On the Development of Microstructure in Collapsible Soils

Locat, Jacques

doi:10.1007/978-94-011-0097-7_6

Cited by 14 publications

(5 citation statements)

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“…The clay-rich aggregates were deposited over a glass sample-holder and analyzed by means of XRD, afterwards undergoing different treatments before analyzed again: a K-saturated sample was heated first at 110°and then at 300°C, while one Mg-saturated sample was exposed to ethylene glycol vapour and a second was heated at 550°C. The observation of peaks in the six different samples (K, Mg, K110°, K300°, Mg550°, MgGlyc) and their shifts after treatments allowed us to identify the presence of kaolinite and vermiculite and minor swelling clays; both these minerals often occur in collapsible soils, as highlighted by Locat (1995). The mineralogical composition identified by means of XRD fully confirms the presence of the bioclastic and litoclastic component as observed in optical microscopy on thin sections and a minor content in clay minerals.…”

Section: Chemical Analysismentioning

confidence: 99%

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The open metastable structure of a collapsible sand: fabric and bonding

Zimbardo

Ercoli

Megna

2015

Bull Eng Geol Environ

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This paper deals with the compositional and textural characteristics determining open metastable structures in the pleistocenic sand outcropping in the Agrigento district (Sicily). The aim of the study was to individuate the bonding types occurring between grains that could generate matric suction phenomena. The composition and microfabric were characterised by means of granulometry, porosimetry, permeability, optical and ESEM-EDS microscopy, thermogravimetry and XR diffractometry, electric conductivity, and ionic chromatography. The data thus acquired show that the skeleton of the sand is constituted mostly by bioclasts and microfossils, calcite and quartz monocrystalline grains. Moreover, assemblages of silt and clay minerals are interposed among them. Cementation is generally absent even at the sites of contact between grains. Porosity is due mainly to interparticle voids. The spatial arrangement of sand, silt and limey grains, the pore geometry, volume and size distribution and network connectivity allow both capillary condensation and effective capillary transport of water. It appears that bonding is due mainly to capillary forces related to the texture and to the type of pores rather than being ruled by composition.

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Section: Chemical Analysismentioning

confidence: 99%

“…Thin sections and SEM images allowed pore types to be distinguished. Interparticle pores are more numerous than intraparticle pores, according to Locat (1995). Interparticle macroporosity is sparse and of irregular shape.…”

Section: Texture and Compositionmentioning

confidence: 99%

The open metastable structure of a collapsible sand: fabric and bonding

Zimbardo

Ercoli

Megna

2015

Bull Eng Geol Environ

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“…The effect on the settling mode boundaries of adding 10% smectite, was comparable to increasing the clay-size content to 79% by a procedure which did not change the mineral suite, but would have increased the abundance of illite and chlorite relative to quartz and feldspar in the total material (Kondo and Torrance 2003). Because the clay size fraction of Leda clay commonly contains more total quartz and feldspar than phyllosilicates (Locat 1995), the texture manipulation led to very little change in relative mineral abundance in the clay fraction; the decrease in quartz and feldspar was associated primarily with the decrease in the amount of silt. Unfortunately, the very high water contents in the accumulated sediment at the end of 14 days precluded the taking of undisturbed samples for microstructural analysis.…”

Section: Sedimentation Modes Of Smectite Addition Experimentsmentioning

confidence: 99%

“…They also observed that these materials, in which the dominant clay mineral is a low-swelling, high-iron-content smectite (Egashira and Ohtsubo 1981;Egashira 1993), have similar settling patterns and immediately post-accumulation sediment volume responses as the non-swelling illites rather than as the swelling smectites. In earlier experiments, Torrance (1984) found major similarities between the rheological responses of an Ariake clay and the sensitive marine clays of eastern Canada, which are dominated by quartz, feldspar, illite and chlorite (Torrance 1975(Torrance 1988Locat 1995) and contain only very small amounts of smectite, principally in the fine clay fraction (Berry and Torrance 1998).…”

Section: Introductionmentioning

confidence: 95%

Effects of smectite, salinity and water content on sedimentation and self-weight consolidation of thoroughly disturbed soft marine clay

Kondo

Torrance

2005

Paddy Water Environ

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Addition of a high-swelling smectite to lowactivity-mineral-dominated Leda clay influenced the settling mode, settling/consolidation rates and the final sediment water contents attained when suspensions ranging in water content from 500 to 6000% were allowed to settle under salinity conditions ranging from 30 to 0.5 g/l, and to undergo self-weight consolidation for 14 days. The presence of high-swelling smectite extended the salinity and water content ranges over which consolidation settling and zone settling occurred and the final water content for any initial-water-content/salinity condition increased as the amount of high-swelling smectite increased. The settling and consolidation rate patterns change with time in a manner that is dependent on all of settling mode, water content and salinity. At high-swelling smectite content <5%, the lowest sediment water content is attained under brackish (8-2 g/l salinity) conditions with initial suspension water contents below 1000%. For contents >10%, the lowest sediment water content is attained at high salinity and the lowest possible initial suspension water content.

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“…Since agricultural irrigation began almost five decades ago, high-frequency landslides (3-5 episodes/year) and large-scale surface collapse and subsidence events (with a maximum collapse settlement of 5.96 m) have occurred at Heifangtai area of Gansu, China (Peng et al 2001;Locat, 1995;Zhang et al 2022). Terrace collapses in the Heifangtai area are multi-dimensional deformation processes.…”

Section: Introductionmentioning

confidence: 99%

Effect of collapse-type lateral pressure induced by irrigation

Xia

Zhu

2023

Preprint

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Loess collapse-type lateral pressure may have a landslide-promoting effect in loess slope areas. However, research on the magnitude and characteristics of collapse-type lateral pressure and its impact on slope stability remains blank. A study on the variability of loess collapse-type lateral pressure in the Heifangtai area and its sliding mechanism has been analyzed. Collapse tests and numerical simulations by FLAC3D of loess were conducted according to local safety field theory. The results indicate that Heifangtai loess is self-weighted collapsible loess; soil of the irrigated area at depths of 0-15 m are slightly collapsible; soil at depths of 20-25 m are moderately collapsible loess, and the loess in the unirrigated area regardless of depth is highly collapsible. As the depth or moisture content increases, the lateral pressure gradually increases, correspondingly the deformation becomes greater. In saturated state, the maximum lateral pressure reaches 123 kPa when collapsible deformation occurs, the collapse-type lateral pressure coefficient increases of up to 1.4 times, and horizontal deformation is also correspondingly large. As the water content of the slope increases from 4% to 20%, the total slope displacement increases from 12 mm to 140 mm and covers a large part of the slope, the lateral pressure coefficient also gradually increases, and the range of increase gradually expands; the slope safety coefficient also decreases, the area of failure becomes gradually wider until the slope toe is penetrated; the shear fractures move gradually toward the slope toe, and shear failure occurs at the 1/3 of the slope toe in the collapse deformation process. Collapse action leads to tensile stresses in the upper part of the slope, making it prone to collapse-type crack formation, resulting in dominant channels of surface water infiltration and forming landslide scarps. What’s more, collapse action also enables the formation of compressive stresses in the lower part of the slope, resulting in outward extrusion of deep soil, increased sliding force, and landslide formation.

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On the Development of Microstructure in Collapsible Soils

Cited by 14 publications

References 50 publications

The open metastable structure of a collapsible sand: fabric and bonding

The open metastable structure of a collapsible sand: fabric and bonding

Effects of smectite, salinity and water content on sedimentation and self-weight consolidation of thoroughly disturbed soft marine clay

Effect of collapse-type lateral pressure induced by irrigation

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