Laboratory assessment of swelling pressure of expansive soils

Basma, Adnan A.; Al‐Homoud, Azm S.; Husein, Abdallah I.

doi:10.1016/0169-1317(94)00032-l

Cited by 94 publications

(52 citation statements)

References 1 publication

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“…The results show that the final void ratio was higher at lower vertical stresses. A linear best fit curve was plotted in order to estimate the swelling pressure following the "restrained swell test" procedure described by Basma et al [33]; the swelling pressure corresponds to the stress where no expansion occurs. In the present study, the initial void ratio was equal to 0.95; the vertical stress corresponding to this value was 60 kPa (Fig.…”

Section: Oedometer Testsmentioning

confidence: 99%

Investigation of the hydro-mechanical behaviour of compacted expansive clay

Cui

Tang

et al. 2010

Front. Archit. Civ. Eng. China

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International audienceThe hydro-mechanical behaviour of compacted expansive Romainville clay was investigated. The soil was air-dried, crushed, and passed through a 2 mm sieve before being statically compacted to a dry density of 1.35 Mg/m3. The mechanical behaviour was investigated by tests in oedometer with controlled suction using the vapor equilibrium technique (suction s = 0, 9, 39, and 110 MPa). The vertical stress was applied in the range of 0-800 kPa. The experimental results are shown as follows: 1) wetting-induced swelling was higher at lower vertical stresses; 2) the vertical stress under which no swelling occurred during water flooding was estimated at 60 kPa, which can be considered as the swelling pressure of the soil tested; 3) the soil compressibility (changes of volume upon stress increases) was strongly influenced by the soil suction: the lower the suction, the higher the compressibility. The hydraulic behaviour was investigated using a large-scale inltration chamber (800 mm × 1000 mm in section and 1000 mm high). The large size of the soil column allowed burying the volumetric water content sensors (ThetaProbe) without signicantly affecting the water transfer and the soil swelling during inltration. The soil suction was monitored along the soil height (every 100 mm) using various relative humidity sensors and psychrometers. In the inltration test, water was kept on the soil surface and changes in suction and volumetric water content were monitored for 338 d. The wetting front has reached the bottom of the soil column at the end of the test. The data from the simultaneous monitoring of suction and water content were used to determine the water retention curve and the unsaturated hydraulic conductivity using the instantaneous prole method. It has been observed that the soil water retention curve depends on the soil depth; that is to be related to the soil depth-dependent swelling. The unsaturated hydraulic conductivity was found to be quite low, comprised between 3 × 10−11 m/s (at saturated state) and 10−14 m/s (at about 100 MPa suction)

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Section: Oedometer Testsmentioning

confidence: 99%

Investigation of the hydro-mechanical behaviour of compacted expansive clay

Cui

Tang

et al. 2010

Front. Archit. Civ. Eng. China

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“…SEM study must be performed on the dried system, but properties and microstructure of clays both depend on the drying conditions [7,8]. Here the simplest method was chosen of air drying at two constant temperatures, i.e.…”

Section: Microstructural Study By Semmentioning

confidence: 99%

Thermal study of an aged dredged sludge

Stepkowska

Yariv

Pérez-Rodríguez

et al. 1997

Journal of Thermal Analysis

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A dredged sludge was studied to investigate the influence of ageing and of pretreatment on its drying rate, water sorption/retention, thermal mass loss, XRD and microstructure (SEM).Ageing caused change in particle thickness and specific surface, a gradual aggregation to form units of the size 10-50 Ixm, formation of macropores of similar size, unhomogeneity and fissures between aggregates and "super-aggregates". Macropores were detectable by the initial drying rate especially at 45~ They indicated a tendency of collapsing at a lower drying rate at 30~ This is consistent with SEM observations. With ageing the aggregates were more compact and less sensitive to drying.The aggregated system indicated a higher initial drying rate (higher permeability), whereas stirring induced a lower drying rate, favouring the formation of compact laminar structure.XRD peak intensity was lowered with ageing due to decrease in crystallinity (stacking faults and/or decrease in crystallite size). The content of amorphous material was lowered as well, reducing water sorption/desorption, which indicated that the specific surface is lower.From the suitable microstructure induced by ageing some new phases may form (feldspar, zeolites), preferably in the coarser fraction of the sludge. This is disturbed by stirring which operation expels also carbonates from the particle edges and this may reduce the structural strength of the sludge. In aged bentonite suspension a similar tendency was observed of formation of specific microstructures capable of phase transformation, e.g. to feldspar.

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“…They represent the percent increase in height of the sample in one dimensional condition at zero surcharge, the swelling percent of a sample under 6.9 kPa surcharge that is compacted at optimum water content of standard compaction energy [44], and the amount of pressure that prevents the soil sample from swelling [45] respectively. Several studies and investigations analyze the factors and parameters that can be related to the swelling of clayey soils [46][47][48][49]. Among them, the physical properties of soil, such as the initial water content, the initial dry density [50,51], the type and the amount of clay minerals or the clay content, and the Atterberg limits, are the best-researched and considered in relationship with the phenomenon.…”

Section: The Energy Of the System And The Swellingmentioning

confidence: 99%

Squeezed Interstitial Water and Soil Properties in Pleistocene Blue Clays under Different Natural Environments

et al. 2018

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Studies dating almost a century relate clay properties with the structure of the diffuse double layer (DDL), where the charged surfaces of clay crystal behave like an electric capacitor, whose dielectric is the interstitial fluid. The intensity of the inner electric field relates to the concentration and type of ions in the DDL. Other important implications of the model are less stressed: this part of the clay soil system, energetically speaking, is conservative. External contribution of energy, work of overburden or sun driven capillarity and long exposure to border low salinity waters can modify the concentration of pore-waters, thus affecting the DDL geometry, with electric field and energy storage variations. The study of clay soils coming from various natural geomorphological and hydrogeological contexts, determining a different salinity of interacting groundwater, shows how the clay interaction with freely circulating waters at the boundaries produces alterations in the native pore water salinity, and, at the nano-scale, variations of electric field and stored energy from external work. The swelling and the shrinkage of clay soil with their volumetric and geotechnical implications should be regarded as variations of the electrostatic and mechanical energy of the system. The study is based on tests on natural clay soil samples coming from a formation of stiff blue clays, widespread in southern Italy. Geotechnical identification and oedometer tests have been performed, and pore waters squeezed out from the specimens have been analyzed. Tested samples have similar grain size, clay fraction and plasticity; sorted according to the classified geomorphological/hydrogeological contexts, they highlight good correlations among dry density, mechanical work performed in selected stages of the oedometric test, swelling and non-swelling behaviour, and electrical conductivity of the squeezed pore waters. The work performed for swelling and non-swelling samples shows well-defined differences; this endorse the relevance of pore-water salinity in determining the volumetric state of clay soils under overburden and specific hydrogeological border conditions, which together define a specific energetic state.

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Laboratory assessment of swelling pressure of expansive soils

Cited by 94 publications

References 1 publication

Investigation of the hydro-mechanical behaviour of compacted expansive clay

Investigation of the hydro-mechanical behaviour of compacted expansive clay

Thermal study of an aged dredged sludge

Squeezed Interstitial Water and Soil Properties in Pleistocene Blue Clays under Different Natural Environments

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