scholarly journals Experimental Study on Microstructure of Unsaturated Expansive Soil Improved by MICP Method

2021 ◽  
Vol 12 (1) ◽  
pp. 342
Author(s):  
Xinpei Yu ◽  
Hongbin Xiao ◽  
Zhenyu Li ◽  
Junfeng Qian ◽  
Shenping Luo ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Cement Content ◽  
Characteristic Curve ◽  
Expansive Soil ◽  
Spherical Particles ◽  
Water Stability ◽  
Soil Water Characteristic Curve ◽  
Engineering Characteristics ◽  
Unsaturated Expansive Soil

The soil water characteristic curve and microstructure evolution of unsaturated expansive soil improved by microorganisms in Nanning, Guangxi were studied by means of filter paper method and scanning electron microscope imaging (SEM). Based on Fredlung & Xing model, the influence law of different cement content on the soil water characteristic curve of improved expansive soil is proved. According to the analysis of SEM test results, the influence mechanism of MICP method on the engineering characteristics of improved expansive soil is revealed. The results show that with the increase of cement content, the saturated water content and residual water content of the improved expansive soil gradually increased. At the same time, the water stability gradually increased while the air inlet value gradually decreased. The improved expansive soil changes from the superposition of flat particles and flake particles to the contact between spherical particles and flake particles, which indicates that the aggregate increases significantly. With the increase of the content of cement solution, the contact between particles tends to be smooth and the soil pores gradually tend to be evenly distributed. The particle size and microstructure of soil particles was changed and the connection between particles was enhanced in the improved expansive soil. Eventually the strength and water stability of expansive soil were improved. The conclusions above not only provide a theoretical basis for the in-depth study of engineering characteristics of unsaturated expansive soil improved by MICP method, but also offer theoretical evidence for perfecting engineering technology of expansive soil improved by MICP method.

The Experiment on Soil Water Characteristic Curve Considering the Effect of Urea Concentration

2014 ◽  
Vol 919-921 ◽  
pp. 795-799
Author(s):  
Gai Qing Dai ◽  
Dong Fang Tian ◽  
Yao Ruan ◽  
Lang Tian ◽  
You Le Wang
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Characteristic Curve ◽  
Urea Concentration ◽  
Test Method ◽  
Materials Selection ◽  
Valuable Data ◽  
Soil Water Characteristic Curve ◽  
Concentration Test ◽  
The Impact

A new soil water characteristic curve (SWCC) experiment contemplating urea concentration is presented in the paper. We focus on the impact of the SWCC considering urea concentration test method for materials selection and introduction, experimental results, and finally, we have conducted some experiments of SWCC and obtained some valuable data which could affect urea concentration. By using linear fitting, an exponential function between water content and suction and urea concentration is established.

Soil Water Characteristic Curve and its Applications in Tunnel

2011 ◽  
Vol 261-263 ◽  
pp. 1039-1043
Author(s):  
Yu You Yang ◽  
Qin Xi Zhang ◽  
Gui He Wang ◽  
Jia Xing Yu
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Land Subsidence ◽  
Unsaturated Soil ◽  
Characteristic Curve ◽  
Tunnel Construction ◽  
Coupling Theory ◽  
Engineering Analysis ◽  
Soil Water Characteristic Curve ◽  
The Relationship

A soil water characteristic curve (SWCC) can describe the relationship between unsaturated soil matric suction and water content. By analyzing and researching the test data of the soil water characteristic curve researchers can initially establish the SWCC equation and apply this equation to the actual engineering analysis. In another words, this article is based on the fluid-solid coupling theory of unsaturated soil used to analyze and study the problem of land subsidence caused by tunnel construction. Numerical calculations show that the coupling results agree well with the measured curve works.

A Soil Water Characteristic Curve Model Considering Urea Concentration

2013 ◽  
Vol 798-799 ◽  
pp. 157-160
Author(s):  
You Le Wang ◽  
Dong Fang Tian ◽  
Gai Qing Dai ◽  
Yao Ruan ◽  
Lang Tian
Keyword(s):  
Experimental Data ◽  
Water Content ◽  
Soil Water ◽  
Exponential Function ◽  
Characteristic Curve ◽  
Urea Concentration ◽  
Exponential Functions ◽  
Valuable Data ◽  
Soil Water Characteristic Curve ◽  
Curve Model

A new soil water characteristic curve (SWCC) model considering urea concentration is presented in the paper. Two assumptions are used to obtain the model. One is SWCC which could be described by exponential functions in the experiments. Another is relationship between the parameters of exponential functions and urea concentration which is linear based on experimental data. In the research, we have carried out some experiments of SWCC and obtained some valuable data which could affect urea concentration. By using linear fitting, an exponential function between water content and suction and urea concentration is established.

Aggravated water deficit in the Loess Plateau of China as indicated by the soil available water content

2020 ◽  
Author(s):  
Xiao Zhang ◽  
Wenwu Zhao ◽  
Paulo Pereira
Keyword(s):  
Land Cover ◽  
Water Content ◽  
Soil Water ◽  
Water Deficit ◽  
Loess Plateau ◽  
Characteristic Curve ◽  
The Loess Plateau ◽  
Land Cover Types ◽  
Soil Water Characteristic Curve ◽  
Available Water Content

<p>The soil available water content (AWC) has a strong ability to indicate the soil water conditions under different land cover types. Although the AWC has long been calculated, soil water characteristic curve estimation models and the distribution of AWC, as well as the impact factors, have rarely been evaluated in the Loess Plateau of China. In this study, four typical land cover types were selected: introduced shrubland, introduced grassland, natural restored shrubland and natural restored grassland. Four widely used models were compared with the van Genuchten (VG) model, including the Arya and Paris (AP) model, Mohammadi and Vanclooster (MV) model, Tyler and Wheatcraft (TW) model, and linear fitting (LF) model to estimate the wilting point. The distribution of AWC and the relationships with environmental factors were measured and analyzed. The results showed the following: (1) the MV model was the most suitable model to estimate the soil water characteristic curve in the Loess Plateau; (2) the factors impacting the AWC varied under different precipitation gradients, and the area with a mean annual precipitation of 440-510 mm was the most sensitive zone to environmental and vegetation factors; and (3) the soil water deficit was more severe when considering AWC than when considering soil water content (SWC), and the water deficits were different under introduced grassland and introduced shrubland. Consequently, the construction of vegetation restoration should be more cautious and consider the trade-off between soil conservation and water conservation. During restoration, policy makers should focus on the AWC in addition to the SWC to better assess the soil moisture status.</p>

scholarly journals Evaluation of prediction models applied to the soil-water characteristic curve of ideal materials

2020 ◽  
Vol 195 ◽  
pp. 02024
Author(s):  
Roberto Dutra Alves ◽  
Gilson de F. N. Gitirana ◽  
Sai K. Vanapalli
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Soil Water ◽  
Grain Size Distribution ◽  
Characteristic Curve ◽  
Empirical Models ◽  
Spherical Particles ◽  
Soil Water Characteristic Curve ◽  
Varying Coefficients ◽  
Semi Empirical

The development of theoretical and semi-empirical models to study capillary mechanisms and predict the soil-water characteristic curve (SWCC) generally requires the idealization of pore space and pore water, considering simplifying hypotheses. The study of ideal materials comprised of particles with controlled shape and size allows the evaluation of such simplifying hypotheses and the subsequent generalization to actual soils. In this paper, four theoretical and semi-empirical models for the prediction of the SWCC are applied to the prediction of artificial materials comprised of spherical particles. Nineteen grain-size distribution curves, with varying coefficients of uniformity are considered. The dataset is comprised of materials previously published and additional tests carried out by the authors, under highly controlled conditions. The analyses allowed the evaluation of the effect of grain-size distribution curve and shape of the particles. The limitations and advantages of each prediction model was investigated, and a detailed comparison is presented, guiding future implementations of improved models.

Soil water characteristic curve and improvement in lime treated expansive soil

2015 ◽  
Vol 8 (5) ◽  
pp. 687-706 ◽  
Author(s):  
Ahmed M. Al-Mahbashi ◽  
Tamer Y. Elkady ◽  
Talal O. Alrefeai
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Expansive Soil ◽  
Soil Water Characteristic Curve

Effect of Compaction Degree on Soil-Water Characteristic Curve of Chongming Clay

2011 ◽  
Vol 90-93 ◽  
pp. 701-706
Author(s):  
Jing Song Qian ◽  
Hang Lu
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Filter Paper ◽  
Characteristic Curve ◽  
Liquid Limit ◽  
Degree Of Saturation ◽  
Paper Test ◽  
Soil Water Characteristic Curve ◽  
Gravimetric Water Content ◽  
Compaction Degree

The soil-water characteristic defines the relationship between the soil suction and gravimetric water content, w, or the volumetric water content, θ, or the degree of saturation, S. It is a convenient method to predict water content in the subgrade using the curve. But in the field tests of subgrades, the compaction degree of soil became lower with time than initially designed. With the purpose of finding out effect of compaction degree on soil-water characteristic curve, a study to the SWCC (soil-water characteristic curve) of Chongming low liquid limit clay using filter paper method was carried out and is presented in this paper. Specimens of different water contents were prepared by absorbing different amount of water, in order to better simulate the process of wetting of subgrade soil. After the filter paper test, the soil-water characteristic curve was fitted with two models, and then the effect of compaction degree on the curve was analyzed. The figures show that the compaction degree of the specimen will decrease with higher water content, and from the gravimetric water content-matric suction curve, it is found that compaction degree has an effect on air-entry value and water storage capacity.

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