Formation mechanism of collapsing gully in southern China and the relationship with granite residual soil: A geotechnical perspective

AbstractThe climate is a significant factor affecting the collapsing gully in weathered granite areas, and most of the surface layers of the collapsed area comprise granite residual soil. Granite residual soil has complex disintegration characteristics under different initial water content conditions. Besides, its disintegration characteristic is an essential factor for collapsing gully. Therefore, disintegration tests, triaxial shear tests, nuclear magnetic resonance tests, and hydraulic conductivity tests are conducted under torridity and rainstorm conditions in order to study the disintegration characteristics of granite residual soil. The results of disintegration test showed that the initial disintegration rate of granite residual soil increased rapidly with the decrease in water content, while the relationship between disintegration rate and water content in the later stage of disintegration is unclear. When soaked, the maximum decrease in cohesion was 44.48%, the hydraulic conductivity became six times larger, and the amplitude of the T2 curve increased by about 40%, which reduced the strength of the soil and provided better access for rainwater infiltration to deeper stratum. The results show that the microstructure of granite residual soil would be damaged and the disintegration would occur after a rainstorm at low water content. Micropores would be formed inside the sample after soaking, resulting in destroying the continuity of the material.

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Laboratory model test study of the hydrological effect on granite residual soil slopes considering different vegetation types

Scientific Reports ◽

10.1038/s41598-021-94276-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jie Chen ◽

Xue-wen Lei ◽

Han-lin Zhang ◽

Zhi Lin ◽

Hui Wang ◽

...

Keyword(s):

Root System ◽

Heavy Rainfall ◽

Storage Capacity ◽

Water Storage ◽

Laboratory Model ◽

Residual Soil ◽

Vegetation Types ◽

Water Storage Capacity ◽

Granite Residual Soil ◽

Stem Leaf

AbstractThe problems caused by the interaction between slopes and hydrologic environment in traffic civil engineering are very serious in the granite residual soil area of China, especially in Guangdong Province. Against the background of two heavy rainfall events occurring during a short period due to a typhoon making landfall twice or even two typhoons consecutively making landfall, laboratory model tests were carried out on the hydrological effects of the granite residual soil slope considering three vegetation types under artificial rainfall. The variation in slope surface runoff, soil moisture content and rain seepage over time was recorded during the tests. The results indicate that surface vegetation first effectively reduces the splash erosion impact of rainwater on slopes and then influences the slope hydrological effect through rainwater forms adjustment. (1) The exposed slope has weak resistance to two consecutive heavy rains, the degree of slope scouring and soil erosion damage will increase greatly during the second rainfall. (2) The multiple hindrances of the stem leaf of Zoysia japonica plays a leading role in regulating the hydrological effect of slope, the root system has little effect on the permeability and water storage capacity of slope soil, but improves the erosion resistance of it. (3) Both the stem leaf and root system of Nephrolepis cordifolia have important roles on the hydrological effect. The stem leaf can stabilize the infiltration of rainwater, and successfully inhibit the surface runoff under continuous secondary heavy rainfall. The root system significantly enhances the water storage capacity of the slope, and greatly increases the permeability of the slope soil in the second rainfall, which is totally different from that of the exposed and Zoysia japonica slopes. (4) Zoysia is a suitable vegetation species in terms of slope protection because of its comprehensive slope protection effect. Nephrolepis cordifolia should be cautiously planted as slope protection vegetation. Only on slopes with no stability issues should Nephrolepis cordifolia be considered to preserve soil and water.

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Evaluating of the spatial heterogeneity of soil loss tolerance and its effects on erosion risk in the carbonate areas of southern China

Solid Earth ◽

10.5194/se-8-661-2017 ◽

2017 ◽

Vol 8 (3) ◽

pp. 661-669 ◽

Cited By ~ 9

Author(s):

Yue Li ◽

Xiao Yong Bai ◽

Shi Jie Wang ◽

Luo Yi Qin ◽

Yi Chao Tian ◽

...

Keyword(s):

Soil Erosion ◽

Spatial Heterogeneity ◽

Soil Loss ◽

Carbonate Rock ◽

Southern China ◽

Clastic Rock ◽

Erosion Risk ◽

Soil Loss Tolerance ◽

Loss Tolerance ◽

The Relationship

Abstract. Soil loss tolerance (T value) is one of the criteria in determining the necessity of erosion control measures and ecological restoration strategy. However, the validity of this criterion in subtropical karst regions is strongly disputed. In this study, T value is calculated based on soil formation rate by using a digital distribution map of carbonate rock assemblage types. Results indicated a spatial heterogeneity and diversity in soil loss tolerance. Instead of only one criterion, a minimum of three criteria should be considered when investigating the carbonate areas of southern China because the one region, one T value concept may not be applicable to this region. T value is proportionate to the amount of argillaceous material, which determines the surface soil thickness of the formations in homogenous carbonate rock areas. Homogenous carbonate rock, carbonate rock intercalated with clastic rock areas and carbonate/clastic rock alternation areas have T values of 20, 50 and 100 t/(km2 a), and they are extremely, severely and moderately sensitive to soil erosion. Karst rocky desertification (KRD) is defined as extreme soil erosion and reflects the risks of erosion. Thus, the relationship between T value and erosion risk is determined using KRD as a parameter. The existence of KRD land is unrelated to the T value, although this parameter indicates erosion sensitivity. Erosion risk is strongly dependent on the relationship between real soil loss (RL) and T value rather than on either erosion intensity or the T value itself. If RL > > T, then the erosion risk is high despite of a low RL. Conversely, if T > > RL, then the soil is safe although RL is high. Overall, these findings may clarify the heterogeneity of T value and its effect on erosion risk in a karst environment.

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Effect of cementation on the small-strain stiffness of granite residual soil

SOILS AND FOUNDATIONS ◽

10.1016/j.sandf.2021.02.001 ◽

2021 ◽

Vol 61 (2) ◽

pp. 520-532

Author(s):

Xinyu Liu ◽

Xianwei Zhang ◽

Lingwei Kong ◽

Xinming Li ◽

Gang Wang

Keyword(s):

Small Strain ◽

Residual Soil ◽

Small Strain Stiffness ◽

Granite Residual Soil

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Small strain stiffness for granite residual soil: effect of stress ratio

Canadian Geotechnical Journal ◽

10.1139/cgj-2021-0308 ◽

2021 ◽

Author(s):

Xianwei Zhang ◽

Xinyu Liu ◽

Lingwei Kong ◽

Gang Wang ◽

Cheng Chen

Keyword(s):

Stress Ratio ◽

Small Strain ◽

Residual Soil ◽

Resonant Column ◽

Residual Soils ◽

Column Tests ◽

Small Strain Stiffness ◽

Deviator Stress ◽

Granite Residual Soil ◽

Stress Ratios

Most previous studies have focused on the small strain stiffness of sedimentary soil while little attention has been given to residual soils with different properties. Most studies also neglected the effects of the deviator stress, which is extensively involved in civil engineering. This note considers the effects of the deviator stress on the small-strain stiffness of natural granite residual soil (GRS) as established from resonant column tests performed under various stress ratios. Although increasing the stress ratio results in a greater maximum shear modulus for both natural and remolded residual soils, remolded soil is more sensitive to changes in the stress ratio, which highlights the effects of soil cementation. The data herein offers new insights to understand the stiffness of residual soil and other weathered geomaterials.

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New Understandings of the Relationship and Initial Formation Mechanism for Pseudo-lignin, Humins, and Acid-Induced Hydrothermal Carbon

Journal of Agricultural and Food Chemistry ◽

10.1021/acs.jafc.8b04754 ◽

2018 ◽

Vol 66 (45) ◽

pp. 11981-11989 ◽

Cited By ~ 22

Author(s):

Banggui Cheng ◽

Xiaohui Wang ◽

Qixuan Lin ◽

Xiao Zhang ◽

Ling Meng ◽

...

Keyword(s):

Formation Mechanism ◽

Initial Formation ◽

The Relationship

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Experimental study on cementation strength of unsaturated granite residual soil

Green Building, Materials and Civil Engineering ◽

10.1201/b17568-168 ◽

2014 ◽

pp. 807-812

Keyword(s):

Experimental Study ◽

Residual Soil ◽

Granite Residual Soil

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The President’s Influence on the Formation of Lithuanian Foreign Policy: A Shift of the Power Center During Grybauskaitė’s Term

Politologija ◽

10.15388/polit.2019.94.1 ◽

2019 ◽

Vol 94 (2) ◽

pp. 8-55

Author(s):

Tomas Janeliūnas

Keyword(s):

Foreign Policy ◽

Formation Mechanism ◽

Policy Making ◽

Policy Formation ◽

Foreign Affairs ◽

Power Center ◽

And Behavior ◽

The Relationship

This article raises the question of what role does the presidential institution hold in the Lithuanian foreign policy formation mechanism and how a particular actor (president) can change their powers in foreign policy without going beyond the functions formally defined in the Constitution. The period of President Grybauskaitė’s term and her efforts as an actor to define her role in shaping Lithuanian foreign policy are analyzed. This is assessed in the context of the activities and behavior of former Lithuanian presidents and in the context of relations with other institutions involved in foreign policy making – the Ministry of Foreign Affairs (MFA) and the Seimas in particular. This article analyzes the relationship between the actor (Grybauskaitė) and the already established structure of domestic foreign policy formation and the ability of the actor to change this structure. The analysis suggests that it is precisely because of the choices made by Grybauskaite during 2009–2019 that a relationship between the structures of foreign policy making in Lithuania has changed considerably, and that the center of power of foreign policy formation has shifted to the presidency.

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