| As a kind of problematic and regional soil,red clay has generalities of common clays and special engineering characteristics different from common clays.It has high plasticity,strength and compression resistance.Numerical researches show that the particular engineering characteristics of red clay mainly result from the physical-chemical interaction of clay minerals and cementitious substances and water in the soil.Because of large specific surface area?SSA?and activity of clay minerals,clay minerals such as montmorillonite and illite have special physical-chemical characteristics such as strong water adsorption ability and deformation property.Bound water,the special product of the interaction between clay minerals and water,which also has special physicochemical characteristics.It is one of the important factors to control the plasticity,heat transfer,deformation and strength of clay.In this paper,two typical red clays in two sites of Guilin and Liuzhou are taken as the research objects.The influence of water content on the thermal conductivity,deformation and strength of Guilin and Liuzhou red clay are studied by macro-tests?thermal properties test,consolidation compression test and undrained direct shear test?.Considering the mechanism of clay-water interaction and the content of bound water and type of bound water in 2 red clays obtained by isothermal adsorption method,the influence mechanism of bound water on the thermal properties,deformation and strength of 2 red clays are discussed.All the studies above reached conclusions as follows:?1?The relationship between the thermal conductivity of 2 red clays and the water content?K-??show the law of piecewise linear growth.The boundary point of contiguous stages of the relationship between thermal conductivity and water content is determined as"critical water content";Due to the change of water content and the transition of water form in different red clays,the influence of water content on thermal-physical properties of 2 red clays are different.Combined with the experimental results and analysis,it is shown that when the water content is in the range of?a,that is,???a,the formation of bound water on the surface of clay particles and the discharge of pore air are the main factors affecting the rapid growth of thermal conductivity of red clay.When?>?a,the change of Guilin red clay's thermal conductivity undergoes a brief transition period with the increase of water content.With the formation of the“liquid bridge”between the large number of aggregates of fine clay particles,the heat transfer performance of red clay is further improved.With the increase of water content,except for incompressible closed air bubbles,the air in clay pores is basically discharged.Therefore,the water content does not increase any more,leading to the slow increase of thermal conductivity;?2?The e-logP curves under different water content and Cc-?curves of 2 red clays all have distinct boundary points corresponding to the bound water content??a?of 2 red clays respectively.In the range of???a,2 red clays have the advantages such as stable structure of soil skeleton,high compression resistance and low compressibility.With the increase of water content,the compressibility of 2 red clays is high while water content is greater than?a;?3?With increasing of water content,both the shear strength(?max)and cohesive force?c?increase to the maximum and then decrease.And the water contents corresponding to the maximums of?maxax and c are very close for the same red clay,which are also very close to the?a measured in the red clay.It is largely related to the formation of bound water film adhering to clay particle surface as well as the interaction between bound water film and soil;The shear strength of red clay comes from the cohesive force between clay particles,and the influence of water content on the shear strength of red clay is mainly expressed in the influence of water content on the cohesive force.The cohesive force of red clay mainly comes from the binding force between bound water film and cementitious material on the surface of clay particles;?4?The content of bound water??a?in red clay could be regarded as an important referance point to judge that the physical-mechanical properties of red clay such as deformation,strength characteristics and thermal conductivity of red clay obviously change with the change of water content in red clay. |
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