Study on negative friction of pile foundation in single homogeneous soil layer in collapsible loess area of Northwest China

2021 ◽  
Vol 14 (12) ◽  
Author(s):  
Shuaihua Ye ◽  
Zhuangfu Zhao ◽  
Yanpeng Zhu
Keyword(s):  
Pile Foundation ◽  
Soil Layer ◽  
Northwest China ◽  
Loess Area ◽  
Collapsible Loess ◽  
Homogeneous Soil ◽  
Negative Friction

scholarly journals Analysis of Vertical Load Transfer Mechanism of Assembled Lattice Diaphragm Wall in Collapsible Loess Area

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Mingtan Xia ◽  
Xudong Zhang ◽  
Gengshe Yang ◽  
Liu Hui ◽  
Wanjun Ye
Keyword(s):  
Failure Modes ◽  
Load Transfer ◽  
Diaphragm Wall ◽  
Vertical Load ◽  
Soil System ◽  
Loess Area ◽  
Collapsible Loess ◽  
Negative Friction ◽  
Vertical Bearing ◽  
Soil Interface

Based on analysis of the formation mechanism and characteristics of the negative friction in collapsible loess areas, this study investigates the load transfer law of a wall-soil system under a vertical load, establishes the vertical bearing model of a lattice diaphragm wall, and analyzes the vertical bearing capacity of an assembled latticed diaphragm wall (ALDW) in a loess area. The factors influencing the vertical bearing characteristics of the ALDW in a loess area are analyzed. The vertical bearing mechanism of the lattice diaphragm wall in the loess area is investigated. The failure modes of the ALDW in the loess area are mainly shear failure of the soil around the wall and failure of the wall-soil interface. In the generation and development of negative friction, there is always a point where the relative displacement of the wall-soil interface is zero at a certain depth below the ground; at this point, the wall and soil are relative to each other. The collapsibility of loess, settlement of the wall and surrounding soil, and rate and method of immersion are the factors affecting the lattice diaphragm wall. The conclusions of this study provide a reference for the design and construction of ALDWs in loess areas.

scholarly journals Assessment of Carbon Density in Natural Mountain Forest Ecosystems at Northwest China

2021 ◽  
Vol 18 (4) ◽  
pp. 2098
Author(s):  
Li Dai ◽  
Yufang Zhang ◽  
Lei Wang ◽  
Shuanli Zheng ◽  
Wenqiang Xu
Keyword(s):  
Carbon Content ◽  
Carbon Storage ◽  
Forest Ecosystems ◽  
Soil Layer ◽  
Northwest China ◽  
Biomass Carbon ◽  
Forest Age ◽  
Carbon Density ◽  
Old Growth Forest ◽  
Content Ratio

The natural mountain forests in northwest China are recognized as a substantial carbon pool and play an important role in local fragile ecosystems. This study used inventory data and detailed field measurements covering different forest age groups (young, middle-aged, near-mature, mature, old-growth forest), structure of forest (tree, herb, litter and soil layer) and trees (leaves, branches, trunks and root) to estimate biomass, carbon content ratio, carbon density and carbon storage in Altai forest ecosystems. The results showed that the average biomass of the Altai Mountains forest ecosystems was 126.67 t·hm−2, and the descending order of the value was tree layer (120.84 t·hm−2) > herb layer (4.22 t·hm−2) > litter layer (1.61 t·hm−2). Among the tree parts, trunks, roots, leaves and branches accounted for 50%, 22%, 16% and 12% of the total tree biomass, respectively. The average carbon content ratio was 0.49 (range: 0.41–0.52). The average carbon density of forest ecosystems was 205.72 t·hm−2, and the carbon storage of the forest ecosystems was 131.35 Tg (standard deviation: 31.01) inside study area. Soil had the highest carbon storage (65.98%), followed by tree (32.81%), herb (0.78%) and litter (0.43%) layers. Forest age has significant effect on biomass, carbon content ratio, carbon density and carbon storage. The carbon density of forest ecosystems in study area was spatially distributed higher in the south and lower in north, which is influenced by climate, topography, soil types and dominant tree species.

scholarly journals Response Site Analyses of 3D Homogeneous Soil Models

2018 ◽  
Vol 2 (5) ◽  
pp. 238 ◽  
Author(s):  
Davide Forcellini ◽  
Marco Tanganelli ◽  
Stefania Viti
Keyword(s):  
Soil Type ◽  
Soil Depth ◽  
Site Response ◽  
Soil Layer ◽  
Shear Velocity ◽  
Seismic Intensity ◽  
Eurocode 8 ◽  
Seismic Input ◽  
Homogeneous Soil ◽  
Response Site

The seismic excitation at the surface can be determined through Site Response Analyses (SRA) as to account for the specific soil properties of the site. However, the obtained results are largely affected by the model choice and setting, and by the depth of the considered soil layer. This paper proposes a refined 3D analytical approach, by the application of OPENSEES platform. A preliminary analysis has been performed to check the model adequacy as regards the mesh geometry and the boundary conditions. After the model setting, a SRA has been performed on various soil profiles, differing for the shear velocity and representing the different soil classes as proposed by the Eurocode 8 (EC8). Three levels of seismic hazard have been considered. The seismic input at the bedrock has been represented consequently, through as much ensembles of seven ground motions each, spectrum-compatible to the elastic spectra provided by EC8 for the soil-type A (bedrock). Special attention has been paid to the role of the considered soil depth on the evaluation of the surface seismic input. Different values of depth have been considered for each soil type and seismic intensity, in order to check its effect on the obtained results.

scholarly journals Study on Bottom Damp-Proof Method of Cave Dwelling

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
Rong Wan ◽  
De-quan Kong ◽  
Li-xin Zhang
Keyword(s):  
Cultural Heritage ◽  
Environmental Protection ◽  
Northwest China ◽  
Living Environment ◽  
Practical Significance ◽  
Construction Technology ◽  
High Moisture ◽  
Loess Area ◽  
Ancient Times ◽  
Poor Ventilation

The cave dwelling, as one of the most typical and traditional characteristic local housing styles in the loess area of Northwest China, has been adopted widely in many areas since ancient times. The construction of the cave dwellings supports environmental protection, makes use of innovative construction technology, and preserves historical cultural heritage. The cave dwellings have practical significance and play an important role in the current society. Although there are many natural advantages to use cave dwellings, they also pose many problems, such as high moisture, inadequate lighting, poor ventilation, insufficient strength, and so on. The most serious problem is related to moisture, which affects the comfort, security, and safety of the residents; it needs to be addressed. The authors propose to resolve this problem by developing a method of building a damp-proof course in the bottom of these cave dwellings. Meanwhile, specified experiments were carried out to validate the feasibility of this method. The results show that the method is reasonable and practical, and it can be implemented easily and conveniently in the future. This research has significant practical value; the results can improve people’s living environment and increase comfort and safety of cave dwelling.

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