Ecological Slope Protection Research Articles

Instability and deformation behaviors of root-reinforced soil under constant shear stress path

Climate change is becoming a greater global challenge, leading to more frequent and intense extreme weather events, which in turn increase mountain hazards like shallow landslides and soil erosion. Ecological slope protection using vegetation has gained in- creasing attention to mitigate natural disasters in recent years. While numerous studies have demonstrated the contribution of root systems to soil reinforcement, the comprehensive impact of roots on soil mechanical response under rainfall scenarios remains elusive. This study investigates the instability and deformation behaviors of root-reinforced soil through constant shear drained (CSD) tests. The role of root characteristics, including biomass, diameter, and length, in modulating the shear strength, instability and deformation behaviors of soils is investigated. The results indicate that the shear strength and stability of root-reinforced soil, as well as the inhibition effect of root on contractive deformation after the initiation of instability, increasing with greater root biomass and length and smaller root diameter. Moreover, due to the potential weak interfaces, fine or stiff long roots appear to increase the likelihood of volumetric dilation in root-reinforced soil at the later stage of unstable deformation. However, this dilatancy can be effectively resisted by increasing root planting density to form the root network. Furthermore, our experiments suggest that herbaceous vegetation with finer and longer roots is more effective in mitigating static liquefaction of soils induced by rainfall infiltration. This study helps develop a predictive constitutive model for root-reinforced soils and supports future bioengineering slope design.

Failure Mechanisms and Protection Measures for Expansive Soil Slopes: A Review

Due to the significant hydrophilicity and cracking properties of expansive soils, expansive soil slopes are prone to destabilization and landslides after rainfall, seriously threatening the safety of buildings, highways, and railroads. Substantial economic losses often accompany the occurrence of expansive soil slope disasters; thus, it is of great significance to understand the slope failure mechanisms experienced by expansive soil slopes and to prevent expansive soil slope disasters. In this paper, the current research status of the landslide failure mechanism of expansive soil slopes is systematically reviewed based on three research methods: field test, model test, and numerical simulation. The failure mechanisms of expansive soil slopes and the main influencing factors are summarized. Based on the failure mechanisms, three protection principles (waterproofing and water blocking, swelling–shrinkage deformation limitation, and crack inhibition and strength enhancement) that can be followed for disaster prevention of expansive soil slopes are proposed. The research status and advantages and disadvantages of these protection methods are reviewed, and future researchable directions of the stability of expansive soil slopes and slope protection methods are explored. Based on the previous work, a new flexible ecological slope protection system with a double waterproof layer is proposed for expansive soil slopes to realize ecological, efficient, and long-term protection. This paper thus aims to provide technical reference for the prevention and control of slope engineering disasters in expansive soil areas.

Study of loess ecological slope protection optimization measures and prediction of the erosion control effect

Study of loess ecological slope protection optimization measures and prediction of the erosion control effect

Study on the Optimization and Experimental of Fly Ash and Sludge in Ecological Slope Protection Substrate

Study on the Optimization and Experimental of Fly Ash and Sludge in Ecological Slope Protection Substrate

Effect of freeze‒thaw cycles on root-Soil composite mechanical properties and slope stability.

Natural disasters such as landslides often occur on soil slopes in seasonally frozen areas that undergo freeze‒thaw cycling. Ecological slope protection is an effective way to prevent such disasters. To explore the change in the mechanical properties of soil under the influence of both root reinforcement and freeze‒thaw cycles and its influence on slope stability, the Baijiabao landslide in the Three Gorges Reservoir area was taken as an example. The mechanical properties of soil under different confining pressures, vegetation coverages (VCs) and numbers of freeze‒thaw cycles were studied via mechanical tests, such as triaxial compression tests, wave velocity tests and FLAC3D simulations. The results show that the shear strength of a root-soil composite increases with increasing confining pressure and VC and decreases with increasing number of freeze‒thaw cycles. Bermuda grass roots and confining pressure jointly improve the durability of soil under freeze‒thaw conditions. However, with an increase in the number of freeze‒thaw cycles, the resistance of root reinforcement to freeze‒thaw action gradually decreases. The observed effect of freeze‒thaw cycles on soil degradation was divided into three stages: a significant decrease in strength, a slight decrease in strength and strength stability. Freeze‒thaw cycles and VC mainly affect the cohesion of the soil and have little effect on the internal friction angle. Compared with that of a bare soil slope, the safety factor of a slope covered with plants is larger, the maximum displacement of a landslide is smaller, and it is less affected by freezing and thawing. These findings can provide a reference for research on ecological slope protection technology.

Ecological flexible protection method of expansive soil slope under rainfall

In this study, a new ecological slope protection method—Anchor Reinforced Vegetation System (ARVS) was applied to the newly excavated expansive soil slope. To explore the effect and mechanism of ARVS protection of newly excavated expansive soil slopes, expansive soil slopes with three different protection methods (bare slopes, grassed slopes, and ARVS slopes) were built. The continuous natural rainfall test and artificial rainfall tests were carried out. The results show that: compared with the bare slope and the grassed slope, ARVS could effectively adjust the moisture and heat balance of newly excavated expansive soil slopes and achieve a satisfactory soil and water conservation performance. Under different rainfall intensities, the runoff and soil loss rates of the ARVS-protected slope were smallest. Under the combined action of vegetation, high-performance turf reinforcement mats (HPTRMs) and anchors, the ARVS provided a superior erosion resistance. The higher the rainfall intensity is, the more significant the anti-erosion effect of the ARVS compared to that of grass protection technology. The ARVS could also effectively limit vertical and horizontal deformation of newly excavated expansive soil slopes. Therefore, the ARVS could effectively reduce the negative influences of the atmospheric environment on newly excavated expansive soil slopes and provide a new solution for shallow protection of newly excavated expansive soil slopes.

The influence of palm fiber reinforcement on the cement content of vegetated concrete substrate under the condition of equal strength.

Vegetated concrete substrate (VCS) is a kind of ecological cemented soil, which has very wide application prospect in high and steep rock slope eco-protection. Cement is an important component of VCS, but it has high energy consumption and environmental pollution. Fiber reinforcement plays an positive role in improving the mechanical properties of soil, and its use as a substitute for cement content in VCS under the condition of equal strength is rarely investigated. In this study, the unconsolidated-undrained (UU) triaxial compression test of unreinforced substrate as blank control samples (BCS) and reinforced substrate as fiber reinforced samples (FRS) were carried out. The test results showed that the stress-strain curve of VCS can be divided into compaction stage, elastic stage, plastic stage and strain hardening stage. The average peak strength increased by 34.3kPa, 53.6kPa, 218kPa and 81.8kPa as cement content of VCS was 0%,4%, 6% and 8%, respectively. The relationship between the peak strength and cement content of VCS could be better fit by Boltzmann function. The mathematical model of fiber instead of cement in VCS under the condition of equal strength was established. It is found that there is a critical point of cement content according to the mathematical model. The cement of VCS can be completely replaced by plam fiber as the cement content is less than the critical point. While the cement content is higher than the critical point, the cement of VCS can be partially replaced by plam fiber. The decrease of average cement content was 17.23%, 19.00%, 24.27% and 25.34% with 0.2%, 0.4%, 0.6% and 0.8% fiber content in reinforced substrate, respectively. The theoretical method and interpolation method for fiber substitute cement content of VCS under equal strength condition were proposed, which can provide technical guidance for ecological slope protection engineering practice of vegetated concrete.

Potensi Dan Cabaran Bahan Biokomposit sebagai Struktur Kejuruteraan dalam Perlindungan Cerun Ekologi: Satu Tinjauan

Ecological slope protection technology has gained popularity as a sustainable and eco-friendly approach for slope restoration and conservation. The integration of ecological considerations into slope protection techniques has resulted in more sustainable and environmentally friendly solutions. In order to advance the development of ecological self-cycling, this study conducts a comprehensive review of the latest advancements in ecological slope protection technology materials. A systematic literature search was conducted using four databases (Web of Science, Scopus, Science Direct, and Google Scholar) and based on the keywords: ecological slope protection; slope protection; bio-composite material; bio-material; eco-material; eco-friendly building material; mycelium based material; natural fiber composite and biochar. This article provides a detailed discussion of the fundamental types of ecological slope conservation and the properties of materials used in ecological slope protection technology. The usage of environmentally friendly innovative materials has overtaken traditional engineered structures as the primary mode of ecological slope protection innovation. In particular, this study focuses on the structural basis of ecological slope protection, conducting a comparative analysis of the properties of existing bio-composites and evaluating whether they could replace the base structure of ecological slope protection. The findings of this study will contribute to the development of more sustainable and effective ecological slope protection techniques, thereby promoting ecological conservation and restoration.

Experimental Research on Erosion Characteristics of Ecological Slopes under the Scouring of Non-Directional Inflow

Considering environmental sustainability, ecological embankments are often adopted in rivers, which benefit both the erosion resistance and the ecological balance of the bank. In this paper, the effectiveness of different types of dominant grass species in ecological slope protection and their impact mechanisms, as well as the impact of non-directional inflow on erosion characteristics, were investigated. Based on the principle of similarity theory in hydraulic modeling and the characteristics of flood erosion in riverbanks, a test model system for hydraulic ecological simulation was designed, including a vegetation bank slope and channels. Three types of dominant grass species were selected, and 12 series of erosion experiments were conducted in the grassed slope of the test model. Three types of root–soil composites and a reference plain soil were involved in the tests, and soil mechanical indicators such as shear strength were collected. Experimental results show that root–soil composite is a special elastic–plastic material, which provides additional cohesive force to the soil due to its root consolidation and reinforcement effects, Δc. The shear strength index reflecting soil cohesion was increased by 15% to 20%. The primary factor affecting slope erosion is the flushing velocity, and both the average erosion depth and the unit soil erosion loss present an exponential function with respect to this factor, while presenting a linear function with the angle of incoming flow. Compared with the plain soil slope, the ecological slope could decrease erosion significantly. The sand loss of the ecological slope is only 50~60% that of the plain soil slope as the flushing velocity is 3–4 m s−1. In vertical flushing, the sand loss in the plain soil slope is 1.73–2.43 times that of the ecological slope. This research might provide technical support for the anti-scourability design of the ecological embankment.

Effects of freeze-thaw cycling on the engineering properties of vegetation concrete

Vegetation concrete has been widely applied for the ecological restoration of bare steep slopes in short-term frozen and non-frozen soil regions in China. However, field experiments conducted in seasonally frozen soil regions have revealed decreases in the bulk density, nutrient content and vegetation coverage. This study aimed to clarify the evolution process and mechanism of the engineering properties of vegetation concrete under atmospheric freeze-thaw (F-T) test conditions. The physical, mechanical, and nutrient properties of vegetation concrete were investigated using six F-T cycles (0, 1, 2, 5, 10 and 20) and two initial soil water contents (18 and 22%). The results revealed decreases in the acoustic wave velocity and cohesive forces and an increase in the permeability coefficient of the vegetation concrete owing to F-T action. X-ray diffraction tests indicated that the decreased cohesive force was closely related to the overall decrease in the content of gelling hydration products in the vegetation concrete. Additionally, the contents of NH4+–N, PO43–P and K+ in the vegetation concrete increased, whereas that of NO3−–N decreased. The loss rates of these soluble nutrients increased, indicating that the nutrient retention capacity of the vegetation concrete had decreased. Specifically, the decreased nutrient retention capacity was mainly related to the disintegration and fragmentation of larger aggregates due to F-T action. This study provides theoretical support for future research on improving the anti-freezing capability of ecological slope protection substrates in seasonally frozen soil regions.

Differences in the distribution, availability, and sorption-desorption isotherms of phosphorus fractions in soil aggregates from cut slopes with different restoration methods

The construction of highways and other transportation facilities resulted in a large number of exposed cut slopes, leading not only to the alteration of soil structure but also to phosphorus (P) losses from soils with low utilization rates. These negative effects can result in stunted plant growth and the occurrence of heavy rainfall and earthquakes-associated landslide and mudslide disasters, threatening people's lives. However, few studies have investigated soil aggregates P in cut slopes restored with different methods in the Alpine Mountainous areas of Southwest China. Therefore, three types of cut slopes (cut slopes restored by three-dimensional mesh (TCS), cut slopes restored by galvanized wire mesh (GCS), and cut slopes restored by nature (NCS)) were selected for the study, and the present study aims to assess the total phosphorus (TP), available phosphorus (AP), and P fractions, as well as the P sorption-desorption isotherms in cut slope soil aggregates. The obtained results are as follows: (1) The TP contents in the soil aggregates did not differ significantly between the three types of cut slopes (p > 0.05), In addition, the AP contents and P activation coefficient (PAC) showed significant differences between TCS, GCS, and NCS, while the H2O-Pi, NaHCO3-Po, NaOH-Pi, NaOH-Po, HHCl-Pi, and HHCl-Po contents were significantly different between the three types of cut slopes (p < 0.05); (2) The AP contents in the three types of cut slopes showed a decreasing trend with increasing soil aggregate size from < 0.25 mm to > 5 mm; (3) H2O-Pi, NaOH-Pi, and HHCl-Pi were the main P fractions affecting the AP contents in the study area, among which NaOH-Pi exhibited the greatest effect on the AP contents; (4) The lowest P adsorption of soil aggregates was observed in NCS. The maximum P adsorption (Qm) values of the < 0.25 mm aggregates in TCS and GCS were higher than those of the other soil aggregate sizes. In addition, the trend of P desorption to increase with P adsorption was more obvious in large aggregates than in small aggregates. The present study provides a theoretical basis for P management in cut slope soils restored by different methods in the Alpine Mountainous region of Southwest China. Moreover, it provides some references for improving cut slope restoration and ecological slope protection techniques.

Mechanical properties and microstructure evolution of two ecological slope-protection materials under dry-wet cycles

Owing to the occurrence of rain and heat during the same period in the Loess Plateau, the strong dry–wet cycle results in shallow damage such as erosion. As a result, applying new ecological protection technologies has become important in solving this problem. In this study, polypropylene fiber and guar gum were mixed with loess in a certain proportion to form two kinds of slope ecological protection materials, i.e., polypropylene fiber reinforced soil (PFS) and guar gum mixed soil (GGS). Sixteen dry-wet cycle tests were carried out on the two slope protection materials, and the shear mechanical tests were conducted on the samples after cycling. On this basis, the microstructure evolution characteristics of the samples were observed by scanning electron microscope. Results showed that the mechanical properties of the two slope protection materials deteriorated after 16 dry-wet cycles. Among them, the c and φ of PFS under the three levels of water content decreased by an average of 21.3% and 8.9%, respectively, whereas GGS decreased by 55.8% and 21.7%, respectively. Moreover, the mechanical deterioration characteristics of the two slope materials showed strong unity with their internal microstructure. The field tests of the two slope protection materials both performed good ecological protection effect, and the deterioration process was in good agreement with the laboratory phenomena. The microscopic action mechanism inside the material was closely related to the macroscopic performance. Polypropylene fiber can act as a “bridge” among soil particles to prevent the development of cracks, and guar gum and its hydration products can enhance the cementation among soil particles. This study could provide reference for further combining the two materials reasonably, using their respective advantages and improving the ecological protection effect of loess slopes.

Ecological membrane for slope engineering based on red bed soil.

Ecological slope protection projects (such as the reinforcement of low slopes by plants and ecological restorations of the soil of high steep rocky slopes) are essential for restoring the natural environment. In this study, red bed soil and composite polymer adhesive materials were used to develop an ecological membrane for application in slope ecological protection. The basic physical and mechanical properties of the ecological membranes with different material percentages were studied through tensile strength test and viscosity test, the effect of different material percentages on the properties of ecological membranes was studied, and the soil protection performance and ecological restoration performance were studied through anti-erosion and plant growth tests. The results show that the ecological membrane is soft and tough, with high tensile strength. The addition of the red bed soil can enhance the strength of the ecological membrane, and the ecological membrane with 30% red bed soil has the highest tensile strength. The ecological membrane has considerable tensile deformation capability and viscosity, and up to 100% by mass, the more composite polymer adhesive materials added, the greater the tensile deformation capability and viscosity. And the ecological membrane can enhance the anti-erosion performance of the soil. This study clarifies the development and technology of the ecological membrane, reveals the effect of different material percentages on the properties of ecological membrane, and analyzes the slope ecological protection mechanism of the ecological membrane, thereby providing theoretical and data support for its development, improvement, and application.

Application Analysis of Ecological Slope Protection Technology for Mountain Highway Slope

With the standard of living in China is improved constantly, the construction of expressway in northeast Chongqing has also witnessed a rapid growth. The process of the construction of mountain road, the cuttings and embarkment of the road would definitely cause the distortion and movement of the high slope and create a large amount of lose sand, which seriously threat the safety of high slopes. Meanwhile, the engineering also causes destruction the original vegetation, which is hard to restore. Therefore, in the construction of expressway in mountainous areas, we should hold on to the idea of green development and adopt the combination of engineering protection and vegetational protection. The project should be revised constantly according to the situation and reduce its negative affect on ecological environment as much as possible.

Experimental and Numerical Simulation Study on Mechanical Properties of Shallow Slope Root-soil Composite in Qinghai Area

Natural disasters such as landslides often occur in Qinghai under the double deterioration of earthquake and freeze-thaw cycles, ecological slope protection is an effective way to prevent and control this type of disaster. In this paper, the mechanical properties of root-soil composites are investigated experimentally using triaxial apparatus and dynamic single shear (DSS) apparatus, and based on the discrete element method, a contact model more suitable for reinforced soil materials is proposed to study the dynamic properties of root-soil composites under cyclic shear from a fine viewpoint. Based on the results of the study, the following conclusions were drawn: 1) The presence of roots under the action of freeze-thaw cycles increases the strength properties of the soil. At the same number of freeze-thaw cycles, the shear strength and cyclic resistance of the root-soil composites are higher than those of the loess. And the strength of the root-soil composites decreases with the increase of the number of freeze-thaw cycles and then flattens out; 2) The proposed contact model can better simulate the softening effect of reinforced loess material under cyclic shear, which is more suitable for simulating the mechanical behavior of loess and laying the foundation for further study of reinforced loess material from a fine viewpoint.; 3) The presence of the root system will improve the stability of the slope soil, and the root system will have a positive effect on the shear strength of the soil when the moisture content is within a certain range. The presence of the root system also increases the cyclic resistance of the soil. Under the same cyclic shear stress conditions, the number of damage cycles of the root-soil composites is higher than that of the loess, the cumulative shear strain is less than that of the loess. However, the root system no longer exerts positive effects under saturated conditions. The research results can provide some guidance for the construction of ecological slopes in loess areas, and provide a new way to investigate the dynamic properties of root-soil composites from a fine viewpoint.

Effects of Planting Density of Poaceae Species on Slope Community Characteristics and Artificial Soil Nutrients in High-Altitude Areas

Ecological restoration of slopes in high-altitude areas is usually difficult. Gramineae species are widely used in slope vegetation restoration due to their strong adaptability and rapid growth. In the process of ecological slope protection, increasing the seeding rate of gramineous species usually improves the success rate of slope vegetation restoration, but the long-term effect is not obvious. Therefore, choosing an appropriate planting density of grass species is beneficial to the sustainable restoration of slopes in high-altitude areas. This study evaluated the effects of different planting densities of Poaceae species on community characteristics and artificial soil nutrients on high-altitude slopes. The slope ecological protection engineering experiment was carried out in Jiuzhaigou County, Sichuan Province. Commercial seed mixtures of five grasses and legumes were sown at three different planting densities of Poaceae species (10, 5, and 1 g/m2). Plant community species composition, community diversity index, and soil-available nutrients were determined annually. The results showed that there were differences in the species composition of the slope plant community under different planting densities. There was a significant negative logarithmic correlation between the community diversity indices and the planting density of grass species, and it changed with the recovery time. There were significant differences in hydrolyzed nitrogen, available phosphorus and available potassium in artificial soil, and they decreased with a logarithmic function of the recovery time. There was a positive correlation between the community diversity indices and the soil nutrient content. Overall, our study shows that low planting densities of Poaceae species are beneficial to the long-term stability of ecological restoration when ecological slope protection works are performed on slopes in high-altitude areas.

Soil stabilization using synthetic polymer for soil slope ecological protection

Polymer treatment can protect soil slopes by enhancing topsoil macro-properties and promoting vegetation growth. In the present study, laboratory and field application tests were performed on polyurethane (PU)-treated soil to investigate its effect on soil slope ecological protection, and the mechanism related to achieving the ecological protection of soil slopes was revealed. Laboratory tests show that PU addition could greatly enhance the unconfined compression strength of silty sand and its tensile and shear strengths, especially the first two, which increased from about zero to 952.61 and 211.47 kPa, respectively. The addition of PU also led to a reduction in permeability and an enhancement in water retention capacity. The permeability coefficient decreased by an order of magnitude, whereas the water retention capacity remained at a high and stable level for a long period with little water supplementation. In addition, the PU-treated soil showed satisfactory erosion resistance and protected vegetation growth to some extent, both depending on the amount of PU, whereas a competitive relationship was observed between the contribution of the PU amount to anti-erosion and the environment for plant growth caused by the PU content. Field observations showed that PU treatment could effectively and ecologically protect soil slopes by enhancing topsoil erosion resistance, mechanical strength, and water retention, thereby accelerating vegetation growth and cover. The PU stabilization effect benefits from the improvement in the microstructure of silty sand caused by PU adsorption, connection, and filling effects. This induced a denser and stiffer whole that covered on the slope surface, which, on the one hand, enhanced the stability of the slope surface and weakened the influences induced by rainfall and runoff and, on the other hand, promoted vegetation growth by reducing soil erosion and providing moisture.

Experimental Study on the Influence of Substrate Properties on Rainfall Infiltration and Runoff from Ecological Slopes

Rain is an important factor influencing the instability of ecological slopes. There is little research on the inherent quantitative influence of substrate properties on slope runoff and water infiltration to support accurate ecological slope protection design. In this paper, the influence of substrate characteristics on slope runoff and water infiltration is quantitatively analyzed by constructing large physical models with different substrate characteristics for artificial rainfall simulations. The experimental results showed that the cumulative runoff volume and slope runoff rate were positively correlated with the cement content and substrate thickness in a 4 h, 60 mm/h artificially simulated rainfall. Specifically, the cumulative runoff volume increased by 2.06% for every 1% increase in cement content, and the cumulative runoff volume increased by 3.93% for every 1 cm increase in substrate thickness. The substrate inhibited the advance of the wetting front, and at different slope locations, the transport rate of the wetting front exhibited a mid-slope &gt; upslope. Moreover, the transport rate of the wetting front showed a non-linear relationship with time as a power function V = a·tb, with the cement content showing a linear relationship with parameters a and b, and the substrate thickness showing a non-linear relationship with parameters a and b. The cumulative infiltration and infiltration rate were negatively correlated with cement content and substrate thickness, as shown by a 2.2% decrease in cumulative infiltration for every 1% increase in cement content and a 4.73% decrease in cumulative infiltration for every 1 cm increase in substrate thickness.

The novel vegetation concrete blocks for embankment protection incorporating the light aggregates recycled by lake-dredged sediments

The recycling of lake-dredged sediments (LDS) is an environmental issue of great concern, and its reuse in ecological slope protection is a new endeavor with economic and environmental advantages. However, the feasible process and reasonable parameters of this recycling concept are still unrevealed. In this paper, we presented a guiding framework for recycling lake-dredged sediments into lightweight aggregate for eco-friendly porous vegetation concrete blocks. The laboratory tests show that the LDS from Dongting Lake could be directly sintered the lightweight aggregates under the optimal processing parameters (preheating temperature of 800 °C and time of 5 min, and sintering temperature of 1150 to 1250 °C and time of 8 to 10 min). After that, porous matrix was manufactured using the LDS lightweight aggregates and cement with an optimal mix proportion (w/c of 0.27, lightweight aggregate with a particle size of 1.5 cm and a target porosity of 25%). Moreover, the porous matrix and hexagonal concrete blocks were combined and produced as vegetation concrete blocks, which have shown good performance in the slope protection project of the Dongting Lake embankment. Compared with the traditional embankment blocks, this scheme saves about 38% costs in raw materials and LDS treatment.

Ecological Restoration of Engineering Slopes in China—A Review

As the protection of the environment gains more public attention in China, a large number of engineering slopes, which are not conducive to the growth of vegetation and are prone to natural disasters caused by constructions, are in urgent need of restoration. Herein, we explain the theoretical basis for the ecological restoration of engineering slopes and introduce the technologies commonly used in this regard, including soil improvement, bioremediation, and ecological slope protection. The benefits and evaluation of the impact of ecological restoration of engineering slopes are also detailed. Finally, we discuss the current problems in ecological restoration and put forward some future research prospects. By summarizing the existing techniques and evaluation systems for ecological restoration, this study provides a reference for its implementation and evaluation, contributing to the long-term, stable, and rapid development of ecological restoration of engineering slopes.