scholarly journals Hydrological and mechanical properties of loess landslides under different vegetation restoration types

2021 ◽  
pp. 795-801
Author(s):  
Lei Shi ◽  
Zhongzheng Liu ◽  
Liangyan Yang
Keyword(s):  
Mechanical Properties ◽  
Soil Samples ◽  
Vegetation Restoration ◽  
Saturated Soil ◽  
Vegetation Coverage ◽  
Natural Soil ◽  
Stability Prediction ◽  
Loess Landslide ◽  
Landslide Stability ◽  
Loess Landslides

Loess landslide is a common geological disaster in northern Shaanxi, which seriously affects people's life and property safety and social and economic development. The research on vegetation restoration types and hydrological and mechanical properties of loess landslides can provide basic data support for landslide stability prediction, and further provide reference for landslide prevention and treatment. In the present study, the loess landslide point of Zhang Zi Gou in Gan Quan County, Yan’an City was taken as the research object. On the basis of the existing natural condition data, the basic physical and mechanical properties and hydrological characteristics were obtained by collecting field landslide soil samples for indoor experimental analysis. The indoor analysis shows that the landslide is mainly distributed in dry land, medium coverage and low coverage grassland, indicating that the surface vegetation coverage can affect the stability of landslide. The worse the vegetation coverage, the more landslides occur. The void ratio and porosity of landslide soil decrease with the increase of dry density. The cohesion of natural soil is obviously higher than that of saturated soil, and the internal friction angle of natural soil is slightly lower than that of saturated soil. In general, due to the influence of water content, the shear strength of natural soil samples is higher than that of saturated soil samples. Therefore, in order to improve the accuracy of prediction and early warning system, it is necessary to consider the response of hydrological and mechanical properties of loess to vegetation restoration. The results provide basic data support for the establishment of loess landslide stability prediction system and provide reference for geological disaster management. Bangladesh J. Bot. 50(3): 795-801, 2021 (September) Special

In Situ Shear Experimental Study on Loess Landslide

2011 ◽  
Vol 94-96 ◽  
pp. 63-66
Author(s):  
Xin Jian Chen ◽  
Jing Zhang ◽  
Fa Suo Zhao
Keyword(s):  
Experimental Study ◽  
Shear Crack ◽  
Friction Angle ◽  
Experimental Methods ◽  
Soil Samples ◽  
Geological Environment ◽  
Native State ◽  
Loess Landslide ◽  
Landslide Stability

On the basis of analysis on the geological environment of highway loess landslide, three in-situ loess samples,500mm×600mm×600mm, were cut on the shear crack of landslide. The residual shear experiment of soil samples were accomplished in native state and saturated case. Compared with the residual cohesive force and residual internal friction angle of slide face soil in native state by indoor shear experiment, that of landslide shear crack soil in saturated state by in situ shear experiment is grater with the degree of 12.25% and 29.38%.The reason of difference between two experimental methods is proposed. It shows that in situ shear experiment is very important to the landslide stability analysis and the optimization of landslide engineering treating, specially to the creep landslide.

scholarly journals Quantifying the Responses of Evapotranspiration and Its Components to Vegetation Restoration and Climate Change on the Loess Plateau of China

2021 ◽  
Vol 13 (12) ◽  
pp. 2358
Author(s):  
Linjing Qiu ◽  
Yiping Wu ◽  
Zhaoyang Shi ◽  
Yuting Chen ◽  
Fubo Zhao
Keyword(s):  
Climate Change ◽  
Loess Plateau ◽  
Dominant Role ◽  
Vegetation Restoration ◽  
Vegetation Coverage ◽  
Ecological Planning ◽  
The Loess Plateau ◽  
Canopy Interception ◽  
Community Land Model ◽  
Spatiotemporal Trends

Quantitatively identifying the influences of vegetation restoration (VR) on water resources is crucial to ecological planning. Although vegetation coverage has improved on the Loess Plateau (LP) of China since the implementation of VR policy, the way vegetation dynamics influences regional evapotranspiration (ET) remains controversial. In this study, we first investigate long-term spatiotemporal trends of total ET (TET) components, including ground evaporation (GE) and canopy ET (CET, sum of canopy interception and canopy transpiration) based on the GLEAM-ET dataset. The ET changes are attributed to VR on the LP from 2000 to 2015 and these results are quantitatively evaluated here using the Community Land Model (CLM). Finally, the relative contributions of VR and climate change to ET are identified by combining climate scenarios and VR scenarios. The results show that the positive effect of VR on CET is offset by the negative effect of VR on GE, which results in a weak variation in TET at an annual scale and an increased TET is only shown in summer. Regardless of the representative concentration pathway (RCP4.5 or RCP8.5), differences resulted from the responses of TET to different vegetation conditions ranging from −3.7 to −1.2 mm, while climate change from RCP4.5 to RCP8.5 caused an increase in TET ranging from 0.1 to 65.3 mm. These findings imply that climate change might play a dominant role in ET variability on the LP, and this work emphasizes the importance of comprehensively considering the interactions among climate factors to assess the relative contributions of VR and climate change to ET.

scholarly journals Effect of Check Dam on Sediment Load Under Vegetation Restoration in the Hekou-Longmen Region of the Yellow River

2022 ◽  
Vol 9 ◽  
Author(s):  
Zeyu Zhang ◽  
Junrui Chai ◽  
Zhanbin Li ◽  
Li Chen ◽  
Kunxia Yu ◽  
...  
Keyword(s):  
Human Activities ◽  
Sediment Load ◽  
Yellow River ◽  
Reduction Rate ◽  
Vegetation Restoration ◽  
Vegetation Coverage ◽  
Dam Construction ◽  
Check Dam ◽  
Reduction Effect ◽  
Sediment Reduction

With years of vegetation restoration and check dam construction on the Loess Plateau, the sediment load of the middle reaches of the Yellow River have decreased sharply; however, the effects of check dam on this decrease of sediment load with such extensive vegetation restoration remains unclear. In order to further clarify the effects of check dam on sediment load reduction under vegetation restoration, we calculated vegetation coverage and check dam index based on multi-source remote sensing data, and calculated sediment reduction rate caused by human activities by Mann-Kendall statistical test and double cumulative curve, then established regression equations incorporating the check dam index and the sediment reduction rate using data from different geomorphic regions with different vegetation coverages. The results showed that sediment load in the Hekou-Longmen region and its 17 tributaries decreased significantly every year, and the change in sediment load could be divided into 3 typical periods: the base period (P1), the period mainly impacted by check dam construction (P2) and the period with comprehensive impact of check dam construction and vegetation restoration (P3). Compared with sediment load of the tributaries during P1, the sediment load decreased by 60.96% during P2 and by 91.76% during P3. Compared with the contribution of human activities to the reduction in sediment load in P2, the contribution of human activities in P3 increased significantly, while that of precipitation decreased slightly. The sediment reduction effect of check dams is greater in basins with low vegetation coverage than in basins with high vegetation coverage. There are differences in sediment reduction effect of vegetation restorations in different geomorphic regions, and the effect of vegetation restoration alone have certain upper limits. Such as, the upper limit of sediment reduction rate of vegetation restoration for rivers flowing through the sandstorm region is 47.86%. Hence, only combined the construction of check dam with vegetation restoration can it achieve more significant sediment reduction benefit and control soil erosion more effectively.

TO DETERMINE THE PHYSICAL AND MECHANICAL PROPERTIES OF THE SOIL OF LANDSLIDE SLOPES FROM THE DEGREE OF POROSITY AND HUMIDITY

InterConf ◽  
2021 ◽  
pp. 917-933
Author(s):  
Аkbota Serikkyzy ◽  
A. Baimakhan ◽  
A. Makhanova ◽  
Baimakhan Baimakhan ◽  
G. Baimakhanova
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
Local Stress ◽  
Saturated Soil ◽  
Degree Of Saturation ◽  
Stress Concentrations ◽  
Mountain Slope ◽  
Experimental Works ◽  
Water Saturated

The results of theoretical and experimental works devoted to the determination of the physical and mechanical properties of water–saturated soil are analyzed. On the basis of a comprehensive analysis, conclusions are formulated, and a method is proposed for determining the Young’s modulus and Poisson’s ratio for water-saturated soil, depending on humidity (degree of saturation) and porosity. Tables of data on the physical and mechanical properties of water–saturated soil are proposed. The study established the places of formation of local stress concentrations along the inclined layer. The values of dangerous stress concentrations found in various areas of the mountain slope that are vulnerable to collapse are shown in the tables.

scholarly journals Research on Wetting-Drying Cycles’ Effect on the Physical and Mechanical Properties of Expansive Soil Improved by OTAC-KCl

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Bao-tian Wang ◽  
Can-hong Zhang ◽  
Xue-lian Qiu ◽  
En-yue Ji ◽  
Wen-hui Zhang
Keyword(s):  
Mechanical Properties ◽  
Expansive Soil ◽  
Physical And Mechanical Properties ◽  
Cyclic Strength ◽  
Soil Samples ◽  
Engineering Properties ◽  
Swelling Potential ◽  
Wetting And Drying ◽  
Strength Tests ◽  
Free Swell

Expansive soil experiences periodic swelling and shrinkage during the alternate wet and dry environments, which will result in severe damage to the slope stability. In this study, a promising modifier OTAC-KCl is introduced, which has a good diffusivity and is soluble in water or other solvents easily. Firstly, a reasonable combination of ameliorant 0.3% STAC and 3% KCl is chosen referring to the free swell test. Then, the best curing period, 14 days, is gotten from UCS tests. The effect of wetting and drying cycles on engineering properties of expansive soil improved by OTAC-KCl admixtures after 14-day curing is also studied accordingly. Both treated and untreated expansive soil samples are prepared for the cyclic wetting-drying tests which mainly include cyclic swelling potential and cyclic strength tests. Experimental results show that the swelling potential of expansive soil samples stabilized with OTAC-KCl is suppressed efficiently, and the untreated soil specimens will collapse when immersed in water while the treated specimens keep in good conditions. Moreover, expansive soil samples modified with 0.3% OTAC + 3% KCl show enough durability on the swelling ability, shear strength, and unconfined compressive strength, which means, that both the physical and the mechanical properties of stabilized expansive soil have been improved effectively.

A Study of Frost-Heave Mechanics of High-Clay Content Soils

1984 ◽  
Vol 106 (4) ◽  
pp. 502-508
Author(s):  
R. N. Yong ◽  
P. Boonsinsuk ◽  
A. E. Tucker
Keyword(s):  
Mechanical Properties ◽  
Construction Projects ◽  
Clay Content ◽  
Experimental Information ◽  
Frost Heave ◽  
Natural Soil ◽  
Scanning Electron Micrographs ◽  
Eastern Canada ◽  
Freeze Thaw ◽  
Soil Fabric

In this study, the problem of frost penetration in high-clay content soils is examined with the view to assessment of cyclic freeze-thaw effects on initial virgin unfrozen natural clays. The requirements for control of the frost-heave problem in many construction projects in the northern regions of Eastern Canada demand that proper prediction be made for both frost-heave pressures and magnitudes of frost heaving in the high-clay content soils. Laboratory cyclic freeze-thaw and frost-heave tests conducted have shown that the mechanical properties of the clay soils, which are virgin unfrozen natural soil samples obtained from Northern Quebec, are sensitive to cyclic freeze-thaw. In the cyclic freeze-thaw tests conducted, scanning electron micrographs taken from samples after various cycles show that the original soil fabric becomes more disturbed after the first few cycles. Particles are re-arranged, and a regrouping of particles into larger stable (or apparently stable) soil fabric units are formed after a certain number of cycles. In essence, this study provides the experimental information concerning the cyclic freeze-thaw effects on mechanical properties for some high-clay content soils, not initially subject to freezing.

scholarly journals Experimental Study on Vegetation Restoration of Abandoned Land in Desert Steppe Nonferrous Metal Mine

2021 ◽  
Vol 293 ◽  
pp. 03005
Author(s):  
Rong Hao ◽  
Shan Dan ◽  
Zhang Tiegang ◽  
Wang Xiaoli ◽  
Wu Xunan
Keyword(s):  
Nonferrous Metal ◽  
Organic Matter Content ◽  
Vegetation Restoration ◽  
Vegetation Coverage ◽  
Desert Steppe ◽  
Efficacy Evaluation ◽  
Metal Mine ◽  
Natural Restoration ◽  
Comprehensive Benefit ◽  
Restoration Measures

Taking the mine dump in nonferrous metal mine as the research object in desert steppe Inner Mongolia, according to the artificial remodeling of the landforms and the characteristics of water and soil erosion, the vegetation restoration model tests on the dumping site were carried out. The ecological effects of four vegetation restoration measures on soil and water storage were analyzed which including shrubs, shrubgrass, grass and natural restoration of vegetation. The research results showed that compared with the natural restoration plant community, the soil surface water content of the three planting restoration measures increased obviously, the soil organic matter content increased but the change difference was not obvious. The vegetation coverage of shrub-grass was 67%, and the aboveground biomass was 132 g/m2. The vegetation restoration measure of shrub-grass had stronger wind-proof and soil-fixing ability than other measures, the vegetation coverage reaches 67% and the above-ground biomass is 132 g/m2. Efficacy evaluation was carried out by the grey correlation method, and Comprehensive benefit of shrubs, shrub-grass and grass all reached higher value. The most comprehensive benefit was the shrub-grass measure, which reached 0.68, and the smallest was shrubs measure also reached 0.60. Three measures cloud be applied to the vegetation restoration of desert steppe metal mining areas, and shrub-grass measure was the best.

scholarly journals The loess landslide on 15 march 2019 in Shanxi Province, China

Landslides ◽  
2020 ◽  
Vol 17 (3) ◽  
pp. 677-686
Author(s):  
Wenhui Shi ◽  
Yanrong Li ◽  
Weiwei Zhang ◽  
Jin Liu ◽  
Shengdi He ◽  
...  
Keyword(s):  
Lessons Learned ◽  
Shanxi Province ◽  
Deep Soil ◽  
Weak Zone ◽  
Loess Landslide ◽  
Perched Water ◽  
Landslide Event ◽  
Loess Landslides ◽  
Triggering Mechanisms ◽  
Mass Volume

AbstractOn 15 March 2019, a fatal deep-seated landslide occurred at the village of Zaoling in Xiangning County of Shanxi Province, China. Extending to an area of about 120 m by 85 m, with an estimated displaced mass volume of 72,000 m3, the landslide left 20 people dead, 13 injured, and 8 buildings destroyed. There were no precursory signals prior to the event, and usual triggering mechanisms for a landslide were absent. Investigation conducted immediately after the incident revealed that the landslide was initiated in a 1.0 to 1.5-m thick-softened layer located at 40 m depth along the contact between the loess and interbedded paleosol layer. This softened layer was highly saturated due to the perched water on top of the relatively impervious paleosol layer and became a critical weak zone since the shear strength of loess is very sensitive to water content. We suggest that the perched water originated from extensive long-term unsaturated seepage of rainwater and local rapid percolation along preferential channels such as sinkholes and root network. The Zaoling landslide confirms that unlike most landslides in non-loess areas, loess landslides can occur without identifiable triggering events. They can result from gradual build up of instability due to slow (in the span of hundred years) accumulation of deep soil water. Based on the lessons learned from this landslide event, suggestions are given for the planning of urban and rural development in loess areas. Due to the fact that the process leading to the development of such a landslide is largely concealed, further research should be aimed at gaining a more thorough understanding of the mechanism of this landslide type.

scholarly journals Response of Preferential Soil Flow to Different Infiltration Rates and Vegetation Types in the Karst Region of Southwest China

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1778
Author(s):  
Xiaoqing Kan ◽  
Jinhua Cheng ◽  
Fang Hou
Keyword(s):  
Preferential Flow ◽  
Vegetation Restoration ◽  
Water Infiltration ◽  
Vegetation Coverage ◽  
Blue Staining ◽  
Karst Region ◽  
Vegetation Types ◽  
Vegetation Communities ◽  
Natural Grasslands ◽  
Matrix Flow

The widespread preferential flow phenomenon has an important impact on the water resource allocation of vegetation restoration in karst regions. In this study, four kinds of water infiltration experiments were conducted on six kinds of vegetation types (Pinus yunnanensis Franch. var. tenuifolia plantation forestlands, Eucalyptus robusta Smith plantation forestlands, Platycladus orientalis (L.) Francoptmxjjkmsc plantation forestlands, secondary forestlands, scrublands, and natural grasslands) separately to evaluate the effect of vegetation restoration on preferential flow in karst regions. The distribution of soil water infiltration was visualized via Brilliant Blue staining (290 images of soil vertical section staining) and data were processed via structural equation model (SEM). Results showed that 15–35 mm water accumulation was beneficial to the visualization of preferential flow. The experimental statement of a higher matrix flow in grassland than in plantations made it possible to draw conclusions of economic importance. Therefore, undergrowth of vegetation coverage in plantation forestlands should be increased. Experimentally analyzing the water-vegetation-soil interaction, shows an increase in vegetation coverage inhibits the development of matrix flow, an increase in soil erodibility may inhibit the development of preferential flow, and an increase in soil clay content may promote the deepening of matrix flow depth. The artificial forest can improve the soil structure and can effectively restore the degree of soil fragmentation; vegetation can be restored reasonably to prevent desertification in karst regions. Therefore, identifying and analyzing the structure characteristics of the soil macropore network under the conditions of natural vegetation communities and artificial vegetation communities in karst-geologic settings is an urgent study, which can provide a reference for improving the restoration measures of artificial forests and sustainable forestry development in karst desertification areas.

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