Effects of Thermo-Osmosis on Hydraulic Behavior of Saturated Clays

Abstract

17Despite a body of research carried out on thermally coupled processes in soils, understanding 18 of thermo-osmosis phenomena in clays and its effects on hydro-mechanical behaviour is 19 incomplete. This paper presents an investigation on the effects of thermo-osmosis on 20 hydraulic behaviour of saturated clays. A theoretical formulation for hydraulic behaviour is 21 developed incorporating an explicit description of thermo-osmosis effects on coupled hydro-22 mechanical behaviour. The extended formulation is implemented within a coupled numerical 23 model for thermal, hydraulic, chemical and mechanical behaviour of soils. The model is 24 tested and applied to simulate a soil heating experiment. It is shown that the inclusion of 25 thermo-osmosis in the coupled thermo-hydraulic simulation of the case study provides a 26 2 better agreement with the experimental data compared with the case where only thermal 27 expansion of the soil constituents was considered. A series of numerical simulations are also 28 presented studying the pore water pressure development in saturated clay induced by a 29 heating source. It is shown that pore water pressure evolution can be considerably affected by 30 thermo-osmosis. Under the conditions of the problem considered, it was found that thermo-31 osmosis changed the pore water pressure regime in the vicinity of the heater in the case where 32 value of thermo-osmotic conductivity was larger than 10 -12 m 2 .K -1 .s -1 . New insights into the 33 hydraulic response of the ground and the pore pressure evolution due to thermo-osmosis are 34 provided in this paper.

Thermo-osmosis in hydrophilic nanochannels: mechanism and size effect

“…This mechanism is encountered in many areas of biology, 1 chemistry, 2 energy, 3,4 separation and membrane technologies 5 and energy geo-structures. 6,7 Although its discovery has been reported as early as 1907, 8 the need for an in-depth understanding of thermo-osmosis has re-emerged recently due to the important role of thermo-osmosis in a wide range of engineering processes and technologies (e.g. membrane systems, thermo-osmotic energy conversion heat recovery; geo-energy systems).…”

“…shale) and clay soils is essential for underpinning the design and safety assessments of many geotechnical infrastructures such as nuclear waste repositories and groundsource heat or energy foundations. 6,7 Compared to the theoretical studies of thermophoresis, in particular thermal diffusion, [9][10][11][12][13] the microscopic mechanistic understanding of thermo-osmosis is rather incomplete, although its macroscopic thermodynamical description has been widely discussed and used both in modelling multiscalemultiphase couplings problems 14,15 and in experimental works. 16,17 In fact, there is a debate between two approaches for describing the underlying mechanism for thermo-osmosis, namely the interfacial approach and the energetic approach.…”

Underground coal gasification – A numerical approach to study the formation of syngas and its reactive transport in the surrounding strata

“…The THCM model of the COMPASS code has been extensively verified, validated and applied for a range of geoenvironmental/geo-energy applications. In regards to the thermo-chemical model used in this work, the thermal aspects of the model have been verified against analytical solutions and validated against experimental data on heat propagation in various types of soils and rocks [34,43,44]. Also, the multicomponent high pressure ideal and real gas transport and its sorption in coal have been verified against analytical solutions for pure diffusive and advective-diffusive gas transport as well as the comparison of simulation results with those presented in the literature for an alternative numerical model and validated against experimental data [30,45].…”

Reactive Transport of Chemicals in Compacted Bentonite under Nonisothermal Water Infiltration

“…This observation suggests that there can be further processes involved in controlling the hydraulic conductivity evolution which are not fully captured by the hydraulic conductivity model adopted. This includes thermally coupled processes such as thermal osmosis (e.g., Zagorščak et al 2017). Fig.…”