transport layer. The porous transport layer is also expected to be efficient in diverting infiltrating water and decreasing the interface's suction distribution between Grade VI and Grade V soil layers. HIGHLIGHTS The water built up within the residual soil slope is one of the common factors of rainfall-induced residual soil slope failure thus porous transport layer introduced The detailed laboratory testing and numerical modelling conducted in order to identify the performance of porous transport layer within residual soil slope The application of porous transport layer sandwiched between residual soil is effective to decrease the water built up and matric suction thus decrease the risk of slope failure GRAPHICAL ABSTRACT

Deformation characteristics and reactivation mechanism of an old landslide induced by combined action of excavation and heavy rainfall

The reactivation mechanism of old landslides has been extensively studied from building load, erosion of the slope toe, heavy rainfall, and slope cutting for existing research. However, previous research on the reactivation of old landslides pays little attention to the combined action of engineering disturbance and heavy rainfall is rarely studied. This paper describes an old landslide in Wushan County, Chongqing, China, that was reactivated in August 2019 due to engineering disturbance and heavy rainfall. The deformation of the old landslide was first observed in 2007 and 2008, resulting from excavation and rainfall, respectively, and remained stable for about 11 years after treatment. In August 2019, the landslide was reactivated by slope cutting and damaged anti-sliding piles at the toe, and entered a state of imminent sliding due to the concentrated heavy rainfall events that occurred from October 4 to 22, 2019. In order to reveal the deformation features and reactivation mechanism of the landslide, field investigations, drilling activities and monitoring were performed. The results showed that tectonic effects and the stratigraphic lithology were the main reasons for the formation of the old Dashuitian landslide. The cut slope and damaged anti-sliding piles at the toe of the landslide provided the sliding space and reduced the anti-sliding force, and therefore resulted in the reactivation of the landslide. Continuous intense rainfall increased the weight of the landslide, decreased the mechanical properties and increased the pore water pressure of the weak interlayer, which accelerated the deformation rate. Therefore, 1.5 million m3 of rock and soil masses slid along the weak interlayer under the action of gravity, threatening the safety of Wuliu Road, Ring Road, National Road G42 and the Wu-Da Expressway. Our research provides a theoretical basis for reducing the hazard of similar engineering projects involving slopes.

Effect of crevice density on biological soil crust development on rock cut slope in mountainous regions, Sichuan, China

BackgroundThe rock cut slope (RCS) could cause damage to regional ecological functions and landscapes and requires recovery. Biological soil crusts (BSCs) are pioneer and dominant colonizers during the initial recovery stage. To accelerate the natural recovery of RCS, the development process and influencing agents of BSC should be revealed. Thus, the area index of crevices (IR), BSC coverage (COV) and biomass (BM), soil weight (SW), and major soil nutrients [organic carbon (OC), total nitrogen (TN) and total phosphorus (TP)] content, collected from 164 quadrats on 13 RCSs in the mountainous area of west Sichuan Province, China, were measured, to explore the effect of crevice of RCS on BSC development.ResultsSoil OC, TN and TP on RCSs ranged from 18.61 to 123.03 g kg−1, 0.96 to 6.02 g kg−1 and 0.52 to 2.46 g kg−1, respectively, and were approximately to or higher than those on natural slopes. The OC, TN and TP contents in soils elevated unsystematically with recovery time of RCSs. BSCs on RCS distributed along crevices generally and firstly. During the first 13 years of natural recovery, COV, BM and SW ranged from 6.5 to 28.2%, 14.43 to 67.25 g m−2, and 127.69 to 1277.74 g m−2, respectively. COV, BM and SW increased linearly with IR on RCSs. The positive correlation between COV and BM and IR was insignificantly impacted by bedrock, slope aspect and altitude within the recovery time less than 13 years. COV and BM on RCSs increased significantly when the recovery time is more than 27 years.ConclusionsCrevice on RCSs could be a major environmental factor which is conducive to BSC development and soil accumulation through creating a space for water and soil particle. Furthermore, with the increase of recovery time of RCSs, BSCs may grow and reach a stable state with the promotion of soil nutrients, plant growth and microbial activity. These results provide a development process of BSC that from inside to outside the crevices on RCSs. In the areas with stable rock strata and a low risk of geological disasters, purposeful improvement in crevice density on RCS may effectively accelerate BSC development.

Research on the application of a cement and soil aggregate for the ecological restoration of vegetation in artificial soil.

The construction of high-speed roads has resulted in large amounts of steep and exposed cut slopes, posing more potential hazards in areas with mountains and hills. Vegetation restoration is an effective and environmentally-friendly way to restore exposed slopes using outside soil spray seeding, though it is difficult to establish a vegetation cover. Spraying artificial soil on high and steep slopes is a challenging task as it is difficult to keep the fluid mixture on sloped surfaces. Because of these challenges, this study applied different combinations of cement and soil aggregates in artificial soil, measuring final soil properties after one growing season. Experimental results showed that there were substantial differences in all basic soil parameters and in the soil quality index after different treatments. In particular, adding 5-10% cement content could improve the adhesion of artificial soil without remarkably reducing soil quality; adding 0.09% of soil aggregate was also beneficial to soil nutrient availability. These findings indicate that the combination of cement and soil aggregates could be applied in artificial soils for the ecological restoration of steep slope vegetation. Adding cement to the soil increased the alkaline levels of the soil, so it is important to reduce artificial soil pH in the future. The application of a cement and soil aggregate should be considered in the field for the ecological restoration of slope vegetation, and the impact of this addition on slope stability and vegetation growth should be explored with further research.

Evaluation of Geological Hazard Susceptibility Based on the Regional Division Information Value Method

The traditional susceptibility evaluation of geological hazards usually comprises a global susceptibility evaluation of the entire study area but ignores the differences between the local areas caused by spatial non-stationarity. In view of this, the geographically weighted regression model (GWR) was used to divide the study area at regional scale. Seven local areas were obtained with low spatial auto-correlation of each evaluation factor. Additionally, 11 evaluation factors, including the aspect, elevation, curvature, ground roughness, relief amplitude, slope, lithology, distance from the fault, height of the cut slope, multiyear average rainfall and the normalized difference vegetation index (NDVI) were selected to establish the evaluation index system of the geological hazard susceptibility. The Pearson coefficient was used to remove the evaluation factors with high correlation. The global and seven local areas were evaluated for susceptibility using the information value model and the global and regional division susceptibility evaluation results were obtained. The results show that the regional division information value model had better prediction performance (AUC = 0.893) and better accuracy. This model adequately considers the influence of the geological hazard impact factors in the different local areas on geological hazard susceptibility and weakens the influence of some factors that have higher influence in the global model but lower influence in local areas on the evaluation results. Therefore, the use of the regional division information value model for susceptibility evaluation is more consistent with the actual situation in the study area and is more suitable for guiding risk management and hazard prevention and mitigation.

Application of Modified Slope Mass Rating (M-SMR) System in Ultrabasic Rock: A Case Study in Telupid, Sabah, Malaysia

Modified Slope Mass Rating (M-SMR) was proposed as a geomechanically classification scheme for sedimentary Crocker Formation rock slope in the Kota Kinabalu area, but has never been applied in ultrabasic rock. Then, this study was conducted on ultrabasic rock cut slopes in Telupid, Sabah, Malaysia. This system was used to characterize and to propose preliminary rock cut slope design, slope stabilization, protection measures, and recommendation levels for slope re-investigation. The UCS test, Deere RQD method, a weighted average of discontinuity set spacing, weighted average and statistical mode, weighted average, and new approach of adjustment factor (NAAF) methods were used to evaluate the uniaxial compressive strength (UCS), RQD, discontinuity spacing, discontinuity condition, water flow and discontinuity orientation parameters, respectively. The result of this study shows that the M-SMR classes for the slopes are class III (moderate), IV (poor,) and class V (very poor). Recommended and highly recommended for slope re-investigation by well-trained, experienced, or expert engineering geologist/geotechnical engineer are for classes III, IV, and V, respectively. The recommendation for slope stabilization and protection measures are local trimming, surface drainage, horizontal drain, weep hole, systematic bolting, dowels, concrete detention or buttress, shotcrete, wire mesh or rope nets, and rock trap ditch.

Geotechnical assessment of rock masses in metallic mineral deposits, a view on the “hidden” issues in open-pit design

Defining rock mass geotechnical properties is a critical step in the process of open-pit slope design. Geotechnical engineers assess the frequently highly altered rocks of metallic mineral deposits by applying standardized geotechnical classifications primarily developed for underground mining operations or design of civil structures such as tunnels and cut slopes. In some cases, the projects do not consider additional aspects of the rock masses, such as: zoning according to rock mass alteration schemes, prediction of blasting disturbance and weathering depth, rock strength loss over time, swelling effects, etc. Unfortunately, in some mineral deposits, many of these aspects appear to overlap, leading to difficulties in the process of open-pit design. In the case of neglecting such complex issues, there can be serious consequences in regard to future safe mine operation or even failure of slope/s. The paper presents findings from Macedonian legislation and literature overview on these aspects, regulations from other countries where available, as well as personal experiences of the authors. Some suggestions on the scope of geotechnical investigation works are briefly presented. It is considered that a more serious approach is needed in order to achieve a better understanding of the “long term” geotechnical behaviour of rock masses in such high risk environments.

Three Decades of Road and Trail Runoff and Erosion Work in the Northeastern Caribbean – a Research Program Perspective

HighlightsThe infiltration capacities of unsurfaced roadways are frequently exceeded by rain intensity, promoting overland flow.Erosion rates from unsurfaced roadways and cut slopes are 101 to 104 times greater than on undisturbed hillslopes.Roads in steep, subtropical wet terranes may increase landslide erosion by a factor of 5 relative to areas without roads.The hydro-geomorphic impact of roads is so prominent that they must be explicitly considered in watershed assessments. ABSTRACT. Erosion is a key environmental concern in the northeastern Caribbean because it can diminish soil productivity, damage infrastructure, and threaten human life. Additionally, sediment released by erosion can be delivered to streams where it can degrade water quality and aquatic habitat, reduce reservoir storage capacity, and threaten critical marine resources such as sea grass beds and coral reefs. Road erosion has been a concern in the region since the 1990s, and a considerable body of research has been conducted over the last ~30 years. This article reviews the key findings and identifies additional research needs. In some tropical dry coastal watersheds of the US Virgin Islands and Puerto Rico, unpaved roads and foot or off-road vehicle trails are the primary sediment sources. Watershed scale sediment production rates in these tropical dry settings are 0.3 to 3.7 Mg ha-1 yr-1, depending on unpaved road density, and these are 3 to 40 times greater than under undisturbed conditions. In wetter settings, like the forested and actively cultivated landscapes of highland Puerto Rico, sediment contributions include those from unpaved farm roads but also those from croplands, streambanks, and landslides. Watershed scale sediment production rates in actively cultivated tropical wet settings are 15 to 60 Mg ha-1 yr-1, with road-induced surface erosion and landslides accounting for 50% to 95% of total sediment production. Designing management alternatives will require additional research to improve our understanding of road-to-stream and road-to-coast connectivity, develop effectiveness metrics of applied management practices, and establish the specific causes of road-induced landslides. Keywords: Connectivity, Coral reefs, Landslides, Puerto Rico, Sedimentation, Surface erosion, Virgin Islands.

Satellite-based monitoring of an open-pit mining site using Sentinel-1 advanced radar interferometry: A case study of the December 21, 2020, landslide in Toledo City, Philippines

Understanding the causal factors and mechanisms behind catastrophic landslides and debris flows is crucial for accurate forecasting and disaster risk reduction. Synthetic aperture radar (SAR) data and interferometric SAR (InSAR) technologies provide valuable information for early warning systems’ landslide and debris flow detection and monitoring strategies. This paper applied the Sentinel-1 Persistent Scatterer InSAR (PSInSAR) technique to detect and monitor precursory slope movements over the open-pit mining site in Toledo City, Cebu Island, in the Philippines. The results show that the slope showed instabilities between December 30, 2019, to December 12, 2020, before the actual failure on December 21, 2020. The landslide initiation zone moved with velocities exceeding –10 mm/yr and reaching –90 mm/yr. The topography and morphology of the mining site contributed to the cut slope instabilities. The mining operations and hydrometeorological conditions during the analysis period aggravated the situation, leading to the cut slope failure. Overall, with favorable slope geometry, surface characteristics, and SAR data availability, the Sentinel-1 PSInSAR technique can serve as a landslide early warning system tool and aid decision-making in an actively operating open-pit mine and other landscapes.

Analytical solutions for annual probability of slope failure induced by rainfall at a specific slope using bivariate distribution of rainfall intensity and duration

In risk assessment and management of rainfall-induced landslides, annual frequency or probability of slope failure has often been used as a straightforward index for quantitatively measuring landslide risk. It is therefore of great interest to predict the annual failure probability of a specific slope when subjected to rainfall infiltration. This study derives analytical solutions, respectively, for assessing the probability of slope failure caused by a single rainfall event, the annual probability of slope failure induced by rainfall, and slope failure probability over some years. The analytical solutions rely on two key elements: (1) a bivariate distribution of rainfall intensity and duration which reflects local rainfall characteristics for a given slope, and (2) a critical rainfall pattern curve (CRPC) that comprehensively represents a slope's rainfall-induced performance under a wide spectrum of rainfall patterns. The proposed method is illustrated and verified by an engineered cut slope in South Korea. The estimated high annual failure probability is consistent with the observed slope failure in the field. The proposed method can be implemented easily and efficiently. The proposed method can also be used to quantitatively evaluate the landslide risk (e.g., annual failure probability) with or without stabilization, leading to risk-informed slope designs.

Analysis of factors affecting vegetation cover for stabilization of granite weathered soil forest road cut slopes

Analysis of factors affecting vegetation cover for stabilization of granite weathered soil forest road cut slopes

A New Technique of Lattice Beam Construction with Pre-Anchoring for Strengthening Cut Slope: A Numerical Analysis of Temporary Stability during Excavation

In consideration of the temporary stability of the cutting slope during construction and its permanent stability under long-term service, a new technique of lattice beam construction with anchors pre-set in the slope from the original ground surface before cutting was proposed, and its construction process was briefly introduced. Compared with the model without pre-set anchors, the effectiveness of pre-setting anchors to strengthen the cutting slope during multi-excavation was verified in the numerical software FLAC3D. Various factors such as the factor of safety (FOS) and the maximum shear strain increment (MSSI) as well as the displacement for different stages were discussed. The results show that the anchors pre-set in the slope provide reinforcement step-by-step with excavations which changes the mechanical responses of the cutting slope and increases the factor of safety with a variation of 15.9–44.1% compared to the case without setting anchors. In addition, with excavations, the axial forces of the anchors pre-set in the stratum increase gradually, and the positions of the maximum axial forces gradually transfer from the vicinity of the cutting surface to the depth of the design slope. Numerical simulations prove that this new technique is beneficial for ensuring the temporary stability of the slope during excavations and is especially suitable for the advance anchorage of the cutting slope, in which the inclined original ground surface is cut at an angle steeper than it can stand safely and is close to the design slope surface after cutting. After the completion of slope excavation, the cast-in-place concrete lattice beam is immediately set on the design slope surface and connected with the anchor heads exposed on the cut slope surface to ensure the permanent stability of the slope. Therefore, this new technology has important guiding significance for both the temporary stability of slopes during construction and the permanent stability of slopes in service.

Active fault investigation and slope stability evaluation for Aso Bridge in Japan

The Aso Bridge in Japan is located near the Futagawa Fault, which is considered to be the epicentre fault of the Kumamoto earthquake. This paper presents the technical findings obtained through the investigation and design of the Aso Ohashi Bridge replacement project after the Kumamoto earthquake, including (a) extraction of active fault zones, (b) evaluation of fault activity found on the cut slope and (c) stability evaluation of the excavated surface behind the bridge piers considering the mechanical properties of the columnar joints.

A simulated ecological restoration of bare cut slope reveals the dosage and temporal effects of cement on ecosystem multifunctionality in a mountain ecosystem

Cement is a critical building material used in the restorations of bare cut slopes. Yet, how cement affects ecosystem's functions and their undertakers remains elusive. Here, we revealed the dosage and temporal effects of cement on plant and soil traits, extracellular enzymes, greenhouse gas fluxes and microbiome using simulation experiments. The results showed that soil pH increased with the cement content at 1st day but relatively constant values around 7 to 7.5 were detected in the flowing days. The β-1,4-glucosidase, phenol oxidase, leucine aminopeptidase and acid phosphatase showed high activities under high cement content, and they generally increased with the cultivations except for acid phosphatase. CH4 fluxes at 16th day were less than zero, and they increased to peak around at 37th to 44th days followed by decreasing until reaching to relatively stable fluctuations around 0. Despite of decrease patterns, N2O fluxes stayed around zero across the temporal gradient except for the maximum around at 30th day in 2%, 5% and 8% cement treatment. Microbial diversity decreased with the cement content, in which there were a recovery trend for bacteria. By integrating above- and belowground ecosystem traits into a multifunctionality index, we identified a potential optimum cement content (11%). PLSPM showed that multifunctionality was affected by the shifts in soil bacterial community, enzyme activity and greenhouse gases while these components were effected by other environmental changes resulted from cement. Our results demonstrate that cement determines multifunctionality through mediating microbial community and activity, providing new insights for designing in situ experiments and ecological restoration strategies for bare cut slopes.

Numerical Analysis Method That Considers Weathering and Water-Softening Effects for the Slope Stability of Carbonaceous Mudstone.

The mechanical behavior of carbonaceous mudstone deteriorates greatly when exposed to wet environments, and the precise evaluation of its slope stability has been a difficulty. This study aims to establish a numerical analysis method for the instability problems of its slopes; this method considers the effects of weathering and water-softening by establishing their mathematical expressions. The weathering and water-softening effects are reflected by variations in the mechanical properties (e.g., elastic modulus, angle of internal friction, and cohesion) of carbonaceous mudstone, with the depth following a logistic function and the shear strength parameters varying with wetting duration and degree of saturation. Their weathering and water-softening effects are reproduced with the use of the ABAQUS finite-element software and MATLAB programming. The proposed numerical method is applied to analyze the seepage field and stability of a highway cut slope with and without protection structures; the application results show that the proposed numerical method is reliable in analyzing the slope's instability problem. The use of the herringbone skeleton structures can reduce the water-softening effects and thus increase the safety factor of the slope. The findings of this study could provide guidance to the design and construction of highway cut slopes in mountain areas that are rich in carbonaceous mudstone.

GIS Based Assessment and Analysis of Terrain Variables in Kampung Baru, Jeli, Kelantan

Kampung Baru is one part of Jeli district that has abundant natural resources and contains several geological features of interest.The landscape of this area is divided into three parts which are mountainous, hilly, and plain areas. This research aims to perform terrain analysis and determine the suitability zone for the construction area. To achieve the objective, the mapping aspect is mainly based on field observations such as geomorphological features, elevation, drainage patterns, etc. Besides, elevation data extracted from Digital Elevation Model (DEM) was employed to characterize the physical features of the landscape for terrain mapping and analysis. All this field-related data was then processed in ArcGIS software to generate thematic maps. The terrain classification was carried out based on five terrain variables: slope gradient, terrain code, activity code, erosion & instability. Then, the suitability of the site for development and construction is created using the terrain attributes. There were five types of classes created in the study area: class I (37.9 %), class II (23.3 %), class III (1.7 %), class IV (29.3 %), and class IV cut slope (7.6 %). The study area was dominated by class I, which means it has few geotechnical constraints and is highly suitable for development. Some cutting and filling of slopes are not expected to be difficult due to their low elevation. From the slope terrain analysis, only 4.89 % of the site is covered by a very steep slope (>60°). The site is mainly high slopes (35° - 60°), equal to 32.20% of the total area, with most of it contributed by the cut slopes. Gently sloping (5° - 15°) to moderate slope rate (15° - 25°) covers about 19.93% and 14.19% of the area respectively. The percentage of flat to gently sloping (0° - 15°) area is shown as 15.34 % of the project site. In conclusion, the parameters including the map prepared using the Weighted Overlay Method (WOM) can be beneficial to engineering geology for the planning of site investigations, preliminary design of foundation systems, and the project layout of the research area.

Stability Analysis of Cut Slope Using RMR and SMR

The Planjan - Tepus road is built on a slightly steep karst morphology, necessitating slope excavation works. Slope stability is one of the elements to consider, particularly in slope excavation work. The excavation depth of the slopes sampled in this research is up to 48 meters. It is critical to undertake slope stability analysis quickly, precisely, and safely. For rapidly examining slopes, empirical approaches such as Rock Mass Rating (RMR) and Slope Mass Rating (SMR) can be utilized. An examination of the limit equilibrium method was performed using Rocscience Slide v.6.0 software to assure the slope stability level further. The limit equilibrium method used is Morgenstern-Price and Spencer. The value of slope stability analysis using the RMR method is 41-53, and the rock mass quality is categorized as class III (fair). The value of slope stability analysis using the SMR method 41-53, the rock mass quality is categorized as class III (normal), with slope stability in partially stable conditions. Slope stability using the limit equilibrium method produces a safety factor value of 1.670 - 1.680 for conditions without seismic loads and 1.137 - 1.154 for conditions with seismic loads. According to the findings of this analysis, the slope is in stable (safe) conditions.

The distribution and availability of phosphorus fractions in restored cut slopes soil aggregates: a case study of subalpine road, southwest China

The distribution and availability of phosphorus fractions in restored cut slopes soil aggregates: a case study of subalpine road, southwest China

Serviceability of cut slope and embankment under seasonal climate variations

Serviceability of cut slope and embankment under seasonal climate variations