Heat-induced Moisture Movement Research Articles

A finite element model for hygro-thermo-mechanical analysis of masonry walls with FRP reinforcement

Modeling the effects of humidity and temperature gradients on the structural behavior of masonry walls reinforced with fiber reinforced polymer (FRP) composite is of great importance. Study of interfacial stresses, in particular, is a key factor in predicting the durability of the bond between the reinforcing FRP laminate and the host masonry. In this paper, a finite element modeling procedure for analyzing the hygro-thermo-mechanical response of multi-layered structures constructed with distinctive permeable materials was developed by incorporating structural stress analysis into the coupled moisture/temperature finite element model based on the governing equations proposed by Phillips and De Vries. The hygro-thermo-mechanical finite element model was used to analyze the response of a concrete block reinforced with a unidirectional glass/epoxy FRP composite laminate. The results demonstrated that the effect of temperature gradient on the moisture distribution, i.e., heat-induced moisture movement, resulted in an accumulation of moisture at the interface, and induced interfacial stresses even in the absence of a moisture gradient. The presented finite element modeling procedure can be used to aid with the design of FRP/masonry structure or other similar structures for minimizing interfacial stresses induced due to the mismatch of moisture swelling and thermal expansion properties of the constituent materials.

Heat-induced moisture transport in the vicinity of a spherical heat source

The present paper develops an analytical approach to the problem of heat-induced moisture movement in the vicinity of a spherical heat source embedded in an undeformable, moist porous solid of infinite extent. A transient-state distribution of temperature within the infinite medium is assumed to induce the moisture transport process. The numerical results, presented in the paper, illustrate the influence of the moisture transport characteristics on the time-dependent distribution of moisture within the porous medium. © 1998 John Wiley & Sons, Ltd.

Heat-induced moisture movement in a clay barrier II. Computational modelling and comparison with experimental results : A. P. S. Selvadurai, Engineering Geology, 41(1–4), 1996, pp 219–238

Heat-induced moisture movement in a clay barrier II. Computational modelling and comparison with experimental results : A. P. S. Selvadurai, Engineering Geology, 41(1–4), 1996, pp 219–238

Heat-induced moisture movement in a clay barrier I. Experimental modelling of borehole emplacement : A. P. S. Selvadurai, Engineering Geology, 41(1–4), 1996, pp 239–256

Heat-induced moisture movement in a clay barrier I. Experimental modelling of borehole emplacement : A. P. S. Selvadurai, Engineering Geology, 41(1–4), 1996, pp 239–256

On some aspects of a nonlinear convection-diffusion equation arising in heat-induced moisture transport in porous media

This paper focuses on the problem of the heat-induced moisture movement in a porous medium. In particular, the paper addresses the nonlinear convection-diffusion processes arising from such moisture transport under steady thermal gradients. The character of the governing differential equation is examined in relation to its solution structure. Conclusions with regard to the residual moisture distribution within an annular porous medium are established.

Moisture movement under a temperature gradient in highly compacted bentonite

The heat induced moisture movement in buffer materials to be used for the geologic disposal of high-level radioactive waste is investigated by a series of experiments and numerical simulations. Highly compacted blocks of Japanese Na bentonite are used in the experiments as the buffer materials. Mechanistic models including those proposed by Philip et al. and Ewen et al. are formulated to the finite-element program which are applied to interpret the experimental results. The applicability of the mechanistic models to the compacted bentonite is examined. The numerical results agree well with the experimental results qualitatively, though a few quantitative discrepancies are found. Those discrepancies demand better descriptions for material properties on compacted bentonite and introducing an effect of volume change associated with change in water content.

Heat-induced moisture movement in a clay barrier II. Computational modelling and comparison with experimental results

The paper presents the application of a Galerkin finite-element technique for the numerical solution of the differential equations governing coupled heat flow and moisture movement in a clay buffer. Attention is focussed on the axisymmetric modelling of the hygro-thermal processes encountered in the single borehole emplacement configuration developed for laboratory simulation. The numerical results derived for the time-dependent temperature distributions within the granite block and the residual moisture distribution within the buffer are compared with the respective experimental results.

Heat-induced moisture movement in a clay barrier I. Experimental modelling of borehole emplacement

The paper presents the results of a series laboratory experiments which were conducted to study the heat-induced moisture movement in a bentonitic clay buffer region. In the experimental investigations, hygro-thermal phenomena are induced by a cylindrical heater which is placed within the compacted buffer material located in a borehole centrally situated in a granite block. The paper summarizes the experimental methodologies and presents results for the time-dependent distribution of temperatures within the granite block and the residual moisture distribution within the buffer at the termination of the experiment.

Experimental Determination of Parameters Governing Heat-Induced Moisture Movement in A Clay Buffer

ABSTRACTThis paper discusses the experimental evaluation of the hygro-thermal parameters governing coupled heat and moisture movement within a moist clay buffer, which is developed as an engineered barrier for the isolation of heat emitting nuclear waste containers in either a borehole environment or in an in-room emplacement scheme.

Heat-induced moisture movement within a clay-based sealing material

The bentonite-sand buffer material, which isolates the nuclear-fuel waste containers from the host rock mass, is a vital component of the multiple engineered barrier scheme advocated by the Canadian Nuclear Fuel Waste Management Program. This paper presents results of laboratory investigations which examine the influence of the container surface temperatures on the moisture migration within a compacted buffer in a borehole environment.

Hygrothermal Performance of an Engineered Clay Barrier

ABSTRACTA series of laboratory experiments was conducted to establish the heat-induced moisture movement in a bentonitic clay buffer. The buffer material is proposed as an engineered barrier to isolate a heat-emitting high-level nuclear fuel waste container from its emplacement borehole located in a deep rock repository. In the experimental simulation, the hygrothermal phenomena are initiated by a cylindrical heater placed within the compacted buffer material in a borehole centrally located in a granite block. The experimental results illustrate the time-dependent distribution of temperatures within the rock mass and the residual moisture distribution at the termination of the experiment.

Modelling the in Situ Performance of Bentonite-Sand Buffer

ABSTRACTIn the Canadian nuclear fuel waste management concept, a number of engineered barriers, such as the bentonite-sand buffer which surrounds the waste container in the emplacement boreholes, are used to inhibit the transport of radionuclides. The buffer material is also required to effectively conduct heat from the fuel-waste containers to the surrounding rock. To a large extent, in situ buffer performance will depend on the degree of moisture within the buffer. The moisture content will in turn depend on temperature, temperature gradients, and buffer initial and moisture flux boundary conditions. Modelling of coupled heat and moisture transport in the buffer before resaturation is necessary to assess in situ buffer performance. This paper describes the results of a parametric study using the Philip and de Vries coupled heat and moisture transport model to assess the effects of variations in the moisture diffusivity parameters and the boundary conditions on buffer performance.The results show that the thermal performance of the buffer is affected by heat-induced moisture movement. In particular, the thermal vapour diffusivity, DTvap, has the most significant effect on thermal drying in a closed system. Work is currently underway to improve our capability to model coupled heat and moisture transport in buffer. Laboratory experiments are in progress to more accurately define the moisture diffusivity parameters and the model is being modified to include the effects of boundary moisture fluxes and pressure potentials so that the resaturation process may be modelled. A full scale buffer/container experiment is currently being planned for conduct in AECL's Underground Research Laboratory to assess further the effects of scale and in situ boundary conditions on buffer performance and to qualify the model.