(Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources，Changjiang River Scientific Research Institute，Wuhan，Hubei 430010，China)
Abstract：Swelling mudstone exhibits distinct physical behaviors of softening and expansibility when exposed to water，which have a significant impact on the stability of engineering rock masses. In order to investigate the effects of hydration and expansion on the mechanical properties of mudstone，this study introduces the Weibull distribution statistical damage theory and the humidity stress field theory. The expansion strain of mudstone is used to represent its expansive behavior，while the influence of moisture content reflects the water weakening effect. A statistical damage constitutive model considering both hydration and expansion effects is developed. The model?s validity is verified by compression test results of mudstone specimens with varying water contents，establishing a quantitative relationship between the statistical parameters in the model and the water content. The effect of linear swelling coefficient，residual strength，confining pressure，proportional parameters and shape parameters on the mechanical response of mudstone is analyzed. The results demonstrate that：(1) The constructed statistical damage model effectively describes the mechanical response of mudstone under different water content conditions. The proportional parameters and shape parameters in the model are expressed as nonlinear functions of water content，influencing the peak strength and post-peak softening characteristics of mudstone，respectively. (2) Mudstone exhibits significant water weakening characteristics in terms of elastic modulus，peak strength and residual strength，with the degree of hydration significantly influencing the damage evolution process，making the mudstone microelements more susceptible to failure as the water content increases. (3) The linear swelling coefficient shows a negative linear relationship with the peak strength，and the swelling effect facilitates the transition of the rock to enter the post-peak softening stage. The residual strength determines the final bearing capacity after the peak，enhancement the post-peak deformation ductility. Moreover，increase of confining pressure，results in corresponding enhancements in peak strength and residual strength of mudstone，consistent with experimental observations，indicating the rationality and reliability of the proposed statistical damage constitutive model.
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2023, Vol. 42 
