Conditions to induce water repellency in soils with dimethyldichlorosilane

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Permeability and compressibility of wax-coated sands

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Wettability of crushed air-dried minerals

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Comparison of three silane compounds to impart water repellency in an industrial sand

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Testing surfactants as additives for clay improvement: compaction and suction effects

Environmental Geotechnics (Joint TC106-TC215 Session)This paper presents an exploratory study on surfactants as additives to improve soil properties. It is hypothesized that surfactant molecules populate the air-water interfaces reducing surface tension and suction thus allowing a control of the mechanical response of the soil. Suction measurements by means of a high suction tensiometer, compaction tests and Atterberg limits were conducted in mixtures of sand and kaolin, with and without a surfactant solution. The results revealed a prominent effect on suction, but to a lesser extent on the Atterberg limits and compaction behavior (the maximum dry density). This targeted effect of the surfactants suggests its molecules populate, not only the air-water interfaces decreasing surface tension, but may be adsorbing to the clay particles and forming micelles in the pore water as well. Therefore the interplay between the three may influence the soil behavior.published_or_final_versio

Effect of particle size on the measurement of the apparent contact angle in sand of varying wettability under air-dried conditions

Session: Advances in Experimental Methods: Mechanical PropertiesChanges in the wettability of soil are known to affect several processes such as infiltration and the shear strength of soil. In this study, the wettability of a medium to fine sand was chemically modified by using different concentrations of dimethyldichlorosilane (DMDCS). The sessile drop method (SDM) was used for the assessment of wettability of hydrophobised Leighton Buzzard Sand (LBS). The results demonstrate that beyond a concentration of 2 g per kg of LBS, the finer fraction had its apparent contact angle (ACA) increased up to 115° while the maximum ACA attained by the coarser fractions was 100°. At such high concentration of DMDCS, the effect of trapped air, which is known to increase the ACA, was found to be either small or insignificant. The standard deviations of the ACAs agreed well with past studies. The most important factors contributing to the water-repellent behaviour of chemically synthesised sand were attributed to the characteristics of the particles; these include surface area and particle shape.published_or_final_versio

Synthetic water repellent soils

Organised by American Society of Civil Engineers (ASCE), Hong Kong Section and Department of Civil and Environmental Engineering, Hong Kong Polytechnic UniversityThe seminar will explore the potential of synthetic water repellent soils in geotechnical engineering. New laboratory research by our team has demonstrated that wetting in soils can be controlled by inducing and adjusting water repellency. Existing soils can be treated on a construction site to become water repellent; once treated, they are non-intrusive, integrate with the surrounding environment and are mechanically stable (due to their non-wettable behaviour). This ongoing research will provide Hong Kong with a novel technology forconstructing water-tight barriers and fills that is both inexpensive and reliant on an abundant local resource – soils. Our research is aimed at verifying its stability, so that perceived risks to practical implementation are identified and alleviated

Impacts of soil wettability in ground engineering and earth surface processes: early results

Contrary to a prevailing assumption in geotechnical engineering, soils can exhibit low wettability. Water repellent behaviour has been identified in contaminated, engineered and natural soils, and waste. Despite research on the hydrological implications of naturally-occurring soil water repellency such as reduced infiltration, enhancement of soil erodibility by wind and water and post-wildfire debris flows, very little is known on the influence of water repellency on soil behaviour. Drawing from research in soil science where water repellency is widely recognised, early results linking wettability (through contact angles) to some soil physical properties and processes will be presented, including potential applications to natural and infrastructure slopes

The 2010 flash floods in Madeira Island: characteristics and the role of soil water repellency in future events

Poster Session 2: B2 Landslides: abstract no. P103Conference Theme: Geotechnical Engineering for Infrastructure and DevelopmentOn the morning of February 20, 2010, a storm triggered flash floods and shallow landslides on the surrounding hillslopes of Madeira’s capital city Funchal causing 46 deaths and an estimated 210 million Euros of rebuilding costs. Funchal is located in a coastal basin that drains three major streams. These streams are in deeply incised valleys and drain sediment and water from the centre of the island to the shore. On February 20, the cumulative rainfall exceeded 300mm within hours in different parts of the Island initiating surface runoff that eroded and entrained loose sediments into the streams and generated the flash floods. The loose, coarse nature of the volcanic soils, together with sparse vegetation at altitudes above 1500m and the rugged geomorphology may have contributed towards the scale of the disaster. The paper presents an historical overview of natural hazards in Madeira, followed by a description of the main event, with a focus on rainfall data, sediment transport dynamics, deposits characteristics, and impacts on built infrastructure. Particular attention was given to the occurrence of soil water repellency after wildfires and its impact on future flash floods

Water repellent soils for slope stability

Discussion Session B1a: Slope InstabilityConference Theme: Geotechnical Engineering for Infrastructure and DevelopmentThis manuscript provides insight into a new approach to chemically induce water repellency in soils with silanes, in particular dimethyldichlorosilane (DMDCS). Silanes create a water repellent surface on any silica-based material resulting in a near permanent effect. Wettability measurements were conducted with the Sessile Droplet Method via contact angles to evaluate the influence of DMDCS modification on the particle surface of several soils (from sands to kaolin). Overall, these results suggest that soil particle modification with DMDCS may have wide application in geotechnical and geoenvironmental engineering. Here, we demonstrate their potential as a capping method for slopes to prevent or reduce infiltration