Advanced Unsaturated Soil Mechanics and Engineering

Ng, Charles Wang Wai; Menzies, Bruce

doi:10.1201/9781482266122

Cited by 78 publications

(90 citation statements)

References 0 publications

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“…The presence of clay minerals in TBJ agree with the behavior of collapsible soils [13][14] which are soils composed by silts and fine sand sized particles with small amounts of clays and have low density, but are relative stiff and strong in their natural state. The cementation of the collapsible soils could consists of dried clay, salts, oxides, interparticle forces in clayey soils and chemical precipitates, which may have been added after deposition.…”

Section: Properties Of Tierra Blanca Joven (Tbj)supporting

confidence: 54%

“…The proper study in the lab and field, into the framework of unsaturated soils mechanics, will help to understand the connection between the moisture quantity and behavior of the tephras. The use of soil-water retention curves (SWRC) into finite elements software will assist in obtaining the shear strength and permeability properties [10,14,[16][17][23][24].…”

Section: Methods and Resultsmentioning

confidence: 99%

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Unsaturated Volcanic Tephra and Its Effect for Soil Movement in El Salvador

Chávez¹

2013

EARTH

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Abstract:In El Salvador during the rainy season or when major earthquakes affect the area, processes like mass movements, liquefaction, erosion and floods affect the territory leaving environmental, social and economic damages. The volcanic tephras called "Tierra Blanca Joven" (TBJ) which is a product of the last plinian eruption of the Ilopango Caldera are the more problematic region in the Metropolitan Area of San Salvador. In El Salvador during the summer and rainy season the groundwater level remains low in most of the areas, this means that the soils in the country are unsaturated and there are capillary forces that act on the soil structure making that an "apparent cohesion" (suction) improve the strength of the soil; this circumstance makes that the slopes are almost vertical and temporally stable, but will collapse when wetted or during seismic events. To that problematic is possible to add that the majority of the water pipelines are in bad condition and when they fail is possible to expect the collapse of entire streets or houses. Wetting of the soil is likely to occur following construction development, because evaporation is reduced by covering the ground surface with a structure. For unsaturated soils the use of two independent stress variables: net stress and suction are needed. Suction values of TBJ "G" unit of the proximal facie were obtained using pressure plate, tensiometer and filter paper to obtain a Soil-Water Retention Curve (SWRC); the use of this curve into finite elements software can help to obtain the shear strength and permeability properties. For monitoring, the use of Quickdraw tensiometers (suction) and TMS3 (soil moisture content) is proposed, because it could be a way to build a field methodology for early warning system for the slopes for urban planning and risk assessment.

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Section: Properties Of Tierra Blanca Joven (Tbj)supporting

confidence: 54%

Section: Methods and Resultsmentioning

confidence: 99%

Unsaturated Volcanic Tephra and Its Effect for Soil Movement in El Salvador

Chávez¹

2013

EARTH

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“…Despite being widely used for predicting the performance of fills and for routine investigation of their dynamic properties, a limited number of relationships between the small strain shear modulus (G 0 ) and other compaction properties for unsaturated compacted soil have been established. Recent studies on the small strain behavior of unsaturated soils showed that an increase in matric suction contributes to enhanced stiffness of the soil skeleton which in turn leads to higher values of G 0 (Wu et al, 1984;Cho and Santamarina, 2001;Mancuso et al, 2002;Menzies, 2007, Ng andYung, 2008;Sawangsuriya et al 2009;Asslan and Wuttke (2012) and Biglari and Ashayeri, 2012).…”

Section: Introductionmentioning

confidence: 99%

Laboratory study of small-strain behavior of a compacted silty sand

2013

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Small-strain behavior is a key indicator for assessing the performance of compacted fills. Compaction conditions, i.e., initial moisture content and applied energy, govern compaction effectiveness and thus, the structure and matric suction of compacted soil. This paper presents an experimental study of the small-strain behavior of compacted silty sand prepared with different compaction conditions. Specimens with varying initial moisture contents and compaction energies were tested with bender elements to determine the smallstrain shear modulus (G0), while the post-compaction matric suction was measured using the filter paper method and tensiometer. The experimental data suggest a pronounced relationship between G0 and the degree of saturation (Sr) of the as-compacted soil specimens. X-ray computed tomography (CT) scans were performed to examine structural changes of selected specimens upon compaction. The laboratory results are also examined in light of common end-product specifications, which show that it is beneficial to compact the soil slightly dry of optimum moisture content from the modulus point of view. Abstract: Small strain behavior is a key indicator for assessing the performance of compacted fills. Compaction conditions i.e. initial moisture content and applied energy, govern compaction effectiveness and, thus, the structure and matric suction of compacted soil. This paper presents an experimental study of the small strain behavior of compacted silty sand prepared with different compaction conditions.Specimens with varying initial moisture contents and compaction energies were tested with Bender elements to determine the small strain shear modulus (G 0 ), while the post-compaction matric suction was measured using the filter paper method and tensiometer. The experimental data suggests a pronounced relationship between G 0 and the degree of saturation (S r ) of the as-compacted soil specimens. X-ray computed tomography (CT) scans were performed to examine structural changes of selected specimens upon compaction. The laboratory results are also examined in light of common end-product specifications, which show that it is beneficial to compact the soil slightly dry of optimum moisture content from the modulus point of view.CE Database subject headings: small strain shear modulus, compaction energy, degree of saturation, matric suction.3

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“…The method was first formally described by Gardner (1937), and has recently been accepted as a standard method of measuring soil potential (ASTM, 2003), reaching far higher ranges of water potential in comparison to other techniques (Likos and Lu, 2004), and is based on the principle of moisture absorption by filter paper until there is a balance in potential between filter paper and soil (Ng and Menzies, 2007).…”

Section: Filter Paper Methods For the Determination Of The Soil Water mentioning

confidence: 99%

Filter Paper Method for the Determination of the Soil Water Retention Curve

Almeida

Teixeira

Filho

et al. 2015

Rev. Bras. Ciênc. Solo

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high cost and long time required to determine a retention curve by the conventional methods of the richards Chamber and haines Funnel limit its use; therefore, alternative methods to facilitate this routine are needed. The filter paper method to determine the soil water retention curve was evaluated and compared to the conventional method. undisturbed samples were collected from five different soils. Using a Haines Funnel and Richards Chamber, moisture content was obtained for tensions of 2; 4; 6; 8; 10; 33; 100; 300; 700; and 1,500 kPa. in the filter paper test, the soil matric potential was obtained from the filter-paper calibration equation, and the moisture subsequently determined based on the gravimetric difference. The van Genuchten model was fitted to the observed data of soil matric potential versus moisture. Moisture values of the conventional and the filter paper methods, estimated by the van Genuchten model, were compared. The filter paper method, with R² of 0.99, can be used to determine water retention curves of agricultural soils as an alternative to the conventional method.

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Advanced Unsaturated Soil Mechanics and Engineering

Cited by 78 publications

References 0 publications

Unsaturated Volcanic Tephra and Its Effect for Soil Movement in El Salvador

Unsaturated Volcanic Tephra and Its Effect for Soil Movement in El Salvador

Laboratory study of small-strain behavior of a compacted silty sand

Filter Paper Method for the Determination of the Soil Water Retention Curve

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