Anisotropy Of Argillaceous Slate Swelling Evolution In Water-rich Environment

Anisotropy is one of the important characteristics of rocks.As a regional metamorphic rock,argillaceous slate is rich in clay minerals such as montmorillonite,kaolinite and illite.Due to the occurrence of different angles of slate,the area of clay minerals contacted with water will be different.In the water-rich environment,water penetrates into the rock mass through the plate surface and pores,and reacts with clay minerals in physical and chemical ways,resulting in wedge effect between grains or crystals of mineral particles,resulting in obvious anisotropy of the swelling characteristics of slate.The anisotropy of argillaceous slate affects the swelling characteristics to a large extent.It is of great significance to correctly understand and master the anisotropic characteristics of argillaceous slate for the construction and design of argillaceous slate areas.In this thesis,the swelling anisotropy of argillaceous slate is studied based on the swelling problem of argillaceous slate.Because argillaceous slate belongs to vulnerable rock mass,it is difficult to drill samples.Therefore,the swelling characteristics of argillaceous slate remolded samples were studied based on orthogonal design by preparing argillaceous slate remolded samples;The swelling characteristics test,nuclear magnetic resonance（NMR）and scanning electron microscope（SEM）were carried out on remolded argillaceous slate samples with different dip angles.The macroscopic evolution law and microstructure change characteristics of swelling anisotropy of argillaceous slate were analyzed;The 3-D swelling constitutive model of argillaceous slate considering anisotropy is derived based on Kinnick condition and single discontinuity theory.The microscopic formula of swelling stress considering anisotropy is constructed by using the theory of granular physics and mechanics.The mechanism of swelling anisotropy of argillaceous slate is analyzed based on tested results and theoretical derivation.The main conclusions are as follows:（1）Through material optimization,argillaceous slate particles of 0<d≤1mm and 1<d≤2mm were selected as aggregate and rosin alcohol solution as binder to prepare argillaceous slate remolded samples.The swelling characteristics test and NMR were carried out by designing three factors and four levels L₁₆（4³）orthogonal test scheme.The results showed that:（1）The axial ultimate swelling rate,axial ultimate swelling stress,coefficient of water saturation,total T₂ peak area of NMR and porosity of remolded samples were negatively correlated with the mass ratio of binder and binder concentration,and positively correlated with the mass ratio of small-size argillaceous slate particles;（2）The remolded argillaceous slate samples under different mactching are mainly small pores and medium pores after water swelling,and the large pores are less;（3）The concentration of binder has the greatest influence on the swelling characteristics of argillaceous slate remolded samples,followed by the rock-cement ratio,and the mass ratio of small particle size argillaceous slate particles has the least influence;（4）According to the test requirements,the mass ratio of binder was 5%,the concentration of binder was 8%,and the proportion of small particle size argillaceous slate particles was 25%,which were selected as the optimal ratio of argillaceous slate remodeling samples.（2）The argillaceous slate remolded samples with 0°,15°,30°,45°,60°,75°,and 90°structural planes were prepared by using the optimal ratio of self-designed sample pressing mould.The swelling characteristic test,NMR and SEM were carried out,the results showed:（1）Under the influence of the dip angle of the structural plane,the swelling load-swelling rate of the sample shows a nonlinear relationship,which is consistent with the trend of the natural argillaceous slate curve;（2）Under the same axial load,the axial ultimate swelling rate of the specimen is negatively correlated with the inclination angle of the structural plane,showing an obvious linear relationship;（3）The laterally constrained axial ultimate swelling rate of specimens with different inclination angles and the axial ultimate swelling stress under constant volume show obvious anisotropy,both of which are negatively correlated with the inclination angle of structural planes.（4）After the specimen swelled stably,the main pores are small and medium pores,and the large pores are less.（5）The microscopic basic unit of the sample is mainly flake particles,some are block particles,and the orientation of particle space arrangement is obvious.The surface contact between particles is mainly flake body,and the stack is tower;With the increase of dip angle of structural plane,the number of pores,pore area and porosity extracted based on PCAS gradually decrease,and the pore edge tends to be complicated.（3）Based on the experimental data in Chapter 3 and the existing swelling constitutive model,the swelling constitutive model considering anisotropy is derived by combining relevant theories,and the following conclusions are drawn:（1）The existing one-dimensional swelling constitutive model of slate is used to compare and verify the axial swelling stress and axial swelling rate of argillaceous slate remolded samples with different inclination structural planes,indicating that the model is suitable for remolded samples.（2）Combined with single discontinuity theory,based on the existing swelling constitutive model,the 3-D swelling constitutive model of argillaceous slate considering anisotropy is derived.（3）The probability density function is introduced to construct the microscopic formula of swelling stress of argillaceous slate considering anisotropy.