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Analysis of influencing factors of Rayleigh surface wave exploration depth
Published in Mohd Johari Mohd Yusof, Junwen Zhang, Advances in Civil Engineering: Structural Seismic Resistance, Monitoring and Detection, 2023
The thickness and softness of the overburden have a great influence on the exploration depth. The geological conditions of the overburden often determine the maximum exploration depth in this area, such as the loess overburden. Loess is a silty soil-like deposit formed through hundreds of thousands of years of weathering, erosion, and accumulation. The thickness is large, distributed from tens to hundreds of meters. Soft and loose loess not only has low Rayleigh wave speed but also has a strong absorption and attenuation effect on seismic waves. Therefore, the exploration depth of loess is generally within 10~20m, and it can reach 40~50m on some dense soils, but these are all up to less than the buried depth of most loess.
Collapsibility of Egyptian loess soil
Published in H. Rahardjo, D.G. Toll, E.C. Leong, Unsaturated Soils for Asia, 2020
F. M. Abdrabbo, R. M. El Hansy, K. M. Hamed
Some collapsible soils are deposited in such a way that they exist in a loose honeycomb-type structure at a relatively low density. At their natural low moisture content they possess high apparent strength, but are susceptible to a large reduction in void ratio upon wetting. Some other collapsible soils are generally composed of uniform, silt-sized particles, which were loosely deposited, and are bonded together with relatively small fraction of clay forming the typical loess structure. Normally, loess has high shearing resistance and withstands high stresses without great settlement, when natural moisture content is low. However, upon wetting, the clay bond tends to soften and cause collapse of the loess structure inducing large settlement under low level of stresses. Therefore, it is dangerous to construct on these soils without improving their characteristics.
Empirical relationships of the landslides in the Chinese Loess Plateau and affect factors analysis
Published in Geomatics, Natural Hazards and Risk, 2022
Jianqi Zhuang, Penghui Ma, Jiewei Zhan, Yi Zhu, Jiaxu Kong, Xinghua Zhu, Yanqiu Leng, Jianbing Peng
Loess which, occupies approximately 10% of the Earth’s landmass, is a loose aeolian deposit of yellowish silt-sized dust formed during the past 2.5 Ma (Liu 1985; Li et al. 2020). It is widely distributed in arid and semi-arid regions in Eurasia, North America, Latin America, and Central Asia (Pécsi 1990; Li et al. 2020). In China, loess is primarily distributed on the Chinese Loess Plateau (CLP), which has an area of approximately 640,000 km2 and is located in the center of the Yellow River (Liu 1985, Figure 1(a)). The thickness of the loess deposits in this area varies from a few meters to more than 300 meters and has the largest and thickest loess deposits in the world (Liu 1985). Loess is naturally deposited by accumulating wind-blown fine sand and clay components. The fine sand and clay components of loess contain various salt substances, such as KCl and NaCl, which are the primary substances that contribute to the solubility of loess in water (Zhang et al. 2013; Li et al. 2020; Zhang et al. 2020; Feng et al. 2020, 2021; Zhuang et al. 2021). This characteristic makes the loess very sensitive to water and environmental change and increases the loess’s susceptibility to erosion and loess-related geohazards (Derbyshire et al. 2000; Zhang and Liu 2010; Xu et al. 2014; Zhuang et al. 2018a). The slope failures are the most frequent form of loess-related geohazards with more than 50 landslides occurring every year in the CLP, resulting in human life loss, destruction of roads and railways, as well as decreasing useable farmland (Zhuang et al. 2018a; Juang et al. 2019).
In situ tests on improvement of collapsible loess with large thickness by down-hole dynamic compaction pile
Published in European Journal of Environmental and Civil Engineering, 2020
Yu-chuan Zhang, Yong-guo Yao, An-gang Ma, Chen-lin Liu
Loess is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust (Dijkstra, 2001; Lecturer, 1996; Pye, 1995). When soaked by water, some of loess will occur prominent and rapid collapse under the self-weight pressure of overburden soil or self-weight pressure and additional pressure, which is called collapsible loess (Derbyshire, 2001).The loess is spread widely over the world, with an area of about 1.3 × 107 km2 (Wang, Zhu, & Huang, 2014). In China, the loess covers 6.4 × 105 km2, the collapsible loess accounts for 4.3 × 105 km2, mainly distributing in central and eastern Gansu, southern Ningxia, north-west and central Shaanxi or other areas (Figure 1). Among these areas, in eastern and western Gansu, collapsible loess thickness is between 15 and 40 m (local than 50 m) and self-weight collapsibility is outstanding, belongs to the large-thickness self-weight collapsible loess (Zhang, Yang, & Zhang, 2010).
Size distribution and size of loess slides in response to slope height and slope gradient based on field survey data
Published in Geomatics, Natural Hazards and Risk, 2019
Haijun Qiu, Yifei Cui, Sheng Hu, Dongdong Yang, Yanqian Pei, Shuyue Ma, Zijing Liu
This area has been uplifting since the early Quaternary and is covered by a thick loess-paleosol sequence. Stratigraphically, the loess in this study area can be divided into 4 formations from bottom to top: Late Pliocene Red Clay Formation, Wucheng Loess, Lishi Loess and Malan Loess. Loess is a clastic, homogeneous and predominantly silt-sized sediment formed by the accumulation of wind-blown silt, and it covers approximately 10% of the Earth's surface (Liu 1985). Loess has a loose and porous structure with a large difference between its wet and dry strength (Xu et al. 2012). Loess is a collapsible soil and instantaneously collapses, softens and distorts in the presence of water (Liu 1985; Derbyshire 2001). In contrast to other rock and soil types, vertical jointing in loess is particularly well developed, which influences the hydrological process in loess soil (Liu 1985; Derbyshire 2001). These distinctive properties make the loess area highly susceptible to erosion and landslides (Derbyshire et al. 1991; Zhang et al. 2014).