Analyses of Anti-Seepage Measure for Expansive Soil Subgrade in Hefei

2014 ◽  
Vol 580-583 ◽  
pp. 552-555
Author(s):  
Yuan Wei ◽  
Wei Zhong Xing ◽  
Yan Shao
Keyword(s):  
Numerical Calculation ◽  
Moisture Content ◽  
Water Content ◽  
Engineering Design ◽  
Control Measure ◽  
Expansive Soil ◽  
Large Change ◽  
Time Range ◽  
Seepage Control ◽  
Unsaturated Expansive Soil

Deformation of expansive soil subgrade depends on moisture content. Anti-seepage measure of unsaturated expansive soil was carried out using ABAQUS as for the influence of atmosphere. The results show that there is large change in water content using anti-seepage measure measure. After using anti-seepage measure, range of water content decreases. At the same time, range of water content value obviously decreases with the increase of the depth of seepage control. Therefore, damage of pavement caused the deformation can decrease by seepage control measure. The results could be used for engineering design and numerical calculation.

scholarly journals Study on Creep Characteristics of Expansive Soil in High-Fill Channel of South-to-North Water Transfer Project

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Jianhua Guo ◽  
Zhangjun Dai ◽  
Shichang Li ◽  
Nadeem Muhammad ◽  
Hui Gao
Keyword(s):  
Moisture Content ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Water Transfer ◽  
Load Level ◽  
Dry Density ◽  
Creep Characteristics ◽  
North Water ◽  
Consolidation Coefficient ◽  
Unsaturated Expansive Soil

In the Nanyang section of the midroute of the South-to-North Water Transfer Project, the expansive soil is often used as a filler for high-fill channels. After the channel is stabilized, the expansive soil undergoes creep deformation over time. Studying the creep characteristics of expansive soils in different environments is particularly important for evaluating the safe operation of high-fill channels. In the current study, the creep test of expansive soil under different moisture content and dry density was carried out. It is proposed that the slope of the fitted straight line in the compression curve of the expansive soil can be used to represent the secondary consolidation coefficient of unsaturated expansive soil, and the variation law of the secondary consolidation coefficient under different environmental factors is obtained. The modified Bjerrum calculation method considering the influence of additional load and lateral deformation yields the postexpansion soil settlement curve model to determine the control index range of the project site. Moreover, it is also observed that the secondary consolidation coefficient of unsaturated expansive soil increases with the increase of moisture content and decreases with the increase of dry density. The coefficient of secondary compression of unsaturated expansive soil is linearly related to dry density and moisture content. After the preconsolidation treatment of the expansive soil, when the load level is less than the preload, the secondary consolidation coefficient is smaller, otherwise the secondary consolidation coefficient is larger.

Field study of rainfall infiltration into a grassed unsaturated expansive soil slope

2007 ◽  
Vol 44 (4) ◽  
pp. 392-408 ◽  
Author(s):  
Tony LT Zhan ◽  
Charles WW Ng ◽  
Del G Fredlund
Keyword(s):  
Field Study ◽  
Water Content ◽  
Pore Water ◽  
Surface Runoff ◽  
Expansive Soil ◽  
Rainfall Infiltration ◽  
Slope Instability ◽  
Simulated Rainfall ◽  
Soil Slope ◽  
Unsaturated Expansive Soil

A full-scale field study was conducted to investigate the effects of rainfall infiltration on a natural grassed expansive soil slope in China. A 16 m wide × 28 m long area was selected for instrumentation. The instrumentation included jet-filled tensiometers, moisture probes, a tipping bucket rain gauge, and a vee-notch flow meter. One artificial rainfall event amounting to about 370 mm rain depth in total was applied to the slope. The monitored results suggested that there was about a 3 day delay in the response of surface runoff, pore-water pressure, and water content to the commencement of the simulated rainfall. The depth of influence of the rainfall, depending on the elevation along the slope, ranged from 2.8 to 3.5 m. Positive pore-water pressures were measured within the influence depth, and there existed significant subsurface downslope flow at the end of the simulated rainfall, particularly near the lower part of the slope. A comparison of infiltration rates between the grassed area and a bare area nearby indicated that the presence of grass significantly increased the infiltration rate and reduced surface runoff. The cracks and fissures developed in the unsaturated expansive soil played an important role in the hydrological process.Key words: expansive soil, slope instability, infiltration, vegetation cover, grass, soil suction, water content, unsaturated soil.

Stability Analysis of Unsaturated Expansive Soil Slope Covered by Geo-Membrane

2015 ◽  
Vol 744-746 ◽  
pp. 597-600
Author(s):  
Hong Yu Zhang ◽  
Jiang Hu Chen ◽  
Wen Qing Wu ◽  
Jun Hua Wu
Keyword(s):  
Stability Analysis ◽  
Water Content ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Expansive Soil ◽  
Construction Process ◽  
Soil Slope ◽  
Seepage Field ◽  
Lower Slope ◽  
Unsaturated Expansive Soil

In view of the holes appearing in different area of geo-membrane when the geo-membrane technology is applied to the unsaturated expansive soil slope, the VADOSE/W is used to analyze the wetting-drying cycles caused by rainfall and evaporation on slopes covered by geo-membrane. The influence on the pore-water pressure and volume water content were discussed just caused by the holes. The results show that the hole is nearer to the toe of slope, its impact on the whole seepage field is greater. In addition, the hole appears on the top of slope that the wetting-drying cycle effect is remarkable. It is ensured that the integrity of the geo-membrane which in the lower slope and take some drainage measures in the construction process.

Numerical Study of Unsaturated Expansive Soil Canal Slope Covered by Geo-Membrane

2015 ◽  
Vol 744-746 ◽  
pp. 551-554
Author(s):  
Wen Qing Wu ◽  
Jiang Hu Chen ◽  
Hong Yu Zhang ◽  
Jun Hua Wu
Keyword(s):  
Water Content ◽  
Water Level ◽  
Soil Water ◽  
Soil Water Content ◽  
Pore Water Pressure ◽  
Numerical Study ◽  
Water Pressure ◽  
Expansive Soil ◽  
Seepage Field ◽  
Unsaturated Expansive Soil

In view of the holes appearing in different areas of geo-membrane when the geo-membrane technology is applied to the unsaturated expansive soil canal slope, the VADOSE/W is used to analyze the pore-water pressure of the internal canal slope by changing the falling water level. The results show that the hole is nearer to the toe of slope, its effect on the whole seepage field is greater. The greater the rate is, the soil water content is greater.

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.

scholarly journals Estimation of Water Content Curve Using Soil Properties Analysis Data

2019 ◽  
pp. 394-403
Author(s):  
Muhannd Waleed Majeed ◽  
Lubna Mohammed Abd ◽  
Mohammed Nsaif Abbas
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Water Content ◽  
Clayey Soil ◽  
Expansive Soil ◽  
Analysis Data ◽  
Moisture Distribution ◽  
Dry Density ◽  
Natural Ecosystems ◽  
Maximum Dry Density

Soil moisture content is one of the most important ecological factors affecting natural ecosystems. This study deals with the soil moisture distribution and its effect on the different types of soil used such as sandy soil, clayey soil, expansive soil and gypsum soil. Each type is brought to the laboratory to determine the physical properties then prepared for compaction test to determine the maximum dry density and optimum water content and discussed the result by comparing the values with them. The largest value of maximum dry density was for clayey soil while the smallest value was for gypsum soil. The largest optimum moisture content was for expansive soil while the smallest value was for gypsum soil too.

scholarly journals Study on Runoff and Infiltration for Expansive Soil Slopes in Simulated Rainfall

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 222
Author(s):  
Wenkai Lei ◽  
Hongyuan Dong ◽  
Pan Chen ◽  
Haibo Lv ◽  
Liyun Fan ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Moisture Content ◽  
Expansive Soil ◽  
Slope Gradient ◽  
Initial Soil Moisture ◽  
Initial Soil

In order to understand the hydrological process of expansive soil slopes, simulated rainfall experiments were conducted to study the effects of slope gradient and initial soil moisture content on runoff and infiltration for expansive soil slopes located in south China. The field program consisted of four neighboring slopes (70%, 47%, 32%, and 21%) instrumented by a runoff collection system and moisture content sensors (EC-5). Results from the monitored tests indicate that there was delay in the response of surface runoff. The runoff initiation time decreased with initial soil water content and increasing slope gradient. After the generation of runoff, the cumulative runoff per unit area and the runoff rate increased linearly and logarithmically with time, respectively. The greater the initial soil moisture content was, the smaller the influence of slope gradient on runoff. A rainfall may contribute from 39% to about 100% of its total rainfall as infiltration, indicating that infiltration remained an important component of the rainwater falling on the slope, despite the high initial soil water content. The larger the initial sealing degree of slope surface was the smaller the cumulative infiltration per unit area of the slope. However, the soil moisture reaction was more obvious. The influence of inclination is no longer discernible at high initial moisture levels. The greater the initial soil moisture content and the smaller the slope gradient, the weaker was the change of soil water content caused by simulated rainfall. The influence of initial soil moisture content and slope gradient on the processes of flow and changes of soil water content identified in this study may be helpful in the surface water control for expansive soil slopes.

Diametric splitting tests on unsaturated expansive soil with different dry densities based on particle image velocimetry technique

2021 ◽  
Vol 18 (1) ◽  
pp. 15-27
Author(s):  
Junran Zhang ◽  
Lijin Wang ◽  
Tong Jiang ◽  
Miao Ren ◽  
min Wei
Keyword(s):  
Tensile Strength ◽  
Particle Image Velocimetry ◽  
Water Content ◽  
Particle Image ◽  
Expansive Soil ◽  
Dry Density ◽  
Particle Image Velocimetry Technique ◽  
Image Velocimetry ◽  
Test Process ◽  
Unsaturated Expansive Soil

There is a close relationship between tensile strength of soil and crack development, but the tensile stress-strain in full failure process is rarely studied because challenges exist in accurately measuring shear strain using traditional methods. In this paper, we employed a newly developed diametric splitting testing apparatus and particle image velocimetry (PIV) system to study the tensile strength of compacted unsaturated expansive soil with different water contents and initial dry densities. Soil water characteristic curves of compacted expansive soil with different initial dry densities were determined using the filter paper method. Test results show that the tensile strength increases first and then decreases with increasing water content, and there is a critical water content for the peak load vs. water content curve. The diametric splitting test process can be divided into four stages on the basis of the plotted load-displacement curves: a stress contact adjustment stage (I); stress approximately linear increasing stage (II); tensile failure stage (III); and residual stage (IV). Under the same water content, the angle between the major directions of the displacement vector and the major crack decreases with increasing the dry density, especially when the fissure appears. Using the particle image velocimetry technique, the displacement and strain during the test process recorded is helpful for better understanding the soil failure mechanism.

scholarly journals Experimental Study on Relationship between Free Load Swelling Rate and Water Content of Medium Expansive Soil

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Cheng Song ◽  
Ligong Yang ◽  
Wei Xia ◽  
Wendong Ji ◽  
Yuting Zhang
Keyword(s):  
Moisture Content ◽  
Water Content ◽  
Moisture Absorption ◽  
Initial Moisture Content ◽  
Expansive Soil ◽  
Experimental Tests ◽  
Expansion Rate ◽  
Dry Density ◽  
Initial Water Content ◽  
Initial Water

Expansive soil has the property of water swelling, which is related not only to the hydrophilic mineral composition of soil particles and the microstructure of soil, but also to the initial moisture content, dry density, and overburden condition of soil. Based on the typical expansive soil in a certain area, the samples were sampled and remodeled at the site. Extensive experimental tests were conducted to investigate the relationship between the hygroscopic expansion rate and the water content of the expansive soil under different initial moisture content, dry density, and free load. The results showed that, under the condition of natural initial water content and dry density, although the hygroscopic expansion rate of the medium expansive soil was nonlinear with the subsequent water content, in the range of large water content (within about 50%), the expansive soil swelled linearly. There was a linear relationship between the rate and the water content. With the increase of the initial water content, the hygroscopic expansion rate and expansion rate of the expansive soil decreased. With the increase of the dry density, the hygroscopic expansion rate and the expansion rate of the expansive soil increased. The water absorption performance did not decrease, and the soil continued to maintain the previous moisture absorption rate and expansion rate after the soil reached saturation, while after the water content reached 1.5∼2.0 times the saturated water content, the soil moisture absorption expansion rate gradually decreased until it finally stabilized. The slope k of the expansion rate increased with the initial dry density and decreased with the initial moisture content. As dry density was increased, the slope k was increased at an increased rate. Moreover, as the initial moisture content was decreased, the slope k was increased at an increased rate.

Sign in / Sign up

Export Citation Format

Share Document