scholarly journals Effect of Admixture on the Hydraulic Conductivity of Compacted Loess: A Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Pan Liu ◽  
Xuejiao Zhang ◽  
Min Zhang ◽  
Xueqiang Yang
Keyword(s):  
Hydraulic Conductivity ◽  
Land Surface ◽  
Safety Evaluation ◽  
Loess Soil ◽  
Local Area ◽  
High Density ◽  
Lateritic Soil ◽  
Distribution Area ◽  
Engineering Practice ◽  
Compacted Loess

Hydraulic characteristic of the exposed ground plays an important role in the construction of “sponge city,” which is a popular concept in the world recently. Loess soil, which is a common geomaterial in its distribution area approximately 9.3% of the world’s land surface, usually could not satisfy the engineering requirement only by compacting without any other treatments. This paper aims to investigate the effect of a natural geomaterial, lateritic soil, which is more economical and environmental than the traditional admixtures such as cement and lime, on the saturated hydraulic conductivity (ksat) of compacted loess. A series of falling-head permeability tests on pure loess and lime-treated loess were carried out firstly for comparison; then lime-treated loess mixed with different contents of lateritic soil was tested. To verify the availability of the coverage of high density lateritic soil on pure loess for antipermeability, which is a common treatment in local area, tests of different thickness of the coverage were conducted. The test results revealed that the admixture of lime could obviously decrease ksat of pure loess and 3% might be the most economical content. An empirical algorithm was proposed based on the results to estimate ksat of lime-treated loess of which the lime content is out of the scope studied in this paper, and it would be useful for engineering design and numerical simulation of safety evaluation. The addition of lateritic soil in the 3% lime-treated loess could further decrease ksat and its performance for antipermeability was better than increasing the lime contents simply. The coverage of high density lateritic soil could also improve the antipermeability of loess, and thickness at least of 30 mm was suggested for engineering practice.

Test Investigation on Mechanical of Unsaturated Loess

2012 ◽  
Vol 204-208 ◽  
pp. 22-27
Author(s):  
Yan Zhu ◽  
Yun Xu Chen
Keyword(s):  
Water Content ◽  
Horizontal Plane ◽  
Mechanical Characteristics ◽  
Loess Soil ◽  
Dry Density ◽  
One Dimensional ◽  
Test Investigation ◽  
Unsaturated Loess ◽  
Test Result ◽  
Compacted Loess

Compression and collapse of unsaturated compacted loess are studied by using dry density and water content which easily controlled in engineering, the controlling range of dry density and water content are confirmed respectively. Then the deformation of compression and collapse and the frequency of engineering damager occurrence can be decreased. In addition, the mechanical characteristics of loess in different directions may differ because the loess was consolidated only under the condition of its upper weight of soil and load. The conventional mechanical experiments, including one-dimensional compress and collapse test, were conducted with the specimen of loess soil in different angle from the original horizontal plane. The test result shows that the loess is anisotropic

Reliability Evaluation of Hydraulic Conductivity Characteristics of Waste Wood Ash Treated Lateritic Soil

2018 ◽  
Vol 37 (2) ◽  
pp. 533-547 ◽  
Author(s):  
Johnson R. Oluremi ◽  
Stephen T. Ijimdiya ◽  
Adrian O. Eberemu ◽  
Kolawole J. Osinubi
Keyword(s):  
Hydraulic Conductivity ◽  
Reliability Evaluation ◽  
Wood Ash ◽  
Lateritic Soil ◽  
Waste Wood

scholarly journals Quantifying the Effects of Urban Form on Land Surface Temperature in Subtropical High-Density Urban Areas Using Machine Learning

2019 ◽  
Vol 11 (8) ◽  
pp. 959 ◽  
Author(s):  
Yanwei Sun ◽  
Chao Gao ◽  
Jialin Li ◽  
Run Wang ◽  
Jian Liu
Keyword(s):  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Urban Form ◽  
Urban Areas ◽  
Thermal Environment ◽  
High Density ◽  
Cooling Effects ◽  
Urban Thermal Environment ◽  
The Impact

It is widely acknowledged that urban form significantly affects urban thermal environment, which is a key element to adapt and mitigate extreme high temperature weather in high-density urban areas. However, few studies have discussed the impact of physical urban form features on the land surface temperature (LST) from a perspective of comprehensive urban spatial structures. This study used the ordinary least-squares regression (OLS) and random forest regression (RF) to distinguish the relative contributions of urban form metrics on LST at three observation scales. Results of this study indicate that more than 90% of the LST variations were explained by selected urban form metrics using RF. Effects of the magnitude and direction of urban form metrics on LST varied with the changes of seasons and observation scales. Overall, building morphology and urban ecological infrastructure had dominant effects on LST variations in high-density urban centers. Urban green space and water bodies demonstrated stronger cooling effects, especially in summer. Building density (BD) exhibited significant positive effects on LST, whereas the floor area ratio (FAR) showed a negative influence on LST. The results can be applied to investigate and implement urban thermal environment mitigation planning for city managers and planners.

Impact of an Exponential Profile of Saturated Hydraulic Conductivity within the ISBA LSM: Simulations over the Rhône Basin

2006 ◽  
Vol 7 (1) ◽  
pp. 61-80 ◽  
Author(s):  
B. Decharme ◽  
H. Douville ◽  
A. Boone ◽  
F. Habets ◽  
J. Noilhan
Keyword(s):  
High Resolution ◽  
Hydraulic Conductivity ◽  
Land Surface ◽  
Large Scale ◽  
Saturated Hydraulic Conductivity ◽  
Rooting Depth ◽  
Surface Model ◽  
Low Resolution ◽  
The Impact ◽  
Hydrological Applications

Abstract This study focuses on the influence of an exponential profile of saturated hydraulic conductivity, ksat, with soil depth on the water budget simulated by the Interaction Soil Biosphere Atmosphere (ISBA) land surface model over the French Rhône River basin. With this exponential profile, the saturated hydraulic conductivity at the surface increases by approximately a factor of 10, and its mean value increases in the root zone and decreases in the deeper region of the soil in comparison with the values given by Clapp and Hornberger. This new version of ISBA is compared to the original version in offline simulations using the Rhône-Aggregation high-resolution database. Low-resolution simulations, where all atmospheric data and surface parameters have been aggregated, are also performed to test the impact of the modified ksat profile at the typical scale of a climate model. The simulated discharges are compared to observations from a dense network consisting of 88 gauging stations. Results of the high-resolution experiments show that the exponential profile of ksat globally improves the simulated discharges and that the assumption of an increase in saturated hydraulic conductivity from the soil surface to a depth close to the rooting depth in comparison with values given by Clapp and Hornberger is reasonable. Results of the scaling experiments indicate that this parameterization is also suitable for large-scale hydrological applications. Nevertheless, low-resolution simulations with both model versions overestimate evapotranspiration (especially from the plant transpiration and the wet fraction of the canopy) to the detriment of total runoff, which emphasizes the need for implementing subgrid distribution of precipitation and land surface properties in large-scale hydrological applications.

Safety evaluation of truss structures using nested discrete Bayesian networks

2020 ◽  
Vol 19 (6) ◽  
pp. 1924-1936 ◽  
Author(s):  
Sheng-En Fang ◽  
Jia-li Tan ◽  
Xiao-Hua Zhang
Keyword(s):  
Bayesian Network ◽  
Conditional Probability ◽  
Network Topology ◽  
Safety Evaluation ◽  
System Level ◽  
Truss Structures ◽  
Engineering Practice ◽  
Directed Edge ◽  
Civil Structures ◽  
Nested Network

Truss structures have been widely adopted for civil structures such as long-span buildings and bridges. An actual truss system is usually statically indeterminate having numerous members and high redundancy. It is practically difficult to evaluate the truss safety through traditional reliability-based approaches in view of complex failure modes and uncertainties. Moreover, monitoring data are generally insufficient in reality due to limited sensors under cost consideration. Therefore, a nested discrete Bayesian network has been developed for safety evaluation of truss structures. A concept of member risk coefficient is first proposed based on the mechanical relationship between load effects and member resistance. According to the coefficients of all members, member risk sequences are found as the basis for establishing the topology of a member-level Bayesian network. Each network node represents a truss member and a nodal variable having three states: elasticity, plasticity, and failure. Two relevant member nodes are connected by a directed edge whose causality strength is expressed by a conditional probability table. Meanwhile, a system-level network topology is established to reflect the effects of member states on the truss system. The system is assigned with a node having two states: safety and failure. The directed edge of each member node directly points to the system node. Then, the two networks are combined to form a nested network topology. By this means, direct topology learning is avoided in order to find rational and concise topologies satisfying the mechanical characteristics of civil structures. After that, the conditional probability tables for the nested network are obtained through parameter learning on complete numerical observation data. The data acquirement procedure takes into account uncertainties by defining the randomness of cross-sectional areas and external loads. With the conditional probability tables, the nested network is ready for use. When new evidence from limited monitored members is input into the nested network, the state probabilities of the other members, as well as the system, are simultaneously updated using exact inference algorithms. The inference ability using insufficient information well accords with the demand of engineering practice. Finally, the proposed method has been successfully verified against both numerical and experimental truss structures. It was found that the network estimations could be further confirmed with more evidence.

Lateritic Soil Treated with Waste Wood Ash As Liner in Landfill Construction

2019 ◽  
Vol 25 (2) ◽  
pp. 127-139 ◽  
Author(s):  
Johnson R. Oluremi ◽  
Adrian O. Eberemu ◽  
Stephen T. Ijimdiya ◽  
Kolawole J. Osinubi
Keyword(s):  
Compressive Strength ◽  
Hydraulic Conductivity ◽  
Unconfined Compressive Strength ◽  
Wood Ash ◽  
Engineering Properties ◽  
Volumetric Shrinkage ◽  
Lateritic Soil ◽  
Waste Wood ◽  
K Value ◽  
British Standard

ABSTRACTInherent variability in engineering properties of lateritic soil in relation to its plasticity, permeability, strength, workability, and natural moisture content, has made it an unpredictable material for use in civil engineering works, resulting in the need for its treatment by stabilization. A lateritic soil classified as A-6(6) and CL, according to American Association of State Highway and Transportation Officials and Unified Soil Classification System of ASTM (2011), was treated with up to 10 percent waste wood ash (WWA). Compaction was carried out using four energies, namely, reduced British Standard light, British Standard light (BSL), West African Standard, and British Standard heavy, on samples, which were then examined for hydraulic conductivity, volumetric shrinkage, and unconfined compressive strength as major criteria for use as liner and for the development of acceptable zones. Specimens with 4 percent WWA content compacted with a minimum BSL energy satisfied the maximum hydraulic conductivity (k) value of 1 × 10−9 m/s, maximum volumetric shrinkage strain of 4 percent, and minimum unconfined compressive strength value of 200 kN/m2 required for use as liner in engineered landfills. The overall acceptable zone was enlarged for up to 4 percent WWA content, thereby accommodating higher moulding water content, but the minimum compactive effort required to achieve it became reduced. The beneficial treatment of lateritic soil with up to 4 percent WWA will perform satisfactorily as liner and covers in waste containment application and will minimize the pollution and environmental impact of wood waste disposal.

Safety evaluation of different acids in high-density polyethylene container loading

2020 ◽  
Vol 63 ◽  
pp. 103991
Author(s):  
Bin Laiwang ◽  
Shang-Hao Liu ◽  
Jen-Hao Chi ◽  
Mao-Sen Wen ◽  
Chi-Min Shu
Keyword(s):  
High Density Polyethylene ◽  
Safety Evaluation ◽  
High Density ◽  
Container Loading ◽  
Polyethylene Container

High Density Turbo TDMR Detection With Local Area Influence Probabilistic Model

2017 ◽  
Vol 53 (2) ◽  
pp. 1-8 ◽  
Author(s):  
Xueliang Sun ◽  
Krishnamoorthy Sivakumar ◽  
Benjamin J. Belzer ◽  
Roger Wood
Keyword(s):  
Probabilistic Model ◽  
Local Area ◽  
High Density

Application of the Comprehensive Geophysical Prospecting Techniques in Hidden Trouble Detection of Tailings Dam

2012 ◽  
Vol 166-169 ◽  
pp. 2562-2565
Author(s):  
Hai Yan Ju ◽  
Jiang Qian Zhao ◽  
Jian Hua Li ◽  
Bin Xu ◽  
Chang Tai Luo
Keyword(s):  
Surface Wave ◽  
Mine Tailings ◽  
Safety Evaluation ◽  
Transient State ◽  
High Density ◽  
Tailings Dam ◽  
Wave Method ◽  
Geophysical Prospecting ◽  
Resistivity Method ◽  
Surface Wave Method

Geophysical detecting methods are used widely in hidden trouble exploration of embankments and dams because of their portability and efficiency. The high-density resistivity method and the transient state surface wave method are used to investigate the mine tailings dam, combining the hidden trouble characteristic and feature of the mine tailings dam, the distribution range, the defect feature and the density of the dam material are found out by using the comprehensive methods. The techniques would be offering reference for controlling mine tailings dam seepage and stability and safety evaluation.

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